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 27th September 2008, 06:16 AM   #11
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
For you reference only, I have built monoblocks of Aleph-X with 100W Class A output, with +/-24V rails and 7.7A bias, per channel. Power suplly is CRCRC, and the R's were also mounted on the same heatsink as the power devices.

I used 2 large heatsinks which were rated at below 0.2 C/W, and the heatsink temperature at steady state (after 2 hours) is 40 degC above ambient. They are vertically mounted, black anodised, as they are designed to be operated. Using a low noise 120x120mm PC fan on each sink will reduce the temperature to 25 degC above ambient, with ease. But it is personal decision to use fans or not. I don't, as I have very efficient heat transfer from heatsink to transistor.

If you want to have the temperature rise at 25 degC without fans, you need to improve the heatsink rating (which is normally defined at 60 degC above ambient) by about a factor of 2; factor of 1.6 to go down from +40 degC to +25 degC, and another 30%+ or so for the reduced temperature difference.

A good heatsink supplier (like the one I used) would tell you that the only way to predict temperature rise properly would be to used full 3D simulation, or a published rating curve plotting dissipation vs temperature rise, based on a predefined heatsink geometry.

Or go to Pass Labs site and have a look at how big the sinks are for an AX100. That will give you a very good idea as to whether your 2x Conrad is sufficient. (I am not using Conrad, as you might have guessed.)



Patrick


PS I have been able to predict my heatsink and transistor case temperature to within 3 degC between calculation and measurement, in case you might be interested to know.

  Reply With Quote
Old 27th September 2008, 06:58 AM   #12
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
For those interested in doing their own thermal simulations, you may wish to try the "natsink" software at :

http://www.frigprim.com/



Patrick
  Reply With Quote
Old 27th September 2008, 10:38 PM   #13
diyAudio Member
 
Join Date: Apr 2005
Location: rochester
Just out of curiosity, where does everyone typically get their heat sinks for their projects? I'm actually having a bit of trouble finding anyone that sells heat sinks this big. Any recommended sites/manufacturers?
  Reply With Quote
Old 27th September 2008, 10:42 PM   #14
diyAudio Member
 
guitvinny's Avatar
 
Join Date: Nov 2005
Location: Québec
R-Theta
  Reply With Quote
Old 28th September 2008, 09:20 AM   #15
Magura is offline Magura  Denmark
diyAudio Member
 
Magura's Avatar
 
Join Date: Oct 2003
Location: Denmark, Viborg
Quote:
Originally posted by systemerror909
Just out of curiosity, where does everyone typically get their heat sinks for their projects? I'm actually having a bit of trouble finding anyone that sells heat sinks this big. Any recommended sites/manufacturers?

Scrap metal yards, surplus, and so on. Salvage stuff from old machinery......rob a windmill



Magura
__________________
Everything is possible....to do the impossible just takes a little while longer.
www.class-a-labs.com
  Reply With Quote
Old 29th September 2008, 03:48 PM   #16
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
I buy .187 aluminum sheet stock from onlinemetals and cut it up on the table saw to make my own DIY sinks. This has always worked well for me. The biggest advantage is the lowered stress of knowing that I have unlimited supplies of sink material available off-the-shelf and at the lowest possible price.

Graeme
  Reply With Quote
Old 30th September 2008, 11:16 PM   #17
jpc6204 is offline jpc6204  United States
diyAudio Member
 
Join Date: Sep 2007
I'm looking into the sheet metal idea. One thing that I'm confused about is anodization, is this good or bad? Since anodization creates a thin layer of oxide over the surface (oxide being a thermal insulator) is this helpful or harmful in a heatsink? Obviously natural oxidation is not a good thing, so I'm assuming if I don't get it anodized, any aluminum should be painted.
  Reply With Quote
Old 30th September 2008, 11:49 PM   #18
gl is offline gl  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Sierra Foothills - California
Aluminum anodizes almost instantly when cut and exposed to air. The layer of oxide is extremely thin buts it's there and protects the metal from oxidizing further. Anodizing uses electric current to build the oxide layer up. The oxide is harder than the bare metal so it's a bit less prone to damage. Anodizing also presents the opportunity to color the metal. It doesn't make that much difference to the heat radiating properties of the sink.

There is no need to paint the bare aluminum to protect it. Bare aluminum will, however, pick up fingerprints quite easily and these are a pain to remove. Painting, however, is a good cosmetic thing to do when WAF is important.

As for black paint being a better radiator of heat than bare aluminum - well I'm not sure. I build big heatsinks and for class A operation I haven't noticed a major difference one way or another. So I take the lazy way out and apply paint only in the places where it keeps things looking nice.

Graeme
  Reply With Quote
Old 1st October 2008, 09:46 AM   #19
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
www.infrared-thermography.com/material.htm
__________________
BOXES for crying out loud
  Reply With Quote
Old 1st October 2008, 02:50 PM   #20
diyAudio Member
 
Join Date: Nov 2006
Quote:
Just out of curiosity, where does everyone typically get their heat sinks for their projects? I'm actually having a bit of trouble finding anyone that sells heat sinks this big. Any recommended sites/manufacturers?
There is a seller barrredboss (Russ Boss) on Ebay who sells big heatsinks. I bought mine from him.

JJ
  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
Heatsink for the Aleph 1.2 folkeb Pass Labs 1 23rd January 2006 03:27 AM
Aleph's Heatsink ruangrit Pass Labs 4 1st February 2004 03:29 PM
My aleph 2 heatsink MEGA_amp Pass Labs 12 30th January 2004 10:35 AM
Aleph 2 heatsink thread Gabster Pass Labs 21 29th January 2003 08:44 PM
Aleph 3 heatsink question garnex Pass Labs 2 12th December 2002 06:12 PM


New To Site? Need Help?

All times are GMT. The time now is 03:43 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