JLH 10W audio amp help with parts substitutions - 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 2nd August 2006, 10:47 PM   #1
kiram9 is offline kiram9  United States
diyAudio Member
 
Join Date: Aug 2006
Default JLH 10W audio amp help with parts substitutions

Im new here, but i just tried building my own version of the JLH 10W class A amplifier shown in figure 3 of
http://sound.westhost.com/jll_hood.htm

I had to make some parts substitiutions, Basically I
1. Subsitituted the output transistors (MJ480s) for 2N3055's
2. substituted the 2N3906 for a 2N2907
Substitued the 2n697 for a 4401 NPN transistor

I ran a spice model using thesubstituted parts using LT's switchercadIII and it looked like it would work no problem, but when I prototyped it, I found that at about 15 volts, there would be some sound, but it would be somewhat distorted.

Also when I brought up the voltage to around 22 volts, which is where I ran the simulation, the idle current rose to about .8 amps, what was predicted in the simulation, but the audio level faded away to nothing, (unpredicted).

So I have an amp that makes noise, and not much else. The Oscilliscope shows that when the voltage is too low, (around 10 volts) there is clipping on the upper half of the signal, and when it is too high, there is too much clipping on the lower half of the signal...

Any help would be appreciated, I am a little confused with this design, as the modifications I have made to it under simulation show that there should be no effect, but it does not work.....
  Reply With Quote
Old 3rd August 2006, 07:50 AM   #2
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
I can only advise you to check wiriong and parts as I have built this amp many times with similar parts always with good results !
regards Trev
  Reply With Quote
Old 3rd August 2006, 08:05 AM   #3
rpapps is offline rpapps  Antarctica
diyAudio Member
 
Join Date: Jul 2004
Location: nowhere of interest
Hi Kiram9
<Quote>
2. substituted the 2N3906 for a 2N2907
</Quote>

According to my Towers Transistor Selector book, 2N3906 is NPN and 2N2907 is PNP. You should take another look at suitable substitutes.
Cheers
Rob
  Reply With Quote
Old 3rd August 2006, 09:21 AM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
I have 2n3906 as the PNP complement to 2n3904

Have you found the web site with all the JLH updates and transistor substitutions?
__________________
regards Andrew T.
  Reply With Quote
Old 3rd August 2006, 10:24 AM   #5
rpapps is offline rpapps  Antarctica
diyAudio Member
 
Join Date: Jul 2004
Location: nowhere of interest
Hi Andrew
Yes, you are right.
I must have read the next line, 2n3907.
My eyesight is really getting bad.
Part of the reason I am retired from this sort of work.
My apologies to Kiram9.
I guess it's time I retired from the field.
Cheers
Rob
  Reply With Quote
Old 3rd August 2006, 12:22 PM   #6
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
Dont retire!!!
Get glasses it a real pain i find it hard to read part nos myself !
Regards Trev
  Reply With Quote
Old 3rd August 2006, 03:37 PM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
glasses aren't enough for me, I have an eyeglass (+5D), a magnifier (+3D) on helping hands and a strong halogen spot.
__________________
regards Andrew T.
  Reply With Quote
Old 4th August 2006, 12:56 AM   #8
rpapps is offline rpapps  Antarctica
diyAudio Member
 
Join Date: Jul 2004
Location: nowhere of interest
Hi
I'm using all the aids Andrew mentioned but my problem is Macular Degeneration and whilst it's progress can be slowed, I will eventually lose sight unless a heart attack gets me first.
Cheers
Rob
  Reply With Quote
Old 6th August 2006, 10:59 PM   #9
kiram9 is offline kiram9  United States
diyAudio Member
 
Join Date: Aug 2006
Thanks for your advice, Im still playing with it and I have it working a little better than before... I think my biggest problem is the radio shack parts, which i have already learned, usually have really strange values. Thanks for your advice, I tried building it twice, and I double checked everything, since its not the design, I might try a similar design to see if something else works. I will keep you posted.
  Reply With Quote
Old 6th August 2006, 11:08 PM   #10
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
Yes Please persist Its a worthwhile design. Its performance far outways its small component count !Just think how chuffed you will be when you hear it working correctly.
Best of luck.
Regards Trev
  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
GFA-555 parts upgrade/substitutions? Mac_Hath Solid State 89 12th July 2011 10:23 PM
Trying to source 8700uf @ 56V or substitutions CountryScience Parts 2 17th June 2009 09:24 PM
Tube DI Help, Please: Substitutions slor Tubes / Valves 0 12th April 2008 03:20 AM
Ono semi substitutions and other Q's sbear Pass Labs 3 3rd February 2006 07:24 AM
Help with transistor substitutions trwh Solid State 8 10th September 2002 05:49 PM


New To Site? Need Help?

All times are GMT. The time now is 10:38 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