Is this the best Preamp kit EVER?
ฝัง
- เผยแพร่เมื่อ 17 ต.ค. 2024
- I take a look at a preamp, VERY loosely based on part of the Accuphase C-3850. Available as a blank PCB, full kit or a finished assembled unit.
Lots of tests, lots of details and of course, lots of chat.
NOTE THIS IS NOT SPONSERED OR SUPPLIED FREE. I PAID FOR THIS WITH MY OWN MONEY.
Well, it is now back in stock even from the store I purchased it.
However, it WAS in stock at- www.ebay.com/i...
And at- www.ebay.com/i...
And- www.ebay.com/i...
And a bare board at- www.ebay.com/i...
At suitably inflated prices, of course...
Although this one is not too bad- www.ebay.com/i...
Follow up video here, different transistors, chip, and audiophile components. Will it make any difference??
th-cam.com/video/RajfMVcgTEg/w-d-xo.htmlsi=t4zUORcqHnE5SGBh
Thanks for the great video, and thanks so much fo the kind mentions.
I was more than happy to assist and thank you for recommending this board in the first place, I really like it.
I am using my C-3850 kit board to drive modified L12-2 power amp boards.
In listening tests so far I have been extremely pleased with this combination.🙂
To answer the question about the mix of op amp and BJTs- it is because the combination improves the slew rate and greatly reduces the output impedance, all while using the high gain of the op amp to help lower distortion.
BTW, I am running an LME49720 op amp (same as the LM4562) in my board and it improved the slew rate significantly over the NE5532.
Love this preamp board..!
Please continue making your videos sir. 😀
Somebody has the right idea how hearing and audio works.
@@VEC7ORlt It is all about timbre and how waveforms add up.
I have been running an LM4562-based preamp in my system for years which has been very good, and yet I noticed a definite improvement in clarity and detail using this cheap preamp. Amazingly.
As for what we can or cannot hear, while it is true that one cannot hear steady tones above a certain frequency, we definitely CAN discern sharp rises and falls even as we get older.
Cymbal crashes, tambourines, snare drum hits and so forth are prime examples of such sources.
I listen primarily through decent headphones, not speakers, and totally agree that no affordable (and probably not any) speakers can reproduce super high slew rates.
Fun fact- People can indeed detect tiny shifts in phase or timing emanating from point sources.
We do it all the time because we perceive the positions of sound sources relative to us.
The timing differences to our ears can be on the order of a few microseconds, and yet we all posess that ability.
Of course this is assuming that one's hearing is not severely impared in some manner.
In the end, it is up to individual listeners to decide what suits their listening tastes the best, and who cares what anyone else thinks?
Everyone is different. 🙂
But yes, "Accuphase" is just a rather cheezy marketing term.
And I also doubt that these boards are particularly faithful to the original design.
However with all that being said, I love the sound of this board and for the price it is very hard to beat.
@@ronschauer839 all that wall of text immediately goes out the window the moment anyone asks to demonstrate said audibility in a blind test.
And stop it already with needing more and more slew rate - you're ears are band limited and that puts a hard limit on the max slew rate - they are directly related, and I haven't heard of audiologists testing beyond 20kHz.
nice to see the channel is still going and to see your looking well
Thanks Gary, good to see you here again, aways most welcome.
Terrific to see another totally entertaining video Michael. Yes, I jumped on AliExpress and got me a kit & looking forwards to slotting it in.
My experience with these cheap kits are very good despite them looking "Cheap". Nothing is stopping you from putting in better parts in key areas down the track.
Hope there's more to come.
Lowering the gain makes tons of sense for me. The main reason I like to use a pre-amp is to attenuate down the signal before the amp so that I can keep the digital signal from the DAC at full volume. I always find this sounds the best. If you turn the volume down or the PC or phone, you are sacrificing some of that valuable dynamic range that is possible from the digital source. Everything he says about the pot position is also really important to me.
@8:14 - No need to apologize for being human my friend. Just keep up the good work.
Hello @MichaelBeeny and @ronschauer839, I would like to give you some feedback on the problem of the anomalous square wave when using a potentiometer at the preamplifier input. As both of you suggested the responsible was the input capacitor. I removed them on both channels, and now the square wave anomaly is gone! I tested at various frequencies, and I tested various signal levels using the potentiometer I had inserted at the input. This no longer has the negative effect on the square wave shape, even at 50Khz. Since the circuit is very quiet and does not pick up RF noise, I think I will leave it without the capacitor, as Ron suggested. Thanks again to both of you for helping me solve the problem!
