JLH 10 Watt class A amplifier

[gmphadte]

power xtors=power transistors

[paulb]

I've just finished a prototype of a JLH using Geoff's PCB layouts (thanks, Geoff!). This is a temporary setup while I decide on final packaging.
Here's a populated board. Notice it's single-sided, and only one wire link is needed. This is an easy board to stuff, I'd recommend this project to beginners except for the heatsinking and power supply requirements make it a fairly involved project.

[paulb]

Here's my test arrangement. There are 8 output transistors spread over 5 heatsinks, and it's still not enough without some fan cooling. I'm running just under 2 amps bias current at +/- 18.5VDC.

[paulb]

The power supply is almost 100% recycled parts. The transformers came from a pair of Advent Powered Loudspeakers (that are currently UnPowered); To get the proper voltage, I wired their primaries in series and their secondaries in parallel via the 10W current sharing resistors. I was originally going to add a capacitance multiplier but with the big capacitors I have Geoff suggested it was good enough without. Also, I didn't want to suffer the voltage drop and lower the rail voltages any further.
If I use this for the final arrangement, and it goes somewhere other than my lab, I'll have to hide it away (I've been told).
I think I might just keep it in the lab, though...

[ashok]

Hi Paulb,
Are you sure you didn't pull this out from the UFO that landed in your garden ( or the sidewalk)?

Anyway I like it !
I'd be shot if I tried to keep a thing like this in the living room .
And I don't have a lab for myself

[chris ma]

Hello there Paulb,

Finally you've completed it after all these years! Well, do you like it? How does it sound? Its ok to tell us if you don't like the sound..we can take it...Ha ha

Congrates!

[paulb]

Hi Chris, thanks. I haven't listened to it enough yet, but I like the sound. Even if I didn't, I'd convince myself that I did after how long it has taken. Still have to package it up somehow.
Are you still using yours? I remember, the one on the casters, right?

[chris ma]

I am still using mines everyday!

See picture for the right channel alone.

1 JLH for the Jx150
1 JLH for the Jx53 plus ribbon tweeter
2 Snubber High cap GC, one each for the 2x 12 inches OB H frame subwoofers.

[dutch diy]

My 2 J-amp-2003's are still in use on a daily basis.

I've not even measured the actual DC-offset for the last year.
Probably a check might be nice.

They still have an audible ''thumb'' at power on. but i don't care.

Soundwise I'm still impressed with the fine combination of the J-amp 2003 and my JMLab Symbol II's.

[UltimateX86]

Originally posted by EUVL
Any comments ?

Patrick

hi

This topology interests me

Have you build this amplifier since?

thx