I think the takeaway from this should be know what you're buying and don't fall for the marketing hype on so-called "Tube Preamps" in the low budget range. This is what's called a "starved tube" design. The plates are running on low voltage, the filaments are also under-volted, so they barely glow at all, hence the need for LEDs to make the orange glow from the front panel. Is it a "fraud"? Technically, no. The tube is amplifying signal; however, there isn't enough of an amplification going on for the tube to reach saturation and compress the signal in the way one would expect from a true all-tube preamp for recording use. My advice is don't waste your money unless you just need something to amplify a signal for a basic project studio. If you want actual tube warmth, save your money and buy a high voltage all-tube preamp that is worthy of professional use.
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Thanks for the explanation - I thought that was the case. Technically it does what it says on the tin, but falls short of what an average punter would expect that to deliver them.
I thought it was there as like a technicality or whatever. Like it does nothing except let a signal pass through it, so when you remove the tube then you lose signal, just to make people think that the tube has all the power. I don't repair amps so I wouldn't have had it opened up and ON to be able to see those fake out LEDs glowing like you were able to (those sneaky bastards). I'd probably go "oh the tube glows but maybe it's not good enough. Let me go out and buy a new one." And just waste more time. Thanks for this one!
@@TheGuitologist I have that same preamp. Had it for years, barely used it. It has this "V3" rotary switch on the front that supposedly affects tube saturation / tone. I was wondering if that switch perhaps controls plate voltages. Maybe that's how they saturate the tube, whatever that means, by changing certain voltages. That power supply seems beefy enough to handle more than just a bunch of silicon. Just a thought. If you still have that thing and care enough about this, it might be worth a quick check.
There is no fraud to this. This unit was not designed to make amplification through the tube, but rather the tube only "colors" the signal with variable amounts of distortion and harmonics. The plaintiff in this matter is missing the point (and usefulness) of this design. This unit offers you both a clean sound, which in my opinion is pretty damn good. Add the fact that they actually have a variable impedance knob which can adjust the character of your mic, and this unit becomes a gem. I have 2 of these units and will buy another when the need arises for more inputs. These units are fantastic for giving various instruments a "place" in the mix, and with even the lowliest of microphones you can make them sound like much more expensive flavors with the impedance adjustments. Even for the full price, these units are a steal for what they accomplish. To add a bit more insight on this, since the unit's output volume is not directly related to the tube itself, and since the tube on lower voltage is more prone to signal breakup (harmonic distortion) at lower gain... maybe the owner should consider trying other tubes besides the 12ax7... for example, the 12ay7 has a lower gain and quicker breakup than the 12ax7 and imparts even more warmth. This is evident in the fact that many tube mic designers have made use of the 12ay7 in their tube mics. Why not even try a 12at7? 12at7 will still give a little cleaner emphasis on the upper frequencies. In the 2 units I have one has a 12ay7 RCA and one has a 12at7 JAN and I use them for different purposes. Good Luck!
I can see an irony here ... Maybe they felt that they had to artificially light up the tube to prevent lots of returns because customers couldn't see the tube glow and thought it was faulty ...
I could totally see this being the reason for the LEDs. I've had some gear where it was really difficult to see the filament glow and I was wondering. And the other reason could be just to make it look nice.
Tubes like the 12AX7 don't normally light up brightly, especially when the voltage is low. The heaters on these tubes are dual voltage, with three connection pins. one pin is on one end of the A section heater, one is on one end of the B section heater, and the third goes to the remaining ends of both heaters as a common connection, so the tube can be wired with the heaters in series to run on 12 volts, or in parallel to run on 6 volts, same thing with the related 12AU7 and 12AT7 tubes. Also, these tubes are not intended to run one unit on one channel and one on the other, as there is considerable cross talk between the sections, it is intended to be used as consecutive stages of a single channel only.
At least it’s got wall power for the tube unlike a tube pedal running on a dollar general 9 volt. In pre amps and restaurants it’s all about hot plates
There are many starved plate designs that essentially warm up an otherwise cold solid state tone. Check out the popularity of Matsumins Valvecaster for example. It is best used to give a warmer clean tone into a solid state amp, not as a distortion unit. Or the many examples of rack gear that contained a single tube, to 'warm' up the tone. Just a bit of info as to the general use of these kind of circuits.
@@jrg770 the only WARMING it does comes from the secondary led's........its bullshit,it does next to nothing,its pointless and silly but hooks in the "novice gearheads"who hear "tube" and loose their proverbial shit
@@trillrifaxegrindor4411 You can run a audio signal through a preamp tube, take your pick of what kind, and get a amplified signal. This will add "body" to the sound. And yes, even when running a tube as low as 9v. That would sound pretty ctrappy with a 12AX7 though. The only real function of this kind of unit is to "warm up, fatten, thicken, add body" take your pick of descriptors, the audio signal. And yes, it does in fact do that, as I have built plenty of low voltage 12v/12Au7 preamp boxes. You run your guitar through that box, into the front of a solid state or even a tube amp and you have a boosted and fatter signal going into the amp. That is the purpose of this unit, and it does in fact do that.
Not at all. It is clearly a stage in the amplification, so it's perfectly legit. People with little or no electronic education and experience are in no way qualified to comment on this.
I've got one of these. I've used it a lot. Which preamp circuit is in use depends on what you have selected in the front panel. It has a selector switch that lets you choose between different kinds of preamp circuits... I design my own preamps now. You can run some tubes on a lower voltage and some are okay but some distort too much and lowering the filament voltage can cure that but it's not going to be super clean. I'd rather just use an INA217 or INA849 based preamp for most instruments and a version of INA preamp with a soft limiter for drums...
@@soundknight all behrcrap sounds awful. when the company started out in the early 90's there stuff was pretty good, but they got greedy very quickly and their stuff turned into low-quality crap that sort-of works...
Thanks for that. Ive been using the lil ART tube pre single channel boxes for a condenser Mic..warms it up a little. Works really well in mixer XL loop to saturate the mic sound a hair before recording. Not crazy but enough to hear a pleasant difference. Dig the channel btw.
If you ran that tube at 180 volts like usual it would destroy all the solid state components attached to it. You would make a nice smoke generator and if you're lucky it would also burst into flames. You can't just randomly mix and match components. I'm sure the original design engineer actually worked out the numbers so it would not blow up.
I've seen a schematic for some of the Joyo BantAmp ZoMBie circuitry, traced by some guy at the DIYstompboxes forum. The tube B+ is 50V by a DC-DC-converter from the 18V power brick. The signal passes through both tube stages.
But you tested this with the V3 dial at flat (6 o'clock) on both channels. The tube gets more voltage to saturate and becomes 'warm' when that's turned up. It was at minimum gain when you had a meter on it, so it barely kicked in. 😮
Most of the modern pedals/effects have 'Backlight Leds' to make the tube stand out, but in the ones I've worked on, the tube is actually functioning. Also, tubes can function in very low plate voltages, just in a different part of the load curve. If the signal gain is small enough, it doesn't matter that it it's running in a non linear portion of the curve. Don't know about this item, tho.
I have seen some high dollar “hi-fi” amps that have LEDS under the tubes! The tubes do function the LEDS are just for decoration. I am perfectly happy with the filament glow-and that tells you the filaments do indeed work. The LEDS may mask the fact.
Nice that you kept an objective standpoint throughout. I personally detest these designs where they feed the tube just enough plate and filament to get it to pass signal. I understand why they’re doing it though, that way the tube runs a lot cooler so no issues with thermal management. But the LEDs are just silly, though that’s fairly common, tubes don’t glow enough for marketing purposes. If somebody still made mercury rectifiers I would design some mojo preamp around one, that would give the punters a lot of mojo glow for their money!
The other reason they're doing it is that it turns the thing into an effects box. A well-designed tube stage wouldn't have enough distortion at the signal levels involved to satisfy customers.
This is a trick from late 50's early 60's where running the heater at a lower DC voltage creates more gain with less noise. This can be seen in early Mcintosh tube amplifiers. I believe Audio Research also did this (or may still).
Maybe the colder filament is providing already the litttle current needed with such a low plate voltage. So, maybe the low filament voltage is a just a deliberate choice? Possibly to reduce heating of the entire device. Thanks for sharing Brad!
