Excellent advice supported by professional measurements and professional opinion. What more could we ask for. Your videos make me want to build my own amps even though I have limited need for them; you simply make the process so interesting. About 50 years ago I build a kit from Gilbert’s in Albert street Auckland. It had separate volume bass and treble controls for each channel, because I could. Thanks for taking the time to share your knowledge and opinions.
Hi Mike. Great video. I really enjoyed it. Always fun to see you videos. And, always some nice tricks to pick up from you. Hoping for more videos soon 👍✌️
Hi Michael, is it possible for you to show us how to test for amplifier power supply sag, and the effects it has on say... a square wave ? thank you for your videos and sharing your knowledge.
When I listened to this board I thought that it lacked detail and (for lack of a better term) "impact". That is to say that some more subtle background sounds such as tambourines, snare drum and high hat cymbal hits, hand claps and string plucks were either absent or reduced to vague "hissing" sounds. Things generally seemed to be mushed together as well rather than being discernible as individual sources. The Accuphase clone (C-3850) is much better IMHO, and demonstrably measures better as well. As Mike mentioned, I am primarily a headphone listener (for a number of reasons) even though I do have decent speakers. Just to clarify, when using headphones I am still using a power amp stage (L12-2 presently), so the entire audio chain remains in place. If listening listening through speakers in a typical room with all its reverberations and other acoustic effects, you might well not notice any issues at all. And particularly not if you have nothing else to compare this board to. Also as he mentioned, the differences are relatively subtle. They are not "in your face" as would be cranking down a treble control by 20dB or anything of that sort. Therefore I cannot say this board is bad per-se, it just isn't as good as the Accuphase (at 1/4 to 1/3 the price). To be completely transparent, I ordered my board with a 50K volume control. For that reason the "volume control" effects Mike shows measured *considerably* worse on mine. You will definitely want to change out the input bypass capacitors as he showed, then it becomes more or less OK, However, for the much higher price I still would not personally recommend it. The LF353P op amp is used as a DC servo in this circuit, by the way. Its sole purpose is to reduce or eliminate DC offset at the output and it has little or no effect upon the audio quality. It is also the reason for the distorted waveforms at low frequencies despite the design being a straight through DC-coupled design. 🙂
Off topic, but are the PC boards for the Dual TDA 7293 Amp that you tested still available anywhere? I can't seem to find them. I only see a board with three TDA 7293's in parallel for sale on Aliexpess at this time.
Can you experiment with different resistance at the output which simulates different resistance that different amplifiers have at the input, which can affect the preamplifier. Or different resistors at the input of the preamplifier If you connect the oscilloscope directly to the output, the preamplifier does not have the correct resistance? Correct me if I'm misunderstanding this.
What do u recommend? I just need a basic preamp between dac (2 volt fixed) and powerap at 60 watt. Ideally with remote. I prefer and modify over building from scratch.
Michael, you are an inspiration! Love the videos. Keep telling the audio truth. I keep telling people those ne5532 or opa1612 for a few dollars will sound as good or better. (Subjectively and objectively) than $80 discrete boutique pieces.. People don't believe that some equipment doesn't need to cost an arm and a leg to sound good. The old saying a fool in his money is easily parted comes to mind. Keep up the good work young man!
Hi Michael, Whatever noise advantage they had with the FET's is wasted with a 50k pot for a volume control. The FET's were quieter than a 5534, that was the reason for the cascode pair (subbing them for a cheaper generic pair doesn't help either). The preamp as delivered would be about the same noise as just using the LF353 for 10dB of gain. Removing the output transistor pair just lowers the cable capacitance that it can drive... to the point a 353 would do the same. 50k pot at 25% should be about 10nv/Hz 5534 is about 4nv/Hz JRC LF353 are around 17nv/Hz (that's 72dB below 100mv rms output; not bad except at high volumes -20kHz bandwidth) You'll never hear the difference between a 30pf and a 220pf except with a strong AM radio station or CB'er nearby. You cannot hear square wave edges with ridiculous rise times. PERIOD Graphs & specs sell expensive 'add nothing' components to audiophools and line the manufacturers pockets... edit: What you should be able to hear with a really well recorded source: tiny bit of extra noise and slightly more high frequency distortion with a LF353 compared to 5534. Gotta ask the question? Is $40 more worth the difference? NOPE ! Go buy an LM4562 or OPA1612 and ignore this 'kit'. Use a 5k volume pot and you got somethin' worth building... Enjoy the summer, we just got out our gloves and stocking caps in the good ole USA
I "Wholeheartedly" agree with your edited comment! I've built an Accuphase clone, powered by 18650 batteries and tried various audio ICs (chip rollin') and finally settled on the LM4562. This preamp is really all you need.