Lovely to see you back, Mr Beeny. I was so impressed, I've ordered the made up pre amp in a case. £130 inclusive of shipping and tax. A decent case can cost £50+ , so it's a bargain. Hope to see more of you.
Mr. Beeny Iam very happy that you are making a video again about diy audio....
I’m delighted to see you back on! I always learn so much from your videos.
Thankyou Ryan, good to see you back and still with me.
Nice! And good follow-up video.
I am considering it for a dedicated headphone amp. Two questions, please.
(1) How much voltage can it churn (maximum/all things considered) to be usable as a headphone amp?
(2) The onboard power supply capacitors: Can it benefit with replacement capacitors (of larger capacitance, within reason of course) when used as a headphone amp?
Thanks.
I think all the answers are here, but the short answer is nothing needs to be changed but best watch the video anyway. A few things are explained.
th-cam.com/video/3LOAwXjhMcQ/w-d-xo.htmlsi=1K3BcYLlFm_4EYwD
The fact you have > 3x the number of views as subscribers tell me TH-cam grabbed hold of this one, and is promoting it.
I'm really glad they did, because I'm looking at preamps for a hifi home amplifier project.
It is so nice to see you making the video, you're so calm and 'Mister Rogers' persona . Love your analysis and commentary on the product
It's a pleasure to watch your videos. Nice to see you back.
Love your explanation on square wave and slew rate. I do enjoy your pace of speaking, I'm non native English speaking and feel like I listen to an audio book narration.
I do understand that many of my viewers are not native English speakers. I'm always amazed, I do have viewers from all over the world which I value so much. I do try to keep to "The Queens/Kings" English as much as possible and not use wording that is unique to the UK. Thanks for your kind words.
Мы рады за вас что вы вернулись! У вас отлично получается рассказывать и показывать! Ждем от вас новых проектов! Всего вам доброго!
Hi Michael ! Greetings from Poland, I am very glad you're back on You Tube. I am one of those guys who made L12-2 power amplifier based on your suggestions. So now it would be fine to add a matching preamp to it. Wish you a good health!
It does work well with the L12/2 but you might find the gain a little high. If you find it so, replace the 100 ohm resister, shown in the video to 470 ohms. This will reduce the gain from 14dB to 6dB
Glad to see you back. Great work sir
Hello Michael, nice to see you, I hope you are doing well. This looks like a pretty amazing pre amp, there is even one available with an input selector on Ali express. I will probably be building that one. I find it hard to find a decent volume potentiometer though. Thanks for testing it, the square wave is indeed a very relevant measuring standard.
Really enjoyed your video, glad that the algorithm sent it to me
Thank you for your kind words, much appreciated.
Nicely done. I was just looking for another good preamp. I'm glad I subscribed and turned on notifications. Thank you for saving me time, and effort, and providing so much practical information. It is appreciated.
TH-cam recommended your video immediately! 15 minutes after you posted it :). I am subscribed, of course!
Well, my friend you did say the magic words. You are a subscriber. To which I thank you.
Same here. 🙂
Same here 😎
Great for a great video Michael! I recently built this and its very good but here's my thoughts. Firstly, just because something measures well doesn't mean that it will sound good, there are too many factors including your ears, the rest of your kit and your room. This pre amp does have its own sound signature or colouration if you like. It has a lot of weight in the lower frequencies so if your system is already bass heavy then better off avoiding this. What's missing from Michaels assessment is how this sounds in a well put together and revealing system. My assessment is that for the price it sounds far better than the price would suggest so its very good but not the best pre amp I've ever heard. I pitched it against my upgraded Assemblage L1 Valve hybrid pre amp and although it comes close it doesn't quite match it in a few areas, the most notable being the lack of airiness and clarity/detail around voices. However, given that the L1 is about 30 times the price you have to say that even getting close is quite astonishing :)
Hello Michael, this is Michael from Germany. Great video, I subscribed to your channel immediately. And, since I'm not a native English speaker, I really appreciate your slow and clear pronunciation - terrific. Your videos could also be used as English courses. Many greetings from Germany - Michael
p.s.
And to all the "UNBELIEVERS" - to the statement that we don't hear a square wave signal "when we listen to music". That's not really true. 🤣
According to Fourier analysis, a square wave turns out to be a sinusoidal fundamental wave with harmonics, see Fourier series # square wave pulse
Thank you for your kind words, much appreciated.
Thanks Michael, so lovely to see one of yours video again. Hope all is well, it looks so.