I have a old ART Tube Pac that has 2 12AX7's. It gets really hot, so I set it on its own rack thing(not rack mount). It works well IMO and warms up the sound for digital recording. I can hear a difference. Great video Brad. I had read about this a lot back when I bought this unit I have, but it was worth the money to me.
It would be interesting to consult the tube curves to see, from an engineering perspective, how this tube would perform at those bias voltages. Also consider if this would enhance the "tube sound" and positively impact reliability.
I have a Vox Tonelab ST that uses a 12AX7 in exactly the same way i.e. glowing LED's rather than glowing filaments. There's a video somewhere on TH-cam where a guy removes the valve and still gets a guitar signal through the unit, but as I recall the preset he used didn't require the valve in situ. I also have a couple of the smaller ART preamps and found them to be very flexible and great value for money too.
I have an ART Voice Channel and a Pro MPA II. Both are really nice products for the money. A lot of bang for the buck. Especially after I retubed them with good 12AX7s.
guess you missed the part were the tube does nothing,retubing anything like this were the tube is redundant and pointless just fluffed up your confirmation bias and automatically you "thought" it sounded better ps: it didnt,truly...it didnt,but you sure thought it did
@@trillrifaxegrindor4411 ... I guess you missed the part where I don't have a unit with a starved plate tube configuration. Both of my ART products actually properly utilize the tubes, and yes... there is a difference. If there wasn't... tube companies would go out of business. Also... I tried 12AU7 and 12AT7 tubes to see what differences I could get on a vocal mic, and again... there is a difference.
i used one of the art tube mic preamp models when my mic needed a bit of a boost , it sounded amazing , im not sure how much of that was down to the tube, but it sounded warm and full , i think the tube part is a gimmick , but it worked for what i needed it to do
A couple things came to mind- I had a Behringer guitar amp with a 12AX7 in the front end. They also did the show business with an LED. The tube was definitely active, and the amp sounded good. I wonder how the ART design might be similar to the "Cool Tube" preamp in high end Takamine acoustic guitars. They run on low voltage as well.
If you are using a transistorised circuit to give you the gain then you will have less noise, that leaves the tube free to just add tube flavour to the sound. Because you don't need or want high gain from the tube it can be run at lower heater and much lower anode voltages which will significantly increase the tube's life and simplify the circuit design.
That seems to be the rumor going around. If anyone has specific examples of accusations against a specific make and model, let me know, maybe I'll test it out.
Hopefully this can help out a stop to stuff like this. If you’re buying Behringer tube stuff you might be asking for this but this shouldn’t be common practice
ART is all about the starved plate design for some reason. I've read the designer talking about his preference for how they distort. You could say price is the motivator, but they do make budget models with switchable voltage, e.g. the MPA preamps (which run plate at 150V when switched to "high", if I remember correctly), which are still very cheap for a tube pre at a decent voltage.
I have a cheap ART tube direct box I bought years ago - TUBE MP Preamp. I always thought it was cold to the tube since it was low voltage and did not make a real big difference in sound. The only advantage is is had both XLR and 1/4" So you could use it for phantom power for condenser mic's if your mixer did not have them but not sure if it would help with a vocal breakup. It was fairly cheap so I did not have high expectations but tried it with solid state amp effects loops back in the day to help tone. I couldn't tell any difference. Thanks, for the review. Interesting tidbit I had totally forgot about.
The LED's to light up the tube is classic Marketing requirement ... A bit like sticking a massive 8 outlet exhaust on a small car together with 'go faster stripes' and a limited edition rally badge, without modifying the engine at all. Mind you, even the changed exhaust will affect the sound (not performance) more than this tube affects the amp sound ...
Years ago, before the internet, I bought a preamp kit ( it was called Stack in a Box) out of the back of a magazine that has a 12ax7. The power supply is a wall wort, maybe 12V, I don't remember but it pretty much does same thing, uses low voltage through the tube. I still have it Brad, If you want it to dissect I can send it to you.
As "LoV" (Low Voltage) project over the net : usage of 12AX7 under powered, with non-lethal voltages. It's not "typical" usage, but it work. A different approach is a little project I've seen, is 4*1.5v battery with 230/12v transfo and a square signal generator (on a 6V filament tube), the TR+square makes a high voltage to the tube. Not typical, but for fun is working ^^
Ha, I just made a fake tube amp for my GGBO guitar as an art project. I used a flicker bulb behind the tubes, similar to what they did here with the LED lights.
Curiouser and curiouser - I own a S.M.S.L. SP100 headphone amplifier and I use a Raytheon 5670 "electronic valve" (5670 2C51 396A Raytheon Windmill Getter) a tube in laymen's terms instead of 6N3 supplied, both plates appear to warm up, tube does get hot - sounds amazing and is powerful enough to drive the high ohm headphones I own. Shame the ART Pro Audio "TUBE" mic preamp does not utilize all the tubes potential.
My father told me the battery powered tube radios of his childhood had low filament and plate voltages. Usually like 1.5 to 3v for the filament and 45 to 90v for the plate. Those low voltages in the preamp aren't surprising. A modern tube filament isn't going to put on much of a show at low voltage, hence the hokey LED backlights.
I have one of those radios. It's made to run on ac or battery. It had a big 45VDC "B" battery that I took out because it was leaking. Still works on ac though. BTW the B battery is where B+ comes from on schematics.
I’d also love to see you pull apart some of these “tube” pedals that aren’t necessarily in the low budget range, particularly those incorporating sub-miniatures (that aren’t Seymour Duncan).
The only tube pedal i've ever heard that i actually thought sounded really good was the old Mesa V-twin, which they don't make anymore. definitely the best pedal mesa ever made. their newer distortion pedals don't hold a candle to the V-twin. The tone burst is a really nice boost pedal though. one of my buddies was all line 6'd out and had a multi fx from them back in the day that had a 12ax7 in it. pedal sounded horrible. I hated that thing. of course he was running a spider valve line 6 half stack that also sounded abysmal. that was the 'bogner' labeled line 6 tube amp. thing was a toilet. my old Blue Voodoo smoked it, and that ain't saying much. Vox used to make a flagship multi fx pedal with a 12ax7 in it that i'd love to get my hands on and hear. i could see them doing a pedal right.
I've got a dbx 386 dual channel mic preamp in my recording rack. Marketed as a "vacuum tube mic preamp" with one 12AU7 per channel, B+ is 200V. I've seen a tracing of the circuit; the tube is a parallel gain stage with three op-amp stages before and five op-amp stages after. And yep, there are orange LEDs in the tube socket center holes. The SPDIF and AES/EBU digital outputs are nice, though. Two extra channels into the audio interface, very useful when tracking a fully-miked drum kit :)
Most of these "real tube" devices are actually only running the 12AX7 at about 20 volts! The tube is basically just used to filter and smooth out the signal somewhat... but the actual distortion is produced with clipped diodes, etc.
I'm no electrician, but i've never noticed 12ax7's glowing before in any usage. i certainly believe you that the plate voltage is low on this unit, but wouldn't they need the led's anyway to make it look like the tube was glowing? none of my Tube guitar amps have pre amp tubes that glow significantly, no matter how long or hard i run the amps.
hey brad, i just subcribed to your channel and believe it or not ,your the first youtuber and most likely the only one i bother putting on the computor to watch,..first i want to say that i respect you standing up for your self and your family spite everything else, i would do the same no matter what i stand to lose....besides all that. I just found a fender passport PA system (no speakers) and no power cord but i robbed a cord from my copier machine and Im not sure which way to go with this..i wouldnt mind shipping it to you,but fear it my cost the same to buy it used..i live in NH,..i guess im stuck in a rock and a hard spot with this but again i didnt pay a penny for it so. thats where im at...the things weights about 20 lbs..
Brad... you should reach out to ART and see if they'll supply you with a donor Pro MPA II or one of their channel strips. Would be cool to see you evaluate them. I actually love mine. Best bangs for the buck in my little home studio. Bass sounds great coming through it on the High Z. Got even better with decent tubes too. Their Voice Channel in combination with my budget friendly tube mic (Lauten Audio LA320) sounds great! I just hate to see ART get a bad name for this. Buyers need to be aware that there's a lower limit to buying things, and companies try to provide consumers with low dollar options.
