Output capacitor: subjective and objective views? - 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 27th May 2010, 06:43 PM   #1
Gordy is offline Gordy  United Kingdom
diyAudio Member
 
Join Date: Nov 2006
Default Output capacitor: subjective and objective views?

Capacitors are used at the outputs of some pre and power amplifier designs to block DC offset. Some people have the opinion that these capacitors can be subjectively detected and that they ‘do not sound good’. I would like to ask for your opinion on the subject…

> Preamplifier:

Have you changed a circuit to replace an output capacitor with a DC servo, and if so what was the subjective difference?

Have you made objective distortion measurements with and without the capacitor… any difference?


> Power amplifier:

Large value electrolytic capacitors are placed at the output of single ended transistor amplifiers that use single supply voltages…

Have you heard amplifier designs with electrolytic output coupling capacitors (your own designs or commercial)... what was your opinion of the performance with these capacitors in the circuit?
  Reply With Quote
Old 27th May 2010, 06:49 PM   #2
diyAudio Member
 
Join Date: Mar 2010
I don't believe there is any audible difference. That said, the main reason for using such a circuit is for economy. It only requires a single power supply, mainly.

The capacitor itself is important but most modern units are just fine. There needs to be feedback around the capacitor, not from its input.
  Reply With Quote
Old 27th May 2010, 07:36 PM   #3
diyAudio Member
 
bobodioulasso's Avatar
 
Join Date: May 2008
Quote:
I don't believe there is any audible difference
So do i, provided , in case of an electrolytic, that some consequent dc voltage is present across the cap.
Which is the case of a single supply output stage.

Last edited by bobodioulasso; 27th May 2010 at 07:38 PM.
  Reply With Quote
Old 27th May 2010, 07:43 PM   #4
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
I use a DC servo on my power amp... which is single ended, DC coupled running on split supplies.
http://focus.ti.com/lit/an/sboa092a/sboa092a.pdf

I have built several AC oupled amps over the years and never had cause to suspect the coupling cap was doing anything to the sonics.

Caps in preamps are transparent if the design is right. I have no issues at all with using them.

Built a Radford HD250, that was single ended.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 27th May 2010, 09:17 PM   #5
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
my recent experiences are here (and quoted below)

TGM2 amplifier

Output Capacitor: just for interest, and although not needed, I thought I'd listen to the amplifier through an output capacitor. I found that the bass was noticeably worse off through a 220uF Nichicon MUSE. But through a 2,200uF Nichicon MUSE the bass was fine. I also tried a 10,000uF Nichicon HE cap. Overall I was hard pressed to hear a difference between the use of the two larger capacitors but I could hear a very subtle difference between cap and no cap. The output without a capacitor seemed to have just a tad more 'space' around the upper mids. That's about all I know how to explain what I heard. I concluded that I could be happy with an amplifier that used an output cap.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 27th May 2010, 09:24 PM   #6
PMA is offline PMA  Europe
Design engineer, consultant
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Even input non-polarized coupling capacitors are audible, you can hear a difference between polyester (mylar) and polypropylene, of course depending on resolution of the whole system.
__________________
Pavel Macura
http://web.telecom.cz/macura/audiopage.html
  Reply With Quote
Old 27th May 2010, 09:48 PM   #7
diyAudio Member
 
EBM_dude's Avatar
 
Join Date: Aug 2009
Location: Germany
Capacitors do funky stuff with the signal's phase. I *think* I can hear the difference between 4700µF caps and no caps on my TDA2030A amp.
  Reply With Quote
Old 27th May 2010, 10:03 PM   #8
Telstar is offline Telstar  Italy
diyAudio Member
 
Join Date: Dec 2007
Location: Italy
I hate passive components across the signal. I have speakers without crossovers and although i havent done proper tests, i'm sure that the effect of the ouput capacitor can be heard.

If it has to be used, bigger is usually better.
__________________
"The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938
  Reply With Quote
Old 28th May 2010, 12:39 AM   #9
diyAudio Member
 
bobodioulasso's Avatar
 
Join Date: May 2008
When looking at the output currents, the output cap of an amp is in the signal path the same way the supply caps are in the signal path in a symetrical supply.
Provided the output cap is big enough, it has no influence.
  Reply With Quote
Old 28th May 2010, 02:21 AM   #10
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Quote:
Originally Posted by bobodioulasso View Post
When looking at the output currents, the output cap of an amp is in the signal path the same way the supply caps are in the signal path in a symetrical supply.
Provided the output cap is big enough, it has no influence.
I agree that even without a dc coupling cap on the output you still have capacitors in the signal path because of the PSU. However, doesn't mean that it's good for sound. There are many reports (look at the Class A web site dedicated to JLH) of people improving the sound by swapping out the PSU caps with higher quality units.
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  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
AES Objective-Subjective Forum SY Everything Else 229 20th September 2008 06:17 PM
more objective vrs subjective (from snubberized GC PS thread) Upupa Epops Everything Else 30 30th January 2005 09:55 PM


New To Site? Need Help?

All times are GMT. The time now is 12:17 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