JLH Direct-Coupled High Quality Stereo Amplifier

kimbo · 17th January 2007, 09:53 AM

I recall a couple of friends constructing a pair John Linsley Hood integrated stereo amp kits in the early/mid 70s. They were solid state and somewhere in the region of 50-70w, and included (I think) a parametric tone control. I think the articles appeared in Wireless world, but I could be wrong. A search of the web came up with the "Direct-Coupled High Quality Stereo Amplifier" but I can't be sure if this was the one. At the time we thought they were the 'ants pants', but remember ....this was the 70's!

Anyway, my questions are....
Does anyone have more details?
Can anyone comment on the performance of the amp?

Cheers,
Kim

poynton · 17th January 2007, 10:05 AM

Quote:

Originally posted by kimbo
I recall a couple of friends constructing a pair John Linsley Hood integrated stereo amp kits in the early/mid 70s. They were solid state and somewhere in the region of 50-70w, and included (I think) a parametric tone control. I think the articles appeared in Wireless world, but I could be wrong. A search of the web came up with the "Direct-Coupled High Quality Stereo Amplifier" but I can't be sure if this was the one. At the time we thought they were the 'ants pants', but remember ....this was the 70's!

Anyway, my questions are....
Does anyone have more details?
Can anyone comment on the performance of the amp?

Cheers,
Kim

Hi.

I remember this well.
I don't recall the details but I think a company called Hart (?) marketted a kit form.

Reviews were excellent.

Andy

Geoff · 17th January 2007, 10:23 AM

You will find an (almost) complete list of JLH articles on my website:

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

The 'Direct-Coupled High Quality Stereo Amplifier' was published in Hi-Fi News and Record Review between Nov '72 and Feb '73. I have a copy of the power amp schematic but unfortunately not the full article. This amp used a BJT output stage and was rated at 75W.

As you will see from the list of articles, there were later designs with a similar power rating but using a MOSFET output stage published in WW and ETI in the early '80s.

pgbhat · 18th January 2007, 05:04 AM

Hi Geoff,
Can u display the circuit here.
Thanks
pgbhat

Geoff · 18th January 2007, 09:00 AM

Quote:

Originally posted by pgbhat
Can u display the circuit here.

My hardcopy of the schematic is rather old and so, in order to remain legible, would probably need a file size larger than can be attached here. Email me and I will scan the schematic and send you a copy.

EUVL · 18th January 2007, 09:08 AM

Geoff,

Why not put it on your website ?

Patrick

Jonathan Bright · 18th January 2007, 10:17 AM

Yes, Geoff's right Re: reference. (A) it didn't have a parametric tone control. But it wasn't a completely conventional tone control either. The difference was that JLH included switched capacitors to allow the turn over frequencies to be varied. Other than that it was a classic Baxandall feedback type. (B) performance. JLH always placed a high premium on stability and square wave performance. It had low THD, good stability. The other feature is that he used a shunt feedback RIAA circuit that seems to get better response from listeners that the series type.
It would still sound good in the 21st Century!!!

Kimbo, I've just reviewed your post and notice that you live in Melb'. I see also that you are "incomunicado" via email. But as an ex-Melbournian (and Essendon fan) can I ask that you contact me via my email (bright@gil.com.au) and, as they say in the movies "you will learn something to your advantage". Just a hint. None of the Melb' libraries carry back copies of HFN/RR that go back that far (bitter experience)..........but "Brisvagas" does (deep joy)......
Jonathan Bright

Geoff · 18th January 2007, 07:19 PM

Quote:

Originally posted by EUVL
Why not put it on your website ?

Patrick

Done (plus one or two others

)

http://www.tcaas.btinternet.co.uk/index-5.htm

Geoff

EUVL · 18th January 2007, 08:57 PM

Geoff,

How can we ever do without you !!

Cheers,
Patrick

pgbhat · 19th January 2007, 04:17 AM

Hi Geoff,
Thank you
-pgbhat

17th January 2007, 09:53 AM	#1
kimbo diyAudio Member Join Date: Mar 2004 Location: Melbourne	JLH Direct-Coupled High Quality Stereo Amplifier I recall a couple of friends constructing a pair John Linsley Hood integrated stereo amp kits in the early/mid 70s. They were solid state and somewhere in the region of 50-70w, and included (I think) a parametric tone control. I think the articles appeared in Wireless world, but I could be wrong. A search of the web came up with the "Direct-Coupled High Quality Stereo Amplifier" but I can't be sure if this was the one. At the time we thought they were the 'ants pants', but remember ....this was the 70's! Anyway, my questions are.... Does anyone have more details? Can anyone comment on the performance of the amp? Cheers, Kim

18th January 2007, 10:17 AM	#7
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	Yes, Geoff's right Re: reference. (A) it didn't have a parametric tone control. But it wasn't a completely conventional tone control either. The difference was that JLH included switched capacitors to allow the turn over frequencies to be varied. Other than that it was a classic Baxandall feedback type. (B) performance. JLH always placed a high premium on stability and square wave performance. It had low THD, good stability. The other feature is that he used a shunt feedback RIAA circuit that seems to get better response from listeners that the series type. It would still sound good in the 21st Century!!! Kimbo, I've just reviewed your post and notice that you live in Melb'. I see also that you are "incomunicado" via email. But as an ex-Melbournian (and Essendon fan) can I ask that you contact me via my email (bright@gil.com.au) and, as they say in the movies "you will learn something to your advantage". Just a hint. None of the Melb' libraries carry back copies of HFN/RR that go back that far (bitter experience)..........but "Brisvagas" does (deep joy)...... Jonathan Bright __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

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17th January 2007, 10:23 AM	#3
Geoff diyAudio Member Join Date: Apr 2001 Location: UK	You will find an (almost) complete list of JLH articles on my website: http://www.tcaas.btinternet.co.uk/jlharticles.htm The 'Direct-Coupled High Quality Stereo Amplifier' was published in Hi-Fi News and Record Review between Nov '72 and Feb '73. I have a copy of the power amp schematic but unfortunately not the full article. This amp used a BJT output stage and was rated at 75W. As you will see from the list of articles, there were later designs with a similar power rating but using a MOSFET output stage published in WW and ETI in the early '80s.

18th January 2007, 05:04 AM	#4
pgbhat diyAudio Member Join Date: May 2003 Location: Bangalore	Hi Geoff, Can u display the circuit here. Thanks pgbhat

18th January 2007, 09:08 AM	#6
EUVL diyAudio Member Join Date: Oct 2003	Geoff, Why not put it on your website ? Patrick

18th January 2007, 08:57 PM	#9
EUVL diyAudio Member Join Date: Oct 2003	Geoff, How can we ever do without you !! Cheers, Patrick

19th January 2007, 04:17 AM	#10
pgbhat diyAudio Member Join Date: May 2003 Location: Bangalore	Hi Geoff, Thank you -pgbhat

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