I agree on the need to supply the low end of the market with gear. I would have preferred they just make the best solid state unit they could possibly make and skip the tube pretense.
Fascinating! I wonder if you would find something similar with the Vox Valvetronix!? I have always been suspicious that the tube (which they sort of admit might have limited use in the amp's design, and describe it's function as "POWER AMP BUFFER". Brilliant marketing scheme, as most ppl mistakenly believe it's a "tube" amp. Any experience with the valvetronix, Brad?
I have seen LEDs doing this in other equipment, yes. Can't recall having a that model open, but it wouldn't surprise me if it was something very similar and the tube was doing very little to the signal.
Blimey, this is still a thing? Behringer had the same thing going on nearly 15 years ago with their Composer Compressor. It was just a bunch of LEDs in the back. The tube sort of was hooked up, it was just a starved plate design and account for not much more than a LPF. Korg even had the same bs going on with some of their stompboxes back in the day. Will watch the rest of the vid though, I had no idea this sort of bumph was still going on.
I've actually seen a number of different units by different companies that put LEDs behind the tube. I have a Presonus tube mic preamp that has a red one behind the 12AX7- the first time I turned it on the color freaked me out!! 🤣🤣 I popped it open to see why the tube was bright red, only to see the LED. The tube itself had a nice gentle orange glow that was only visible at the end of the tube, where you see the heaters come out the end of the mica.
This preamp also has a FET circuit. And depending on where you set your V3 knob, it may engage the tube differently. Curious to know where he had that set for this test.
Interesting design, glad to see art wasn't straight up faking it, since they've produced quite a few decent units for entry level prices. For studio and guitarists.
I’d like to know if the Presonus Tube Pre is the same way. It has a little red LED that glows behind it also. I was always suspicious that it even did anything
I got one of those little ART tube preamps about 10-12 years ago. I've liked it. Which it's old now and is starting to get a little noisy. But you can feel the heat coming off the tube when you use it. And I mainly use it for vocals. So it's not like I need a ton of overdrive or anything. But if you crank up the preamp it does have plenty of saturation and compression, which could be from something else, I don't know. But you said you had one before, so I'm sure you know all of this. But yeah, I was thinking of buying another one. But what you showed us here makes me wonder if they've started skimping on the small ones since I bought mine.
I also have it. Most likely it does nothing but add some noise. A mod in my forum brought that up when I proudly told everyone that I add some warmth to my vocal recordings, haha. If your's got noisy maybe you should swap the tube against a fresher one. Or you could have a leaking capacitor or so. It's funny that these things even won awards in recording magazines! I had one from an australian brand before and the saturation was always present even when not dialed in much. It was always visible in the waveform.
You get what you pay for. This is a entry level unit. I have a simple cheap art mic pre. It has one 12ax7. It definitely glows and most likely is designed to not get very hot. Which makes since for what it is. It will add sonic quality and warmth without burning out too soon and also have a nice signal to noise ratio/quiet operation. Sounds good and definitely enhances the sound of any mic or instrument signal. They add the lights behind the tube because it looks cool and they don't need to try and explain the pros and cons of a starved tube design to people that won't understand lol. Use your ears and not your eyes and you can tell that it actually does exactly what it is designed to do. It's not going to glow like a guitar tube amp. If you want multiple hot tubes that glow bright and have the ability to saturate big time get your wallet out and your going to pay out big time. Same deal with tube guitar amps.
I was working in a studio that records almost everything with ART Tube MP and it sounds good. I bought TPS II because I had a chance to try V3, and I think those presets are useful, especially I got sweet compressions conveniently for my bass. It doesn't mean I don't care about their design under the cover, but as long as it's not a fraud and I'm happy with the results, then they deserve my money. Maybe the design is to prolong tube life? I checked this videos because the tube gone bad, so I watched tube replacement guides and related videos. I upgraded to Sovtek long plate, get my jobs done with overkilled quality for my clients, so no regret, although the price is getting higher during the war in Russia.
No problem at all to run the plates at 25v, it just limits swing and available headroom. In theory, the tube will compress a signal and perform like any other running at far higher voltages but with very small input and output in this case. The LEDs? Cosmetics.
I did hear a difference between a 12au7 and the stock 12ax7, enough for me to leave it there, it did not turn into an entrance to an enchanted harmonics land but to my ears it did the trick, it was a behringer tube mic 200, might be gimmicky but beats the input of my budget interface in my budget life
I have the little 1 channel ART mic preamp with a tube in it...........Got it for 25$ from craigslist. It was a quiet mic preamp that worked OK, so I never dug deeper than putting a good tube in it. I've done some stomp boxes with tubes in them, and those run with a 12v AC power supply, then ramped up to about 100v...... I've also done a distortion that drives the grid with a Darlington transistor to get it to crunch up... that works ok also.
I have worked on the small preamp, filament voltage was 5.7V and the plate has 48V phantom power. I modified the filament supply, added an extra diode in the ground reference path of the 7805, now it's almost dead on 6.3V.
Aww man i have a couple of those i use on my Hammonds...they seem to work correctly...icalso have several Behringer units with tubes, and i replaced allcthe Chinese made bottles w vintage Baldwins, probably for nothing
I got one of those, actually good sounding preamp for condenser mike, phantom power included, used it for guitar too... gee well, what do you know, gonna open that thing up i guess.
Yeah they actually worked pretty good. I used one of the old ones from late 80s on my Hammond XB-2 for an extra gain stage. You could pull out the AX-7 and the gain staging still worked. Supposedly the tube was to 'warm' things up. But I don't know. Hard to tell everything was so friggin loud back then.
I've been avoiding tube devices because I don't need to waste my time chasing light bulbs, but with the voltage so low, do the tubes last pretty much indefinitely, or do they still burn out, or what service schedule should one expect ? could a person place a jumper wire or such to make these units work without the tube ? I saw a unit with a solid state by-pass, maybe the switch is a jumper. I think I may have helped a friend change a bulb in an Art doodle one time, it seemed a waste of recording time. I think I remember LEDs behind the tube.
You probably never heard about Matsumin Valvecaster preamps... google about it, this will explain you a lot of things about low voltage tube circuits...
Personally, I doubt I'll be touching another Orange/Vox/Korg/Blackstar product. Korg is very bad about pulling the marketing wool over the eyes of consumers and they won't come off schematics or stand behind their products in long-term meaningful ways. Plus, build quality is questionable. It's stuff destined for landfill.
The question I have is what is the classic design for the old studio mic preamps? That's what I'd expect this to be judged against, not a guitar preamp. Given the hours studio rack mount equipment would accumulate, I can see the desirability to run the tube cold. And way back when, they wanted a good preamp, not necessarily one that had tube distortion. If you wanted your solid state guitar amp to sound like a tube amp, this isn't the device a player would reach for.
It would have been interesting to see scope waveforms on the tube output with different drive levels, see what the tube is actually doing to the signal
I use an ART Pro Channel 2. It runs a 12AX7 stage at both low and high voltage, switch selectable. I used a FFT scope to see what it did. The low voltage setting (starved plate) had a lot more harmonics than the high voltage setting. So the person who said that the starved plate design could be called an effect circuit has merit. I use it in my bass amplifier setup. When I want a dirty tube sound I run it low voltage and overdrive it all I can. No, it doesn't sound like a tube Ampeg but I like the sound. When I want a clean sound I use high voltage and keep the gain indicator in the green or slight yellow area.
Appears to me that the cabinet is designed with minimal ventilation (only slots for cooling are on the front panel). Maybe the circuit is designed to run the tube as cool as possible due to this .
I owned one of these units and it was great. I wish I still had it. I would like it if ART made some high voltage tube preamps as well. I can't imagine it would cost much more to make them. Whatever the case, I think ART makes unbeatable gear for the price IMO.
Yeah, it will be much more expensive, you'll need two input and two output balanced audio transformers. Decent ones are at least 60$ a pop, wholesale. That will be 300 retail only for the transformers.put everything else in there and it will easily reach at least 800$.