Hi Jim; kind of wondered what company, but no big deal...I worked as AE at Tek, Agilent, R&S, and r&d for a handset company in Salo, but doing power management... Did a lot of work with Tek RTSA, high-end scopes, TDR, R&S AMIQ, SMIQ, HP ENA, PSA, ESF and R&S oscilloscopes at HQ in DE. Nice noise comments... Most audio folks probably don't think about noise contribution of passives, but RF guys are always down in the dirt 😉
@@JBBrown-hh4rc For $100 you can parallel a half dozen on the + - sides of 100r twisted pair cat6 cable, 500 feet long and still be below .001%thd @ 100kHz. And listen with any lo Z headphones you like! LM4562's are beasts. I have cascaded up to 10 thru state variable filters (Q
@@lohikarhu734 Technical Director of Helper Instruments Company (land mobile radio repair test equipment & 1st gen cell)). Audio Specialties Company (1980), 25 years doin' live sound reinforcement and recording for FUN and profit. Built quite a few 3000 seat systems that studio engineers, band managers, record execs, etc have said things like "these are better than any of our monitors" "best sound we have ever heard" "where did you get those?" "how much to build me a set?" Turned down national acts, I was busy. Component level design DC - GHz, microwatts to 10's of kilowatts. Dozen patents (spread spectrum oscillators). ...retired since '97 Helped start a school for troubled youth; 240 boys graduated, Thank God! I watch, and am as a sparrow alone upon the house top. Psalm 102;7 Bible student, join us at Ebiblefellowship .org
Great video Professor Beeny Just when I think I don't need any more gear, along you come with a tempting board! (I want you to do a Sugden a21a from Ali.)
Many years ago, I was in retail. We did sell the Sugden A21. It was only 12 watts output but was the only class A amplifier we sold. Personally, I did not like it. I thought the sound was weak, compressed, lack any bass power and somewhat under powered. Nothing to do with being class A. In fact later the model was changed to 20watts class A/B. Still did not like it much. We sold quite a few mail order but only a couple through a dem in the shop. Draw your own conclusion from this story.
Why hesitate to review it? I don't expect that every board you review is top notch. Having some boards which are not price/performance interesting is good to know as well.
I do have a number of projects/videos that I have never published. I'm either not happy with the video or I cannot get the points over. One or two are just abandoned the video because it's just c**p. Even my good videos take ALOT of editing lol.
@@MichaelBeeny I think you are a bit hard on yourself. Your videos are always great. Why not make some kind of summary video of the boards which didn't make it to do a proper video?
The preamp will or should work, without that cap. It is part of one pole low pass filter, designed to keep things above the audio band out. We live in a world of stray RF. You just moved the corner frequency up. Change it at your own risk.
I have never found any issue removing or lowering the value. We have an FM repeater just over the horizon. I have never had any issue picking that up. I understand that might be an issue for some people.
Watch out for "Alps" volume pots from China, as quite a lot of them appear to be fake. They're more expensive than the usual cheap pots, but still a fair bit cheaper than the real Alps.
15:41 "If one measures better than the others, then it's better". There are a lot of audiofools with PS Audio products that would disagree with that statement.
Test gear is far more sensitive than the human ear. The test equipment is fact, the ear is very subjective. Sadly however, test gear does not deal in personal preferences.
Hi Michael, Test gear can only synchronize certain frequency at one time and ignore other frequency which may sound bad while human ear has no such limitations. If user only play fixed frequency sine wave as music, than test gear is more accurate to judge the amplifier output quality. Simply put : what you see on the scope is not what you hear ! @@MichaelBeeny
@@MichaelBeeny How a piece of equipment misbehaves from ideal is what different people 'prefer'. Some folks will tolerate noise (and like it because it burries IMD artifacts). Some get their opinion based on visual ques, some know it sounds better if it costs more. Past listening experience and the level of 'educated/trained' ears a person has, largely determines what they can/will discern and accept. The vast majority of audiophiles have never been in an anechoic chamber - they don't have a clue what 3D sound fields in their listening environment add or subtract from the sound. And most have NO idea how dirty most recordings really are compared to the 'live' sound when it was recorded. They cannot, they were NOT there, they are illiterate! (don't judge a book by its cover, till you've been to the printer's shop and read the manuscript) Sadly, the comparison is usually between flaws they are not even aware of... Test equipment provides a completely accurate record of what is actually happening with a signal. Sufficient for the task, of course - not super expensive SOTA gear is necessary either - our ears just ain't that great when you know how they also misbehave (psycho-acoustics). edit: The test equipment is available that is at least an order of magnitude better in any respect than our ears. The expertise is greatly lacking in knowing how to use it effectively. ...and the more money involved, the bigger the bag of deceptions inflates by the unlearned! BS comes naturally, truth is a gift.
