Aleph30 PSU - +v/-V .6vdc difference - 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 22nd February 2006, 06:03 PM   #1
diyAudio Member
 
hifimaker's Avatar
 
Join Date: Oct 2003
Location: San Jose
Question Aleph30 PSU - +v/-V .6vdc difference

Hi,

I have built an Aleph30 and the +v side of the PSU is .6vdc higher than the -V side under load for 2 channels.

I'm using a single mini-Aleph PSU board from Brian using a CRC design. Under load the trafo is vac levels are the same for both sides. I built a second PSU with different parts of the same spec, but I'm getting the same results.

I imagine the +-V should be the same values correct?

The amp sounds incredible, even with the .6vdc difference.

I was thinking of adjust the R to a slightly lower resistence value to bump up the -v value to match +v.

Any thoughts on the root cause?

Thanks!

-David
  Reply With Quote
Old 22nd February 2006, 06:32 PM   #2
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
Are you measuring the voltage on the first C or the second? What is the R? Does the R measure the same on both sides?

GL
  Reply With Quote
Old 22nd February 2006, 08:09 PM   #3
diyAudio Member
 
hifimaker's Avatar
 
Join Date: Oct 2003
Location: San Jose
The voltage difference is consistent with every stage in the CRC chain. I'm getting 20.2VAC off the trafo, 25.4 and 25.9 off each DC side of the bridge rectifer. The .6vdc difference is consistent before and after each stage of the CRC.

-David
  Reply With Quote
Old 22nd February 2006, 08:16 PM   #4
MikeW is offline MikeW  United States
diyAudio Member
 
MikeW's Avatar
 
Join Date: Sep 2002
Location: North of Boston
It seems that your center tap is not quite in the center.
__________________
MikeW
  Reply With Quote
Old 22nd February 2006, 08:32 PM   #5
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
David,

Mike could be right. So make sure that you have 20.2V between each secondary leg and the CT. If you do then the only thing I can think of at this point is to check the diode drop voltage across each diode of the bridge with your multimeter. The .6 value is really suspicious looking - being one diode drop. It seems unlikely that the problem is with the diodes but I've had stranger things happen. Good luck.

Graeme
  Reply With Quote
Old 1st March 2006, 05:51 AM   #6
diyAudio Member
 
hifimaker's Avatar
 
Join Date: Oct 2003
Location: San Jose
Thumbs up Faulty DMM

Well.... I found the problem. My trusty old DMM was off calibration.

Just took delivery of a new B&K 5360 and the difference between the +-Vdc sides of the PSU was actually .1vdc.

I'm not going to worry too much about a .1vdc difference.

Thanks for the help!

-David
  Reply With Quote
Old 1st March 2006, 03:18 PM   #7
diyAudio Member
 
hifimaker's Avatar
 
Join Date: Oct 2003
Location: San Jose
Actually after letting the amp warm up properly I measured a PSU +-vdc difference of .01 volts; -25.03 and +25.04.

Hope this is OK.

-David
  Reply With Quote
Old 1st March 2006, 04:16 PM   #8
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
Hi David,

Glad to see you found the problem. Your supply voltages look fine. The .01V difference can be ignored.

Graeme
  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
6VDC Wall worts, 2 amp... chipco3434 Chip Amps 2 11th December 2007 04:10 AM
Help Aleph30 Kooka Pass Labs 9 18th February 2007 02:03 PM
6Vdc from 6,3Vac resident Tubes / Valves 21 5th April 2005 01:06 PM
Aleph30 very very hot arold19 Pass Labs 7 12th February 2005 01:55 PM
1 Ohm For Aleph30 gema Pass Labs 2 30th May 2002 07:40 PM


New To Site? Need Help?

All times are GMT. The time now is 09:55 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