I would prefer a preamp amplifying from 200 mV to 2 Vrms, that's 20 dB, but we're all different.
I think you have shown it before, haven't you? It still very good!
Peaople shuld know that a squere contains all freqvences! Showing a perfect 300 kHz is very rare. The fun is the output is better than the input!
Keep up the good work a stay healty!
It was recommended to me as well, and I'm thrilled it did (I subscribed right after watching it).
Thanks for the time & thoughtful work you've put in on your videos. I imagine I have several to catch up on.
Cheers!
I have 198 for you to watch. Two or three are actually quite good lol
@@MichaelBeeny haha!
Thank you my friend. I've purchesed a kit already asambled. 2 scenarios. Headphone amplifier & universal preamp.
It is now back in stock even from the store I purchased mine from.
Also available from these stores.
www.ebay.com/itm/134650296053
And at- www.ebay.com/itm/134719323800
And- www.ebay.com/itm/126011222570
And a bare board at- www.ebay.com/itm/166235656448
At suitably inflated prices, of course...
Although this one is not too bad- www.ebay.com/itm/186461148803
@@CarlVanDoren61 Yes, many DACs do have a low output impedance with a highish output. You can indeed drive many amplifiers directly. In fact, I have done just that myself.
I bought pcb only at 5 usd from a ebay seller.
@@hmjeon8609 Sounds like a great deal. Watch my follow up video before you populate the board.
Young man, I thank you so much for all the time and effort that you have put into this video. Simply put, you are the best. Your presentation style and manner are second to none. I, like you, have been in this business for quite some time but I learn something every time I watch you. Again, thank you, be well and hope to see more of you. p.s. I am going to get this kit!
Indeed! Having built a similar kit that contained relays for switching inputs, I agree with your comments. Another kit to consider is the "MBL based" with ne5534 or ad797.
This is my first time with your channel, I'm rather impressed so far. I found it much easier to follow your explanations and demonstrations than I do with most other TH-cam content creators. You aren't stuffing information at such a rate so as to require frequent pauses to take in what was just said, or trying to pause on just the right frame to see an oscilloscope display or schematic. I can follow you more easily while paying more attention to details and I don't feel like I'm in an EE cram session.
Learning about using square waves to check the frequency response will very useful. Considering how the square wave consists of the sum of odd harmonics, that makes a lot of sense to me and I'm interested to try it on my own equipment when I again get access to it. I have a sense of foreboding about how my equipment will fare when testing the square wave over 50 kHz. Oh well, this is how one learns!
Thank you
Thank you for your kind words, most appreciated, but most all "welcome"
@@MichaelBeeny I feel very similar - watch a few youtube channels about electronics and sound reproduction , but your video is like a caress in the "wilderness" ;-) Thank you very much and greetings from Czech.
@@jackgrey3340 I'm very pleased you liked my video, thank you for your kind words.
You do a great job explaining and demonstrating. Thank sir.
Thankyou cshis your comments are most appreciated.
Nice to see you again. Very informative.
Thankyou Robert, welcome back.
The square wave looks really good. I may try this pre-amp as well
Well at least you will not need to sell a body organ to pay for it. lol
@@MichaelBeeny I found it on AliExpress cost only £6.50
Bless you! Thank you for the video, and the how the board measured🙂
I've built a few things from Chinese kits/PCBs - phono pre-amp, headphone amp, power suppliers... and they've all been excellent. And yes, that square wave response is astonishing!
Great video. Matching gain to your poweramp for best pot position is really important. Not just for sensitivity and range, but (in this case) your input impedance changes as the pot is turned. I much prefer a buffer between input and the volume pot to negate any issue with impedance and any possible DC going through the pot which causes noise.
I've tried a few transistor preamp circuits, they can be hit and miss. Output impedance is often an issue when the poweramp has
Please report back once you have it working and had a good listen. I would be most surprised if you don't like it.
Thank you Mike for another brilliant informative Video. I built the 3850A preamplifier with the 3 input switching relays. Combined with the Twin TDA 7293 Amplifier it's IMOA a superb combination, just only slightly better than the 3850A-L12-2 combination. Combined with TDL studio 1M speakers and using a demonstration quality CD ( Mahler 3 LPO track 1 klaus tennstedt !!! )
I remember TDL speakers from when they first started. I used to sell them in my shop in Cambridge.
@@MichaelBeeny The smallest real model they made before the company went insolvent and the name got sold on
@@max79444 Sadly Max the way a number of good British company's end up.