So, I made a spelling error. I've known brilliant engineers that cannot solder. Does that diminish them as engineers? Maybe you are on the wrong channel.
Don't be shy, add a comment! The like button does work, but you gotta press it!
That's my father in a cameo role, now sadly deceased.
sir i hope you can also review wuzhi audio ZK-PRO1 preamp... coz i'm planning to buy but i want to see from you if it is good to buy
@@thegrowl8874 Sorry, I have not heard of this preamp.
@@MichaelBeeny it's okay sir... thanks!
Excellent advice supported by professional measurements and professional opinion. What more could we ask for. Your videos make me want to build my own amps even though I have limited need for them; you simply make the process so interesting. About 50 years ago I build a kit from Gilbert’s in Albert street Auckland. It had separate volume bass and treble controls for each channel, because I could. Thanks for taking the time to share your knowledge and opinions.
Thank you for your insight and audio wisdom. Love your videos.
Thank you, much appreciated.
Ditto
Yet another educational and entertaining video michael. Thnx a lot , keep up the great work and take care. Best regards from cold Norway😊
Hi Mike. Great video. I really enjoyed it. Always fun to see you videos. And, always some nice tricks to pick up from you. Hoping for more videos soon 👍✌️
Hi Michael, is it possible for you to show us how to test for amplifier power supply sag, and the effects it has on say... a square wave ?
thank you for your videos and sharing your knowledge.
Great tip about the 220p cap👍
When I listened to this board I thought that it lacked detail and (for lack of a better term) "impact".
That is to say that some more subtle background sounds such as tambourines, snare drum and high hat cymbal hits, hand claps and string plucks were either absent or reduced to vague "hissing" sounds.
Things generally seemed to be mushed together as well rather than being discernible as individual sources.
The Accuphase clone (C-3850) is much better IMHO, and demonstrably measures better as well.
As Mike mentioned, I am primarily a headphone listener (for a number of reasons) even though I do have decent speakers.
Just to clarify, when using headphones I am still using a power amp stage (L12-2 presently), so the entire audio chain remains in place.
If listening listening through speakers in a typical room with all its reverberations and other acoustic effects, you might well not notice any issues at all.
And particularly not if you have nothing else to compare this board to.
Also as he mentioned, the differences are relatively subtle.
They are not "in your face" as would be cranking down a treble control by 20dB or anything of that sort.
Therefore I cannot say this board is bad per-se, it just isn't as good as the Accuphase (at 1/4 to 1/3 the price).
To be completely transparent, I ordered my board with a 50K volume control.
For that reason the "volume control" effects Mike shows measured *considerably* worse on mine.
You will definitely want to change out the input bypass capacitors as he showed, then it becomes more or less OK,
However, for the much higher price I still would not personally recommend it.
The LF353P op amp is used as a DC servo in this circuit, by the way.
Its sole purpose is to reduce or eliminate DC offset at the output and it has little or no effect upon the audio quality.
It is also the reason for the distorted waveforms at low frequencies despite the design being a straight through DC-coupled design.
🙂
Good work Mike. Does it surpass the Accuphase? The specs on the 3850 were impressive.
Hi Bill, it's good but the Accuphase Clone is still one of the best overall.
Another good review , keep doing the good job.
Support your video. I have this pre amp board but haven't assembled them yet. Does this sound good to you?
Thank you for your presentations!
I recently ordered the "accuphase" pre, let's see how it will sound
I'm sure you will be very pleased with-it David.
Off topic, but are the PC boards for the Dual TDA 7293 Amp that you tested still available anywhere? I can't seem to find them. I only see a board with three TDA 7293's in parallel for sale on Aliexpess at this time.
Try this link.
www.ebay.com/itm/166235656448
Still quite a few suppliers. Other links are on the comments of my original video.
