need opnion on my JLH15w PCB - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 November 2003, 05:12 PM   #1
Calebay is offline Calebay  Denmark
diyAudio Member
 
Join Date: Jul 2003
Location: Denmark
Default need opnion on my JLH15w PCB

Hello

i need someone who can tell me if this layout i have been drawing, have some problems, and if its might be humming

its made from the JLH 'update' schematics

JLH 10 Watt class A amplifier

here it is:
Attached Images
File Type: jpg jlh3.jpg (47.8 KB, 850 views)
  Reply With Quote
Old 26th November 2003, 06:25 PM   #2
Nisbeth is offline Nisbeth  Denmark
diyAudio Member
 
Nisbeth's Avatar
 
Join Date: Jan 2001
Location: Denmark
Hey Carsten, maybe you should post this in the "solid state"-forum

/U.
  Reply With Quote
Old 26th November 2003, 06:28 PM   #3
dhaen is offline dhaen  Europe
diyAudio Moderator Emeritus
 
dhaen's Avatar
 
Join Date: Jun 2002
Location: U.K.
Moved
  Reply With Quote
Old 26th November 2003, 06:38 PM   #4
Calebay is offline Calebay  Denmark
diyAudio Member
 
Join Date: Jul 2003
Location: Denmark
ohh

what forum did i post in?


thx for moving it
  Reply With Quote
Old 26th November 2003, 06:39 PM   #5
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
I still plan to look at this, but probably won't get to it until the weekend.
When are you planning to build boards? Do you think you'd be willing to offer your layout for a a group purchase?
  Reply With Quote
Old 26th November 2003, 08:49 PM   #6
Geoff is offline Geoff  United Kingdom
diyAudio Member
 
Join Date: Apr 2001
Location: UK
Calebay

I have not checked the track/device connections in detail but would offer the following observations.

I would prefer to see a separate return to the star earth point for the ground connections of R2, C2 and R6. That is to say, a 'clean' (signal) earth return and a 'dirty' (rail decoupling etc) earth return.

Space should be provided on the pcb for a heatsink on Q3. Even if a heatsink is not strictly necessary to keep the junction temperature of Q3 at a safe level, it will help to reduce the output dc offset variation during the warm-up period.

The feedback take-off point (R8) is not optimal in that it is taken from a point on the Q1c/ Q2e connection that is remote from the feed to the output. Although this is not as critical as for a Class-AB amp, performance can be improved by arranging the feedback take-off point as shown on the schematic (I don't draw the schematic this way just for the fun of it :-).

I have had bad experiences of fuses and relay contacts in the feed to the speaker, but this is down to personal preference and your requirements may differ.

Geoff
  Reply With Quote
Old 27th November 2003, 12:07 AM   #7
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
Good to see your name here again, Geoff.
  Reply With Quote
Old 27th November 2003, 04:21 AM   #8
Calebay is offline Calebay  Denmark
diyAudio Member
 
Join Date: Jul 2003
Location: Denmark
Hello

tnx Geoff

understand the most. but the part about R8, i don't get. where are the feed to the output in the schematic?

and what kind of bad bad experiences do you have whit fuses and relays on the output?

Mvh. Carsten. A
  Reply With Quote
Old 27th November 2003, 10:57 AM   #9
Geoff is offline Geoff  United Kingdom
diyAudio Member
 
Join Date: Apr 2001
Location: UK
Carsten

You have a pcb trace from Q1c to Q2e. At one point along this trace you have taken the feed to the output. At another point you have connected the feedback resistor. There will be a resistance between these two points which will cause the feedback signal voltage to difer from the output voltage and so distortion will be higher than it need be. See 'Distortion 7' (near the bottom of the page) in Doug Self's article for more detail.

http://www.dself.dsl.pipex.com/ampins/dipa/dipa.htm

IMO, an output fuse should be avoided. If its rating is selected so that it blows before an output transistor fails then it will also more than likely also blow during normal use. If it is sized so that it doesn't blow during normal use then in all probability, under fault conditions, an output transistor will fail before the fuse blows. Also, I do not like the idea of having a modulting resistance which varies with temperature, time and signal voltage directly in the signal path.

With regard to relay contacts in the signal path, there may be better (hermetically sealed?) relays available now, but those I have experience in commercial products, many years ago, have all developed noticeably noisy contacts after a year or two and I am sure that the sonic degradation began long before the contacts began to crackle. If you do use a relay, remember that its contacts must be rated to handle any potential dc fault current, not just the ac currents present in normal operation.

Geoff
  Reply With Quote
Old 27th November 2003, 06:50 PM   #10
Calebay is offline Calebay  Denmark
diyAudio Member
 
Join Date: Jul 2003
Location: Denmark
hello

i have now tryed to change the things you pointed out. but it is more than posible i have made new problems.

here it is:
Attached Images
File Type: gif jlh5.gif (76.3 KB, 617 views)
  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



New To Site? Need Help?

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