New Doug Self pre-amp design... - Page 51 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th August 2012, 10:20 PM   #501
Bonsai is offline Bonsai  Taiwan
diyAudio Member
 
Bonsai's Avatar
 
Join Date: Jul 2003
Location: Taipei, Taiwan
Nereus, yes, this is what I am proposing. I'd be interested to hear if there is a difference.
__________________
bonsai
Amplifier Design and Construction for MUSIC! http://hifisonix.com/
  Reply With Quote
Old 14th August 2012, 01:21 AM   #502
owdeo is offline owdeo  Australia
diyAudio Member
 
Join Date: Jun 2003
Location: Sydney
Guys, thanks for the suggestions. Bonsai, I can't see there's anything here to challenge Mr Self with anyway - he's done the measurements that show there is no problem technically.

I know as much about feedback from control theory at uni as any other EE that hasn't used it since (ie not a huge amount, but I remember finding the transform maths tedious), but I agree that technically there should be no problem with the way it's used in audio amplifiers per se. The trouble is, I'm fairly sure what I'm hearing is not something that will be picked up using conventional measurements so it seems pointless to insist that feedback can't be the culprit. Certainly no different than speculating that it's due to opamp class B operation when we already have the measurements that suggest it isn't. I'm describing something that I hear. I don't expect to be able to offer some new previously unknown technical phenomenom by way of explaning what I'm hearing - the best I can hope for is offer my opinion that as is, the design sounds a certian way, but by changing this or that it sounds better/different to me but I don't have any rational explanation why. I don't think this will be at all useful to anyone that isn't also building the design and agrees with my opinions on SQ

I think the first thing I'll try is increasing the value of the 680R at the inverting input of the final gain stage in the active gain control - the buffer fed from the pot wiper is driving this and since the other end is virtual gnd this is a pretty taxing load on the buffer, even though the signal voltage level is lower here. I'll try 1k - this should be an easier load that is less likely to cause any class B operation while not increasing noise significantly. Then I might try the class A bias trick but I'm not keen on this idea to be honest. Might be better to then try just bypassing the whole AG stage as previously discussed. I'll try and let you know how it goes by the end of week if I get a chance.
  Reply With Quote
Old 14th August 2012, 01:26 AM   #503
owdeo is offline owdeo  Australia
diyAudio Member
 
Join Date: Jun 2003
Location: Sydney
Quote:
Originally Posted by AndrewT View Post
Have you measured the Pre-Amp to check that it meets the target specification?
Unfortunately I don't have access to any test gear with the required resolution at the moment. I checked waveforms with a CRO for stability and level, then ran a frequency response test using a DSP speaker measurement system that I've tricked and calibrated for this purpose. All looks ok so I would assume it would also measure well wrt THD and noise.
  Reply With Quote
Old 14th August 2012, 01:31 AM   #504
owdeo is offline owdeo  Australia
diyAudio Member
 
Join Date: Jun 2003
Location: Sydney
Quote:
Originally Posted by SY View Post
Some basic misconceptions never die, do they? I think you have some basic reading to do on control theory and feedback, not to mention basic physics. In another thread, I had just recommended Bruno Putzy's excellent article on feedback that appeared in Linear Audio, and I'll recommend it again- it will clear out much of the nonsense you've been fed.
That may be a good article, however my hobby budget is in big trouble with SWMBO now, so it seems a bit pricey - I agree, is it available elsewhere?

I'm familiar with that name - he's the guy behind the Hypex class D modules isn't he? A company I used to work for insisted on using them in active speakers - I am not at all encouraged by the way they sounded...
  Reply With Quote
Old 14th August 2012, 03:47 AM   #505
diyAudio Member
 
Join Date: Jun 2011
Quote:
Originally Posted by AndrewT View Post
Have you measured the Pre-Amp to check that it meets the target specification?
Quote:
Originally Posted by owdeo View Post
Unfortunately I don't have access to any test gear with the required resolution at the moment.
Despite this, and despite the fact that you have never demonstrated that you can distinguish this preamp from any other in a blind test, you are unconcerned about any possible financial damage you may be doing to another member?
  Reply With Quote
Old 14th August 2012, 04:07 AM   #506
owdeo is offline owdeo  Australia
diyAudio Member
 
Join Date: Jun 2003
Location: Sydney
Could you please clarify the last part of that statement? Are you suggesting that expressing my opinion on the sound quality of audio equipment will affect someone financially?

