Zen v4 variable current source adjustment - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 26th January 2010, 03:29 PM   #1
frags is offline frags  Canada
diyAudio Member
 
Join Date: Aug 2009
Default Zen v4 variable current source adjustment

I've played with a value of R16 to adjust Aleph current source and found that with its value 1k I can get the distortion 0.02% with 8Ohm load at 1kHz and 1W output. My bias current is set at 1.8A. This value of R16 seems too low for me for 1.8A bias or it's OK?. I'm using audiophile sound card Asus Xonar Essence to measure distortions which gives 0.0003% THD with self closed loop.
Any comments?
  Reply With Quote
Old 27th January 2010, 02:04 PM   #2
frags is offline frags  Canada
diyAudio Member
 
Join Date: Aug 2009
Hmm, such low R16 value has a side-effect on higher power level. The amplifier is getting unstable for example at 4Ohm 10W - the distortion gets much higher (~3%) with third harmonic dominating, looks like the amplifier gets converted into push-pull one.
  Reply With Quote
Old 27th January 2010, 05:24 PM   #3
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
You have figured it out correctly. As you raise the current
gain of the bias source, the distortion of the circuit goes
down at lower power, but it will go into Class B at a lower
power level. You might want to take a look at Wen-San's
SRPP thread for more information and solutions.

  Reply With Quote
Old 27th January 2010, 05:39 PM   #4
frags is offline frags  Canada
diyAudio Member
 
Join Date: Aug 2009
Thank you, Mr. Pass

Did you mean "it will go into Class B at a higher
power level." instead of "it will go into Class B at a lower
power level."?
  Reply With Quote
Old 27th January 2010, 06:56 PM   #5
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
It's like this:

Greatest Class A efficiency occurs when the top current
source is supplying about 50% of the AC output current,
this being true of all aleph, mu follower, sepp and srpp
circuits (all of which are simply variations of each other).

If you set the gain of that current source to deliver less,
then you must increase the bias to avoid clipping. If you
set it for more, you must increase the bias to avoid
dropping out of Class A.

In the extreme case of a constant current source, the
maximum undistorted power is at output = bias, which
is 1/4 the potential power of a 50% arrangement.

In the case of very high gain on the current source, it
goes into class B (or AB if you like) at output = bias,
which again is 1/4 power.

And so it would be lower.

  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
Proper Current Source Adjustment highbias Pass Labs 28 1st May 2007 11:25 AM
Has anyone built Zen V9 as a current source amp? jimmyd53 Pass Labs 1 4th January 2007 04:04 PM
Zen v4 vs. Zen v9 Kashmire Pass Labs 3 28th February 2006 07:56 PM
Bride of Zen with cascode and current source. stappvargen Pass Labs 25 29th August 2003 11:12 AM
zen v2 current source behaviour into dead short Arx Pass Labs 2 18th August 2003 08:09 PM


New To Site? Need Help?

All times are GMT. The time now is 08:10 PM.


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