JLH 10 Watt class A amplifier

[The Prof]

The JLH Gateway Part-11:

The JLH Gateway to Class-A :: 11​

The P-N-P Pandemic ! The audio scene, just like the fickle fashion scene, is prone to trends and fads that surface with some regul...

jlhclassicdesigns.blogspot.com

This time it is circuits with PNP output transistors ... anybody for the 'sound of holes' rather than that of electrons ? !

 

[The Prof]

The JLH Memorabilia Part-5 - the 1990s :

https://jlh-memorabilia.blogspot.com/2025/01/jlh-memorabilia-past-perfect-5.html

Do read, comment and share.

 

[stevenrotterdam]

I' ve got a few MJ802 with nice heatsinks from old battery chargers. Would they be OK for the JLH amp?

 

[john_ellis]

They should be OK. According to a 1988 datasheet, the current gain can increase 1.4x from 25 to 175C but decreases 0.9x 1.0 to 1.5A, so with a decent heatsink the Iq should remain in the region 1-1.25A. fT 2MHz, should be better than the old 800kHz 2N3055, but these are obsolete, and a 2N3055 today should be 2.5MHz.

 

[stevenrotterdam]

So time to do some recycling
I have som 2n1711
I guess any high beta first transistor will do

 

[sulcorebutia]

The JLH Gateway Part-11:

The JLH Gateway to Class-A :: 11​

The P-N-P Pandemic ! The audio scene, just like the fickle fashion scene, is prone to trends and fads that surface with some regul...

jlhclassicdesigns.blogspot.com

This time it is circuits with PNP output transistors ... anybody for the 'sound of holes' rather than that of electrons ? !

Just in case if you are collecting PNP JLH circuit example, I posted one with FET differential input back in 2021, post #8,142. https://www.diyaudio.com/community/threads/jlh-10-watt-class-a-amplifier.3075/post-6792143

 

[The Prof]

Thank you, Sulcore...that was a very thoughtful addition.
My current "trawl" of the thread is just reaching Page 300 ...will certainly add your design/mod to the grouping of MOS and FET versions coming up a bit later.

By the way, I had put out an SOS regarding the articles of JLH that appeared in Hi Fi News & Record Review magazine, archives of which are NOT in my collection. In case you or your circle has copies, do PM me and send them as they are the only ones missing -- they will make the Memorabilia collection complete. (I trust you have seen the link to Memorabilia above.)
Please read and comment on the blog instead of cluttering this thread ... Namaste!

 

[The Prof]

And speaking of differential inputs, unless you have a crazy asymmetrical LTP, the output harmonic profile will be affected, and with it the 'sound' of the JLH Classic amplifier, I believe ..

 

[The Prof]

The JLH Gateway / Memorabilia comprehensive index to aid reading and reference:

https://jlhclassicdesigns.blogspot.com/2024/11/the-jlh-gateway.html

 

[The Prof]

The JLH Memorabilia Part-6 - Projects from the 1990s:

https://jlh-memorabilia.blogspot.com/2025/01/jlh-memorabilia-past-perfect-6.html

 

[No ideas]

iw that jlh enough or is it to diffrent to be in this thread?

 

[Dehacs]

Is there anyone using this amplifier with 50w at 8 ohms per channel?

 

[No ideas]

too much heat

 

[OldDIY]

Of all the JLH options I have built the HF devices sounded best to me.

The lower output transistor operates in a common emitter circuit. Therefore, a high frequency (at high F\B) is desirable.
The upper transistor is controlled from both the base and emitter sides. The requirements for it are below.

 

[OldDIY]

Russian Diy offered its own version in 1969...using Ge p-n-p transistors.
It works 🙂

 

[No ideas]

I wonder if anybody ever built JLH amp with op-amp front-end?
This seems to be working (simulating) ok.
Sim attached.

View attachment 1062293

Very late response but q1 is pointless it originally was some kind of gain/feedback transistor, the output stage itself has enough voltage gain on its own, and you also have the op amp which piles up even more gain stages on top of another.

 

[Loudthud]

The PNP input transistor contributes even order THD which is partly responsible for the amp's sound. A long tailed diff pair or opamp would negate that.

 

[The Prof]

https://jlhclassicdesigns.blogspot.com/2025/02/the-jlh-gateway-to-class-12.html

Playing Musical Chairs with a clutch of class-A amplifiers...

 

[Agus Widarto]

Still fresh after being soldered and set to 9VDC voltage and 1Ampere current with a 19volt regulated PSU. I was confused when my friend asked what was so special about 2N1711 and 2N2907?