CFA Headphones amplifier - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems

Headphone Systems Everything to do with Headphones

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 16th March 2015, 11:14 PM   #1
arpagon is offline arpagon  Bulgaria
diyAudio Member
 
Join Date: Oct 2011
Default CFA Headphones amplifier

Hi guys, what do you think - does this schematic will "whistle"?

Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 17th March 2015, 01:13 AM   #2
diyAudio Member
 
Join Date: Feb 2009
LTspice files provided can significantly increase your chances of getting an answer

Last edited by Sergey888; 17th March 2015 at 01:38 AM.
  Reply With Quote
Old 17th March 2015, 08:01 AM   #3
arpagon is offline arpagon  Bulgaria
diyAudio Member
 
Join Date: Oct 2011
Some more pictures:

THD spectrum at 1kHz:
Click the image to open in full size.

THD spectrum at 10kHz:

Click the image to open in full size.

THD spectrum at 100kHz:

Click the image to open in full size.
  Reply With Quote
Old 17th March 2015, 08:15 AM   #4
arpagon is offline arpagon  Bulgaria
diyAudio Member
 
Join Date: Oct 2011
And some more:
OLG:
Click the image to open in full size.

PSRR+
Click the image to open in full size.

PSRR-
Click the image to open in full size.
  Reply With Quote
Old 17th March 2015, 08:19 AM   #5
arpagon is offline arpagon  Bulgaria
diyAudio Member
 
Join Date: Oct 2011
And the last:
Step response 100kHz, 32V p-p:
Click the image to open in full size.

Step response 100kHz, 48V p-p:
Click the image to open in full size.

Last edited by arpagon; 17th March 2015 at 08:23 AM. Reason: picture size too large
  Reply With Quote
Old 17th March 2015, 12:55 PM   #6
diyAudio Member
 
Join Date: Nov 2004
Location: Germany
Looks good, but would probably burn up in practice at higher output amplitudes if really used with +/- 36 V rails. Look up the ratings of your parts.
  Reply With Quote
Old 17th March 2015, 02:27 PM   #7
arpagon is offline arpagon  Bulgaria
diyAudio Member
 
Join Date: Oct 2011
Quote:
Originally Posted by sgrossklass View Post
Looks good, but would probably burn up in practice at higher output amplitudes if really used with +/- 36 V rails. Look up the ratings of your parts.
Of course some transistors must be replaced with high-voltage types - I put in the sim what I have as models. Of course the supply voltages can be lowered too.
I just want to show the ability of schematic.
  Reply With Quote
Old 21st March 2015, 04:44 AM   #8
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
The distortion is too high. can you reduce it to well below -100dB? And what is the slew rate?



THx-RNMarsh
  Reply With Quote
Old 21st March 2015, 10:38 PM   #9
arpagon is offline arpagon  Bulgaria
diyAudio Member
 
Join Date: Oct 2011
Hi Richard,
I'll try to answer you in several stages.
1. THD of the Diamond Buffer itself (without NFB) with 8V/1kHz input signal and 60 Ohm load is ~ 0.2%
2. If we want to evaluate how buffer's THD vary with applied NFB loop gain we have to isolate it from the rest of schematic.
I did that and the results are shown on the picture:

Click the image to open in full size.

Input stage and VAS are substituted with ideal VCVS. Since the real schematic has OLG of aprox. 70dB, VCVS's amplification is set to 4000.
On the picture you can see calculated THDs with VCVS vs. these of the full schematic. It's obvious that they are very close (with exception of 100kHz measurements which is pretty normal). That's why I can say that it's almost all we can squeeze from schematic with 70dB OLG.
3. If we want to lower THDs, we must rise the OLG and hence the loop gain level. Do we really want this? I'm not sure. You can also ask John Curl about his opinion .
4. About slew rate - I gave some values in the pictures above: 374V/us at 38.2V/100kHz output signal.

Regards
Alex
  Reply With Quote
Old 22nd March 2015, 06:24 AM   #10
RNMarsh is offline RNMarsh  United States
diyAudio Member
 
RNMarsh's Avatar
 
Join Date: May 2012
Location: 2457 Cascade Trail; Cool, CA. 95614
That is looking better. No need to add more OLG as long as you are well below -100 ... which you are. SR looks very good also.
Will you make pcb and test and listen?

So, what is next?


_RNM

Last edited by RNMarsh; 22nd March 2015 at 06:27 AM.
  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
Transconductance amplifier for headphones. ErikdeBest Tubes / Valves 3 20th May 2014 05:30 PM
nx-Amplifier: 100 W CFA topology Amp Bonsai Solid State 35 9th July 2013 04:34 PM
Headphones Amplifier HIFI damosound Headphone Systems 2 16th March 2013 08:51 AM
Amplifier for headphones Sponkii Chip Amps 52 20th January 2009 06:07 PM
amplifier for electrostatic headphones silke.wein Solid State 3 6th November 2004 01:07 AM


New To Site? Need Help?

All times are GMT. The time now is 04:34 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2