Mini-A PCB finished... Some questions on it ;) - 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 21st February 2011, 07:29 PM   #1
diyAudio Member
 
Join Date: Sep 2009
Location: Dortmund
Default Mini-A PCB finished... Some questions on it ;)

Hi folks...

Finally finished my layout of Greys "Mini-A-Schematic". Didnt manage to make it one-sided The schematic can be found here in the forum.

Click the image to open in full size.

So... Are the trays thick enough? the "small" ones are 0,7 inch and the "big" ones are 1.5 inch.

Greetz...
  Reply With Quote
Old 22nd February 2011, 05:32 PM   #2
diyAudio Member
 
Join Date: Sep 2009
Location: Dortmund
Sorry... I mean traces, not trays
  Reply With Quote
Old 22nd February 2011, 05:35 PM   #3
gruni is offline gruni  Germany
diyAudio Member
 
Join Date: Feb 2008
also, your traces arent .7 and 1.5 inch. that would be roughly 1.8 and 3.8 centimeters.
  Reply With Quote
Old 22nd February 2011, 06:16 PM   #4
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
Small signal traces don't need to be anywhere near that big. You can go smaller than shown for all traces except the ones carrying power in the output. Might even allow you to make it single sided, it you really need to. The feedback trace can be small, just the output trace needs to be anywhere near that big. Same for R18 to C2, etc.

Move R16 much closer to the Gate of Q5 - like R14 and Q4.

Try rearranging so the input differential can be back to back - good thermal contact promotes offset stability. BrianGT's board used a chunk of aluminum between teh devices but if you can get them connected (with an isolator and Isolated screws) it would be helpful.

I don't have Grey's schematic, but I'll bet that there was a cap bypassing D1. A 1 uf film cap would be good, but you can go with a 10 uf electrolytic.

Why the fish hooks around R20 and R21?

Verify that the pads for your resistors are big enough to pass a lead through and still have something to solder to.

Last edited by BobEllis; 22nd February 2011 at 06:34 PM.
  Reply With Quote
Old 23rd February 2011, 03:09 PM   #5
diyAudio Member
 
Join Date: Sep 2009
Location: Dortmund
@gruni: Youre right Im using Eagle. The traces are 0.07mil and 1.5mil.

@Bob: Done Have a look at it...

Click the image to open in full size.

Moved R16, added C4 for bypassing D1, reworked some traces to delete those fish hooks. Thermal contact will be established bay using a 3mm thick copper bar and good thermal greese (about 7.2W/m*K). Think that shall work
  Reply With Quote
Old 23rd February 2011, 05:54 PM   #6
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
You mean 70 mil and 150 mil or 0.070" and 0.150"

Looks better. I'm guessing that you plan to use the top of the board as a ground plane.

You have plenty of room if you want to make it a bit more compact. The feedback trace R21 to R8 should be 70 mil. Same with the trace R21 to C2.

I'm curious. Why did you choose to make R12 variable? Leave a pad to place a fixed resistor once you find a gain that works for you. It sets the active current gain. R11 sets bias. That's more often variable.

There's still a fish hook at R9 R11. No big deal, but you could run the trace from C2 diagonally to R10 then up.

Be sure that the holes and pads for resistors are large enough. Eagle defaults to some really small holes and very little pad around the hole. I've had troubles with resistor leads barely fitting, some brands have larger leads than the default holes. this means you'll end up editing your components, but you're in it to learn, right?

Another thing that would make the board interesting would be to add pads for external output devices so you can make a larger Aleph if you want later.
  Reply With Quote
Old 23rd February 2011, 06:30 PM   #7
diyAudio Member
 
Join Date: Sep 2009
Location: Dortmund
Guess what... ^^

Ill drill the holes for the parts min. +1/10mm everytime. That saves some room for changes with parts. And yes im still learning

R12 is variable for setting DC-offset. Or am i wrong? Could bet ive seen this here around...

Ill first try this one as-is, experimenting around with some parts (capacitors, resistors and transistors from different manufacturers). When done testing and fooling around, ill maybe go on and make a design on an Aleph 30 (think this was the next "stage"). I dont pay anything for the PCBs. So if i mind to change something, ill make it^^

Luckily the postman delivered some "presents" for me 25xIRF9610, 10xIRFP150 and a handful BC550C. Everthing for free. Did i mentioned that im also able to become some parts as "samples"? ^^ Im in heaven for DIY XD
  Reply With Quote
Old 23rd February 2011, 06:45 PM   #8
diyAudio Member
 
BobEllis's Avatar
 
Join Date: Sep 2003
Location: Upstate NY
R11 is what you'd make variable for a little bit of offset control. R12 doesn't make a difference in offset.

We each make our own decisions about samples. I don't take them because I am not going to make a production item, just like I won't test drive a Ferrari as much as I would love to see what it feels like. For $100 or so I can get a decent selection of devices to match...
  Reply With Quote
Old 23rd February 2011, 07:12 PM   #9
diyAudio Member
 
Join Date: Sep 2009
Location: Dortmund
No^^

I mean i get some "samples" out of our stock We produce sensors and bus-systems for automation industries. All parts which i declare as "samples" are parts from running systems
  Reply With Quote
Old 14th March 2011, 08:23 PM   #10
diyAudio Member
 
Join Date: Sep 2009
Location: Dortmund
Well... Back again

First channel wired and what shall i say: It works^^ Runs @1A and gets hot (~50-60C). Think thats class a^^

Got some hum at the output... Very silent but it is there...
  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
Finished mini speaker with TB W4-1337SD domtw Full Range 29 23rd February 2013 03:18 AM
A few pics of my finished B3N mini spheres GuyPanico Full Range 9 9th November 2007 09:23 PM
Mini Statements DIY speaker project is finished! jholtz Multi-Way 0 11th September 2007 09:44 PM
Mini Aleph Questions audioboy Pass Labs 6 3rd September 2007 03:02 PM
Finished mini-A rwagter Pass Labs 7 13th December 2004 11:09 PM


New To Site? Need Help?

All times are GMT. The time now is 01:30 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