I have bought several of these and the are kit, unassembled, and they go very well, and the price is ridiculous, I have tried changing operational and some change is noticeable, but it is almost better that brings (less distortion), although the sound in audio is something special, and not always sounds better which has better measures.🤗
Thanks, Michael! Beautiful performance! I’m interested in the headphones application of this.
We are testing this right now. Hope to upload a video very soon with the details.
I have bought the board already. This video really stimulate me to build it. Just one question though. Do you need to use a 50k volume pot or can you use other value and which is most suited? Thanks for the great review 👍
The 50k pot is what my measurements were taken with. A 100K pot will give slightly reduced HF. A possible 25K pot will give a better HF response. These observations are at 50% rotation of the pot. The difference is well above 20khz and only a fraction of a dB.
@@MichaelBeeny thanks 👍🙏 great help
I live in the US, purchased a fully assembled board through eBay for $22.85. It took three weeks to receive it, just got it today 9/11/24. In the near future I'm going to test it as soon as I finish my electronics work bench.
THANKS FOR YOUR VIDEO, I LIKED TO SEE YOU AND YOUR'S VIDEOS, IF POSSIBLE THEN PLESES KEEP UPLOADING
Great video. I plan to buy premade although I have the components in stock. The extra cost is nominal.
TH-cam suggested the video!
Good video. Just a couple of things to add; what you say is the slew limit is only partly true. It is a combination of slew limit and bandwidth. The difference that makes one or the other dominant is amplitude but you didn't (I think) make that variable known, but I could be wrong so my apologies if that is the case. My other point is about bandwidth and the ability of the amplifier to handle frequencies beyond 20kHz. I am, like you, maybe a bit older and maybe we don't quite reach the 20kHz human limit these days but the issue with an amplifier not coping with a wide enough bandwidth is not the bandwidth limit as such, it is more about what happens to that high frequency energy. If the end result is an interference with frequencies that are audible is when issues arise. If the inaudible frequencies do not develop sub harmonics or inter modulation products then there is no problem.
The only way to do that filtering with best effect is at the input. If the amp circuits have to carry the out of band signals that is when they interfere with the in band signals and distortion results.
I also know what you mean about the sharpness of a bass drum. A bass drum does make a surprisingly sharp whack sound which you and I are less and less aware of as our wisdom increases ;) But the 'younger folk' don't hear anything much beyond 20kHz and if there is any energy beyond 20kHz it is only ever heard by a human if it effects signals within our hearing range.
The low frequency response I also noted had a slight overshoot which suggests there is a slight peak in the frequency response curve at the low end which is consistent with the capacitors used to separate the DC and AC characteristics of the stages of the amplifier. (DC bias and AC gain.)
What surprises me though, is the fact that it is stable and has a flat response characteristic given that there is no compensation network around the op amp. The data sheet offers no information about phase and gain margins so nothing to go on, it just seems odd.
I agree with your use of square waves. I say you should ignore the critics on that score. I would think standard sine wave stuff is also good to see and if you could do an inter modulation distortion test that would be the most telling of all tests. Does your CRO have an FFT function? If not, you need a sponsor. I can't help you with that in any way other than I hope you succeed.
Keep up the good work, demonstrating how things work. and thanks for sharing.
Greetings from a former NZ resident. I owned an NZ made Craft setup consisting of a phonograph preamp, a preamp (which auto-selected the input to use), and a power-amp. Power-amp finally gave up.
As i understand the person behind the Craft products went on to join Plinius - another NZ Hifi brand, but out of my league price-wise.
Impressive that NZ can produce world class hifi kit - often a fickle and unforgiving area to do business.
Hi John. Someone once told me. How do you make 1million dollars making HiFi in NZ?
Answer, Spend $2m. I've been in NZ 22 years now and never seen ANY HiFi from NZ
Lovely very very lovely! What a nice fellow you are: and I really enjoyed your presentation! T😅hank you.
Thank you, most appreciated.
Hi Michael. Thanks for this video. I have bought this pre in intend to use it as a mic 2 channels pre. I had to made some mods to increase the gain. I use it with OEP X187B mic input transformers. I'd be glad to share with you the modifications schematic I did and get your opinion on them because I could maybe increase the final quality by exchanging with you. As it is now, it delivers great gain and a clean sound but I don't have any oscilloscope or sinewave generator to analyse that... Best Regards from France
YT recommended your video to me - thanks!
