F5 power amplifier - Page 548 - 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 30th October 2009, 02:01 PM   #5471
juma is offline juma  Germany
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Berlin
There is a very good reason for 2W resistors in that position.
R1 and R2 are part of the feedback network and they see as much as one sixth (16,67%) of amp's output voltage which is 20V peak (max. value).
20V / 6 = 3.33V
Power dissipated on each of those resistors = (3.33 * 3.33) / 10 = 1.11 W (peak).
1/4W is OK only if you don't listen to your amp too loud.
  Reply With Quote
Old 30th October 2009, 02:28 PM   #5472
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally Posted by Russellc View Post
I inquired about this as well. My parts were one of the Tech-DIY kits, and the smaller Peter Daniels boards required standing up many or the resistors. R1 and R2 were 2 watt resistors that were so large I had a little difficulty getting them in.
In discussing this with Peter, he told me he had no problems with 1/4 watt in that position, and he should know.
Trace the current back -- all you will have is a bunch of burned out 1/4W resistors.
  Reply With Quote
Old 30th October 2009, 04:16 PM   #5473
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Quote:
Originally Posted by juma View Post
There is a very good reason for 2W resistors in that position.
R1 and R2 are part of the feedback network and they see as much as one sixth (16,67%) of amp's output voltage which is 20V peak (max. value).
20V / 6 = 3.33V
Power dissipated on each of those resistors = (3.33 * 3.33) / 10 = 1.11 W (peak).
1/4W is OK only if you don't listen to your amp too loud.
I installed the 2 watt blue resistors that came with the kit. Paul Daniels said he uses 1/4 watt in that position with no problems. Maybe just lucky, but as many boards as he's sold with that advice, you'd think he would have had at least one person tell him otherwise.

Anywho, I installed the 2 watt resistors that came with the kit.....

Russellc
  Reply With Quote
Old 30th October 2009, 04:27 PM   #5474
CBRworm is offline CBRworm  United States
diyAudio Member
 
Join Date: Jan 2007
Location: S. Florida
I also used the 2 watt resistors in those positions. It seems like they can see a fair amount of current, and I tend to push things a bit beyond the design specs.





Question for anyone who has built both, how audible is the difference between the Fairchild and IRF P channel MOSFETs?

I saw somewhere a couple hundred pages earlier in this thread that someone was thinking of using the Renesas/Hitachi MOSFETs - did that ever get built?

I am curious with the fairchild parts going away if their is a better substitute for the output devices? I am curious to hear about tested replacements as opposed to simulated replacements.

Last edited by CBRworm; 30th October 2009 at 04:30 PM.
  Reply With Quote
Old 30th October 2009, 04:30 PM   #5475
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Quote:
Originally Posted by jackinnj View Post
Trace the current back -- all you will have is a bunch of burned out 1/4W resistors.
By the way, I sent an email a couple days ago and today sent a PM about
2 missing bourns pots in the kits I received, did you get either?

Know your busy

Russellc
  Reply With Quote
Old 30th October 2009, 04:31 PM   #5476
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
In case of raised voltage/power it seems like it could be an issue
Nice to know

Nelson mentioned slightly bigger source resistors
Maybe thats what he meant to say

Last edited by tinitus; 30th October 2009 at 04:44 PM.
  Reply With Quote
Old 30th October 2009, 04:33 PM   #5477
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Quote:
Originally Posted by CBRworm View Post
I also used the 2 watt resistors in those positions. It seems like they can see a fair amount of current, and I tend to push things a bit beyond the design specs.





Question for anyone who has built both, how audible is the difference between the Fairchild and IRF P channel MOSFETs?

I saw somewhere a couple hundred pages earlier in this thread that someone was thinking of using the Renesas/Hitachi MOSFETs - did that ever get built?

I am curious with the fairchild parts going away if their is a better substitute for the output devices? I am curious to hear about tested replacements as opposed to simulated replacements.
I bought both outputs, just in case. (Fairchild and IRF) It will be a while before I could give an opinion. I am going to build with the IRF devices. It is said they are slightly warmer, I'm betting the difference is trivial.

Russellc
  Reply With Quote
Old 30th October 2009, 04:47 PM   #5478
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Quote:
Originally Posted by CBRworm View Post
substitute for the output devices?
Toshiba J618+K3497

http://www.semicon.toshiba.co.jp/doc...eet_090929.pdf
http://www.semicon.toshiba.co.jp/doc...eet_090127.pdf

Groupy-B at DK for +100 each at $2/pc to get 'm.
  Reply With Quote
Old 30th October 2009, 04:55 PM   #5479
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Nelson mentioned a pot referencing source pin to ground, to adjust sweet spot
I take it "source pin" is referenced to Jfet

Is it something like this
Attached Images
File Type: jpg F5 X3 rev 4x, source pin pot.JPG (25.3 KB, 666 views)

Last edited by tinitus; 30th October 2009 at 05:02 PM.
  Reply With Quote
Old 30th October 2009, 08:44 PM   #5480
Banned
 
Join Date: Nov 2006
Quote:
Originally Posted by jacco vermeulen View Post
I can't read japanese.

http://www.semicon.toshiba.co.jp/doc...eet_090929.pdf
http://www.semicon.toshiba.co.jp/doc...eet_090127.pdf

You could also try
http://www.semicon.toshiba.co.jp/doc...eet_090929.pdf
http://www.semicon.toshiba.co.jp/doc...eet_090929.pdf
  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
Rockford Fosgate Power 20001 bd amplifier power rating?? pachoorion Car Audio 8 8th May 2011 10:49 PM
Power transformers versus amplifier output power..what is your option? destroyer X Solid State 38 9th May 2009 05:23 PM
McIntosh Power Amplifier Power Guard johnnyrt Solid State 2 23rd August 2007 10:22 PM
Output power for a power amplifier Progg70 Solid State 33 10th September 2006 08:44 AM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality MARAVILLASAUDIO Class D 1 5th November 2004 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 08:29 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