Huge thumbs up for this video! It's possibly the best review and explanation of the limitations/design problems I've seen yet. I loved seeing the schematic and explanation of the changes you made.
This is exactly the type of video I needed. I own this box for a while now, and always wondered why it is basically unusable as a load box. I think I will fix it this week.
I know it's an old subject by now but nevertheless, I'd like to mention that my PA-100 came with the mail today (living in Germany) and it's perfectly allright, they soldered a solid ground wire to all output connectors and added proper washers, particularly to the 16ohm connector, which looks quite heavy duty now, nothing like in your video. The line volume decreasing simultaneously with the speaker volume is still an issue however, I changed that according to your advice. There was even plenty of wire protruding from the resistor so I could simply bend it away from the pot. The attenuator works perfectly now, with a strong and clear signal into my interface from the line out. Thanks for the enlightenment, man!!!
@@netman69 You're welcome! What I actually wanted to express was that going public with this issue was probably not in vain, they seem to have adressed the problem. Again, my appreciation for your great work.
@@captainfineweather5610 it does seem they've fixed it, but I do wonder why, I've sent them an elaborate email about the subject and have not gotten a reply.
@@netman69 That seems to be quite common in our times, not just with companies. The majority of people has completely missed the bus... But don't you worry, as long as there are conversations like this one, I mean the entire comment section, there's hope for the rest of us!
@@captainfineweather5610 Well the best way to change a thing is to set a better example, thankfully there are plenty, us included :). I've actually rarely had companies not get back to me when I come to them with serious concerns like this, but who knows maybe HB just missed the email somehow.
Thank you for the most informative review I’ve seen to date on passive power soak. I’ve recently purchased a 30 watt tube amp (Laney IRT30) and was looking for something I could install on a combo amp with a bypass switch. I believe it’s watt control dial is a bit misleading as it is prior to power tubes. I recently saw two other reviews re Bugera PS1 and Harley Benton where line out didn’t work. Wish they had one with a bypass sw so no need to mess with cables. Your comments, details and knowledge earns my respect of your assessment. Thanks again!
They actually do make some amps with a builtin attenuator, often they call it a power soak in the marketing material with that context for whatever reason. Mesa boogie is one brand that has quite a few options in this.
Hello, I just received mine. Didn't even plug it in yet. Just in case people are wondering, mine came with the ground connected to both lugs of the 16ohm jack. Looks like they heard you and fixed it. If you get a new one, it's probably a good idea to check anyway in case mine was just a good batch.
Hey man Thanks so much for this video. You are a huge help. Think I might take this project on myself. My Marshall jcm 900 100w hasn't been blasted up properly in years. Thanks dude
Mine turned up with what appeared to be the wrong nut on the 8ohm input so it wouldn't tighten. That in turn caused the connection to the ground bar between the three input options to break off. Had to salvage a working, correct size nut from my parts bin, get it tight and resolder the connection. For my purposes fine now. May end up replacing the socket as you did, or at least putting some locktite on it if usage loosens it up.
Ik heb mijn pa-100 net even gecheckt na deze video te zien, ik krijg op alle ingangen vrij correcte weerstanden, ongeacht op welke positie de potentiometer staat. Afwijking van max 0,5 ohm op de drie aansluitingen. Ook was de 16 ohm ingang correct geaard 👍🏻. Op basis van wat werkt de ventilator precies? Ik heb die van mij nog niet zien draaien, maar dat is misschien omdat mijn Marshall maar 1 watt geeft en dus niet genoeg warmte produceert? Nog steeds te luid voor een slaapkameramp in een appartement, vandaar de attenuator :) In elk geval merci voor de uitgebreide video, zeer leerrijk om te zien! Grts uit Tongeren
De ventilator werkt op de stroom die binnenkomt via een gelijkrichter, 1 watt is inderdaad niet genoeg daarvoor (en dan is de ventilator ook hardstikke niet nodig).
I made the same mod as you did for the line out but the 16ohms jack was properly wired... I also always use the 8ohms input as it's the safest one! Nice video👍
Great video! I just received the PA100 and what I don't like is that the volume for the line output is the same as that of the attenuator, that is, the attenuator is at 1 and the line volume potentiometer is at 10... listen with very little volume connecting it to a sound card. I mean, I can't play in my room with the amplifier at maximum power, the attenuator at 0 or 1, because I won't hear anything through the line output!! horror!!
Thank you for the video and review. Does the moving of the resistor affect the XLR MicMod out in any way? How does the fan work if it's passive, phantom power via XLR?
Moving the resistor doesn't affect the MicMod thing no, the volume of that will depend on the speaker output volume still. Changing it would probably need a small modification on the circuit board. I should have addressed that in the video, but somehow entirely overlooked it. The fan is powered by the incoming audio, power that otherwise would go to the speaker - but it needs a small enough amount of power that that doesn't affect the impedance significantly. It only runs when you are playing quite loud but that's also the only time it's really needed.
Good review. Did the same with mine as 16 Ohm was playing up and started to doubt it being safe for my Marshall 100w TSL. love the totsiens at the end. lekker!
Can I use this attenuator on my AC30/6TB? Will there be any damage to the amplifier or speaker if used for a long time? I am looking for a hot plate from THD, but they are not for sale. So I am considering purchasing this attenuator to replace it. Any advice on this attenuator would be appreciated in the comments. I want a safe attenuation of 16 ohms ac30/6tb (1997). What's most important to me is that the amplifier and speakers are safe and that they don't catch fire.
Only if you can make sure the issue I show at around 16:40 with the 16ohm input is not present or fix it. The speaker should be safe either way but the 16ohm input wasn't very safe on my unit so if not checked it could be a danger for the amplifier, others here have apparently received units where that issue did not exist.
Thanks for the informative video! Mine has the same line out construction mistake, but fan and 16Ohm out are fine. I also have a different capacitor in there. Its brown but still rated 105°C Thanks again for the video, i finally know how to fix the line out :) What where they thinking with that? Lol
They weren't thinking about paint I guess xD. You'd think they'd have someone try one of these before they start selling them but I guess not... Now that I'm reminded though I just realized I didn't even do the obvious thing to do and tell them, doing that now :D.
Thanks for the in-depth review, I probably would have bought the PA-100 if I didn't see this. I wonder if the PA-250 is much better? I don't have any soldering experience so I really don't want to have to make such changes to whatever I buy
Hiya! What kind of cables do we need? Has to be both speaker cables or can be any instrument jack cable? Just bought one for my combo. The speaker cable i will use the one it's attached on the speakers already, but the extra one I need to plug between the amp and the attenuator, has to be speaker cable? Thanks!
You should use speaker cables on both sides, most importantly between the amp and the attenuator. I've used instrument cables before and lived, but it is not wise.
Hi I used this for a day on my mesa boogie lonestar special combo 1x12 inch. After putting it on the drive channel the amp just powered off and wont turn back on at all.... I am kinda pissed... It was functioning for some time then when I put abit more gain and the master volume and output volume up. the amp just powered off and died and wont power back on at all.... the red light went out... i tried changing the fuse and also swapped the pre amp v1 tube around several times with existing preamp tubes that are 15 years old ... I recently a month ago put in a new set of sovtek mesa spec el84s x4. and a new mesa retifier.. please help... i get the feeling a diode may have blown or at worst a transformer fried.... There was no burning smell so maybe transfoerms ok ? i will take it to a amp tech soon when i have time
Since it isn't powering on I'd sure suspect the fuse was blown, but the rectifier diodes seem like an unlikely culprit, I'd suspect one of the el84s being blown and taking out the new fuse as soon as it's replaced.
