JLH Power Survey - 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 22nd September 2005, 04:29 AM   #1
diyAudio Member
 
astouffer's Avatar
 
Join Date: Jun 2004
Location: Pittsburgh, crumbling wasteland
Default JLH Power Survey

To anyone running a JLH or similar amplifier. What voltage and current do you have the amp biased for? I plan on building a version with MJ15003 output devices and want to use a +/- 24v supply because of the availability of switching power supplies. One site has 24v 2amp supplies for $4.95. Four will cost less than half of what a similar toroid would run. Any HF noise should easily be filtered with some caps and maybe a choke.


Adam
  Reply With Quote
Old 22nd September 2005, 08:32 PM   #2
tlf9999 is offline tlf9999  United States
Account Disabled
 
Join Date: May 2005
Location: none
I got a few of them but mostly running them at about 750ma off 36v rails.

Mine are mostly mosfet versions so they run most like class AB than class A.
  Reply With Quote
Old 23rd September 2005, 11:07 PM   #3
diyAudio Member
 
dutch diy's Avatar
 
Join Date: May 2001
Location: NL, The Hague
Send a message via ICQ to dutch diy
Default J-amp

Well,

my J-amp runs on 29.5 V @ 2.1 A bias for the last 2 years.

It has 4 mj15003 devices per channel.

It was designed to run on a 3 A bias but I had to limit that because of heat build up in my audio cabinet.

Sound: I've had no real comparison made between both setting.
__________________
J-amp powers Avantgarde-Acoustic Trio
  Reply With Quote
Old 23rd September 2005, 11:14 PM   #4
diyAudio Member
 
dutch diy's Avatar
 
Join Date: May 2001
Location: NL, The Hague
Send a message via ICQ to dutch diy
Default Re: JLH Power Survey

Quote:
Originally posted by astouffer
I plan on building a version with MJ15003 output devices and want to use a +/- 24v supply because of the availability of switching power supplies. One site has 24v 2amp supplies for $4.95.
Adam
Be aware that the current drawn from the powersupply is not a steady Ibias. It will run upto 2 times the bias current. Eg: No signal : only Ibias flows through the ouput transistor. On the 'negative' side of the sinus current will be just above 0 A ( [Class A ]. On the 'positive side of the sinus current needs to be double the Ibias.
__________________
J-amp powers Avantgarde-Acoustic Trio
  Reply With Quote
Old 26th September 2005, 03:00 AM   #5
diyAudio Member
 
astouffer's Avatar
 
Join Date: Jun 2004
Location: Pittsburgh, crumbling wasteland
Thanks for the info. It turns out the place selling power supplies is sold out, guess I'll be building my own. Do you use any regulators to reduce hum or should capacitors and chokes be enough?


Adam
  Reply With Quote
Old 26th September 2005, 03:42 AM   #6
Ipanema is offline Ipanema  Malaysia
diyAudio Member
 
Ipanema's Avatar
 
Join Date: Jun 2004
Location: KL
Hi guys,

I built JLH with this circuit http://www.tcaas.btinternet.co.uk/jlhupdate.htm.

The bias is set at 300mA due to small heatsink. I am very dissatisfied with the sound as compared to GC. Also substitue TIP3055 with MJL21194 with no improvement in sound. It has poor control on the lower end, rough top end and not as detail as GC. It only excel with solo female vocal. Can you tell me what's went wrong?

Thanks.
Attached Images
File Type: jpg jlh.jpg (32.5 KB, 482 views)
  Reply With Quote
Old 26th September 2005, 03:43 AM   #7
Ipanema is offline Ipanema  Malaysia
diyAudio Member
 
Ipanema's Avatar
 
Join Date: Jun 2004
Location: KL
Oh yes, my DC supply is +/-26V.

Thanks.
  Reply With Quote
Old 26th September 2005, 08:07 AM   #8
diyAudio Member
 
Greg Erskine's Avatar
 
Join Date: Jan 2002
Location: Sydney/Australia
Hi Ipanema,

I haven't made a JLH yet.

On the schematic, it looks like you missed C6/C6A and C7/C7A. Rail filtering is important on amps with poor PSRR.

Feedback cap C4 may be necessary. I know it is missing off the "final" schematic.

I don't believe running the amp at low bias is a good test for a class A amp. Put some big heatsinks on, and/or use a fan.

You need to post the details of your power supply. It needs to be reasonably ripple free.

A picture of the amp may be useful too.

Regards
__________________
Greg Erskine
  Reply With Quote
Old 26th September 2005, 08:19 AM   #9
diyAudio Member
 
Join Date: Jul 2001
Location: The Netherlands
300mA is too low for such a low feedback BJT design... I run mine from 30Volt single rails at 1.4A bias.. I also build a MOSFET version that sonicall out performed the BJT, regardless of bias...
  Reply With Quote
Old 26th September 2005, 09:20 AM   #10
Ipanema is offline Ipanema  Malaysia
diyAudio Member
 
Ipanema's Avatar
 
Join Date: Jun 2004
Location: KL
Hi Greg,

The local supply decoupling caps are 1000uF + 100nF (ceramic). Power supply circuit is capacitance multiplier as suggested here :

http://www.tcaas.btinternet.co.uk/jlhcapmult.htm


I use Figure 2 which suppose to sound better without C4 albeit higher offset. Offset are 10mV and 80mV for my stereo pair.

Will try higher biasing when I got a macho heasink.

Do you think that BC560C is inferior than 2SA970 in this application?


Thanks.
  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
Power Supply Topologies - Survey Bakmeel Power Supplies 2 27th May 2008 09:11 PM
Survey fun! danielwritesbac Chip Amps 23 27th January 2008 06:26 AM
Survey audio_noob Multi-Way 2 11th September 2003 09:02 PM
Gainclone Cap Survey PaulHilgeman Chip Amps 82 9th May 2003 05:01 PM


New To Site? Need Help?

All times are GMT. The time now is 08:38 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