F5 and Rails 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 29th February 2012, 06:34 AM   #1
wijgers is offline wijgers  Netherlands
diyAudio Member
 
Join Date: Aug 2003
Location: Near Rotterdam
Unhappy F5 and Rails Difference

Finally I could try to start the F5, waiting almost 2 years now.

When trying to stabilize one channel I had a very hard time to get similar values over R11 and R12 0.47 3W there was .1 volt difference between the two resistors.

I did check the power supply and gave an neat 26 V when nothing was attached.

How ever when I checked the rails again while setting up the F5 I discovered a difference in RAILS. There was over 1 V difference between + and - (24.3 and 25.6)

What could be the cause of this difference in RAILS? (bad rectifier?)

Seeing this difference I did not setup the other channel. First I want to have a good supply!

Nils
  Reply With Quote
Old 29th February 2012, 06:31 PM   #2
eyoung is offline eyoung  United States
diyAudio Member
 
eyoung's Avatar
 
Join Date: Aug 2007
Location: Sunny SC,USA 15 min south of Charlotte NC
did you use the F5 p/s board or did you use something else???

Regards, Elwood
__________________
"Lead me not into temptation...I can find it myself."
  Reply With Quote
Old 29th February 2012, 10:51 PM   #3
diyAudio Member
 
Join Date: Sep 2006
Location: Santa Rosa Beach, FL
Wijgers.....no need to post your same item to more than one thread (i.e., here, and on the "F5 Power Amplifier" thread). It's confusing (multiple threads/responses), and only takes up time and space.

Thanks.....
  Reply With Quote
Old 1st March 2012, 01:02 AM   #4
6L6 is offline 6L6  United States
diyAudio Member
 
6L6's Avatar
 
Join Date: Oct 2010
Location: Denver, Colorado
wijgers -

Can you bias both channels of the amplifier to .5v across R11 and R12 with zero offset?

If you can, then measure your rail voltages.
  Reply With Quote
Old 1st March 2012, 07:03 AM   #5
h_a is offline h_a  Europe
diyAudio Member
 
h_a's Avatar
 
Join Date: Sep 2006
Location: Graz, Austria
Quote:
What could be the cause of this difference in RAILS?
Might happen due to slightly different transformer windings, no big deal at all.

Hannes
  Reply With Quote
Old 1st March 2012, 07:55 AM   #6
wijgers is offline wijgers  Netherlands
diyAudio Member
 
Join Date: Aug 2003
Location: Near Rotterdam
@ eyoung: PCB is from CVILLER and also followed his values. and also use the Cvillen F5 PCB v2 using Tech DIY F5 kit for components C's are rated 40V 15000F each

@ CanAm man: Youre right! made a mistake in that respect.

@ 6L6: Will try after measuring unloaded rails, but now the + and - both and not just 1. Hopefully tonight. As far as I could see nothing bad happened to the board

@ h_a: I didn't expect this from a AMPLIMO trafo.

@ triode_al: I cannot measure the precise values of R11 and R12 My meter doesn't go that low. it shows for both the same value.

Thanks all for responding

Nils
  Reply With Quote
Old 1st March 2012, 07:57 AM   #7
diyAudio Member
 
Bksabath's Avatar
 
Join Date: Dec 2007
Quote:
Originally Posted by h_a View Post
Might happen due to slightly different transformer windings, no big deal at all.

Hannes
I got for that especialy no big deal at all part
Or different values on the R part of CRC again no big deal

The P and N chanels are different and require big different VGS
5and a bit V and 3and a bit volt you sorth this out with pots vhen you set bias

1 Volts difference in rails not big deal deal

set it up at half bias null the offset and let it warm up
increase bias and let warm up keep the ofset as low as you can get
repeat till You got right bias
Take your time with this (I let the thing run for 12 hours) then reset Ofset

As long as bias is near about what you need and ofset stay low you be fine.

Ofset main thing to worry about IMO

Once it is stable play same tunes and kepp eye on suply voltagge
If it stay the same no big deal

LOW value resistor mesurament

If you have LM317 see data sheets for constant current
set it up say for 100 mA and mesure V drop across Resistor you need to mesure
Quite precise and cheap

Last edited by Bksabath; 1st March 2012 at 08:01 AM.
  Reply With Quote
Old 2nd March 2012, 05:50 AM   #8
wijgers is offline wijgers  Netherlands
diyAudio Member
 
Join Date: Aug 2003
Location: Near Rotterdam
Default :D

Don't ask why and how, but yesterday evening everything was OK...

I think the figures are good as they are to burn in the components.

0.515 V over R11 and R12, and 4.1 mV DC offset! I probably can tweak it to zero DC.

Both channels at the same BIAS but a slightly different offset.

This weekend will be a good one for further setting up the amp!

Nils
Attached Images
File Type: jpg IMAG0051.jpg (385.7 KB, 79 views)
File Type: jpg IMAG0052.jpg (792.5 KB, 75 views)
  Reply With Quote
Old 2nd March 2012, 06:53 AM   #9
diyAudio Member
 
Join Date: Jan 2012
Location: where women glow and men plunder
my 0.02EUR
Different ESR in caps, swinging values of resistors (resulting in different cumulative resistance of cRc) could affect PSU to supply different volts under idetincal load. I seriously doubt bi-wound torroids or bad graetz-bridge would fault like this but it is not excluded.

get 2 pairs of 12V/50W downlight reflector globes in series and connect each pair to your PSU. If any difference in + or - volts, swap pairs accross (just to cancel error in globe wattage) and if volt difference exists at same half, it narrows down fault to previously mentioned.

2 identical Amp meter in series with + and - rails on amp will confirm balance in current draw.
  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
1M-F5 - A 1 MHz F5 project triode_al Pass Labs 43 25th October 2012 08:28 AM
F5 Amps - Building a Quartet of Amps in search of the Ultimate F5 NYCOne Pass Labs 123 29th September 2011 12:04 AM
Benefits/Drawbacks of Dual rails vs Single Rails buzzforb Pass Labs 2 25th May 2011 01:06 PM
F5 Cascoded - an alternative for my interest in the Balanced F5 NYCOne Pass Labs 159 24th March 2011 05:23 AM
Need 16V rails from an F5 Power Supply NYCOne Power Supplies 1 17th December 2010 07:04 PM


New To Site? Need Help?

All times are GMT. The time now is 07:33 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