@@netman69 thanks for your feedback, I changed the fuse and it didnt help, also the el84s power valves are brand new. so I believe it cant be them. although I have a pair of new el84s as spare so I will try them
@@ukguitaryogi2888 the reason I suspect the power valves they'd be the first thing to go if the amp is run without a load (say the pa100 if it went open circuit because of some defect) and could explain the fuse blowing repeatedly
Hi, I could not get one thing, can I use any speaker impedance on the speaker output regardless of the amp input of the attenuator? I am planning to connect 16 ohm output to 8 ohm speakers using this. On full volume, the impedance in total, in this case, is 12,7 ohm. If I connect the correct speaker it is 15,2 ohm. Half volume, 10,66 vs 11,43 ohm. I wonder if this causes a problem.
The way the HB is set up, the impedance on it's inputs is closer to the correct value with a higher impedance speaker connected to the output (with no speaker at all it's pretty close to spot on). I don't think you'd have a problem with an 8 ohm speaker using the 16 ohm input though, this should be fine. On a more general level it's hard to answer this question straightforwardly though, as there's a whole range from maybe okay to certainly fine. Using the 4 ohm input with a 4 ohm speaker connected to the output at full volume would be the worst case scenario I think, which I wouldn't recommend although it's probably still just about okay if the amp is fairly robust.
That should be quite fine I believe, do keep an eye on the amp the first time you try. The resistance would be a bit under 4 ohms but most amps have no issue with that.
Hello, i have questions : Does volume level of Line output and Speaker output are totally separated ? you can reduce speaker cab volume to very low or totally silent maybe and have good line out volume level ? Can you also totally unplug the speaker cable from the Attenuator to cabinet to have a sort of loadbox (no sound at all goes to the cab) and just use the Line output of the PA-100 box to plug into audio interface for using IRs ? No hazard to do that for the amp ? Thanks you !
As it comes from the factory, the line output depends on the speaker volume. If you're comfortable taking it apart and moving the resistor that goes between the speaker potentiometer and line out one by resoldering it, you can change it to be independent. I describe this in the video, at 9:12 and then explain how I went about fixing it at 12:45 and at 18:58 i show what i did - less clearly so than I recall doing, may have accidentally cut some explanation of it away while editing xD. Unplugging the speaker and using the attenuator as a loadbox alone is safe, but do beware of the caveats I noted in the video (16 ohm input wasn't safe from the factory regardless of a speaker being connected, at least on my unit, and the 4 ohms input isn't entirely safe if you connect a low impedance speaker). If you intend to get one of these (or anything in this price range) I do recommend watching the entire video careful so you understand the caveats about the 4 and 16 ohm input properly, you have to solder an extra wire before the 16 ohm input is safe at all. The 4 ohm input may or may not be safe, but personally I would not recommend using that with a speaker below 16 ohms connected to the speaker out. And regardless of that, for any load box or speaker I would recommend to check with a multimeter whether what you connect it is safe or not, if it is say within about 20% of what it says on the label you'll be fine.
Hey Netman, thanks for sharing all the info regarding this unit. From what you mentionen in the video, do I understand this right, that if i connect the 8ohm out from my tube amp (60 watt) to the 8 ohm in of the HB PA-100, and the out of the attenuator to a 4 ohm cab it works fine? Thanks in advance for your reply.
That should indeed work fine, if all you want to do is adapt impedances do keep in mind the max volume of that setup is gonna be a fair bit quieter than using a cab of the right impedance straight
@@netman69 Thanks a lot. It is just a bedroom set up to get tube sound without tube volume so no volume competition. The box is Marshall VS212 (2x12) with 4ohm in mono (parallel) and 8 ohm per speaker stereo. Amp is a Engl fireball 60 from 2009. With either 8ohm (2x16 parallel) or 16 ohm (2x8 serial) out. Without attenuator there is an easy connection and great sound wit 2x8 ohm. However the HB PA-100 accepts only one in and one out. You seemed like someone who could have answers to a quite specific case. Hence the question.
@@evgenijloginov3412 16 ohms on the output of the HB would give less power to the speaker but have the 8 ohm input better matched to actual 8 ohms. If that's loud enough (depends on your definition of bedroom level) it's a nice option. Just be mindful of the ground issue my video mentions, but it seems HB might have fixed that by now :).
@@netman69 Thank you for the fast response. My concern was the difference in impendace 8ohm from amp vs 4ohm in box. Without the attenuator no questions left. But as HB does not provide the output resiatnce of the unit I had this qurstion. Just to wrap it up amp out 8ohm -> HB PA-100 -> box 4ohm will work? Thanks for your patience. This entire ohm-thing is quite black megic to me😅. Thank you!
@@evgenijloginov3412 HB seems to have entirely ignored output impedance in the design of the box xD. It's resistance is right on without any speaker connected, with a 4 ohm on the output, the 4 ohm input becomes a bit low for comfort (like about 2 ohms). The other inputs are close enough, 8 ohm input would be about 6 or 7 ohms with a 4 ohm speaker connected, being off like 50% is not something most valve amps really care too much about.
If it goes on every time you hit a chord it's definitely advisable to turn down the master. The real concern would be for the resistors inside to overheat, which would take some time with any normal amp (at least a minute or so), the light will give a rough guideline on when you're pushing it a bit too much but it is not very accurate. If it occasionally gives you a small blip when playing I wouldn't be too concerned, against better judgement I've given mine some serious hot supper before playing with a 200w solid state amp for minutes on end and it survives that just happily.
Hey there @netman Thank you for this informative video! I just bought this unit, because I needed a dummy load at home so I could use my IR loade and practice to playalongs at home. If I would have known that this unit is dangerous, I wouldnt have bought it :-) But anyway: I think for my 50W fender style amp in 8 Ohm it should be safe to use. But in the and the box is totally useless since it can't be used as a dummy load because the line out is muted in dummy mode. So you mention in the video an easy fix: Only resolder the resistor on the pot from the blue to the yellow cable. You go on in the video so quickly so I wasn't sure if this is the whole trick? I am in need to do this mod, becaus I just bought it for this silent practicing idea... Thanks for your help!
Moving that resistor really is the entire trick. It is wired deliberately to the speaker output, presumably because then the speakers response can affect the output, so moving it will slightly change the sound but if you want to record while muted that is inevitable. If you want to practice entirely silently, you could also just disconnect the speaker from the attenuator ;).
@@netman69 Hey thanks for the super fast response! OK, so I will move the resistor. But I am thinking of what you said: I my understanding your option is not working. The only setting where I can safely disconnect the speaker and the correct dummy load is provided is, when the attenuation is completely turned to max. At least on my Weber Mass Lite this is actually the case, The Weber support told me so...
@@semiforte This is not the Weber though, with no speaker connected the HB will behave as if the speaker output volume is set to 0 regardless of the controls position, that is to say you'll have 6, 9 and 18 ohms or thereabouts for the 4, 8 and 16 ohm inputs respectively. For the 8 and 16 input that's entirely fine and in the ballpark of what a real speaker could be, the 4 ohm input I would avoid if your amp has an 8 or 16 output, but you'll be fine regardless. The things I would actually be concerned about with the HB are the ground issue with the 16ohm input I show in the video, and using the 4 ohm input with a 4 ohm speaker on the output at the higher end of the volumes. If you are aware of those two issues I reckon you can make it work for your situation :).
@@netman69 OK. Well, it seems that you know what you're talking about so I will trust this information, but somehow it is still weird, because in the manual there it says, that if I use the box only as a resistor with no cabinet connected, I should set the control betwee 2-3, here's the quote: [Out Speaker] Output jack for connecting a passive speaker box. The device can be used as a load resistor when operated with tube amps without speaker box. If you do not connect a loudspeaker and use one of the other two outputs set the knob to ‘2’ - ‘3’. So if you're right, what is that information about?
@@semiforte Is this from the Harley Benton or the Weber? I should double check that i am not somehow missing something, I did double check the resistance of the inputs with no output connected for the HB, about Weber I know nothing. If the HB manual says this it may just be they suggest it so to have the line-out working.
