Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Flat heatsink for F1 ?
Flat heatsink for F1 ?
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
Thread Tools Search this Thread
Old 24th December 2012, 06:36 PM   #1
pixpop is offline pixpop  United States
diyAudio Member
pixpop's Avatar
Join Date: Jan 2005
Location: Los Angeles
Flat heatsink for F1 ?
Default Flat heatsink for F1 ?

Let's say I wanted to mount some F1 PCBs on flat Aluminum plate about 1/8" (3mm) thick, using the Al as the heatsink (i.e. no fins...).

Is there any amount of Al sheet that would suffice? How would I calculate how big the sheet would need to be?
  Reply With Quote
Old 24th December 2012, 10:37 PM   #2
HIPCHECK is offline HIPCHECK  United States
diyAudio Member
Join Date: Jun 2004
Location: ARKANSAS
Might want to look here:
He is using single plates per mosfet IIRC.

With the AX spreadsheet you can see how much per fet each plate is able to burn?

If a inch of duct tape will fix it, 3 feet should fix it for life!!!!
  Reply With Quote
Old 24th December 2012, 11:12 PM   #3
Andrew Eckhardt is offline Andrew Eckhardt  United States
diyAudio Member
Join Date: Nov 2005
If I looked at the design right he has 13.5 watts burning in each output transistor. IRFP240's being what they are, it's probably ok, but I would personally be interested in the case temperature rather than the temperature at the edge of the plate directly above the transistor, especially in the usual 20C room rather than 7C. 1/8" material at that distance is going to show a very large gradient between the case and the plate edges. I would recommend 3/16 or 1/4 with the same area plate at that dissipation. Obviously this would cost more and take up greater space. Or you could run 1 transistor per 1/8" plate.
  Reply With Quote
Old 26th December 2012, 09:14 PM   #4
gl is offline gl  United States
diyAudio Member
Join Date: Dec 2003
Location: Sierra Foothills - California
I don't think you gentlemen have read and understood the first few posts in the AX100 thread completely.

The main heat sink is comprised of 3/16" thick aluminum plates. The .125" thick plates are used only for the end plates. The end plates don't have any transistors on them.

When the amps were first powered up I ran 13.5 watts of dissipation per transistor for a week or two to see how the sink would perform. All was good. I THEN increased the dissipation to 15 watts per transistor. The sink temperature rise was still modest and is given in the thread. These amplifiers have been in constant use since they were built in 2006, both in summer heat as well as winter. The measured temps were made with a Fluke infrared hand held thermometer pointed down into the heat sink at the transistor cases. This not a rigorous methodology but IMO it's close enough. So I would rate the heat sinks a success even though they are, as I said in the thread, very ugly.

I have used this heat sink construction method many times and I am currently building a pair of 200W class A monoblocks with 16 main plates, each 18" x 7". The plan is to once again to use 3/16" plate and put 2 transistors on each plate. I am shooting for 18W of dissipation per transistor this time. We'll see how it goes. I will increase the plate thickness to .25" if I need to, and if I'm willing to deal with the added weight.

The thickness of the plates makes a huge difference on the efficiency. I have tried .125 and even .1 and I wouldn't recommend either thickness for class A. There is a heat sink calculator somewhere on the web for flat plate stock but I don't remember where it is. Rod Elliot's site maybe.

I have found that the dominant thing in heat sink pricing is the cost of the raw aluminum. Whether extruded stock or simple flat sheet stock, the cost is pretty close. The sheet stock, however, is far easier to find and in my view, is much easier to work with. All you need is a table saw and a drill, and there are no threaded holes -Yay.


Last edited by gl; 26th December 2012 at 09:20 PM.
  Reply With Quote
Old 27th December 2012, 08:04 AM   #5
LineSource is offline LineSource  United States
diyAudio Member
LineSource's Avatar
Join Date: Sep 2003
Location: SiliconValley
Hi pixpop,

To help the discussion, I have attached pics of the Jungson, and McIntosh MC1 2000W monster amp which use a type of aluminum plate output transistor heat sink. You can estimate physical plate fin sizes from the pics.

There are a few heatsink simulation programs on the web. I have used R-Tools. There are also simple tables for heat spreading on the web which can give reasonable estimates for a single fin.

I have also attached a pic of highly regarded extruded aluminum heatsink profiles to aid in comparison. Heatsink USA is a DIYaudio vendor. It is sometimes valuable to have all transistor junctions operate near the same temperature. Bipolar Class A/B amps bias optimization often assumes a uniform temperature on all transistors. ThermalTrak bipolars include an on-header diode which provides fast time constant response, but still only averages thermal drops over several transistors.
Attached Images
File Type: jpg jungson_09.jpg (83.2 KB, 97 views)
File Type: jpg mc-1.jpg (37.0 KB, 95 views)
File Type: jpg mc-2.jpg (33.8 KB, 96 views)
File Type: jpg Al_HS_Extrusions.jpg (74.9 KB, 95 views)
  Reply With Quote


Flat heatsink for F1 ?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
F1 heatsink? MrMajestic Pass Labs 7 25th December 2012 11:32 PM
Flat FR, Flat Power Response, in-phase crossover? RockLeeEV Multi-Way 15 7th February 2012 09:07 PM
Large Flat Heatsink x 4 Pieces Michael Rothacher Swap Meet 1 14th June 2010 08:52 PM
flat sub for flat TV Artmaster Subwoofers 0 17th December 2008 12:15 PM
How Flat is "Flat"? (XT18WO + 27TBFC-G = MTM) zenon Multi-Way 3 21st January 2007 04:15 PM

New To Site? Need Help?

All times are GMT. The time now is 09:59 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio