Vr9
Hello Edmond
I can't find VR9 on your schematic are your sure you dont mean VR6 .
Regards
Arthur
Hello Edmond
I can't find VR9 on your schematic are your sure you dont mean VR6 .
Regards
Arthur
Re: Re: Re: Re: Re: AD797
I use to have the same problem with R35 value, so I replaced it with diode connected NPN Tr and ,as far as I can see, that do the trick.
Edmond Stuart said:
I use to have the same problem with R35 value, so I replaced it with diode connected NPN Tr and ,as far as I can see, that do the trick.
Actually, since you brought it up, John Curl ought to write a book!!
However I think that he may need a collaborator perhaps, someone who can do a good job of putting things into a proper format as is required for a book.
This thread could even be used as a "backbone" for it, need be (not sure it is needed at all).
Really John, you ought to go for it.
😀 😀
_-_-
However I think that he may need a collaborator perhaps, someone who can do a good job of putting things into a proper format as is required for a book.
This thread could even be used as a "backbone" for it, need be (not sure it is needed at all).
Really John, you ought to go for it.
😀 😀
_-_-
Re: Re: Re: Re: Re: AD797
Sorry, I must have missed the discussion on the output transistors. What is the significance of the "emitter sizes"??
_-_-bear
Edmond Stuart said:
Sorry, I must have missed the discussion on the output transistors. What is the significance of the "emitter sizes"??
_-_-bear
Thanks to a little help I was able to resurrect a complete working sim of the 797
Edmund - these are the values of the currents in your schematic (the published one).
The voltages on the collectors of Q16 and Q17 are (vout = 0) -.580, -.672.
Q61 BTW is part of the Ib comp circuit. You won't be able to get the output stage to
bias right without the correct area ratios, but the front end has so much degeneration
that it should be close.
I1 = 1.84ma ,I2 = .3mA ,I3 = 2.6mA ,I4 = .51mA ,I5 = .49mA ,I6 = .215mA
John - I will gladly run sims for you now that I have the real circuit
and models, just give me the conditions. I will also sim an external
class A current with the real models that minimizes the 7th in your circuit.
On my own time just for you, fair enough?
EDIT - Edmund I missed your post above.
Edmund - these are the values of the currents in your schematic (the published one).
The voltages on the collectors of Q16 and Q17 are (vout = 0) -.580, -.672.
Q61 BTW is part of the Ib comp circuit. You won't be able to get the output stage to
bias right without the correct area ratios, but the front end has so much degeneration
that it should be close.
I1 = 1.84ma ,I2 = .3mA ,I3 = 2.6mA ,I4 = .51mA ,I5 = .49mA ,I6 = .215mA
John - I will gladly run sims for you now that I have the real circuit
and models, just give me the conditions. I will also sim an external
class A current with the real models that minimizes the 7th in your circuit.
On my own time just for you, fair enough?
EDIT - Edmund I missed your post above.
bear said:
History has shown again and again that new concepts, new ideas, new ways of doing things do not come about by those with the new ideas convincing those established in the art.
Rather, the new ideas, concepts and ways come into play because the old gurus eventually die off and are replaced by the ones with the new ideas.
Sad as it is, but the older one gets, one becomes more and more an impediment to progress. And yes, I'm one of them. And the best you can do is to encourage those with the new ideas, the heresies, to go out on that limb and just do it. Not to say that it has already been tried and disourage them.
Jan Didden
(currently soaking up some sunshine on the Spanish Costa Blanca)
Clarke´s first law comes into mind:
"When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong." 🙂
"When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong." 🙂
Hi Scott
I'd like to see if the simplified circuit sims were at all indicative - still no response on assumptions about feedback load, signal levels in my "unacceptable 7th" sim a day ago
http://www.diyaudio.com/forums/showthread.php?postid=1813250#post1813250
in that sim the simplified AD797 circuit didn't seem to have readily measureable audio frequency 7th ( -151 dB 21KHz from 3KHz input )
but what was there was reduced >20dB by the simple small signal mosfet follower
John still hasn't explained why he's searching for a "magic" output stage bias current setting when a buffer in the loop can be so cheap and apparently effective
I'd like to see if the simplified circuit sims were at all indicative - still no response on assumptions about feedback load, signal levels in my "unacceptable 7th" sim a day ago
http://www.diyaudio.com/forums/showthread.php?postid=1813250#post1813250
in that sim the simplified AD797 circuit didn't seem to have readily measureable audio frequency 7th ( -151 dB 21KHz from 3KHz input )
but what was there was reduced >20dB by the simple small signal mosfet follower
John still hasn't explained why he's searching for a "magic" output stage bias current setting when a buffer in the loop can be so cheap and apparently effective
jcx said:
Wow, that good with generic 2N3904/6's. I was thinking of just doing 3K at 10V p-p into 600 Ohms as a starter. I can't quite read some of the values on your schematic. I think JC is on a bit of a soapbox about this.
If some of you could only see yourselves as I do. 🙄
First, I don't have the will or the resources to write a book. I have written chapters for books that went unpublished, and I have written LTE's and short articles for different publications.
However, Dimitri, here on this website, put together at least 150 pages of my previous inputs ON THE INTERNET, before this thread became popular, and it is available to everyone. It is the equivalent to a small book, already, called 'Words of Wisdom by John Curl', or something like that.
I find that my material input has diminished over the years. I used to write better and more concise. I'm just tired of repeating myself to a bunch of 'sophomores', who know just enough about this field to be troublesome. It has not always been the same 'sophomores' over the decades, just as if I was teaching junior college, but I did not elect, and I don't get paid, to put up with them, repeatedly, either. I do, because I have nothing better to do, since I am semi retired, and have been so for many years.