If you had been reading this thread earlier on you'd know that I've done some blind testing and had no trouble picking the preamp - I don't expect this to impress any hard line objectivist though.
  Reply With Quote
Old 14th August 2012, 04:25 AM   #507
owdeo is offline owdeo  Australia
diyAudio Member
 
Join Date: Jun 2003
Location: Sydney
I'll take that as a yes, in which case thank you, I'm flattered. Unfortunately I think you're mistaking me for someone claiming to know all the amazing secrets of the art of audio or some incredible technical whiz and therfore having much influence on this forum. Not the case - I'm just some guy y'know. Can't see anyone being too bothered by my opinion either way
  Reply With Quote
Old 14th August 2012, 04:38 AM   #508
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Blog Entries: 6
Quote:
Originally Posted by counter culture View Post
Despite this, and despite the fact that you have never demonstrated that you can distinguish this preamp from any other in a blind test, you are unconcerned about any possible financial damage you may be doing to another member?
counter culture I have previously asked you to desist from this line of badgering. What you are in fact advocating is censorship, one more comment of this nature and you will spend the next week in the bin. I suggest strongly that your participation in this thread is at an end if you cannot adhere to moderation directives. FINAL WARNING
__________________
"Extraordinary claims require extraordinary evidence." - Carl Sagan
  Reply With Quote
Old 14th August 2012, 06:00 AM   #509
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by owdeo View Post
That may be a good article, however my hobby budget is in big trouble with SWMBO now, so it seems a bit pricey - I agree, is it available elsewhere?
It's online here:
http://www.linearaudio.net/images/on.../volume1bp.pdf
If you find the math intimidating, at least read the three 'storylines'.

jan
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!

Last edited by jan.didden; 14th August 2012 at 06:11 AM.
  Reply With Quote
Old 14th August 2012, 06:52 AM   #510
MOER is offline MOER  United States
diyAudio Member
 
Join Date: Aug 2003
Location: SIMI VALLEY CA
Default D Self Preamp

This reminds me of a similar argument regarding transformers I had many years ago with one of these HiFi gurus who could hear from DC to light.

He moaned about the output transformer in the final stage of a tube amplifier and said that he hates sound that must travel through an transformer.

My answer was that in a good old analog recording studio the signal passed through... now let's count the number of transformers.
1) The Mic has a balanced drive xfr
2) The input to the console has an input xfr
3) The output of the 24 track console has 24 output xfrs.
4) The 24 input Studer has 24 input xfrs
5) Hell the tape heads are essentially xfrs.

Now that the signal was on 24 track tape it had to be mixed down to 2 track. So here we go again.

1) The 24 track Studer was played back and we have the playback heads
2) The signal passed through the 24 output xfrs into the console
3) The console has 24 input xfrs.

The mix down is done and converted to two channel

1) Now the signal must pass from the two channel format through the console and out to the 2 track Studer through two more output xfrs....Yikes!
2) Now the signal is passed through the recording heads (more xfrs) and we finally had a 2 track master tape.

Now had to make the vinyl "mother"

1) So off again the Studer is in playback and signal comes off the heads = xfr.
2) Passes out of Studer through the output xfrs to the cutting amplifier.
3) Cutting amplifier has input xfrs.
4) Cutting heads are big *** coils.

Total count of signal passing through copper + iron = 14 and this does not take into account the signal ever passing from balanced xfr line outs to other gear (Compressors, de-essers etc all with more iron)

So what does one more output transformer mean? if it is of good quality - nothing.

Same issue with the opamp story. The signal in the recording chain goes through a "mudbath" of ICs, bad capacitors, bad cable and the gurus moan and groan about a few opamps in a pre-amplifier.

I admit my preference is tubes and in my sold state designs I prefer discrete.

The NE5532/NE5534 are great parts vs their cost.

A NE5532 costs me $0.18 and we use tens of thousands of them.

The other low cost IC I like is the NJM2068M


Steve Mantz
Zed Audio Corp.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Doug Selfs NE5532 Power Amp. Thoughts anyone ! Mooly Chip Amps 87 15th June 2012 08:08 PM
blameless amp and doug self streetera Solid State 17 16th July 2007 10:06 PM
4th Ed. of Audio Power Amplifier Design Handbook (Doug Self) nickds1 Solid State 4 9th November 2006 12:02 PM
Doug Self Advanced Pre Amplifier PCBs macka Swap Meet 0 9th October 2006 07:41 AM
Help me design pre-amp PS hardcore Tubes / Valves 7 10th November 2004 06:32 AM


New To Site? Need Help?

All times are GMT. The time now is 06:16 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2