Aleph J-X Amp Project - Page 131 - 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 26th January 2012, 12:17 PM   #1301
diyAudio Member
 
SCAIFF001's Avatar
 
Join Date: Feb 2010
Location: Toronto & Innisfil
Default Transformer Power Supply Ground

Quote:
Originally Posted by Peter Daniel View Post
When you check traces it shows that GND and SG are connected; SG means signal ground and is the same as GND.

I used two separate pads: one for input signal ground, the other to connect ground reference from the power supply.

I can't be much help in troubleshooting as I didn't built AJ-X yet, however the boards were tested and work fine if properly set up.

Hi,

when you say "ground reference from the power supply" are you referring to the two Bridge Rectifier(s) positive & negative outputs that are connected together along with connecting to the positive & negitive from the power supply capacitors, then all of these are connected to the Ground on the "front end pcb", I believe that this is what I have seen on the schematics ? A reply to this will help me out because connecting the "+" & "-" together with the ground seems counter intuitive to me, so it is responsible for my project taking so long to build because I dred reaching this point.

Thank You

Ian
  Reply With Quote
Old 26th January 2012, 12:22 PM   #1302
oiphy is offline oiphy  Norway
diy newbie
diyAudio Member
 
oiphy's Avatar
 
Join Date: Sep 2011
Location: norway
scaiff001: tips. solder 1 or to points then clean tip with sponge. if it dont help fill the soldertip with solder before the sponge treatment. if this dont help I guess your tip is already broken. worked for me in 20 years both prof. and private. and I still have tips that are 10-15 years old and they are fine.
__________________
" If you're going throu hell, keep going"
  Reply With Quote
Old 26th January 2012, 06:11 PM   #1303
Itsmee is offline Itsmee  England
diyAudio Member
 
Itsmee's Avatar
 
Join Date: Feb 2009
I find this rather handy for cleaning iron clad tips.

Buy Soldering Iron, Tips and Accessories TTC-LF Soldering iron tip cleaner/tinner Multicore 706397 online from RS for next day delivery.
  Reply With Quote
Old 27th January 2012, 10:26 AM   #1304
diyAudio Member
 
Join Date: Jan 2006
Location: Spain
Samoloko, you have a PM
  Reply With Quote
Old 19th February 2012, 08:55 PM   #1305
jerfer is offline jerfer  Canada
diyAudio Member
 
Join Date: Jan 2005
Location: Montreal
Default Heatsink Question

Hi all,

I'm contemplating building an Aleph-J and then converting it to a J-X channel once I'm comfortably experienced. A few questions before I jump in, though.

Dissipating around 30W per fet and, ideally, thermally connecting all of the fets (4) of one channel means that I would need to find a heatsink with

C/W = 30 deg. C / 120 watts / 1.25 (de-rating factor)
or
C/W = 0.2

Looking through the various heatsink manufacturers' websites nothing comes close, even at 12" lengths, unless I blow air across the sink. So here are the first questions:

1. How do you do it, do you just build using multiple widths of smaller heatsinks thus not end up thermally joining the fets?

2. Where do you draw the line, in the A-J's case would you go down to one-fet-one-sink?

HeatsinkUSA has a nice heatsink on offer with a C/W of 0.8. Going to a 12" length should yield a C/W of around 0.4.

3. How much would black anodizing further improve the C/W of this heatsink?

One thing I've been thinking of is building the case with some sort of chimney to generate a stack effect, like in buildings and chimneys, where rising hot air escaping from the top of the stack draws cool air in from the bottom. Building a case with the heatsink flat, fins pointing up, and covering the sink with a chimney assembly should cause an appreciable amount of flow. By my calculation a 20"-high chimney topping a 12"x12" heatsink (sealed on all but the fin edges) should cause a ~50cfm airflow. This assumes a heatsink temperature of 50 C, and an external temperature of 20 C. I can't be the first to think this would work, so:

4. What am I missing this with line of reasoning?

Being that I want to ultimately build a J-X I'd like to size the transformer to be good for two A-J channels or one A-JX. Antek offers a 600VA 18V toroid which, from comments here, will be under-powered. They also offer a 800VA 20V toroid which would probably be sufficient. Here's my PSUD simulation:

Click the image to open in full size.

Note that the only reliable values in this simulation are the ESR values for the parallel caps (3x56mF). The transformer and current sink I'm not sure I configured correctly.

5. Can I use the 800VA/20V trafo in a CRC configuration without having to cascode (and learn how to do so, at least not now) the JFETs?

Thanks for any help and advice you can offer, it is much appreciated.