There is a term for tube based devices like this - "starved plate." Most budget tube items from ART and Behringer are starved plate tubes. Depending on the application, and the actual voltage applied, this can be A. preferred and beneficial to the intended use case, B. inconsequential to the intended usage, falling to preference, or C. snake oil and bullshit. The V3 range of products from ART is notoriously bad, to begin with, in all fairness, of which the TPS II is a member, and they fall squarely in "category C - Snake Oil and Bullshit." I own a lot of ART preamps and power units, from old Tube MP Studio and Tube MP/C preamps to the SLA-1 power amp, and more than a few big producers/recording engineers swear by their higher end rack preamp and compressor units, both solid state and tube. The starved plate tube preamps are mostly good for use with condenser mics, low output dynamics like the SM7b, or as DI boxes when you plan to use VST amp sims or reamp with a modeler later. They can also liven up the sterile, stale sound of sub-par, low-end amp modeling from cheap Multi-FX units, making them sound more on level of a Helix, for example, if you set it so higher gain pushes them into a bit of drive, but clean gives you more of an "edge of breakup" kind of tone, and will also improve the distortion character/quality of higher end modelers like AxeFX. If you're not doing something like that, then buying one of these is a complete waste of money. Their viable usage being preferable to a PURE solid state preamp or a true tube preamp, with actual benefit, is decidedly niche.
Standard for most cheap tube preamps. By running the tube in a rather non-linear region it would certainly be a bit of an "effects box", which a lot of people buying a cheap tube preamp are looking for. I'd be interested to see the distortion on something like this- I expect it's very high. Furthermore, such low plate voltages will make it a lot easier to drive that stage into distortion. Again, this is an effects box. Someone wanting a clean mic preamp would just use an SSM2019 in a box. A traditional 2-channel tube preamp is going to require upwards of $150 in input transformers alone.
Well done. I played with the Presonus Studio Channel, also a staved design. Yes the tube modifies the sound, it adds a lot of harmonics controlled with the "Tube Drive" control, but it doesn't sound like a high voltage preamp. An interesting experiment is to use the ART Pro Channel 2 and there is a front panel switch to change the voltage high or low on one of the tubes. It does change the sound .
i know this is an old video.. i just happen to have this mic pre in my rack and ran across this and recall this video.. remember, this is a mic pre.. not a 1st gain stage for a guitar amp.. it's not designed to push to crazy distortion.. it's made to warm up a voice or smooth out an instrument.. not the same as your typical 12ax7 in your fender deluxe.. used at low voltage like this.. it should last forever.. and will do enough shaping to work for budget needs.. no need to red-plate it to death for vocals.. the led trick to illuminate a tube has been used in amps of all kinds and is nothing new.. strictly for visual effect.. you wanna see the tube glow, but no need to run the filament hot.. add a LED and problem fixed.. if they pushed the filament to glow then they would need ventilation/fans then you have a tube roasting in a rack.. none of which is needed to smooth vocals in the sub $300 range... that's
Okay, the LED trick is excusable, because so many people would complain if the glow was not visible through the outside of the unit (like the whole tube glow-hype thing) but the sub 50 volt on the plates is completely ridiculous. Also I know of two other companies who do the LED trick just so it looks cooler
In most products like this including headphone amplifiers, the tube is used as a unity gain cathode follower buffer stage. Supposedly this allows you to get the harmonic structure of the tube. With no amplification from the tube, I doubt it.
Actually with all these low priced "tube" preamps I was in the assumption (and that this is even told be the manufacturer) the tubes are not part of the amplification but just used to add some harmonic distortion to the already amplified signal. You can blend in the amount of the tube's soft distortion but you never will increase the amplification by the tube circuit. For real tube amps you'd have to pay way more just for one channel and there aren't that many on the market. Even SLP's well recognized preamps (450-900 €) the tubes are not main part of amplifications. So I wonder if ART really stated this is a tube amplified preamp or as I remember (since I had that piece, maybe the previous model but looked the same) they somehow mentioned the tubes is only "creaming" the sound of the signal? :) Now continuing to watch the video :)
I have seen plenty of rack mount preamps with tubes in them that use the LEDs for aesthetic‘s as well as models that were not designed or equipped with tubes that also used LEDs to simulate the glow of a tube. No mystery here.
LEDs are for effect. My guess is that the tube is tubing just fine but it’s not enough power to push the filaments. The lights are so the consumer looks at his amp and says, “Yup, she’s a glowin.....she must be a tubin’
I feel like there's just not any point to this product; If you want a tube preamp, get a good tube preamp - if you don't, there are tremendous transistor designs that will do the job really well. As for this thing...there's a tube, and it's in the signal path, but it's running outside of most all tube design envelopes (especially with the underrun heaters) and not really imparting anything of value.
they run it cold for clean amplification, the old single units distort if you run a HOT signal into but the new ones have a safety system that auto mutes the signal once it's too loud. The old ones make solid guitar boost pedals but the new ones are good as mic preamps. it's more of a tube theater, but if it sounds good, why does it matter?
Hybrid car radios of the early '60's used 12v plate voltage for all tubes in the radio. They were called "space charge" tubes and were optimized for this use, but most tubes will work in this configuration. A doorknob germanium transistor provided the output stage, as the tubes could not provide sufficient power output at that low plate voltage. These radios worked very well and eliminated the vibrator high voltage supply. They were only used for a few years until cheap, reliable transistors suitable for radio frequency were developed. There is nothing fake about your amplifier. Whether it provides "the tube sound" is a matter of opinion, but the tube is, as you found, in the signal path and working.
Considering that the tube is likely to last practically forever at that usage level I found it amusing that they apparently included a spare tube ... ! 😂 Now that is taking the Marketing BS to a whole other level ...
I think the takeaway from this should be know what you're buying and don't fall for the marketing hype on so-called "Tube Preamps" in the low budget range. This is what's called a "starved tube" design. The plates are running on low voltage, the filaments are also under-volted, so they barely glow at all, hence the need for LEDs to make the orange glow from the front panel. Is it a "fraud"? Technically, no. The tube is amplifying signal; however, there isn't enough of an amplification going on for the tube to reach saturation and compress the signal in the way one would expect from a true all-tube preamp for recording use. My advice is don't waste your money unless you just need something to amplify a signal for a basic project studio. If you want actual tube warmth, save your money and buy a high voltage all-tube preamp that is worthy of professional use.
Thanks for the explanation - I thought that was the case. Technically it does what it says on the tin, but falls short of what an average punter would expect that to deliver them.
@ Yes. That about sums it up.
Do you get any changes in audio quality or composition?
I thought it was there as like a technicality or whatever. Like it does nothing except let a signal pass through it, so when you remove the tube then you lose signal, just to make people think that the tube has all the power. I don't repair amps so I wouldn't have had it opened up and ON to be able to see those fake out LEDs glowing like you were able to (those sneaky bastards). I'd probably go "oh the tube glows but maybe it's not good enough. Let me go out and buy a new one." And just waste more time. Thanks for this one!
@@TheGuitologist I have that same preamp. Had it for years, barely used it. It has this "V3" rotary switch on the front that supposedly affects tube saturation / tone. I was wondering if that switch perhaps controls plate voltages. Maybe that's how they saturate the tube, whatever that means, by changing certain voltages. That power supply seems beefy enough to handle more than just a bunch of silicon. Just a thought. If you still have that thing and care enough about this, it might be worth a quick check.
There is no fraud to this. This unit was not designed to make amplification through the tube, but rather the tube only "colors" the signal with variable amounts of distortion and harmonics. The plaintiff in this matter is missing the point (and usefulness) of this design. This unit offers you both a clean sound, which in my opinion is pretty damn good. Add the fact that they actually have a variable impedance knob which can adjust the character of your mic, and this unit becomes a gem. I have 2 of these units and will buy another when the need arises for more inputs. These units are fantastic for giving various instruments a "place" in the mix, and with even the lowliest of microphones you can make them sound like much more expensive flavors with the impedance adjustments. Even for the full price, these units are a steal for what they accomplish.