The way it's set up from the factory the line-out volume follows the speaker volume, so you can't turn down the speaker all the way and still get the sound out of the line output (as you also turn the line out volume down while turning the speaker volume down). There is some logic behind that madness though, with the way it's set up from the factory you also get the interactions of the loudspeaker with the amps output recorded even when the volume is set lower, but for me it is more important to be able to get the audio even when the speaker is set very quiet so hence the modification, you can do it or leave it as is depending on your preference.
I dont get it actual problem. 16 ohm socket is damaged? I have 50 watt amp with 8 ohm output (its little bit more than 8 ohm said amp manifacturer) and 16 ohm speaker. 16 ohm speaker connect to 8 ohm input. Do i need this modifications. Can we understand sockets are okey without that equipments? Thank you.
Not damaged, but in my case the ground was not hooked up to it and instead just depended on a connection through the painted metal box which is not great. If you purchased it new and recently your unit probably does not have the same problem (others have reported when they bought on recently it was fine).
@@netman69 I just found used. Unfortunately, Harley benton products are not sold in the countries I live in. I'm not sure I really need attanuator. I'am not interested crunk tubes. I use the master volume at the lowest level, I just doubt that I am getting full efficiency from the amplifier. Thank you for the answer.
@@trebleclef4889 if you want to connect an 8 ohm output to 16 ohm speaker you do probably want the attenuator (assuming the amplifier uses tubes). 8 ohm output into 8 ohm input from the attenuator and then the speaker connect to the speaker out of the attenuator.
@@netman69 My amp already 8 ohm(a little bit more than 8 ohm manifacturer told me) out connected to 16 ohm speaker. Something is wrong about that? Amp is dumble clone and yes tube amp.
@@trebleclef4889 yes, with tube amps it's not a good idea to connect to a mismatching load. If the output says 8 ohms you want to connect to 8 ohm speaker, or for example 8 ohm input on an attenuator. 8 ohm to 16 ohm is no big drama, problems become real when for example you have no speaker at all or 4 ohm output to 16 ohm speaker, or 16 ohm output to 4 ohm speaker, like when it is quite a big difference. I'd recommend using the 8 ohm input on the attenuator in this case though. If you have a multimeter you can check if the input is connected properly inside the attenuator (set to ohms measuring mode and look that it is somewhat close to 8).
If connecting a 4ohm output and 4ohm speaker (i.e Fender Tweed Champ) to this, would I be safer to use the 16ohm input on the attenuator, therefore giving 3.2ohms as worst case?
The lowest possible isn't necessarily the worst, too high of a resistance is worse than a short circuit since could allow the voltage on the transformer to go above what it can handle causing the insulation to break down which can destroy a transformer in literally no time. If the resistance on the amps output is too low, the concern would be the transformer heating up too much or the output valves passing more current than they can handle, which is also bad but at least it wouldn't instantly destroy anything. That's to say... Maaaybe the 8 ohm input would be marginally safer but I really do not know for sure, the 16 ohms input would probably be straight up a bad idea. The 4 ohm input with the volume of the attenuator turned up all the way may not be better than the 8 ohms, so I find it hard to recommend either xD.
@@netman69 Thanks! :) I will likely buy the Bugera version of this design and report back with how it compares internally (I'm guessing very similarly.)
@@PedalScience I have seen internal pics and it looks like the old version of this before they added a fan, if it's like that, in addition to recommending against using it for 4 ohm outputs at all, stay well below the "rated" 100W as it would eventually catch fire and take a set of valves and maybe a transformer to it's grave xD.
If you doesn't afraid of anything (say the amp used going on fire lol), what i'd do for 4 ohms output only amp is start by hooking it to the 4 ohm input on the attenuator, give it some beans and see if the transformer gets scorching hot or the tubes start red-plating or sth. If yes, go up a notch in resistance xD. If you're turning the volume of the attenuator up the whole way anyway though, 8 ohms input will be about 6 though which is probably just fine for a 4 ohm output, but then turning the volume down is somewhat pushing it towards where you may get a failure without warning. Or if you're just after getting it to work happily, stick a 16 ohm speaker on it... Then you'd be allright using the attenuator the normally prescribed way.
This is a great video to check before plugging into a tube amp. When I measure mine its shows: 4 ohm socket = 7 - 9 ohms as I turn the pot 8 ohm socket = 11 - 13 ohms as I turn the pot 16 ohm socket = 19 - 26 ohms as I turn the pot Am I measuring wrong or could something cause this? I am worried about using this on my tube amp until I know its safe. What could cause the ohms to be so far off? Could one of the resistors be broken and how would I check this? Thanks!
That's pretty far off, if you measured it right do not trust it! But first idiot check whether your meter works, short the probes together and check what their resistance is by themselves, maybe also check a known resistance of something. Subtract the resistance of your probe cables from the measurements, but if it's more than like .5 ohms, throw those probes in the bin! If you used any cables to the HB during measuring, also check the resistance of them (tip-to-tip AND sleeve-to-sleeve), expect them to be less than .5 ohm unless they are at least several meters long. Next thing to check is there are 3 pairs of paralleled resistors in the HB you can check individually, pause my video at 12:40 or so for the relevant part of schematic. We can measure the groups of resistors without even opening the thing, measuring mostly between the tip side of the various connectors because later we can worry about the sleeve/ground connection: - Between the tip of the 4 ohm and the tip of the 8 ohm connector you should measure approx 4 ohms (regardless of what's going on otherwise). - Plug a cable in the 16 ohm with the other end unconnected (the switch in the connector has to be opened by a plug to measure this one), you should measure about 7.5 ohms between the tip of 16 ohm connector and the tip of the 4 ohm connector. - Still with a plug in the 16 ohm connector, and no speaker connected to the output, measure between the sleeve and tip of the 4 ohm connector, you should measure about 7.5-8 ohms again. - Tip of the speaker out connector should measure about 0 to the tip of the 4 ohm connector when on full volume, about 8 ohms with the volume turned down all the way (and something in the 16 ohm hole still). If those 4 things check out, all the power resistors are okay! If not, open the thing up and follow the wires to find where's what from the schematic, you'll have narrowed it down to 1 of 2 resistors but have to disconnect one to find which one is bad (or harass the seller for warranty). The other thing to check would be the sleeve connections of all the connectors, are they proper? Check between any combination of them, they should all be tied together proper and have like 0.2 ohm resistance between 2 different ones at most. The 16 ohm is especially suspect, I don't recommend leaving it connected the way it comes from the factory (see: video contents), also check the switch in that one (probably have to open the unit up to measure that one correctly, but resistance of the 4 ohm input tip-to-sleeve should halve from 8 to 4 ohm between having something in the 16 ohm connector or not if to check externally). And with anything that doesn't check out from above things... It's probably worth inspecting the solder connections and looking if not there's a wire broken loose somewhere. Hope that helps :).
@@netman69 Thank you so much for that detailed check list! I have gone through it all and all your checks seem to work out ok after I re-melted some of the solder joints that looked a little off. I think the problem may be my volt meter now as it seems to drift over time with how much ohms it shows. After leaving it on for a while I am now getting these results; Volt meter shorted = 1.4 ohms 4 ohm socket = 6.4 - 7.6 ohms (minus the 1.4 = 5 - 6.2 ohms) 8 ohm socket = 10.3 - 11.4 ohms (minus the 1.4 = 8.9 - 10 ohms) 16 ohm socket = 17.6 - 24.7 ohms (minus the 1.4 = 16.2 - 23.3 ohms) Is this now safe or should I get a better quality volt meter and test again? Like I said, I seem to get the results you listed above when I carry out the tests you mentioned. I am still not sure how close in ohms it needs to be for it to be safe on a tube amp. Thanks again for the help, it has been very useful :)
@@netman69 That was indeed very helpful. I checked all the points before I fired my attentionator (haha) up for the first time, it's completely healthy and it doesn't even get warm. It's connected to an AC30S1 though, which isn't the force wattwise. But soundwise... take shelter if you have no attenuator and crank the power stage all the way up, with the gain on the edge of break up!
