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nicolas888 7th April 2006 06:26 PM

JHL Class A ,Higher power circuit, 40W Class A
Is someone built the :

JHL Class A ,Higher power circuit, 40W Class A ?

I found a guy who done a good job but not finish the amp :

I am looking for any informations expecially how is it in temperature comportement.
I want to use the Capaciter multiplier.

By the way, I already built the JHL Class A, 10W from 1969 and It sound very good.

Thanks for you informations.

dutch diy 8th April 2006 11:20 AM

J amp 2003

I built the amp and, I also published versions of the circuit diagram on my amp site.

Have a look ;)

J-amp 2003 site

Currently it's running at a bias of 2A with railvoltages of 29V.

Because its in an enclosed compartment the temperature rises to roughly 48 degrees Celcius after two hours (with room temp of 21 degrees).

nicolas888 9th April 2006 07:10 AM

Thank you for the information on your Web site.

Actually, I noticed different variant from different schematics.

The last update suggest to replace the LM338K by transistors but I already bought 2 to try the "regulator" configuration.

paulb 9th April 2006 08:37 PM

I just finished getting one running and I've posted the information in the main JLH thread:

nicolas888 10th April 2006 10:36 PM

Thanks for your post.

I already built the 10W a few years ago ( Version of 1969 ) and I always wanted to push it to 40W , what I decide to do now.

My only question is the Power dissipation and thw Capaciter multiplier.

By the way, where do you make the PCB ?

paulb 10th April 2006 10:42 PM

The PCBs came from Olimex:
Somebody emailed me to ask if I would consider doing a Group Buy. I'm waiting to see if there is anyone else interested.
I have the Gerber files from Geoff if you want them (or he may be able to provide them for you - he was going to make some minor changes).

bikehorn 11th April 2006 07:58 PM

i became very interested in capacitance multipliers myself, so i did some reading up on them. Rod Elliot's got a great page/project on capacitance multiplier power supplies, and i will use it myself sometime. remember that you need a higher voltage transformer(by a few volts) because you lose some voltage in the multiplier are driving power transistors after all, kind of like the power supply is itself an amp. you should get all kinds of capacitance this way.

dutch diy 12th April 2006 05:28 PM


Originally posted by nicolas888
Thank you for the information on your Web site.

Actually, I noticed different variant from different schematics.

You're right on that one. The addition of C5 has been following a discussion on Geoff's Class A site.

When R12 changed I don't know.

Soundwise I've never compared a capacitance multiplier vs a regulated psu. Fully regulated is just my preference. The main advantage of a LT1083 over a LM338K is the package.

BTW my amps are still in use almost daily, since being moved tot the living room.

nicolas888 13th April 2006 04:27 PM

I already buy the LM338K so I will try both possibilities.

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