To add a bit more insight on this, since the unit's output volume is not directly related to the tube itself, and since the tube on lower voltage is more prone to signal breakup (harmonic distortion) at lower gain... maybe the owner should consider trying other tubes besides the 12ax7... for example, the 12ay7 has a lower gain and quicker breakup than the 12ax7 and imparts even more warmth. This is evident in the fact that many tube mic designers have made use of the 12ay7 in their tube mics. Why not even try a 12at7? 12at7 will still give a little cleaner emphasis on the upper frequencies. In the 2 units I have one has a 12ay7 RCA and one has a 12at7 JAN and I use them for different purposes. Good Luck!
I can see an irony here ... Maybe they felt that they had to artificially light up the tube to prevent lots of returns because customers couldn't see the tube glow and thought it was faulty ...
I could totally see this being the reason for the LEDs. I've had some gear where it was really difficult to see the filament glow and I was wondering. And the other reason could be just to make it look nice.
yeah that's exactly what I was thinking.
@Dearly Diane ... this ART product is specifically designed with a vent to show you the tube glow ...
@Dearly Diane Yes. It has a very minor decorative purpose ...
Tubes like the 12AX7 don't normally light up brightly, especially when the voltage is low. The heaters on these tubes are dual voltage, with three connection pins. one pin is on one end of the A section heater, one is on one end of the B section heater, and the third goes to the remaining ends of both heaters as a common connection, so the tube can be wired with the heaters in series to run on 12 volts, or in parallel to run on 6 volts, same thing with the related 12AU7 and 12AT7 tubes. Also, these tubes are not intended to run one unit on one channel and one on the other, as there is considerable cross talk between the sections, it is intended to be used as consecutive stages of a single channel only.
At least it’s got wall power for the tube unlike a tube pedal running on a dollar general 9 volt.
In pre amps and restaurants it’s all about hot plates
It’s just legit enough not to get sued lol shady AF.
Yea man.... those amber lights behind the tube make me question ALL of this.
There are many starved plate designs that essentially warm up an otherwise cold solid state tone. Check out the popularity of Matsumins Valvecaster for example. It is best used to give a warmer clean tone into a solid state amp, not as a distortion unit. Or the many examples of rack gear that contained a single tube, to 'warm' up the tone. Just a bit of info as to the general use of these kind of circuits.
@@jrg770 the only WARMING it does comes from the secondary led's........its bullshit,it does next to nothing,its pointless and silly but hooks in the "novice gearheads"who hear "tube" and loose their proverbial shit
@@trillrifaxegrindor4411 You can run a audio signal through a preamp tube, take your pick of what kind, and get a amplified signal. This will add "body" to the sound. And yes, even when running a tube as low as 9v. That would sound pretty ctrappy with a 12AX7 though. The only real function of this kind of unit is to "warm up, fatten, thicken, add body" take your pick of descriptors, the audio signal. And yes, it does in fact do that, as I have built plenty of low voltage 12v/12Au7 preamp boxes. You run your guitar through that box, into the front of a solid state or even a tube amp and you have a boosted and fatter signal going into the amp. That is the purpose of this unit, and it does in fact do that.
Not at all. It is clearly a stage in the amplification, so it's perfectly legit. People with little or no electronic education and experience are in no way qualified to comment on this.
I sometimes use the small ART microphone tube preamp with a loop switch circuit for a boost. It makes a fantastic clean boost into a guitar amp.
12AX7 has about a 2 watt filament (6.3V @ 300 mA / 12.6 V @ 150 mA), so most of them do not produce much of a light show.
I've got one of these. I've used it a lot. Which preamp circuit is in use depends on what you have selected in the front panel. It has a selector switch that lets you choose between different kinds of preamp circuits... I design my own preamps now. You can run some tubes on a lower voltage and some are okay but some distort too much and lowering the filament voltage can cure that but it's not going to be super clean. I'd rather just use an INA217 or INA849 based preamp for most instruments and a version of INA preamp with a soft limiter for drums...
This has been done for years. I had a berhinger mic pre with a tube that had LEDS behind it.
Shiite! Is that why my beringher sounded awful?!?
@@soundknight all behrcrap sounds awful. when the company started out in the early 90's there stuff was pretty good, but they got greedy very quickly and their stuff turned into low-quality crap that sort-of works...
I had one too man . I think this is a widespread gimmick.
At least they're not using blue LEDs this time.
Thanks for that. Ive been using the lil ART tube pre single channel boxes for a condenser Mic..warms it up a little. Works really well in mixer XL loop to saturate the mic sound a hair before recording. Not crazy but enough to hear a pleasant difference. Dig the channel btw.
I think all that happens with the 12ax7 in the signal path is that it adds second order harmoics.giveing a warmer sound.
It would be cool to see a follow-up video modifying this preamp with a high voltage circuit.
@Dearly Diane No, you can use a DC to DC booster.
If you ran that tube at 180 volts like usual it would destroy all the solid state components attached to it. You would make a nice smoke generator and if you're lucky it would also burst into flames. You can't just randomly mix and match components. I'm sure the original design engineer actually worked out the numbers so it would not blow up.
nope,not gonna happen without a major redesign,reconfig,rewire or fire it in the trash and enjoy the sound it makes....
I'm not gonna lie at that point just buy another preamp 🤣🤣🤣
@@BustedJunkStudio seen 1 guy up the volts on a pro vla 2. Including a extra protection layer of added components.
Good conclusion Brad,,, Nice that you got to give him a professional unbiased evaluation of his circuit. Nice job bud.
Thanks Carl. Good to see you, sir, as always.
Wonder if anyone done similar tests with the Joyo bantamp "collection" growing popular lately.
I've seen a schematic for some of the Joyo BantAmp ZoMBie circuitry, traced by some guy at the DIYstompboxes forum. The tube B+ is 50V by a DC-DC-converter from the 18V power brick. The signal passes through both tube stages.
But you tested this with the V3 dial at flat (6 o'clock) on both channels. The tube gets more voltage to saturate and becomes 'warm' when that's turned up. It was at minimum gain when you had a meter on it, so it barely kicked in. 😮
Most of the modern pedals/effects have 'Backlight Leds' to make the tube stand out, but in the ones I've worked on, the tube is actually functioning.
Also, tubes can function in very low plate voltages, just in a different part of the load curve. If the signal gain is small enough, it doesn't matter that it it's running in a non linear portion of the curve.
Don't know about this item, tho.
I love any video where the person doing the video is willing to say that they were wrong about their original thoughts.
Thanks!
I have seen some high dollar “hi-fi” amps that have LEDS under the tubes! The tubes do function the LEDS are just for decoration. I am perfectly happy with the filament glow-and that tells you the filaments do indeed work. The LEDS may mask the fact.
Nice that you kept an objective standpoint throughout. I personally detest these designs where they feed the tube just enough plate and filament to get it to pass signal. I understand why they’re doing it though, that way the tube runs a lot cooler so no issues with thermal management. But the LEDs are just silly, though that’s fairly common, tubes don’t glow enough for marketing purposes. If somebody still made mercury rectifiers I would design some mojo preamp around one, that would give the punters a lot of mojo glow for their money!
Voltage regulator tubes, e.g. OC3 make a nice glow.
The other reason they're doing it is that it turns the thing into an effects box. A well-designed tube stage wouldn't have enough distortion at the signal levels involved to satisfy customers.
This is a trick from late 50's early 60's where running the heater at a lower DC voltage creates more gain with less noise. This can be seen in early Mcintosh tube amplifiers. I believe Audio Research also did this (or may still).
Maybe the colder filament is providing already the litttle current needed with such a low plate voltage. So, maybe the low filament voltage is a just a deliberate choice? Possibly to reduce heating of the entire device.
Thanks for sharing Brad!
no
It's a recording preamp not a Fender Twin. Lower voltage results in lower noise...but still adds color.
I have a old ART Tube Pac that has 2 12AX7's. It gets really hot, so I set it on its own rack thing(not rack mount). It works well IMO and warms up the sound for digital recording. I can hear a difference. Great video Brad. I had read about this a lot back when I bought this unit I have, but it was worth the money to me.
Easiest way is plug it all up and pull the tube and see if it still works!!! thx brad have a great day!!!!!