@@DE-signYourLife Then there's only 3 parts that could be the culprit, the resistor between the big potentiometer for the speaker out and the line out potentiometer, the line out potentiometer itself and the connector. I'd suspect a wire between those to be loose or something actually as most likely problem.
So, i buy a brand new piece of equipment and have to open it up and make modifications i have no idea how to make, using replacement parts or equipment i don't have. That's what's called a straight up rip off! I've seen vid's of people making cheap d.i.y. attenuators, but for all i know using one could damage my amp using them.
That's certainly a fair assessment as consumer, but given you can't buy the parts for the same price I'm still happy I can buy it. Building your own is neither cheaper or easier. I don't know if paying more gets you something that'd be more sensible for a normal end-user, but maybe that is the sensible thing to do. With how close they are to a good product, maybe HB can fix this though, I've contacted them about it last week or so, yet to see a reply.
@@netman69 First of all, thank you very much for contacting them, i expect they'll take you more seriously than i, such shoddy workmanship must be addressed and answered for. I don't know what the more expensive attenuators offer (i'm guessing differing amp simulators and such), do you know of the best affordable one please? Cheers.
@@MahatmaLevolence I wish I had better advice, but I have absolutely no clue which one to recommend if you want a ready-made solution. I did see some other cheap ones that were equally questionable.
@@jaakkokunnas amps are quite tolerant of such mismatch luckily, even like 50% low or high does not mean disaster. It's indeed better to have a too high speaker impedance, then the valves won't see an excessive load but i wouldn't worry too much as long as its somewhat close.
Maybe... Officially it can't because it's outside it's ratings and there is a real chance you'd burn the thing out but with a solid state the amp itself should be fine, so if you're willing to risk the attenuator you could try and find out. I know mine survived a fair bit more than it's rated for, but I didn't push it for a long time.
I sadly don't have anything better than "maybe" and "it depends". If you have a master volume on that amp, turning it down just a bit would be enough to not overload it and the LED will light up if you're giving it too much beans but depending on how well the master volume is implemented that kinda defeats the point of using an attenuator. That said i **think** it would survive the full 120w just fine, but it's only specified for taking 100w so there really isn't a guarantee, especially in the long run. I've given it hot supper like that before so i know for sure it doesn't instantly kill the attenuator but if you do burn out the resistors be aware that could be detrimental to the amplifier also (to the output valves in particular, but maybe even the output transformer). In short though: you'd probably be fine, i've pushed my particular unit with 120w amps before, but I really can't recommend doing that.
@Nicko Lps What you're saying is correct and if you want to play it 100% safe you indeed shouldn't, but I think their rating is generous enough to be intepreted as "it'll do a 100w amp". The resistors in it are derated 50% and the fan does a reasonable enough job of keeping them cool, unless you overload them absolutely massively the limit with resistors is entirely thermal.
@Nicko Lps Also people don't tend to know what's in their attenuator, I can only speak for this particular Harley Benton one in particular, and even this one had an older version without a fan yet the same resistors (and the Bugera PS1 appears to be the same idea), those might not survive at all yet they carry the same rating on the label. Which is to say, if all you know is "100w attenuator", you should absolutely abide by what Weber suggested if to not get burnt xD. And even if you understand all, de-rating devices like this is always a good idea, but unless you're willing to spend literally 10x as much or build your own attenuator, all you can find is ~100w rated attenuators, hence the discussion we're having does have value. Having said that I found out HB now sells a 250w attenuator (for 150ish euros) because I was fact checking myself on that "spend literally 10x as much" claim, so apparently i lied :D... Interesting. If OP is still reading, it may provide more peace of mind having one of those for a 6505, but I have no clue if it's any good personally.
@Nicko Lps Jeez, I'd expect better from dr-z! They weren't tubular rheostats though where they? Ohmite do have those, and they look like this: sc04.alicdn.com/kf/HTB1BUVFaa1s3KVjSZFAq6x_ZXXaD.jpg The OT and output valves do suffer a bit more with a speaker than a resistor, but I doubt it really matters to the point where you have to hold back without an attenuator really... Valves may perish sooner if you go hard but I ain't ever heard of someone blowing out their OT because they were too metal for it xD. The audio world is full of superstition and myth.
@Nicko Lps Yeah, the youtube regime is not one of free speech xD I've searched and found pics of a Dr-Z brake lite internally that look like what we're talking about, and believe it or not I think it's Ohmite removing the epoxy, not Dr-Z, although i haven't ever seen a rheostat like that with multiple taps on it, see this: www.ohmite.com/assets/docs/res_210.pdf?r=false The price of them seems excessive though!
Any thoughts on a possible bright switch mod? I saw one in this video. th-cam.com/video/VbD0plXyzo8/w-d-xo.html I haven't noticed treble being a problem with PA-100, unless the amp is whisper quiet, Fletcher Munson and all that. I'm loving the PA-100, I did your 2 mods :) thanks. I also have to keep the box away from the amp's transformers when using MicMod, otherwise there's a massive constant buzz. This is definitely one of my better acquisitions, a great product with the mods.
Whether a bright switch makes any sense at all probably depends on the cabinet you're connecting to, definitely can't say I've felt the need for something like that myself. If you do add one be sure to use non-polarized electrolytic caps or film caps if you can find them in a big enough value (the typical polarized ones would be destroyed in a hurry xD). I bet the little transformer in the Micmod circuit is what's picking up the buzz from the transfomer, in addition to distance rotating the attenuator 45/90 degrees could help a lot (if you ever wonder why most valve amps have the ouput transformer rotated differently than the power transformer, they do this to reduce magnetic coupling between the two). Also might be worth double checking both parts of the case of the attenuator are properly grounded (as in connected electrically to the outside of the connectors), and if not strategically scrape some paint away so they make connection. The case not being grounded would allow way much noise to be picked up.
Well at the price it's amazing you get an attenuator at all I think. The big knob has some excuse to feel weird being a high power wirewound potentiometer, they often feel like that but I'm sure it can be done better if you pay through the nose :D.
@@netman69 The wirewound potentiometer is perfectly allright, it doesn't look, feel, or sound a bit different from the one in my 1970's high quality iron
Huge thumbs up for this video! It's possibly the best review and explanation of the limitations/design problems I've seen yet. I loved seeing the schematic and explanation of the changes you made.
This is exactly the type of video I needed. I own this box for a while now, and always wondered why it is basically unusable as a load box. I think I will fix it this week.
I'm delighted to hear it's useful, good luck patching it up and know all questions are welcome if you have any :).
I know it's an old subject by now but nevertheless, I'd like to mention that my PA-100 came with the mail today (living in Germany) and it's perfectly allright, they soldered a solid ground wire to all output connectors and added proper washers, particularly to the 16ohm connector, which looks quite heavy duty now, nothing like in your video. The line volume decreasing simultaneously with the speaker volume is still an issue however, I changed that according to your advice. There was even plenty of wire protruding from the resistor so I could simply bend it away from the pot. The attenuator works perfectly now, with a strong and clear signal into my interface from the line out. Thanks for the enlightenment, man!!!
Thank you! It is still great to add to the statistics :-)
@@netman69 You're welcome! What I actually wanted to express was that going public with this issue was probably not in vain, they seem to have adressed the problem. Again, my appreciation for your great work.
@@captainfineweather5610 it does seem they've fixed it, but I do wonder why, I've sent them an elaborate email about the subject and have not gotten a reply.
@@netman69 That seems to be quite common in our times, not just with companies. The majority of people has completely missed the bus... But don't you worry, as long as there are conversations like this one, I mean the entire comment section, there's hope for the rest of us!
@@captainfineweather5610 Well the best way to change a thing is to set a better example, thankfully there are plenty, us included :). I've actually rarely had companies not get back to me when I come to them with serious concerns like this, but who knows maybe HB just missed the email somehow.