Can you experiment with different resistance at the output which simulates different resistance that different amplifiers have at the input, which can affect the preamplifier.
Or different resistors at the input of the preamplifier
If you connect the oscilloscope directly to the output, the preamplifier does not have the correct resistance?
Correct me if I'm misunderstanding this.
What do u recommend? I just need a basic preamp between dac (2 volt fixed) and powerap at 60 watt. Ideally with remote. I prefer and modify over building from scratch.
Seems that accuphase clone you reviewed is unbeatable at this point. Cheaper too!
how did your friend connect the headphones to it? If using the same outputs meant for power amp, then I think the headphones impedance may be too low
It will run headphones directly from the output of the preamp. I tested it with 32 ohm phones. Try it, you will not damage anything.
please continue reviewing china class d amplifier sir... shout out sir from Philippines...
Michael, you are an inspiration! Love the videos. Keep telling the audio truth. I keep telling people those ne5532 or opa1612 for a few dollars will sound as good or better. (Subjectively and objectively) than $80 discrete boutique pieces.. People don't believe that some equipment doesn't need to cost an arm and a leg to sound good. The old saying a fool in his money is easily parted comes to mind. Keep up the good work young man!
Hi Michael,
Whatever noise advantage they had with the FET's is wasted with a 50k pot for a volume control. The FET's were quieter than a 5534, that was the reason for the cascode pair (subbing them for a cheaper generic pair doesn't help either). The preamp as delivered would be about the same noise as just using the LF353 for 10dB of gain.
Removing the output transistor pair just lowers the cable capacitance that it can drive... to the point a 353 would do the same.
50k pot at 25% should be about 10nv/Hz
5534 is about 4nv/Hz
JRC LF353 are around 17nv/Hz (that's 72dB below 100mv rms output; not bad except at high volumes -20kHz bandwidth)
You'll never hear the difference between a 30pf and a 220pf except with a strong AM radio station or CB'er nearby. You cannot hear square wave edges with ridiculous rise times. PERIOD
Graphs & specs sell expensive 'add nothing' components to audiophools and line the manufacturers pockets...
edit: What you should be able to hear with a really well recorded source: tiny bit of extra noise and slightly more high frequency distortion with a LF353 compared to 5534. Gotta ask the question? Is $40 more worth the difference? NOPE !
Go buy an LM4562 or OPA1612 and ignore this 'kit'. Use a 5k volume pot and you got somethin' worth building...
Enjoy the summer, we just got out our gloves and stocking caps in the good ole USA
I "Wholeheartedly" agree with your edited comment! I've built an Accuphase clone, powered by 18650 batteries and tried various audio ICs (chip rollin') and finally settled on the LM4562. This preamp is really all you need.
Hi Jim; kind of wondered what company, but no big deal...I worked as AE at Tek, Agilent, R&S, and r&d for a handset company in Salo, but doing power management... Did a lot of work with Tek RTSA, high-end scopes, TDR, R&S AMIQ, SMIQ, HP ENA, PSA, ESF and R&S oscilloscopes at HQ in DE.
Nice noise comments... Most audio folks probably don't think about noise contribution of passives, but RF guys are always down in the dirt 😉
@@JBBrown-hh4rc For $100 you can parallel a half dozen on the + - sides of 100r twisted pair cat6 cable, 500 feet long and still be below .001%thd @ 100kHz.
And listen with any lo Z headphones you like! LM4562's are beasts. I have cascaded up to 10 thru state variable filters (Q
@@ralfstocker7742 I'm only reporting what I find. I have zero input on the design. If you can do better summit a circuit and we will see.
@@lohikarhu734 Technical Director of Helper Instruments Company (land mobile radio repair test equipment & 1st gen cell)). Audio Specialties Company (1980), 25 years doin' live sound reinforcement and recording for FUN and profit. Built quite a few 3000 seat systems that studio engineers, band managers, record execs, etc have said things like "these are better than any of our monitors" "best sound we have ever heard" "where did you get those?" "how much to build me a set?" Turned down national acts, I was busy.
Component level design DC - GHz, microwatts to 10's of kilowatts. Dozen patents (spread spectrum oscillators).
...retired since '97
Helped start a school for troubled youth; 240 boys graduated, Thank God!