Hi Michael, I have assembled one of the kits and have been doing some experimenting. I changed the 100 ohm gain resistor to a 510 ohm resistor and the 100pf input capacitor to a 27pf (dipped mica) cap per your suggestion. I've changed the op amp to various chips including the LME97420, OPA2134, OPA2604 and OPA1612 (these are chips I had in my parts box). I added a 47mF non-polarized cap in each output but still experimenting with other values. I did this as I'm using this preamp as a headphone amp and was concerned about DC voltage being on the output if there was a component failure. The I.E.M. used in testing was the CCA CRA. Again, thank you for introducing us to this preamp.
I have never tried an AD828, mainly because you do need a conversion board. Incidentally the LME49720 is 100% the same as the LM4562 just cost a lot more.
@@MichaelBeeny I already had the LME39720 in my parts box. Take Care!
I was doing some listening tests and placed my finger on the AD828 IC and had to remove it after about 15 seconds due to heat, the chip was running hot. Possibly due to high frequency oscillation. Anyway, forget about using the AD828 with this circuit. I've gone back to one of the tried and true ICs mentioned previously.
@@JBBrown-hh4rc The finger test is perfect, if you get a burned finger, something is wrong. As you said, probably unstable or oscillation. Either way, not good.
You claim TH-cam doesn’t recommend your channel …. Well …. I don’t want to shock you too much, but it certainly recommended you to ME 🎉🎉
An interesting analysis/review of this preamp. I was surprised you didn’t qualify the use of a square wave to demonstrate good performance on basis of the spectral content associated with generating a true square wave!! However, I do think you explained the overall importance and advantages of looking at square wave response to good effect.
I just wish I had a good application for this circuit 🤔
I think TH-cam has noticed me at last, only took 8 years lol. It's very hard to know what content to use. My viewers range in tech ability considerably. I try not to talk about the obvious or to get into deep technicalities. I try to sale along the middle if I can. Too far either way gets me loads of time-consuming e mail. Do you know I spend over 2 hours a day just answering comments and e mails!
Maybe I will soon make a video on something you simply cannot exist without.
It's easy to build a wideband audio amplifier, but you don't want it that wide. It will amplify all sorts of unwanted out of band signals and increase the noise floor.
Ordered two yesterday. I enjoyed your previous videos and Thanks Much for this video. I'm going to power one using a transformer and the other using lithium-ion 18650 batteries.
Thankyou JB for your kind words. Hope your project goes well.
Very impressive audio pre-amp and I would definitely have built it in my earlier days.
One comment on your scope demonstration; for visual comparison, it would be nice to match the amplitude displayed and then overlaid the traces. Hardly necessary, but it would also show that the sign gen is beginning to loose 'squareness' at the upper end of your demo.
Simple and informative demonstration, thanks so much! 👍
Btw, I did subscribe and like 😁
You are never too old to build. It just takes a little longer lol
where did you find the schematic?
how to wire up the pot.
in another video of yours, you talk about a input cap, how to put it in? in serie on the plus, or between plys and minus ?
Nice to see you active again!
Solved the problem of the square wave distortion (thanks to Michael & Ron !) due to the potentiometer that I had inserted on the preamplifier input, solved eliminating filter capacitors on the preamplifier input, now I have this doubt: since many final amplifiers are also susceptible to having a modification of their characteristics e.g. frequency response if we put a level adjustment potentiometer on the input, what is the best solution, or the best positioning of the regolator if we want to adjust the input volume of our final amplifier? I know that from your videos the suggestion is to use a buffer preamplifier, but how to position it in relation to the potentiometer? and finally, do you have any type of buffer card to recommend? and is the C-3850 useful for this purpose? I suppose all this can be useful for many of us …
Excellent tutorial.
Very informative and understandable.
Thank you 👍🏼👍🏼
Thank you Michael, nice to see your video today!
Thankyou Robert, most appreciated.
nice to see you looking good!
Great video Michael! Thanks! Would you be interested in making a follow-up video, extending this preamp into a headphones amp?
It already is just that. th-cam.com/video/3LOAwXjhMcQ/w-d-xo.htmlsi=s3A-RYluuvaHW3lF
Thank you Michael👍
Hello from India. You have already reviewed another version of c3850 board years ago. Which one you prefer, old one or this one.
The board looks nice indeed.
I have now bought the preamp and am waiting for delivery. It will be used as a headphone amplifier. I will report on the results!
I built a Naim clone preamp and it sounds fantastic. Not all kits are bad.
The Naim pre is excellent.
Which one? NAC 52, NAC 152, other?
@@yellow_noise3 The 152 boards powered with the hicap clone
Micheal…I’m going to change the 100r and the 100pf. There are 2 sets. So, 2x100r and 2x100pf. Do you change each set out? Thnx! Greta content…
Yes, one set for each channel.