Jerry
Attached Images
File Type: jpg AJPS.jpg (183.4 KB, 853 views)
__________________
Jerry
  Reply With Quote
Old 20th February 2012, 06:05 AM   #1306
h_a is offline h_a  Europe
diyAudio Member
 
h_a's Avatar
 
Join Date: Sep 2006
Location: Graz, Austria
Hi,

typically one uses (especially for the monoblocks) 2 heatsinks and puts one fet bank (the paralleled fets) on each of one, so - in case of the Aleph J - one pair per heatsink. Alternatively, contact a large heatsink manufacturer (like R-Theta) directly as these do offer 0.2 heatsinks (but typically not available at the large distributors).

Black anodizing mostly looks good and gives some isolation, no real benefit from a thermal point of view (heatsinks are about heat convection not heat radiation).

Last, with that amount of caps in the PSU you'll likely get problems with inrush currents and max diode currents. Either reduce them or think about soft-start.

Enjoy! Hannes
  Reply With Quote
Old 20th February 2012, 11:20 AM   #1307
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
placing the heatsink with its fins pointing up reduces the efficiency quite markedly
  Reply With Quote
Old 20th February 2012, 12:29 PM   #1308
john65b is offline john65b  United States
diyAudio Member
 
john65b's Avatar
 
Join Date: Jan 2005
Location: Chicago
The heatsinks fins should be parallel to the airflow rising against it like a chimney.

The Black anodizing allows more radiative heat transfer to environment, but is dwarfed by the conductive heat transfer to air at these amp temps. Once you get into very high temps (1000F) then radiative starts to govern and really matter. When Radiative heat transfer is high enough, your bare skin will feel the heat, like sitting next to a campfire.
__________________
All right, but apart from the sanitation, medicine, education, wine, public order, irrigation, roads, the fresh water system and public health, what have the Romans ever done for us? Life of Brian
  Reply With Quote
Old 20th February 2012, 02:16 PM   #1309
jerfer is offline jerfer  Canada
diyAudio Member
 
Join Date: Jan 2005
Location: Montreal
Quote:
Originally Posted by h_a View Post
typically one uses (especially for the monoblocks) 2 heatsinks and puts one fet bank (the paralleled fets) on each of one, so - in case of the Aleph J - one pair per heatsink. Alternatively, contact a large heatsink manufacturer (like R-Theta) directly as these do offer 0.2 heatsinks (but typically not available at the large distributors).
I assumed (wrongly, it seems) that since the four FETs in each A-J channel need to be matched to 0.1 Vgs they would benefit from being thermally connected. This is good news! It opens up a whole new set of possibilities...

Quote:
Originally Posted by h_a View Post
Black anodizing mostly looks good and gives some isolation, no real benefit from a thermal point of view (heatsinks are about heat convection not heat radiation).
Quote:
Originally Posted by john65b View Post
The heatsinks fins should be parallel to the airflow rising against it like a chimney.

The Black anodizing allows more radiative heat transfer to environment, but is dwarfed by the conductive heat transfer to air at these amp temps. Once you get into very high temps (1000F) then radiative starts to govern and really matter. When Radiative heat transfer is high enough, your bare skin will feel the heat, like sitting next to a campfire.

Interesting, so there is no real C/W-effect with black anodizing?

Quote:
Originally Posted by h_a View Post
Last, with that amount of caps in the PSU you'll likely get problems with inrush currents and max diode currents. Either reduce them or think about soft-start.
I was thinking a CL-60 in series with each primary. Not enough?
__________________
Jerry
  Reply With Quote
Old 20th February 2012, 07:27 PM   #1310
vmcfer is offline vmcfer  United States
diyAudio Member
 
Join Date: Mar 2009
Default Aleph-X PCB's

Quote:
Originally Posted by jerfer View Post
I assumed (wrongly, it seems) that since the four FETs in each A-J channel need to be matched to 0.1 Vgs they would benefit from being thermally connected. This is good news! It opens up a whole new set of possibilities...






Interesting, so there is no real C/W-effect with black anodizing?



I was thinking a CL-60 in series with each primary. Not enough?
I group members,
Does anybody an address to buy PCB's to build the Aleph-X amplifier at a correct price?
I am interested in buy 3 of them .
Thanks,
Victor
  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
aleph 30 project traw Pass Labs 24 15th June 2012 05:47 AM
X Aleph Project Down Under macka Pass Labs 111 30th June 2008 01:55 PM
Aleph 2 project Thago Pass Labs 2 21st April 2007 07:44 AM
My aleph 2 project Jean Pass Labs 13 21st January 2004 07:14 AM
Aleph 2 (& others) as a project GRollins Pass Labs 41 11th February 2002 12:05 AM


New To Site? Need Help?

All times are GMT. The time now is 10:11 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