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Old 20th September 2012, 12:56 PM   #2551
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Mike I think I now have the correct schematic from here - can you please confirm.

The Class-A Amplifier Site - A JLH Amp for the Quad ESL57 However, it simulates very poorly I might have a mistake at capturing the schematic.
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Old 20th September 2012, 01:06 PM   #2552
mikelm is offline mikelm  England
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Thx Nico,

The Guy who developed this amp is called Tim Andrews and I've rarely heard of a design that was developed so painstakingly component by component to end up with sound that he thought most accurately reproduced the natural sound of acoustic instruments ( he is a professional pianist so gets to hear the real thing quite often )

I have not heard this version so cannot offer a personal comment but I have to confess I am somewhat amused that such opposite views are excited by a given design and I suspect the F1 / fiesta comparison may be a bit OTT

I thought some people ( like nelson pass ) like the sound of 3rd HD

cheers

mike
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Old 20th September 2012, 01:10 PM   #2553
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JLH is one hell of an amp. Very worth building.
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Old 20th September 2012, 01:11 PM   #2554
mikelm is offline mikelm  England
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Oh - the comments above do not apply to the ESL57 version only the Tim Andrews version
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Old 20th September 2012, 01:17 PM   #2555
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Quote:
Originally Posted by mikelm View Post
Oh - the comments above do not apply to the ESL57 version only the Tim Andrews version
Correct
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Old 20th September 2012, 04:37 PM   #2556
AndrewT is offline AndrewT  Scotland
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maybe we ask:
are you towing a caravan, or transporting a blonde?
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Old 20th September 2012, 04:41 PM   #2557
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by mindutis View Post
JLH is one hell of an amp. Very worth building.
I've been building mine for more than a year. No excuse really, I should get it finished. Perhaps this winter...
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Old 20th September 2012, 04:54 PM   #2558
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I am building one again The chassis i am making weights 15Kg already without anything inside of it I expect total weight of about 25Kg. Found a very nice 2SC2922 output transistors. It needs about 10pcs to match them for a stereo amplifier. Not that many at all. The expected Power dissipation should be around 130W per chassis.

Just have no idea how much capacitance ill be needing with 30V power supply voltage. So far I ordered 90.000uF total. But i think it will be too little.
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Old 20th September 2012, 05:01 PM   #2559
ferret is offline ferret  South Africa
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Hi Nico & Mike,

I am currently driving my stacked ESLs with a Bedini 25.25, itself driven by a vintage Audion Megavox Pre II valve pre (circa 1985 as Audion was forming out of Audio Inovations). They have been an excellent combo. The Bedini needs a major overhaul as the circuit boards are starting to deteriorate. I need to strip one channel down to the bare board and have new ones made albeit slightly modified. The Bedini currently has MJ802s instead of 2n3055Hs and BC550/560 in place of MPS8098 etc. These transistors were replaced some three years ago when lightning damaged the one channel. These new components gave the Bedini a complete facelift - the mids improved by a fair factor, but the bass extension and "resolution" was profoundly better. The top end also improved but not as much. The gent who repaired the Bedini drew the circuit diagram for future reference, and I will post it here soon, as a matter of interest. Anyway, long story short, I want to build the JLH Class-A for ESL so that I can still get the sweet sound of class-a while repairing/modding the Bedini. BTW I asked Bedini USA for assistance with PCB layout and all I got was the middle finger (send it to us a we will repair it - $2000 later). No thanks, I'll do that myself, and have fun doing it.

Regards,

Kevin
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Last edited by ferret; 20th September 2012 at 05:22 PM. Reason: Problem with posting too large a pdf
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Old 20th September 2012, 05:14 PM   #2560
ferret is offline ferret  South Africa
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Oops,

Sorry I can't upload the PDFs they're bigger than allowed - will rescan to fit the forum protocol.

Sorry gents,

Kevin
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