Thank you for the most informative review I’ve seen to date on passive power soak. I’ve recently purchased a 30 watt tube amp (Laney IRT30) and was looking for something I could install on a combo amp with a bypass switch. I believe it’s watt control dial is a bit misleading as it is prior to power tubes. I recently saw two other reviews re Bugera PS1 and Harley Benton where line out didn’t work. Wish they had one with a bypass sw so no need to mess with cables. Your comments, details and knowledge earns my respect of your assessment. Thanks again!
Thank you for your insight and sharing your experience with that attenuator.
I like the line out mod. I'm curious why they don't build these attenuators into valve amps anyway. It'd be a big selling point.
They actually do make some amps with a builtin attenuator, often they call it a power soak in the marketing material with that context for whatever reason. Mesa boogie is one brand that has quite a few options in this.
I didn't know that. Thanks for letting me know. I just ordered one of these and will mod it to give a line out even when fully attenuated..
I checked mine and it was the exact same way. new cliff jack installed and moved the line out so it would work much better. thanks!
Hello, I just received mine. Didn't even plug it in yet.
Just in case people are wondering, mine came with the ground connected to both lugs of the 16ohm jack.
Looks like they heard you and fixed it.
If you get a new one, it's probably a good idea to check anyway in case mine was just a good batch.
Very nice if they did, maybe only a few have it wired wrong. I did try and contact them about it (after the video) but they did not reply.
Mine too. I just modded it and I can't wait to record some riffs with it directly into my soundcard🎉
Looking to purchase this device. These points of improvement may come in handy 👍
Hey man
Thanks so much for this video. You are a huge help. Think I might take this project on myself. My Marshall jcm 900 100w hasn't been blasted up properly in years.
Thanks dude
Mine turned up with what appeared to be the wrong nut on the 8ohm input so it wouldn't tighten. That in turn caused the connection to the ground bar between the three input options to break off. Had to salvage a working, correct size nut from my parts bin, get it tight and resolder the connection. For my purposes fine now. May end up replacing the socket as you did, or at least putting some locktite on it if usage loosens it up.
Did they at least attempt to solder the 16 ohm ground on yours?
@@netman69 hmm not sure but the ground connection between all 3 inputs buzzed out strongly once I was done
Ik heb mijn pa-100 net even gecheckt na deze video te zien, ik krijg op alle ingangen vrij correcte weerstanden, ongeacht op welke positie de potentiometer staat. Afwijking van max 0,5 ohm op de drie aansluitingen. Ook was de 16 ohm ingang correct geaard 👍🏻. Op basis van wat werkt de ventilator precies? Ik heb die van mij nog niet zien draaien, maar dat is misschien omdat mijn Marshall maar 1 watt geeft en dus niet genoeg warmte produceert? Nog steeds te luid voor een slaapkameramp in een appartement, vandaar de attenuator :)
In elk geval merci voor de uitgebreide video, zeer leerrijk om te zien! Grts uit Tongeren
De ventilator werkt op de stroom die binnenkomt via een gelijkrichter, 1 watt is inderdaad niet genoeg daarvoor (en dan is de ventilator ook hardstikke niet nodig).
@@netman69 ok thanks ik vermoedde het al, aangezien de blok ook totaal niet heet werd 😄 nu helemaal zeker, merci voor je snelle reactie!
I made the same mod as you did for the line out but the 16ohms jack was properly wired... I also always use the 8ohms input as it's the safest one! Nice video👍
Great video! I just received the PA100 and what I don't like is that the volume for the line output is the same as that of the attenuator, that is, the attenuator is at 1 and the line volume potentiometer is at 10... listen with very little volume connecting it to a sound card. I mean, I can't play in my room with the amplifier at maximum power, the attenuator at 0 or 1, because I won't hear anything through the line output!! horror!!
Wow, great video, some proper electronic knowledge unleashed on that cheapo attentuator that everybody is tempted by...
Thank you for the video and review. Does the moving of the resistor affect the XLR MicMod out in any way? How does the fan work if it's passive, phantom power via XLR?
Moving the resistor doesn't affect the MicMod thing no, the volume of that will depend on the speaker output volume still. Changing it would probably need a small modification on the circuit board. I should have addressed that in the video, but somehow entirely overlooked it. The fan is powered by the incoming audio, power that otherwise would go to the speaker - but it needs a small enough amount of power that that doesn't affect the impedance significantly. It only runs when you are playing quite loud but that's also the only time it's really needed.
Good review. Did the same with mine as 16 Ohm was playing up and started to doubt it being safe for my Marshall 100w TSL. love the totsiens at the end. lekker!
Can I use this attenuator on my AC30/6TB? Will there be any damage to the amplifier or speaker if used for a long time? I am looking for a hot plate from THD, but they are not for sale. So I am considering purchasing this attenuator to replace it. Any advice on this attenuator would be appreciated in the comments. I want a safe attenuation of 16 ohms ac30/6tb (1997). What's most important to me is that the amplifier and speakers are safe and that they don't catch fire.
Only if you can make sure the issue I show at around 16:40 with the 16ohm input is not present or fix it. The speaker should be safe either way but the 16ohm input wasn't very safe on my unit so if not checked it could be a danger for the amplifier, others here have apparently received units where that issue did not exist.
Thanks for the informative video! Mine has the same line out construction mistake, but fan and 16Ohm out are fine. I also have a different capacitor in there. Its brown but still rated 105°C
Thanks again for the video, i finally know how to fix the line out :)
What where they thinking with that? Lol
They weren't thinking about paint I guess xD. You'd think they'd have someone try one of these before they start selling them but I guess not... Now that I'm reminded though I just realized I didn't even do the obvious thing to do and tell them, doing that now :D.
Great video, thank you.
Thanks for the in-depth review, I probably would have bought the PA-100 if I didn't see this. I wonder if the PA-250 is much better? I don't have any soldering experience so I really don't want to have to make such changes to whatever I buy
I wish I knew, depends entirely on how drunk the HB engineers got that night...
@@netman69 Haha!
Hiya! What kind of cables do we need? Has to be both speaker cables or can be any instrument jack cable? Just bought one for my combo. The speaker cable i will use the one it's attached on the speakers already, but the extra one I need to plug between the amp and the attenuator, has to be speaker cable? Thanks!
You should use speaker cables on both sides, most importantly between the amp and the attenuator. I've used instrument cables before and lived, but it is not wise.
Hi I used this for a day on my mesa boogie lonestar special combo 1x12 inch. After putting it on the drive channel the amp just powered off and wont turn back on at all.... I am kinda pissed... It was functioning for some time then when I put abit more gain and the master volume and output volume up. the amp just powered off and died and wont power back on at all.... the red light went out... i tried changing the fuse and also swapped the pre amp v1 tube around several times with existing preamp tubes that are 15 years old ... I recently a month ago put in a new set of sovtek mesa spec el84s x4. and a new mesa retifier.. please help... i get the feeling a diode may have blown or at worst a transformer fried.... There was no burning smell so maybe transfoerms ok ? i will take it to a amp tech soon when i have time
Since it isn't powering on I'd sure suspect the fuse was blown, but the rectifier diodes seem like an unlikely culprit, I'd suspect one of the el84s being blown and taking out the new fuse as soon as it's replaced.
@@netman69 thanks for your feedback, I changed the fuse and it didnt help, also the el84s power valves are brand new. so I believe it cant be them. although I have a pair of new el84s as spare so I will try them
@@ukguitaryogi2888 the reason I suspect the power valves they'd be the first thing to go if the amp is run without a load (say the pa100 if it went open circuit because of some defect) and could explain the fuse blowing repeatedly
Hi, I could not get one thing, can I use any speaker impedance on the speaker output regardless of the amp input of the attenuator? I am planning to connect 16 ohm output to 8 ohm speakers using this. On full volume, the impedance in total, in this case, is 12,7 ohm. If I connect the correct speaker it is 15,2 ohm. Half volume, 10,66 vs 11,43 ohm. I wonder if this causes a problem.
The way the HB is set up, the impedance on it's inputs is closer to the correct value with a higher impedance speaker connected to the output (with no speaker at all it's pretty close to spot on). I don't think you'd have a problem with an 8 ohm speaker using the 16 ohm input though, this should be fine.