Good explanation, i build high end amps for musicians, and found the explanation for the square wave interesting, but i suppose if you don't cause high amount of db gain on the output to drive the intent source amplifier, but saying that the intent source has to match the frequency response that pre amps gives, the harder you drive the source the more frequency response changes.
Are the two resistors you mention to change the gains, the two that are printed on the board as 100R?
Yes, they are shown on one of the videos.
The low offset is impressive!
A bit surprised that an SMD version is not out ther,e, ...or is there?
Not to my knowledge. Using SMD parts would probably put many home constructors off buying the kit. Parts too small and fiddly. What would you gain any way?
@@MichaelBeeny I meant fully built only. It would be cheaper to sell as it's main benefit.
Been looking for a good preamp, thanks for the nice video !
Interest way to look at an amplifier's response. Have to start looking at some of my little amps with a different light.
If you're after some small 1 watt amps for test gear have a look at the TDA7231A. I quite like using them, simple to build and they are cheap from Uncle Ali. IKf it gets a bit warm you attach a tiny 9mm square heat sinks to it.
Thanks Michael.
Dear Sir, thank you sincerely for the always extremely valuable video I am learning a lot from them Really an impressive kit that i am going to purchase hoping to be able to solder it properly
I have a basic question Clearly the circuit is extremely transparent
There is a lot of discussion going on about volume potentiometers quality and how this impact on the overal performance The pot you have used appears to be just perfect while not looking very expensive Which brand and model is ? it seems to pass the signal completely pure
Just attenuated as it should
Thank you very much again and kind regards gino
FWIW, I am very partial to the ALPS RK27 series and have had very good luck with them.
But be sure to buy genuine ALPS parts, not knockoffs.
The reason for the two respopnse graphs in the video, one with the kit's 100pF input capacitors and one with 47pF capacitors, was to illustrate the differences in frequency response at 100% and 50% (true) volume settings using a typical 50K volume control.
Because of the input filter capacitance there IS a measurable difference at those two volume control settings, and it can be quite severe on some other preamp designs (fortunately not so much on this one).
Regardless, the R/C time constant changes as you change the control percentage.
Some people can hear it, some can't.
@@ronschauer839 hi thank you for the very kind and valuable advice
I heard about fake copies of famous brands parts
Price should be telling when it's too low
I have always in mind the rule that a chain is weak as its weakest link
For sure the preamp circuit is not the weak link
It's so impressive that really deserves a good pot in front of it
Thanks a lot again
Kindest regards Gino
@@ronschauer839 Thanks Ron, I was going to say almost the same thing lol
I enjoyed this video, thanks 🙂 Think I will be buying one for myself, a kit.
A new C-3850 runs $43K. Fully assembled units on Aliexpress sell for $150, shipping included.
Hi Michel, is the preamp voltage feedback or current feedback. I hope the second one.
Thanks
Joost Kist
Unusually it has both current and voltage NFB.
Interesting, thanks.
Thank you Michael. This is a great video which I appreciate. From across the Tasman
I appreciate you watching, welcome.
Best quality products my friend ❤❤
I have the preamp now to be used as a headphone amplifier for AKG701 120 ohm headphones. I have not yet made any changes. I will build the power supply this weekend. Initial operation with a couple of 9V batteries is VERY positive!
I'm slightly puzzled by your comment that you will build the power supply this weekend?? The power supply is already on the board. All you need to do is add a transformer. Or am I missing something? It is early in the morning here in NZ
Great to see you make videos again Michael 👍.
Is it possible to publish the layout of the circuit?
Can you use a 100k pot or is 50k the best option? Thanks for your help
You could indeed use a 100K pot, but at mid rotation it does make the HF roll off a little more. You can measure the difference on a simulator program, will you really hear a difference? possibly not. I might address this on a future video.
Great numbers on the bench. How does it perform at the output if the source has a small amount of DC-offset?
Well, you must be sure you have no DC, even 1 mV. If there is any doubt you must fit a capacitor to the input and for safety, the output. Many amplifiers have cap in its input but if you have any doubt put one. I suggest a Bi Polar audio grade 47mfd. Any other type would be very large and expensive. Any lower value will reduce the LF performance, partially the output because of its low impedance.