It would be interesting to consult the tube curves to see, from an engineering perspective, how this tube would perform at those bias voltages. Also consider if this would enhance the "tube sound" and positively impact reliability.
I have a Vox Tonelab ST that uses a 12AX7 in exactly the same way i.e. glowing LED's rather than glowing filaments. There's a video somewhere on TH-cam where a guy removes the valve and still gets a guitar signal through the unit, but as I recall the preset he used didn't require the valve in situ. I also have a couple of the smaller ART preamps and found them to be very flexible and great value for money too.
I have an ART Voice Channel and a Pro MPA II. Both are really nice products for the money. A lot of bang for the buck. Especially after I retubed them with good 12AX7s.
guess you missed the part were the tube does nothing,retubing anything like this were the tube is redundant and pointless
just fluffed up your confirmation bias and automatically you "thought" it sounded better ps: it didnt,truly...it didnt,but you sure thought it did
@@trillrifaxegrindor4411 ... I guess you missed the part where I don't have a unit with a starved plate tube configuration. Both of my ART products actually properly utilize the tubes, and yes... there is a difference. If there wasn't... tube companies would go out of business. Also... I tried 12AU7 and 12AT7 tubes to see what differences I could get on a vocal mic, and again... there is a difference.
@@trillrifaxegrindor4411 I guess you missed the part where there was no signal without the tube (?)
i used one of the art tube mic preamp models when my mic needed a bit of a boost , it sounded amazing , im not sure how much of that was down to the tube, but it sounded warm and full , i think the tube part is a gimmick , but it worked for what i needed it to do
A couple things came to mind- I had a Behringer guitar amp with a 12AX7 in the front end. They also did the show business with an LED. The tube was definitely active, and the amp sounded good. I wonder how the ART design might be similar to the "Cool Tube" preamp in high end Takamine acoustic guitars. They run on low voltage as well.
06:24 I was playing my '73 Twin Reverb and listening to the video. Thought that sound was from my amp, I got so scared
I'm gonna start putting random sirens and screeching noises in my videos to mess with people. :D
@@TheGuitologist That would be a great way to keep us all on our toes
If you are using a transistorised circuit to give you the gain then you will have less noise, that leaves the tube free to just add tube flavour to the sound. Because you don't need or want high gain from the tube it can be run at lower heater and much lower anode voltages which will significantly increase the tube's life and simplify the circuit design.
This is not news. Some manufacturers just connected up the filaments to make them glow but didn't route any signal through the tube.
That seems to be the rumor going around. If anyone has specific examples of accusations against a specific make and model, let me know, maybe I'll test it out.
Hopefully this can help out a stop to stuff like this. If you’re buying Behringer tube stuff you might be asking for this but this shouldn’t be common practice
ART is all about the starved plate design for some reason. I've read the designer talking about his preference for how they distort. You could say price is the motivator, but they do make budget models with switchable voltage, e.g. the MPA preamps (which run plate at 150V when switched to "high", if I remember correctly), which are still very cheap for a tube pre at a decent voltage.
I have a cheap ART tube direct box I bought years ago - TUBE MP Preamp. I always thought it was cold to the tube since it was low voltage and did not make a real big difference in sound. The only advantage is is had both XLR and 1/4" So you could use it for phantom power for condenser mic's if your mixer did not have them but not sure if it would help with a vocal breakup. It was fairly cheap so I did not have high expectations but tried it with solid state amp effects loops back in the day to help tone. I couldn't tell any difference. Thanks, for the review. Interesting tidbit I had totally forgot about.
I like these types of videos Brad. Help to keep ‘em honest.
The LED's to light up the tube is classic Marketing requirement ... A bit like sticking a massive 8 outlet exhaust on a small car together with 'go faster stripes' and a limited edition rally badge, without modifying the engine at all. Mind you, even the changed exhaust will affect the sound (not performance) more than this tube affects the amp sound ...
I spy a Pepers Pedals sticker on your desk, great stuff.
It’s nice to have you back with regular videos
Years ago, before the internet, I bought a preamp kit ( it was called Stack in a Box) out of the back of a magazine that has a 12ax7. The power supply is a wall wort, maybe 12V, I don't remember but it pretty much does same thing, uses low voltage through the tube. I still have it Brad, If you want it to dissect I can send it to you.
As "LoV" (Low Voltage) project over the net : usage of 12AX7 under powered, with non-lethal voltages. It's not "typical" usage, but it work. A different approach is a little project I've seen, is 4*1.5v battery with 230/12v transfo and a square signal generator (on a 6V filament tube), the TR+square makes a high voltage to the tube. Not typical, but for fun is working ^^
Ha, I just made a fake tube amp for my GGBO guitar as an art project. I used a flicker bulb behind the tubes, similar to what they did here with the LED lights.
Curiouser and curiouser - I own a S.M.S.L. SP100 headphone amplifier and I use a Raytheon 5670 "electronic valve" (5670 2C51 396A Raytheon Windmill Getter) a tube in laymen's terms instead of 6N3 supplied, both plates appear to warm up, tube does get hot - sounds amazing and is powerful enough to drive the high ohm headphones I own. Shame the ART Pro Audio "TUBE" mic preamp does not utilize all the tubes potential.
My father told me the battery powered tube radios of his childhood had low filament and plate voltages. Usually like 1.5 to 3v for the filament and 45 to 90v for the plate. Those low voltages in the preamp aren't surprising. A modern tube filament isn't going to put on much of a show at low voltage, hence the hokey LED backlights.
I have one of those radios. It's made to run on ac or battery. It had a big 45VDC "B" battery that I took out because it was leaking. Still works on ac though. BTW the B battery is where B+ comes from on schematics.
I first learned of this practice, years ago, from buying the Presonus TubePre. Great info Brad! 👍
I’d also love to see you pull apart some of these “tube” pedals that aren’t necessarily in the low budget range, particularly those incorporating sub-miniatures (that aren’t Seymour Duncan).
The only tube pedal i've ever heard that i actually thought sounded really good was the old Mesa V-twin, which they don't make anymore. definitely the best pedal mesa ever made. their newer distortion pedals don't hold a candle to the V-twin. The tone burst is a really nice boost pedal though. one of my buddies was all line 6'd out and had a multi fx from them back in the day that had a 12ax7 in it. pedal sounded horrible. I hated that thing. of course he was running a spider valve line 6 half stack that also sounded abysmal. that was the 'bogner' labeled line 6 tube amp. thing was a toilet. my old Blue Voodoo smoked it, and that ain't saying much. Vox used to make a flagship multi fx pedal with a 12ax7 in it that i'd love to get my hands on and hear. i could see them doing a pedal right.
Hey it said it had a tube, apparently they didn’t say it was actually connected.
I've got a dbx 386 dual channel mic preamp in my recording rack. Marketed as a "vacuum tube mic preamp" with one 12AU7 per channel, B+ is 200V. I've seen a tracing of the circuit; the tube is a parallel gain stage with three op-amp stages before and five op-amp stages after. And yep, there are orange LEDs in the tube socket center holes.
The SPDIF and AES/EBU digital outputs are nice, though. Two extra channels into the audio interface, very useful when tracking a fully-miked drum kit :)
At least there's a bit of juice on tap there to get more out of the tubes.
Most of these "real tube" devices are actually only running the 12AX7 at about 20 volts! The tube is basically just used to filter and smooth out the signal somewhat... but the actual distortion is produced with clipped diodes, etc.
I'm no electrician, but i've never noticed 12ax7's glowing before in any usage. i certainly believe you that the plate voltage is low on this unit, but wouldn't they need the led's anyway to make it look like the tube was glowing? none of my Tube guitar amps have pre amp tubes that glow significantly, no matter how long or hard i run the amps.
hey brad, i just subcribed to your channel and believe it or not ,your the first youtuber and most likely the only one i bother putting on the computor to watch,..first i want to say that i respect you standing up for your self and your family spite everything else, i would do the same no matter what i stand to lose....besides all that. I just found a fender passport PA system (no speakers) and no power cord but i robbed a cord from my copier machine and Im not sure which way to go with this..i wouldnt mind shipping it to you,but fear it my cost the same to buy it used..i live in NH,..i guess im stuck in a rock and a hard spot with this but again i didnt pay a penny for it so. thats where im at...the things weights about 20 lbs..