First, I don't have the will or the resources to write a book. I have written chapters for books that went unpublished, and I have written LTE's and short articles for different publications.
However, Dimitri, here on this website, put together at least 150 pages of my previous inputs ON THE INTERNET, before this thread became popular, and it is available to everyone. It is the equivalent to a small book, already, called 'Words of Wisdom by John Curl', or something like that.
I find that my material input has diminished over the years. I used to write better and more concise. I'm just tired of repeating myself to a bunch of 'sophomores', who know just enough about this field to be troublesome. It has not always been the same 'sophomores' over the decades, just as if I was teaching junior college, but I did not elect, and I don't get paid, to put up with them, repeatedly, either. I do, because I have nothing better to do, since I am semi retired, and have been so for many years.
having John's operating assumptions would be helpful - I assumed a 30dB mc preamp with 10/300 Ohm feedback to keep noise low and guessed that 100mV at the output of a mc phono cart was outragously large signal - presumably a flat gain mc "pre-preamp" output signal still has to go through a more typical RIAA preamp with ~40 dB mid band gain - giving ~20 dB 20KHz gain
[for my test sim from previous page see attached LtSpice file (strip the .txt extension)]
[PS: attached file has .op analysis cmd - for .tran I used 10 mS sim, 10nS max step size]
[for my test sim from previous page see attached LtSpice file (strip the .txt extension)]
[PS: attached file has .op analysis cmd - for .tran I used 10 mS sim, 10nS max step size]
First, JCX, I am trying to retrofit one existing IC for another. I don't have room for a new output stage! I just wanted to see IF you added ONE jfet, as a current source to the output of an existing AD797, if I could reduce the residual 7th harmonic that I see in the distortion residual. You would think that I violated the laws of physics, or asked the impossible!
Now that you, JCX, have PROVEN that the 7th CAN be reduced, thank you.
Now that you, JCX, have PROVEN that the 7th CAN be reduced, thank you.
john curl said:
Thanks John! Probably, it will be a science fiction about particles in speaker wires that sound louder than differential stages, and DA in capacitors that sound louder than emitter followers... 😉
Now I would like to ask for your opinion directly: do you support the idea that mechanical resonances ("linear distortions") are more audible on high SPLs because our ears are guilty and speakers are innocent, or do you support my point of view that our ears are innocent, but it is because of mechanical non-linearities of things that generate, transfer, and reflect the sound? When we discussed this simple question you went off-topic about mind reading, "What Wavebourn thinks of himself, and how it hurts my friends who were thinking similarly 40 years before".
I would like to remind everyone about what is the substance of this thread.
First, it is an ANALOG thread, because the BLOWTORCH PREAMP is an analog preamp.
Since I ONLY design analog designs, then I prefer to talk only about analog subjects. That does not mean that I am prejudiced against digital, it is just that I have little to contribute to it.
Also, ANALOG is an almost lost art. This is because it is not taught well in college, anymore, and people often regard audio design as second rate, and nearly useless.
Still, there is some interest, those who don't think MP3 is enough, and by those who find it fun to make their own analog designs.
It is well known through the ages that the older generation is often an impediment to the new ideas of the younger generation. You know, great ideas like Dolby digital and MP3!
I have hundreds of examples in a book by my side called: 'The Experts Speak'. However, this is not a universal truth, except for the fact that usually younger people come through with the most 'breakthrough' ideas before the age of 30. Look an Einstein, etc. I did my best ideas myself, and laughed with my friend of 40 years, just yesterday, when he asked what I was up to, and I said that I was building amps with the same topology that he and I developed for Alembic, in 1970! Except, now I knew better how to keep them from blowing up! Yes, time has helped me make it work, but the core idea came to me at age 26.
By the time I was 40, I was told that I was a has-been, wash-out, and a loser. Then I started Vendetta Research, and made a few more refinements, culminating the the CTC BLOWTORCH.
Any great breakthroughs in the CTC? No, just refinements, but I challenge each and every one of you to do better.
First, it is an ANALOG thread, because the BLOWTORCH PREAMP is an analog preamp.
Since I ONLY design analog designs, then I prefer to talk only about analog subjects. That does not mean that I am prejudiced against digital, it is just that I have little to contribute to it.
Also, ANALOG is an almost lost art. This is because it is not taught well in college, anymore, and people often regard audio design as second rate, and nearly useless.
Still, there is some interest, those who don't think MP3 is enough, and by those who find it fun to make their own analog designs.
It is well known through the ages that the older generation is often an impediment to the new ideas of the younger generation. You know, great ideas like Dolby digital and MP3!
I have hundreds of examples in a book by my side called: 'The Experts Speak'. However, this is not a universal truth, except for the fact that usually younger people come through with the most 'breakthrough' ideas before the age of 30. Look an Einstein, etc. I did my best ideas myself, and laughed with my friend of 40 years, just yesterday, when he asked what I was up to, and I said that I was building amps with the same topology that he and I developed for Alembic, in 1970! Except, now I knew better how to keep them from blowing up! Yes, time has helped me make it work, but the core idea came to me at age 26.
By the time I was 40, I was told that I was a has-been, wash-out, and a loser. Then I started Vendetta Research, and made a few more refinements, culminating the the CTC BLOWTORCH.
Any great breakthroughs in the CTC? No, just refinements, but I challenge each and every one of you to do better.
Wavebourn, I am not going to comment on your question, because I have no opinion at the moment about it.
Wavebourne:
They are both "guilty".
I know you asked John....
I read your reply to me. Something in it confused me. Thank you. Want to think about.
Later.
They are both "guilty".
I know you asked John....
I read your reply to me. Something in it confused me. Thank you. Want to think about.
Later.
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