I watch, and am as a sparrow alone upon the house top. Psalm 102;7
Bible student, join us at Ebiblefellowship .org
Nice looking board, v 18-0-18 is interesting for opAmp
I did see that on the PCB. I would stick to 15 volts personally. You are pushing the ICs very near maximum. You won't gain anything in performance.
Great video Professor Beeny
Just when I think I don't need any more gear, along you come with a tempting board!
(I want you to do a Sugden a21a from Ali.)
Many years ago, I was in retail. We did sell the Sugden A21. It was only 12 watts output but was the only class A amplifier we sold. Personally, I did not like it. I thought the sound was weak, compressed, lack any bass power and somewhat under powered. Nothing to do with being class A. In fact later the model was changed to 20watts class A/B. Still did not like it much. We sold quite a few mail order but only a couple through a dem in the shop. Draw your own conclusion from this story.
@@MichaelBeeny I would really like to know you all-time favourite amp
@@cobar5342 It's got to be the L12/2 for sure.
@@MichaelBeeny Thank you Michael.
@@MichaelBeeny I do respect your knowledge and wisdom - hence the label of 'Professor'. I was not being flippant
Why hesitate to review it? I don't expect that every board you review is top notch. Having some boards which are not price/performance interesting is good to know as well.
I do have a number of projects/videos that I have never published. I'm either not happy with the video or I cannot get the points over. One or two are just abandoned the video because it's just c**p. Even my good videos take ALOT of editing lol.
@@MichaelBeeny I think you are a bit hard on yourself. Your videos are always great. Why not make some kind of summary video of the boards which didn't make it to do a proper video?
The preamp will or should work, without that cap. It is part of one pole low pass filter, designed to keep things above the audio band out. We live in a world of stray RF. You just moved the corner frequency up. Change it at your own risk.
I have never found any issue removing or lowering the value. We have an FM repeater just over the horizon. I have never had any issue picking that up. I understand that might be an issue for some people.
Watch out for "Alps" volume pots from China, as quite a lot of them appear to be fake. They're more expensive than the usual cheap pots, but still a fair bit cheaper than the real Alps.
I think the rule is, if it's fakeable, someone will fake it!
@@MichaelBeeny Yes indeed, 5532's anyone? 🤔
15:41 "If one measures better than the others, then it's better". There are a lot of audiofools with PS Audio products that would disagree with that statement.
absolutely agree with that !lots of so called audiophiles you tubers talking BS .
Test gear is far more sensitive than the human ear. The test equipment is fact, the ear is very subjective. Sadly however, test gear does not deal in personal preferences.
Think you should be careful about throwing shit around (PS audio). What do you dislike about PS audio?
Hi Michael, Test gear can only synchronize certain frequency at one time and ignore other frequency which may sound bad while human ear has no such limitations. If user only play fixed frequency sine wave as music, than test gear is more accurate to judge the amplifier output quality.
Simply put : what you see on the scope is not what you hear ! @@MichaelBeeny
@@MichaelBeeny How a piece of equipment misbehaves from ideal is what different people 'prefer'. Some folks will tolerate noise (and like it because it burries IMD artifacts). Some get their opinion based on visual ques, some know it sounds better if it costs more. Past listening experience and the level of 'educated/trained' ears a person has, largely determines what they can/will discern and accept.
The vast majority of audiophiles have never been in an anechoic chamber - they don't have a clue what 3D sound fields in their listening environment add or subtract from the sound. And most have NO idea how dirty most recordings really are compared to the 'live' sound when it was recorded. They cannot, they were NOT there, they are illiterate! (don't judge a book by its cover, till you've been to the printer's shop and read the manuscript)
Sadly, the comparison is usually between flaws they are not even aware of...
Test equipment provides a completely accurate record of what is actually happening with a signal. Sufficient for the task, of course - not super expensive SOTA gear is necessary either - our ears just ain't that great when you know how they also misbehave (psycho-acoustics).
edit: The test equipment is available that is at least an order of magnitude better in any respect than our ears. The expertise is greatly lacking in knowing how to use it effectively.
...and the more money involved, the bigger the bag of deceptions inflates by the unlearned! BS comes naturally, truth is a gift.
Not "Duel" voltage, "dual"
Mr. Picky ⛏️ strikes.
Back to video
So, I made a spelling error. I've known brilliant engineers that cannot solder. Does that diminish them as engineers? Maybe you are on the wrong channel.
Oh dear , if you're going to clone an amp clone it or otherwise call it something else and take the knock in hype induced sales. Fat chance, I know.
👍