It's good to have someone really know what happen with all these electronic components, I have owned a Fostex HP-A3 DAC/preamp matched with a Class D Audio SDS-470C power amplifier that I have listened for years, strange that I prefer the smooth "tube' rolling sound produced when power run through a pair of Wharfedale Denton 80th speakers, while it does not sound that relaxed when driven with a Purfi Eigentakt amplifier board instead...Do you think you can figure out what's the Class D Audio SDS-470C do? One thing for sure is it run very hot so much so that I have to keep the cover open and put some coins, seem like a "Class A" issue?
Hello , is this model better then the model of 3 years ago . Thanks Bart
I don't think so, this one is slightly different and does not have the relay option. I had completely forgotten the other one, long since sold.
I am VERY interested in a top quality headphone amplifier. With these specifications, it could be VERY special!
I'm personally not a headphone listener. I will ask Ron (he is) to give it a good listen with any mods needed to use it with a pair of cans. What impedance cans do you use?
@@MichaelBeeny AKG 701, 62 ohms
@@Rowuk2024 He's working on it as I type this message. The results will be quite detailed in the follow up video.
25:53 Note to the younger viewers, about the use of the dB scale. Michael seems to be looking at 0 on the dBm scale. It doesn't look like that to the TH-cam viewership, it seems a smidge to the right. This is a parallax error as evidenced by the reflection on the backscale mirror. You need to line the pointer so it covers the mirror reflection of the pointer to take the reading. Obviously Michael is doing that with his eye but the camera is a bit to the right of centre.
100% correct Roger. When, as in this case, we are talking such small changes, it is quite hard to keep things lined up. The view finders on small LED displays are very difficult to see. Thats why I tend to read out the numbers also. I forget younger viewers possibly have never seen such a meter. For this application its far better than digital meters.
You really need a Spectrum Analyzer to have the dynamic range to see the noise floor, and the harmonic levels of the distortion involved. For IM distortion, a two-tone input is required. In my experience, this can be the harshest distortion to the ear. I'm sure this unit would fare well. Cheers, --bd
If you would like to send me the money, I would love to use it. I make little money on TH-cam. It would never warrant the investment. I'm retired, on a pension.
One of my viewers has made THD tests as follows THD 0.0026% THD + Noise 0.015% not too shabby. lol
Great video Michael. Now I have respect for square waves because I understand their correlation to slew rate. I just wonder if adding a tube buffer say a single 12AU7 would you know kinda give sweat to the sound. I normally use tube preamps on solid state amps.
Adding a 12AU7 will remove all the detail, bandwidth and harmonics present in the original signal and add harmonics to the signal (distortion) not originally present. Leave the valves in the 50s. Things have moved on, mostly for the better.
Valve amps remove detail mostly because of lack of speed. A solid-state amplifier has a much faster speed. Result is that really good recording sounds amazing but on the negative side, a bad recording can sound worse as it makes the distortion clearer, if that makes sense. A valve amplifier makes most recordings sound fair, the so called sweat or warm sound. It's your choice if you want an accurate sound, warts and all, or a NICE sound.
@@MichaelBeeny Hi Michael. I get the importance of speed but here's the question:
We can all agree that vintage vinyl pressings, the monos of Beatles for instance are unmatched in realism, many pressings of the valve era are still sought after for their natural analog purity.
This was the time when all the studios were using valves exclusively. How do you explain this contradiction?
@@sonusancti What we don't know and can NEVER know what the recoding's would have sounded like with modern ICs. From the 70s onward most, mixing disks were full of 5532/4, not a valve in site.
I think the main issues today are the really poor quality of many modern recordings. Lack of dynamic range, over modulated and clipped levels all to make it sound better on cheap nasty equipment and dreadful MP3 players. Ohh dear, maybe I should get a valve amplifier. lol
@@MichaelBeeny Hello Michael. The logical challenge would then be to simulate the sound of the vintage mono pressing with a pure solid state mono pressking with the best recording engineers and compare.
This is why I opted for a hybrid tube preamp with FET power amp. I'm even using a TPA3255 class D right now.
Thank you very much, very interesting! 👍
TH-cam recommended your video - maybe because I watch several HiFi channels.
Best regards from Germany! 🍀
Mostly all of the dacs built in last two decades have low impedance outputs. If I don't have impedance matching problems, why should I use a preamp?
I agree 100%. This is just a presentation for those that need it. Even today, some amplifiers are quite in sensitive and do need a preamp, this one works.
What's the noise floor?
Attach it to a network analyzer and lets see the frequency and phase response plots at different signal levels.
thanks you! very informative! I would like to have this preamp, I never had one or thought I need one.
Maybe you don't need one. Depends on what you are feeding into it. You could use it on the lowest gain as a buffer. Some DACs have a built-in volume pot and a low output impedance already.