On a more general level it's hard to answer this question straightforwardly though, as there's a whole range from maybe okay to certainly fine. Using the 4 ohm input with a 4 ohm speaker connected to the output at full volume would be the worst case scenario I think, which I wouldn't recommend although it's probably still just about okay if the amp is fairly robust.
Hi. If I hook my 4 ohm tube amp output into the attenuator 4 ohm input and use an 8 ohm speaker cab for the output, will that be fine ?
That should be quite fine I believe, do keep an eye on the amp the first time you try. The resistance would be a bit under 4 ohms but most amps have no issue with that.
Hello,
i have questions :
Does volume level of Line output and Speaker output are totally separated ? you can reduce speaker cab volume to very low or totally silent maybe and have good line out volume level ?
Can you also totally unplug the speaker cable from the Attenuator to cabinet to have a sort of loadbox (no sound at all goes to the cab) and just use the Line output of the PA-100 box to plug into audio interface for using IRs ? No hazard to do that for the amp ?
Thanks you !
As it comes from the factory, the line output depends on the speaker volume. If you're comfortable taking it apart and moving the resistor that goes between the speaker potentiometer and line out one by resoldering it, you can change it to be independent. I describe this in the video, at 9:12 and then explain how I went about fixing it at 12:45 and at 18:58 i show what i did - less clearly so than I recall doing, may have accidentally cut some explanation of it away while editing xD.
Unplugging the speaker and using the attenuator as a loadbox alone is safe, but do beware of the caveats I noted in the video (16 ohm input wasn't safe from the factory regardless of a speaker being connected, at least on my unit, and the 4 ohms input isn't entirely safe if you connect a low impedance speaker).
If you intend to get one of these (or anything in this price range) I do recommend watching the entire video careful so you understand the caveats about the 4 and 16 ohm input properly, you have to solder an extra wire before the 16 ohm input is safe at all. The 4 ohm input may or may not be safe, but personally I would not recommend using that with a speaker below 16 ohms connected to the speaker out. And regardless of that, for any load box or speaker I would recommend to check with a multimeter whether what you connect it is safe or not, if it is say within about 20% of what it says on the label you'll be fine.
So does this mean the 8 ohm inpit is safe from the factoey with no modification??
Hey Netman, thanks for sharing all the info regarding this unit. From what you mentionen in the video, do I understand this right, that if i connect the 8ohm out from my tube amp (60 watt) to the 8 ohm in of the HB PA-100, and the out of the attenuator to a 4 ohm cab it works fine? Thanks in advance for your reply.
That should indeed work fine, if all you want to do is adapt impedances do keep in mind the max volume of that setup is gonna be a fair bit quieter than using a cab of the right impedance straight
@@netman69 Thanks a lot. It is just a bedroom set up to get tube sound without tube volume so no volume competition. The box is Marshall VS212 (2x12) with 4ohm in mono (parallel) and 8 ohm per speaker stereo. Amp is a Engl fireball 60 from 2009. With either 8ohm (2x16 parallel) or 16 ohm (2x8 serial) out. Without attenuator there is an easy connection and great sound wit 2x8 ohm. However the HB PA-100 accepts only one in and one out. You seemed like someone who could have answers to a quite specific case. Hence the question.
@@evgenijloginov3412 16 ohms on the output of the HB would give less power to the speaker but have the 8 ohm input better matched to actual 8 ohms. If that's loud enough (depends on your definition of bedroom level) it's a nice option. Just be mindful of the ground issue my video mentions, but it seems HB might have fixed that by now :).
@@netman69 Thank you for the fast response. My concern was the difference in impendace 8ohm from amp vs 4ohm in box. Without the attenuator no questions left. But as HB does not provide the output resiatnce of the unit I had this qurstion. Just to wrap it up amp out 8ohm -> HB PA-100 -> box 4ohm will work? Thanks for your patience. This entire ohm-thing is quite black megic to me😅. Thank you!
@@evgenijloginov3412 HB seems to have entirely ignored output impedance in the design of the box xD. It's resistance is right on without any speaker connected, with a 4 ohm on the output, the 4 ohm input becomes a bit low for comfort (like about 2 ohms). The other inputs are close enough, 8 ohm input would be about 6 or 7 ohms with a 4 ohm speaker connected, being off like 50% is not something most valve amps really care too much about.
Is it a concern if the FULL POWER LED is flashing while playing? Should I keep it off by lowering the amp master?
If it goes on every time you hit a chord it's definitely advisable to turn down the master. The real concern would be for the resistors inside to overheat, which would take some time with any normal amp (at least a minute or so), the light will give a rough guideline on when you're pushing it a bit too much but it is not very accurate. If it occasionally gives you a small blip when playing I wouldn't be too concerned, against better judgement I've given mine some serious hot supper before playing with a 200w solid state amp for minutes on end and it survives that just happily.
Hey there @netman
Thank you for this informative video! I just bought this unit, because I needed a dummy load at home so I could use my IR loade and practice to playalongs at home. If I would have known that this unit is dangerous, I wouldnt have bought it :-) But anyway: I think for my 50W fender style amp in 8 Ohm it should be safe to use. But in the and the box is totally useless since it can't be used as a dummy load because the line out is muted in dummy mode. So you mention in the video an easy fix: Only resolder the resistor on the pot from the blue to the yellow cable. You go on in the video so quickly so I wasn't sure if this is the whole trick? I am in need to do this mod, becaus I just bought it for this silent practicing idea... Thanks for your help!
Moving that resistor really is the entire trick. It is wired deliberately to the speaker output, presumably because then the speakers response can affect the output, so moving it will slightly change the sound but if you want to record while muted that is inevitable. If you want to practice entirely silently, you could also just disconnect the speaker from the attenuator ;).
@@netman69 Hey thanks for the super fast response! OK, so I will move the resistor.
But I am thinking of what you said: I my understanding your option is not working. The only setting where I can safely disconnect the speaker and the correct dummy load is provided is, when the attenuation is completely turned to max. At least on my Weber Mass Lite this is actually the case, The Weber support told me so...
@@semiforte This is not the Weber though, with no speaker connected the HB will behave as if the speaker output volume is set to 0 regardless of the controls position, that is to say you'll have 6, 9 and 18 ohms or thereabouts for the 4, 8 and 16 ohm inputs respectively. For the 8 and 16 input that's entirely fine and in the ballpark of what a real speaker could be, the 4 ohm input I would avoid if your amp has an 8 or 16 output, but you'll be fine regardless.
The things I would actually be concerned about with the HB are the ground issue with the 16ohm input I show in the video, and using the 4 ohm input with a 4 ohm speaker on the output at the higher end of the volumes. If you are aware of those two issues I reckon you can make it work for your situation :).
@@netman69 OK. Well, it seems that you know what you're talking about so I will trust this information, but somehow it is still weird, because in the manual there it says, that if I use the box only as a resistor with no cabinet connected, I should set the control betwee 2-3, here's the quote:
[Out Speaker]
Output jack for connecting a passive speaker box.
The device can be used as a load resistor when operated with tube amps without speaker box.
If you do not connect a loudspeaker and use one of the other two outputs set the knob to ‘2’ - ‘3’.
So if you're right, what is that information about?
@@semiforte Is this from the Harley Benton or the Weber? I should double check that i am not somehow missing something, I did double check the resistance of the inputs with no output connected for the HB, about Weber I know nothing. If the HB manual says this it may just be they suggest it so to have the line-out working.
I dont understand. If i dont put the resistor to the yellow wire what happens?
The way it's set up from the factory the line-out volume follows the speaker volume, so you can't turn down the speaker all the way and still get the sound out of the line output (as you also turn the line out volume down while turning the speaker volume down). There is some logic behind that madness though, with the way it's set up from the factory you also get the interactions of the loudspeaker with the amps output recorded even when the volume is set lower, but for me it is more important to be able to get the audio even when the speaker is set very quiet so hence the modification, you can do it or leave it as is depending on your preference.
