JLH Class A headphone amp from ETI not WW

owenhamburg · 22nd January 2013, 04:26 PM

Dear all,

Being a ETI (Electronics Today International) reader years ago as a teenager I had a recolection of a Class A headphone amplifier by JLH that I had not seen the circuit for in a long time.

Then I saw this link Headphone Class A Amplifier.

The ciruit looks simple, and I should like to build a good headphone amplifier for minimal cost and have an irational desire to have a class A deisgn. This will probably not happen in a short time scale but I would be interested to hear your opinion on this circuit.

My questions:

Do you think its a good design? If not why not?

Do you think I can scale it up to larger powers (Say 20 W) if I like it?

Regards

Owen

RNMarsh · 23rd January 2013, 09:31 AM

It should work well for a small power amp... The electrolytics in the feedback are a neg. Thx -RNM

AndrewT · 23rd January 2013, 09:49 AM

A BJT version of the F5 !

Even the protection is similar. BUT importantly it has an RC to allow transients peaks to pass !!!!!!

JLH is no fool.

owenhamburg · 23rd January 2013, 03:56 PM

Thanks for the feedback, I may look into building it sooner but some other things are more pressing in my DIY like finishing off the subwoofers and some software I want to write/finish.

Telstar · 23rd January 2013, 08:30 PM

JLH was a great designer, no doubt. But the circuit is not original in the way his class A amp was, I would go for that one with lower power devices and lower rails.

forr · 23rd January 2013, 10:44 PM

I remember this circuit. I have always a bit worried by the direct connection of R2 et R3 to the power supply rails.

23rd January 2013, 08:30 PM	#5
Telstar diyAudio Member Join Date: Dec 2007 Location: Italy	JLH was a great designer, no doubt. But the circuit is not original in the way his class A amp was, I would go for that one with lower power devices and lower rails. __________________ "The total harmonic distortion is not a measure of the degree of distastefulness to the listener and it is recommended that its use should be discontinued." D. Masa, 1938

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23rd January 2013, 09:31 AM	#2
RNMarsh diyAudio Member Join Date: May 2012 Location: 2457 Cascade Trail; Cool, CA. 95614	It should work well for a small power amp... The electrolytics in the feedback are a neg. Thx -RNM

23rd January 2013, 09:49 AM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	A BJT version of the F5 ! Even the protection is similar. BUT importantly it has an RC to allow transients peaks to pass !!!!!! JLH is no fool.

23rd January 2013, 03:56 PM	#4
owenhamburg diyAudio Member Join Date: Oct 2009 Location: Hamburg	Thanks for the feedback, I may look into building it sooner but some other things are more pressing in my DIY like finishing off the subwoofers and some software I want to write/finish.

23rd January 2013, 10:44 PM	#6
forr diyAudio Member Join Date: Dec 2004 Location: Next door	I remember this circuit. I have always a bit worried by the direct connection of R2 et R3 to the power supply rails.