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Old 17th January 2007, 09:53 AM   #1
kimbo is offline kimbo  Australia
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Default 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
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Old 17th January 2007, 10:05 AM   #2
poynton is offline poynton  United Kingdom
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Default Re: JLH Direct-Coupled High Quality Stereo Amplifier

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
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Old 17th January 2007, 10:23 AM   #3
Geoff is offline Geoff  United Kingdom
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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.
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Old 18th January 2007, 05:04 AM   #4
pgbhat is offline pgbhat  India
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Hi Geoff,
Can u display the circuit here.
Thanks
pgbhat
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Old 18th January 2007, 09:00 AM   #5
Geoff is offline Geoff  United Kingdom
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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.
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Old 18th January 2007, 09:08 AM   #6
EUVL is offline EUVL  Europe
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Geoff,

Why not put it on your website ?


Patrick
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Old 18th January 2007, 10:17 AM   #7
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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
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Old 18th January 2007, 07:19 PM   #8
Geoff is offline Geoff  United Kingdom
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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
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Old 18th January 2007, 08:57 PM   #9
EUVL is offline EUVL  Europe
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Geoff,

How can we ever do without you !!

Cheers,
Patrick
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Old 19th January 2007, 04:17 AM   #10
pgbhat is offline pgbhat  India
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Hi Geoff,
Thank you
-pgbhat
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