@@netman69 Thanks for the reply🫶. If i only have the line out connected without a speaker will it work?
@@alexcharamis Yes, as long as you either turn up the volume that's meant to be for the speaker (the big knob) first or have it modded as I did.
I keep being amazed over the fuckgin size of these beasts XD
You should see my video about the fender PS300, absolute BEAST of an amp even for valve standards :D
I dont get it actual problem. 16 ohm socket is damaged? I have 50 watt amp with 8 ohm output (its little bit more than 8 ohm said amp manifacturer) and 16 ohm speaker. 16 ohm speaker connect to 8 ohm input. Do i need this modifications. Can we understand sockets are okey without that equipments? Thank you.
Not damaged, but in my case the ground was not hooked up to it and instead just depended on a connection through the painted metal box which is not great. If you purchased it new and recently your unit probably does not have the same problem (others have reported when they bought on recently it was fine).
@@netman69 I just found used.
Unfortunately, Harley benton products are not sold in the countries I live in. I'm not sure I really need attanuator. I'am not interested crunk tubes. I use the master volume at the lowest level, I just doubt that I am getting full efficiency from the amplifier. Thank you for the answer.
@@trebleclef4889 if you want to connect an 8 ohm output to 16 ohm speaker you do probably want the attenuator (assuming the amplifier uses tubes). 8 ohm output into 8 ohm input from the attenuator and then the speaker connect to the speaker out of the attenuator.
@@netman69 My amp already 8 ohm(a little bit more than 8 ohm manifacturer told me) out connected to 16 ohm speaker. Something is wrong about that? Amp is dumble clone and yes tube amp.
@@trebleclef4889 yes, with tube amps it's not a good idea to connect to a mismatching load. If the output says 8 ohms you want to connect to 8 ohm speaker, or for example 8 ohm input on an attenuator. 8 ohm to 16 ohm is no big drama, problems become real when for example you have no speaker at all or 4 ohm output to 16 ohm speaker, or 16 ohm output to 4 ohm speaker, like when it is quite a big difference. I'd recommend using the 8 ohm input on the attenuator in this case though. If you have a multimeter you can check if the input is connected properly inside the attenuator (set to ohms measuring mode and look that it is somewhat close to 8).
If connecting a 4ohm output and 4ohm speaker (i.e Fender Tweed Champ) to this, would I be safer to use the 16ohm input on the attenuator, therefore giving 3.2ohms as worst case?
The lowest possible isn't necessarily the worst, too high of a resistance is worse than a short circuit since could allow the voltage on the transformer to go above what it can handle causing the insulation to break down which can destroy a transformer in literally no time. If the resistance on the amps output is too low, the concern would be the transformer heating up too much or the output valves passing more current than they can handle, which is also bad but at least it wouldn't instantly destroy anything.
That's to say... Maaaybe the 8 ohm input would be marginally safer but I really do not know for sure, the 16 ohms input would probably be straight up a bad idea. The 4 ohm input with the volume of the attenuator turned up all the way may not be better than the 8 ohms, so I find it hard to recommend either xD.
@@netman69 Thanks! :) I will likely buy the Bugera version of this design and report back with how it compares internally (I'm guessing very similarly.)
@@PedalScience I have seen internal pics and it looks like the old version of this before they added a fan, if it's like that, in addition to recommending against using it for 4 ohm outputs at all, stay well below the "rated" 100W as it would eventually catch fire and take a set of valves and maybe a transformer to it's grave xD.
If you doesn't afraid of anything (say the amp used going on fire lol), what i'd do for 4 ohms output only amp is start by hooking it to the 4 ohm input on the attenuator, give it some beans and see if the transformer gets scorching hot or the tubes start red-plating or sth. If yes, go up a notch in resistance xD. If you're turning the volume of the attenuator up the whole way anyway though, 8 ohms input will be about 6 though which is probably just fine for a 4 ohm output, but then turning the volume down is somewhat pushing it towards where you may get a failure without warning.
Or if you're just after getting it to work happily, stick a 16 ohm speaker on it... Then you'd be allright using the attenuator the normally prescribed way.
@@netman69 Thanks! I only have a 20w and 5w so should be okay... :)
This is a great video to check before plugging into a tube amp. When I measure mine its shows:
4 ohm socket = 7 - 9 ohms as I turn the pot
8 ohm socket = 11 - 13 ohms as I turn the pot
16 ohm socket = 19 - 26 ohms as I turn the pot
Am I measuring wrong or could something cause this? I am worried about using this on my tube amp until I know its safe. What could cause the ohms to be so far off? Could one of the resistors be broken and how would I check this? Thanks!
That's pretty far off, if you measured it right do not trust it! But first idiot check whether your meter works, short the probes together and check what their resistance is by themselves, maybe also check a known resistance of something. Subtract the resistance of your probe cables from the measurements, but if it's more than like .5 ohms, throw those probes in the bin! If you used any cables to the HB during measuring, also check the resistance of them (tip-to-tip AND sleeve-to-sleeve), expect them to be less than .5 ohm unless they are at least several meters long. Next thing to check is there are 3 pairs of paralleled resistors in the HB you can check individually, pause my video at 12:40 or so for the relevant part of schematic.
We can measure the groups of resistors without even opening the thing, measuring mostly between the tip side of the various connectors because later we can worry about the sleeve/ground connection:
- Between the tip of the 4 ohm and the tip of the 8 ohm connector you should measure approx 4 ohms (regardless of what's going on otherwise).
- Plug a cable in the 16 ohm with the other end unconnected (the switch in the connector has to be opened by a plug to measure this one), you should measure about 7.5 ohms between the tip of 16 ohm connector and the tip of the 4 ohm connector.
- Still with a plug in the 16 ohm connector, and no speaker connected to the output, measure between the sleeve and tip of the 4 ohm connector, you should measure about 7.5-8 ohms again.
- Tip of the speaker out connector should measure about 0 to the tip of the 4 ohm connector when on full volume, about 8 ohms with the volume turned down all the way (and something in the 16 ohm hole still).
If those 4 things check out, all the power resistors are okay! If not, open the thing up and follow the wires to find where's what from the schematic, you'll have narrowed it down to 1 of 2 resistors but have to disconnect one to find which one is bad (or harass the seller for warranty).
The other thing to check would be the sleeve connections of all the connectors, are they proper? Check between any combination of them, they should all be tied together proper and have like 0.2 ohm resistance between 2 different ones at most. The 16 ohm is especially suspect, I don't recommend leaving it connected the way it comes from the factory (see: video contents), also check the switch in that one (probably have to open the unit up to measure that one correctly, but resistance of the 4 ohm input tip-to-sleeve should halve from 8 to 4 ohm between having something in the 16 ohm connector or not if to check externally).
And with anything that doesn't check out from above things... It's probably worth inspecting the solder connections and looking if not there's a wire broken loose somewhere.
Hope that helps :).
@@netman69 Thank you so much for that detailed check list!
I have gone through it all and all your checks seem to work out ok after I re-melted some of the solder joints that looked a little off. I think the problem may be my volt meter now as it seems to drift over time with how much ohms it shows. After leaving it on for a while I am now getting these results;
Volt meter shorted = 1.4 ohms
4 ohm socket = 6.4 - 7.6 ohms (minus the 1.4 = 5 - 6.2 ohms)
8 ohm socket = 10.3 - 11.4 ohms (minus the 1.4 = 8.9 - 10 ohms)
16 ohm socket = 17.6 - 24.7 ohms (minus the 1.4 = 16.2 - 23.3 ohms)
Is this now safe or should I get a better quality volt meter and test again?