Hi Michael, your test of the C3850 preamp impressed me so I bought a kit from your same seller to be sure to have the same product. I assembled the components and placed a potentiometer on the input to adjust the volume. I had a 20k linear available so I temporarily used that. I did some tests with oscilloscope (the same that you used) and frequency generator to see if my model had the same characteristics as the one you tested. I was surprised that mine has a different behavior on the square wave, already at 20Khz the wave is visibly deformed with inclined rising and falling edges and rounded edges. The defect gets significantly worse by increasing the frequency. At 100Khz the rising edge is completely rounded. The result is greatly different from yours. I strongly suspect that the 5532 chip in my kit is a fake.. I will now test the chip with the multimeter using the technique you described above and let you know. If you would like to receive photos of the oscilloscope during the tests, let me know how I can send them to you. Greetings from Italy and thanks for the work you do!
I'm so sorry your kit is not performing well. Please do send me photos. This is the first negative results I have seen so far. Both Ron and I compared our boards with each other before making the video and not surprisingly very much the same results. I guess the 5532 could be fake but our boards tested OK. Are both channels the same? Try to include good pictures of the top of the board if you can.
regards,
Mike
One thing you may want to try is to change the capacitors at the input. They are 100pF as shipped.
Try changing them to 47pF or even 22pF.
You will not receive radio broadcasts or anything like that, but it will help with the HF response.
Also, try changing the 5532 op amps to LM4562 or LME49720 (same things, different names), or at least be sure that they are genuine 5532's.
LM4562's will greatly increase the slew rate and will therefore improve HF response.
As Mike said, we both experienced the exact same good response waveforms from these boards, independently confirmed using our digital oscilloscopes (different brands and 10,000km separated).
Be careful as well with your scope probes.
Some of them when in either 1X or 10X modes (especially 1X mode) can have surprisingly high capacitances and poor HF response.
Also, some scopes have bandwidth limiter modes.
@@MichaelBeeny done ! let me know if the photos resolution is too low.....
@@ronschauer839 Hi Ron and thanks for the advice. Yes, I mounted the 100pf capacitor, reserving the right to replace it later. The oscilloscope used is the Finirsi1014D which should be the same as Michael's. For the probes, in fact, I used 1x sensitivity... I had also planned to replace the iC with a Ti Opa2134 that I have available, but perhaps I found the problem: I noticed that by varying the level of the input signal with the 20k potentiometer that I put on the input signal, when the potentiometer is at maximum, the square wave is perfect, while reducing the level the wave becomes more and more distorted........ so I think that the problem is all there. If I do the tests with the potentiometer at maximum volume, the response to the square wave is perfectly superimposable to that shown by Michael in the video, in all frequencies, from 20 Hz up to 100Khz...
@@ronschauer839 Thanks Ron, you are being in a different time zone. I've only just gotten up. I have answered much the same, the 100pf cap, gotta be the issue. Or still on max gain.
I was doing some listening tests and placed my finger on the AD828 IC and had to remove it after about 15 seconds due to heat, the chip was running hot. Possibly due to high frequency oscillation. Anyway, forget about using the AD828 with this circuit. I've gone back to one of the tried and true ICs mentioned previously.
Well thank you for this video sir! Do you know if the preamp can be wired with XLR inputs and outputs?
Sorry, not really. It would need to be almost completly re designed. In the domestic world, making it so will really make almost no difference at all.
3:54 I wouldn't agree with that. If it were something like the Graham Slee DAK Novo kit headphone amp which is half the price of the Novo £144 vs £280 and which is an absolute steal even at full price, it would make sense to buy the kit; but a fully working and tested board for $10 extra is a no brainer to me.
So you have proven that this pre-amp is great at the full range of sound people can hear. Great
Impressive flat line there. Do you have its schematic, Or have you come across it in any platform? I'd really like to see.
The circuit diagram is shown in the video, many hours were spent reverse engineering it. Could it be someone did not watch the complete video? lol
Oh Blimey!. My bad.Had thought that the schematic is exclusively for the AccuPhase and not for the kit. Thanks for your reply
Thank you very much. I am just your subscriber now from watching this video.
Thank you, you are very welcome.
Thanks Mike ..Now i need this
Sorry my friend, I think many other will also feel the same.
I am glad that I already received both the full kit and a bare board. I have a feeling that there will be a run on them soon. They really are quite good. 😁@@MichaelBeeny
lovely, thank you sir and love you attitude which made me smile couple times!
Thanks Martin pleased you liked the video.