This seems to be a tube setup in "starving mode" which is quite common.
Brad... you should reach out to ART and see if they'll supply you with a donor Pro MPA II or one of their channel strips. Would be cool to see you evaluate them. I actually love mine. Best bangs for the buck in my little home studio. Bass sounds great coming through it on the High Z. Got even better with decent tubes too. Their Voice Channel in combination with my budget friendly tube mic (Lauten Audio LA320) sounds great! I just hate to see ART get a bad name for this. Buyers need to be aware that there's a lower limit to buying things, and companies try to provide consumers with low dollar options.
I agree on the need to supply the low end of the market with gear. I would have preferred they just make the best solid state unit they could possibly make and skip the tube pretense.
@@TheGuitologist ... I agree. Informative as always, brother.
Fascinating! I wonder if you would find something similar with the Vox Valvetronix!? I have always been suspicious that the tube (which they sort of admit might have limited use in the amp's design, and describe it's function as "POWER AMP BUFFER". Brilliant marketing scheme, as most ppl mistakenly believe it's a "tube" amp. Any experience with the valvetronix, Brad?
I have seen LEDs doing this in other equipment, yes. Can't recall having a that model open, but it wouldn't surprise me if it was something very similar and the tube was doing very little to the signal.
Blimey, this is still a thing? Behringer had the same thing going on nearly 15 years ago with their Composer Compressor. It was just a bunch of LEDs in the back. The tube sort of was hooked up, it was just a starved plate design and account for not much more than a LPF. Korg even had the same bs going on with some of their stompboxes back in the day. Will watch the rest of the vid though, I had no idea this sort of bumph was still going on.
Korg puts LEDs under their Nutube products too.
I've actually seen a number of different units by different companies that put LEDs behind the tube. I have a Presonus tube mic preamp that has a red one behind the 12AX7- the first time I turned it on the color freaked me out!! 🤣🤣 I popped it open to see why the tube was bright red, only to see the LED. The tube itself had a nice gentle orange glow that was only visible at the end of the tube, where you see the heaters come out the end of the mica.
I've had this unit for years, you've answered so many things I have always wondered
This preamp also has a FET circuit. And depending on where you set your V3 knob, it may engage the tube differently. Curious to know where he had that set for this test.
Interesting design, glad to see art wasn't straight up faking it, since they've produced quite a few decent units for entry level prices. For studio and guitarists.
I’d like to know if the Presonus Tube Pre is the same way. It has a little red LED that glows behind it also. I was always suspicious that it even did anything
Chances are it is the same kind of thing. Unless you pay quite more money for a tube preamp, you can assume it is a lowish voltage design
Yep. I have a couple of those from years ago and they are crap. Only good for boosting volume.
So it is a hybrid starved plate preamp. Right?
my comment as well. I've been studying "starved plate" tube designs used in stompboxes. I barely know what that means, but this looks like it.
I got one of those little ART tube preamps about 10-12 years ago. I've liked it. Which it's old now and is starting to get a little noisy. But you can feel the heat coming off the tube when you use it. And I mainly use it for vocals. So it's not like I need a ton of overdrive or anything. But if you crank up the preamp it does have plenty of saturation and compression, which could be from something else, I don't know. But you said you had one before, so I'm sure you know all of this. But yeah, I was thinking of buying another one. But what you showed us here makes me wonder if they've started skimping on the small ones since I bought mine.
I also have it. Most likely it does nothing but add some noise. A mod in my forum brought that up when I proudly told everyone that I add some warmth to my vocal recordings, haha. If your's got noisy maybe you should swap the tube against a fresher one. Or you could have a leaking capacitor or so. It's funny that these things even won awards in recording magazines! I had one from an australian brand before and the saturation was always present even when not dialed in much. It was always visible in the waveform.
You get what you pay for. This is a entry level unit. I have a simple cheap art mic pre. It has one 12ax7. It definitely glows and most likely is designed to not get very hot. Which makes since for what it is. It will add sonic quality and warmth without burning out too soon and also have a nice signal to noise ratio/quiet operation. Sounds good and definitely enhances the sound of any mic or instrument signal. They add the lights behind the tube because it looks cool and they don't need to try and explain the pros and cons of a starved tube design to people that won't understand lol. Use your ears and not your eyes and you can tell that it actually does exactly what it is designed to do. It's not going to glow like a guitar tube amp. If you want multiple hot tubes that glow bright and have the ability to saturate big time get your wallet out and your going to pay out big time. Same deal with tube guitar amps.
I was working in a studio that records almost everything with ART Tube MP and it sounds good. I bought TPS II because I had a chance to try V3, and I think those presets are useful, especially I got sweet compressions conveniently for my bass. It doesn't mean I don't care about their design under the cover, but as long as it's not a fraud and I'm happy with the results, then they deserve my money. Maybe the design is to prolong tube life?
I checked this videos because the tube gone bad, so I watched tube replacement guides and related videos. I upgraded to Sovtek long plate, get my jobs done with overkilled quality for my clients, so no regret, although the price is getting higher during the war in Russia.
No problem at all to run the plates at 25v, it just limits swing and available headroom. In theory, the tube will compress a signal and perform like any other running at far higher voltages but with very small input and output in this case. The LEDs? Cosmetics.
I did hear a difference between a 12au7 and the stock 12ax7, enough for me to leave it there, it did not turn into an entrance to an enchanted harmonics land but to my ears it did the trick, it was a behringer tube mic 200, might be gimmicky but beats the input of my budget interface in my budget life
The 12AU7 seems to work and sound better on lower voltages than 12AX7.
I have the little 1 channel ART mic preamp with a tube in it...........Got it for 25$ from craigslist. It was a quiet mic preamp that worked OK, so I never dug deeper than putting a good tube in it. I've done some stomp boxes with tubes in them, and those run with a 12v AC power supply, then ramped up to about 100v...... I've also done a distortion that drives the grid with a Darlington transistor to get it to crunch up... that works ok also.
I have worked on the small preamp, filament voltage was 5.7V and the plate has 48V phantom power.
I modified the filament supply, added an extra diode in the ground reference path of the 7805, now it's almost dead on 6.3V.
Hey Brad, could you get a hold of a presonus studio channel and do the same test. I'm really curious.
If someone wants to send one, sure, I'll do it.
Dude I get so much information from you man you were the best channel on here about tone man I'm telling you
On the little ART preamp you can pull the tube and it still works. I have never seen the big one.
If true, that's a big red flag right there.
Aww man i have a couple of those i use on my Hammonds...they seem to work correctly...icalso have several Behringer units with tubes, and i replaced allcthe Chinese made bottles w vintage Baldwins, probably for nothing
I got one of those, actually good sounding preamp for condenser mike, phantom power included, used it for guitar too... gee well, what do you know, gonna open that thing up i guess.
Yeah they actually worked pretty good. I used one of the old ones from late 80s on my Hammond XB-2 for an extra gain stage. You could pull out the AX-7 and the gain staging still worked. Supposedly the tube was to 'warm' things up. But I don't know. Hard to tell everything was so friggin loud back then.
@@edwhite7475 not probably,absolutely for nothing
I've been avoiding tube devices because I don't need to waste my time chasing light bulbs, but with the voltage so low, do the tubes last pretty much indefinitely, or do they still burn out, or what service schedule should one expect ?
could a person place a jumper wire or such to make these units work without the tube ? I saw a unit with a solid state by-pass, maybe the switch is a jumper.
I think I may have helped a friend change a bulb in an Art doodle one time, it seemed a waste of recording time. I think I remember LEDs behind the tube.
You probably never heard about Matsumin Valvecaster preamps... google about it, this will explain you a lot of things about low voltage tube circuits...
Makes me wonder about the orange micro terror, is that a starved plate design as well?
Yes, according to someone at Freestompboxes who traced the circuit. 12V B+.
Personally, I doubt I'll be touching another Orange/Vox/Korg/Blackstar product. Korg is very bad about pulling the marketing wool over the eyes of consumers and they won't come off schematics or stand behind their products in long-term meaningful ways. Plus, build quality is questionable. It's stuff destined for landfill.