Like I said, I seem to get the results you listed above when I carry out the tests you mentioned. I am still not sure how close in ohms it needs to be for it to be safe on a tube amp. Thanks again for the help, it has been very useful :)
@@netman69 That was indeed very helpful. I checked all the points before I fired my attentionator (haha) up for the first time, it's completely healthy and it doesn't even get warm. It's connected to an AC30S1 though, which isn't the force wattwise. But soundwise... take shelter if you have no attenuator and crank the power stage all the way up, with the gain on the edge of break up!
will this safely lower volume with a Vox AC10 - without damage to the amp?
If i understand it right that one has a 16ohm output, so only if you repair the 16ohm input as i show in the video.
Please can you help how can i get the line knop to work? If i pluged the cable into Line Out the line knop isnt working... 🤷🏽♂️😢
Did you turn up the SPK level knob also? It has to be up to get the line out to work, unless you modify as I show in the video.
@@netman69 yes i did. But same result. :( I think i have to repair it..
@@DE-signYourLife is the speaker output working?
@@netman69 yes it is. For the first i use the Spkr Output and the Spkr Knop is also working. But cant get the Line Knop working for some how
@@DE-signYourLife Then there's only 3 parts that could be the culprit, the resistor between the big potentiometer for the speaker out and the line out potentiometer, the line out potentiometer itself and the connector. I'd suspect a wire between those to be loose or something actually as most likely problem.
Is that a Fender Amp logo on your guitar, lol
Yes it is :D. The guitar is a stagg, but i like to dream.
Different washer sizes so you can easily see which impedendence
they shoulda used 3 different sizes tho xD
@@netman69 yeah fair point :)
Great info !
So, i buy a brand new piece of equipment and have to open it up and make modifications i have no idea how to make, using replacement parts or equipment i don't have. That's what's called a straight up rip off!
I've seen vid's of people making cheap d.i.y. attenuators, but for all i know using one could damage my amp using them.
That's certainly a fair assessment as consumer, but given you can't buy the parts for the same price I'm still happy I can buy it. Building your own is neither cheaper or easier.
I don't know if paying more gets you something that'd be more sensible for a normal end-user, but maybe that is the sensible thing to do. With how close they are to a good product, maybe HB can fix this though, I've contacted them about it last week or so, yet to see a reply.
@@netman69 First of all, thank you very much for contacting them, i expect they'll take you more seriously than i, such shoddy workmanship must be addressed and answered for. I don't know what the more expensive attenuators offer (i'm guessing differing amp simulators and such), do you know of the best affordable one please? Cheers.
@@MahatmaLevolence I wish I had better advice, but I have absolutely no clue which one to recommend if you want a ready-made solution. I did see some other cheap ones that were equally questionable.
@@netman69 Okay. Thanks for replying.
My amp combo speaker's is 4 ohm but have set amp swich on 8 ohm so which input do i use 4ohm 8ohm
16ohm
The 8 ohm input probably, the amp would be expecting an 8 ohm load with the 8 ohm setting :).
In case of a mismatch: You need to have a bigger resistance reading in the speaker than in the amp. Otherwise the amp may receive damage.
@@jaakkokunnas amps are quite tolerant of such mismatch luckily, even like 50% low or high does not mean disaster. It's indeed better to have a too high speaker impedance, then the valves won't see an excessive load but i wouldn't worry too much as long as its somewhat close.
Could this handle a 120 watt solid state amp?
Maybe... Officially it can't because it's outside it's ratings and there is a real chance you'd burn the thing out but with a solid state the amp itself should be fine, so if you're willing to risk the attenuator you could try and find out. I know mine survived a fair bit more than it's rated for, but I didn't push it for a long time.
I have 6505 amp 120w can i use this attenuator ?
I sadly don't have anything better than "maybe" and "it depends". If you have a master volume on that amp, turning it down just a bit would be enough to not overload it and the LED will light up if you're giving it too much beans but depending on how well the master volume is implemented that kinda defeats the point of using an attenuator.
That said i **think** it would survive the full 120w just fine, but it's only specified for taking 100w so there really isn't a guarantee, especially in the long run. I've given it hot supper like that before so i know for sure it doesn't instantly kill the attenuator but if you do burn out the resistors be aware that could be detrimental to the amplifier also (to the output valves in particular, but maybe even the output transformer).
In short though: you'd probably be fine, i've pushed my particular unit with 120w amps before, but I really can't recommend doing that.
@Nicko Lps What you're saying is correct and if you want to play it 100% safe you indeed shouldn't, but I think their rating is generous enough to be intepreted as "it'll do a 100w amp". The resistors in it are derated 50% and the fan does a reasonable enough job of keeping them cool, unless you overload them absolutely massively the limit with resistors is entirely thermal.
@Nicko Lps Also people don't tend to know what's in their attenuator, I can only speak for this particular Harley Benton one in particular, and even this one had an older version without a fan yet the same resistors (and the Bugera PS1 appears to be the same idea), those might not survive at all yet they carry the same rating on the label. Which is to say, if all you know is "100w attenuator", you should absolutely abide by what Weber suggested if to not get burnt xD.
And even if you understand all, de-rating devices like this is always a good idea, but unless you're willing to spend literally 10x as much or build your own attenuator, all you can find is ~100w rated attenuators, hence the discussion we're having does have value.
Having said that I found out HB now sells a 250w attenuator (for 150ish euros) because I was fact checking myself on that "spend literally 10x as much" claim, so apparently i lied :D... Interesting. If OP is still reading, it may provide more peace of mind having one of those for a 6505, but I have no clue if it's any good personally.
@Nicko Lps Jeez, I'd expect better from dr-z! They weren't tubular rheostats though where they? Ohmite do have those, and they look like this: sc04.alicdn.com/kf/HTB1BUVFaa1s3KVjSZFAq6x_ZXXaD.jpg
The OT and output valves do suffer a bit more with a speaker than a resistor, but I doubt it really matters to the point where you have to hold back without an attenuator really... Valves may perish sooner if you go hard but I ain't ever heard of someone blowing out their OT because they were too metal for it xD. The audio world is full of superstition and myth.
@Nicko Lps Yeah, the youtube regime is not one of free speech xD I've searched and found pics of a Dr-Z brake lite internally that look like what we're talking about, and believe it or not I think it's Ohmite removing the epoxy, not Dr-Z, although i haven't ever seen a rheostat like that with multiple taps on it, see this: www.ohmite.com/assets/docs/res_210.pdf?r=false
The price of them seems excessive though!
Any thoughts on a possible bright switch mod? I saw one in this video.
th-cam.com/video/VbD0plXyzo8/w-d-xo.html
I haven't noticed treble being a problem with PA-100, unless the amp is whisper quiet, Fletcher Munson and all that. I'm loving the PA-100, I did your 2 mods :) thanks.
I also have to keep the box away from the amp's transformers when using MicMod, otherwise there's a massive constant buzz.
This is definitely one of my better acquisitions, a great product with the mods.
Whether a bright switch makes any sense at all probably depends on the cabinet you're connecting to, definitely can't say I've felt the need for something like that myself. If you do add one be sure to use non-polarized electrolytic caps or film caps if you can find them in a big enough value (the typical polarized ones would be destroyed in a hurry xD).
I bet the little transformer in the Micmod circuit is what's picking up the buzz from the transfomer, in addition to distance rotating the attenuator 45/90 degrees could help a lot (if you ever wonder why most valve amps have the ouput transformer rotated differently than the power transformer, they do this to reduce magnetic coupling between the two).
Also might be worth double checking both parts of the case of the attenuator are properly grounded (as in connected electrically to the outside of the connectors), and if not strategically scrape some paint away so they make connection. The case not being grounded would allow way much noise to be picked up.
Wow even the knobs sound like trash when you turn them.
You get what you pay for.
Trash….
I just returned mine
Well at the price it's amazing you get an attenuator at all I think. The big knob has some excuse to feel weird being a high power wirewound potentiometer, they often feel like that but I'm sure it can be done better if you pay through the nose :D.
@@netman69 The wirewound potentiometer is perfectly allright, it doesn't look, feel, or sound a bit different from the one in my 1970's high quality iron