The question I have is what is the classic design for the old studio mic preamps? That's what I'd expect this to be judged against, not a guitar preamp. Given the hours studio rack mount equipment would accumulate, I can see the desirability to run the tube cold. And way back when, they wanted a good preamp, not necessarily one that had tube distortion. If you wanted your solid state guitar amp to sound like a tube amp, this isn't the device a player would reach for.
It would have been interesting to see scope waveforms on the tube output with different drive levels, see what the tube is actually doing to the signal
Yep, some oscilloscope and some spectrum action as well.
I use an ART Pro Channel 2. It runs a 12AX7 stage at both low and high voltage, switch selectable. I used a FFT scope to see what it did. The low voltage setting (starved plate) had a lot more harmonics than the high voltage setting. So the person who said that the starved plate design could be called an effect circuit has merit. I use it in my bass amplifier setup. When I want a dirty tube sound I run it low voltage and overdrive it all I can. No, it doesn't sound like a tube Ampeg but I like the sound. When I want a clean sound I use high voltage and keep the gain indicator in the green or slight yellow area.
Appears to me that the cabinet is designed with minimal ventilation (only slots for cooling are on the front panel). Maybe the circuit is designed to run the tube as cool as possible due to this .
I owned one of these units and it was great. I wish I still had it. I would like it if ART made some high voltage tube preamps as well. I can't imagine it would cost much more to make them. Whatever the case, I think ART makes unbeatable gear for the price IMO.
Yeah, it will be much more expensive, you'll need two input and two output balanced audio transformers. Decent ones are at least 60$ a pop, wholesale. That will be 300 retail only for the transformers.put everything else in there and it will easily reach at least 800$.
ART MPA II
There is a term for tube based devices like this - "starved plate." Most budget tube items from ART and Behringer are starved plate tubes. Depending on the application, and the actual voltage applied, this can be A. preferred and beneficial to the intended use case, B. inconsequential to the intended usage, falling to preference, or C. snake oil and bullshit. The V3 range of products from ART is notoriously bad, to begin with, in all fairness, of which the TPS II is a member, and they fall squarely in "category C - Snake Oil and Bullshit." I own a lot of ART preamps and power units, from old Tube MP Studio and Tube MP/C preamps to the SLA-1 power amp, and more than a few big producers/recording engineers swear by their higher end rack preamp and compressor units, both solid state and tube. The starved plate tube preamps are mostly good for use with condenser mics, low output dynamics like the SM7b, or as DI boxes when you plan to use VST amp sims or reamp with a modeler later. They can also liven up the sterile, stale sound of sub-par, low-end amp modeling from cheap Multi-FX units, making them sound more on level of a Helix, for example, if you set it so higher gain pushes them into a bit of drive, but clean gives you more of an "edge of breakup" kind of tone, and will also improve the distortion character/quality of higher end modelers like AxeFX. If you're not doing something like that, then buying one of these is a complete waste of money. Their viable usage being preferable to a PURE solid state preamp or a true tube preamp, with actual benefit, is decidedly niche.
Standard for most cheap tube preamps. By running the tube in a rather non-linear region it would certainly be a bit of an "effects box", which a lot of people buying a cheap tube preamp are looking for. I'd be interested to see the distortion on something like this- I expect it's very high. Furthermore, such low plate voltages will make it a lot easier to drive that stage into distortion. Again, this is an effects box. Someone wanting a clean mic preamp would just use an SSM2019 in a box.
A traditional 2-channel tube preamp is going to require upwards of $150 in input transformers alone.
Well done. I played with the Presonus Studio Channel, also a staved design. Yes the tube modifies the sound, it adds a lot of harmonics controlled with the "Tube Drive" control, but it doesn't sound like a high voltage preamp. An interesting experiment is to use the ART Pro Channel 2 and there is a front panel switch to change the voltage high or low on one of the tubes. It does change the sound .
Did you try changing the V3 dial ? Apparently this regulates the voltage to the tube. When set to neutral the tube is starved.
i know this is an old video.. i just happen to have this mic pre in my rack and ran across this and recall this video.. remember, this is a mic pre.. not a 1st gain stage for a guitar amp.. it's not designed to push to crazy distortion.. it's made to warm up a voice or smooth out an instrument.. not the same as your typical 12ax7 in your fender deluxe.. used at low voltage like this.. it should last forever.. and will do enough shaping to work for budget needs.. no need to red-plate it to death for vocals.. the led trick to illuminate a tube has been used in amps of all kinds and is nothing new.. strictly for visual effect.. you wanna see the tube glow, but no need to run the filament hot.. add a LED and problem fixed.. if they pushed the filament to glow then they would need ventilation/fans then you have a tube roasting in a rack.. none of which is needed to smooth vocals in the sub $300 range... that's
Okay, the LED trick is excusable, because so many people would complain if the glow was not visible through the outside of the unit (like the whole tube glow-hype thing) but the sub 50 volt on the plates is completely ridiculous. Also I know of two other companies who do the LED trick just so it looks cooler
You can make tubes distort quicker at lower voltages. This may be why they are designed this way.
Last time I was this early, mom went to the hospital a week before her due date..
In most products like this including headphone amplifiers, the tube is used as a unity gain cathode follower buffer stage. Supposedly this allows you to get the harmonic structure of the tube. With no amplification from the tube, I doubt it.
I remember a Takamine guitar serie with a freakin' 12AX7 in the ONBOARD PREAMP for god's sake...
Yeah, that was marketed as a "CoolTube" tech. Wonder if the name speaks for itself;)
I have this product and I think it is great for the price tube or not
Actually with all these low priced "tube" preamps I was in the assumption (and that this is even told be the manufacturer) the tubes are not part of the amplification but just used to add some harmonic distortion to the already amplified signal. You can blend in the amount of the tube's soft distortion but you never will increase the amplification by the tube circuit. For real tube amps you'd have to pay way more just for one channel and there aren't that many on the market. Even SLP's well recognized preamps (450-900 €) the tubes are not main part of amplifications. So I wonder if ART really stated this is a tube amplified preamp or as I remember (since I had that piece, maybe the previous model but looked the same) they somehow mentioned the tubes is only "creaming" the sound of the signal? :) Now continuing to watch the video :)
The intro got the sub for me, great work
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I have seen plenty of rack mount preamps with tubes in them that use the LEDs for aesthetic‘s as well as models that were not designed or equipped with tubes that also used LEDs to simulate the glow of a tube. No mystery here.
LEDs are for effect. My guess is that the tube is tubing just fine but it’s not enough power to push the filaments. The lights are so the consumer looks at his amp and says, “Yup, she’s a glowin.....she must be a tubin’
My jaw dropped as soon as I saw the orange LEDs - shady for sure.
I feel like there's just not any point to this product; If you want a tube preamp, get a good tube preamp - if you don't, there are tremendous transistor designs that will do the job really well. As for this thing...there's a tube, and it's in the signal path, but it's running outside of most all tube design envelopes (especially with the underrun heaters) and not really imparting anything of value.
Some Yamaha amps do have 10 volts DC on the filament. They don't glow so visibly. But plate voltages are more than 140 volts
they run it cold for clean amplification, the old single units distort if you run a HOT signal into but the new ones have a safety system that auto mutes the signal once it's too loud. The old ones make solid guitar boost pedals but the new ones are good as mic preamps. it's more of a tube theater, but if it sounds good, why does it matter?
Hybrid car radios of the early '60's used 12v plate voltage for all tubes in the radio. They were called "space charge" tubes and were optimized for this use, but most tubes will work in this configuration. A doorknob germanium transistor provided the output stage, as the tubes could not provide sufficient power output at that low plate voltage. These radios worked very well and eliminated the vibrator high voltage supply. They were only used for a few years until cheap, reliable transistors suitable for radio frequency were developed. There is nothing fake about your amplifier. Whether it provides "the tube sound" is a matter of opinion, but the tube is, as you found, in the signal path and working.
Considering that the tube is likely to last practically forever at that usage level I found it amusing that they apparently included a spare tube ... ! 😂
Now that is taking the Marketing BS to a whole other level ...
I know, right. I'm sure that was put in there by the owner...surely.