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Old 6th August 2006, 02:04 PM   #1
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Default The Leach Amp

I am looking for some opinions....

I recently acquired a commercial Leach amp: The Leach Amp manufactured by LSR&D back in the 80's. It is based on the Leach Low TIM amp design. The specs are fairly impressive, and the power supply is massive. I have had the opportunity to listen to a Leach Double Barrelled amp in a fairly high end system and was impressed with the sound. Listening to this amp for a short period left me disappointed. The sound was veiled and undetailed. The sound stage was almost non existent.

I am driving a pair of Martin Logan Aerius electrostats, but it shouldn't be a problem for the amp. My source is a McCormack CDP and a Curcio Daniel pre amp. My system amp is a Radford ESA225 tube amp (25 wpc Class A) and the basis of my comparison.

So, are the Leach and Radford in two different classes and should I move on in my quest for better sound? Could the Leach be out of spec (it seems to have had a hard life before coming to me!).

Comments and suggestions welcome.

thanks,

Paul
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Old 7th August 2006, 10:15 AM   #2
djk is offline djk
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That amp is at least 25 years old. It's junk, just send it to me.

A clapped-out one (like yours) went on eBay last month for $442, and a Heath-Kit Leach in the same kind of shape went last week for $572. A newer Threshold S200 only brought $595.

Replace the two 22F power supply bypass caps per channel, the two 100F caps in the front end per channel, and the 470F cap in the feedback loop for each channel before you bad-mouth it. Then consider an up-grade of all the 0.1F mylars to polypropylene.
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Old 7th August 2006, 10:57 AM   #3
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Default Leach Amp

DJK

Thanks for your response. I wasn't necessarily bad mouthing the Leach, just stating the facts. My Radford is at least as old as the Leach and sounds excellent, albeit having the tubes upgraded recently.

I will replace the recommended caps and have another listen.

Paul
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Old 7th August 2006, 11:13 AM   #4
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All the listed original caps were made by Callins. They sounded better than almost anything available, but they die after a short life, 7~10 years. If you like 'warm' bass leave out the 22F caps.

The LSR&D 101 is one of my favorite amps. The latest version is even better, but is only available as DIY.
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Old 7th August 2006, 10:27 PM   #5
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Default Leach Amp

djk;

I wasn't aware that LSR&D were still in business. Do they have a website?

thanks,

Paul
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Old 8th August 2006, 06:41 AM   #6
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LSR&D isn't, that's why I mentioned DIY.

WM Leach still sells the boards for the v4.5, there was a group buy here at DIY Audio for a new version with plastic ouputs, it looks well thought out. There was also a group buy on a Krell design that is more similar than different.

http://users.ece.gatech.edu/~mleach/lowtim/
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Old 14th November 2006, 12:36 PM   #7
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Only a question, on many amplifier I see a resistor that separates
Ground signal from Ground Chassis.
(as the leach) which are the advantages?

tnx !
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Old 14th November 2006, 12:53 PM   #8
AndrewT is offline AndrewT  Scotland
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Hi Gold,
Quote:
see a resistor that separates Ground signal from Ground Chassis. (as the leach)
no, it doesn't.
Leach has a signal ground connection from PCB to audio ground and correctly runs a power ground connection from the PCB to audio ground.

These two routes could be quite long, so he has added a short route, with lower and consistent impedance, on the PCB between signal ground and power ground.

There is a mistake in the PSU schematic where he shows the same symbol for the safety earth and the PSU 0volt. This implies these should be connected. Don't.

Keep the safety earth separate from the audio ground.

Run a wire from PSU 0v to audio ground.

Run a wire from safety earth to a disconnecting network and then a wire from the other side of the disconnecting network to audio ground.
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Old 14th November 2006, 01:15 PM   #9
sreten is offline sreten  United Kingdom
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Hi,

Hmmm.......

As this is a DIY site consider converting your speakers to bi-wiring
and then bi-amping them with both amplifiers, one of them with
adjustable gain.

just a thought ........

/sreten.
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Old 14th November 2006, 01:42 PM   #10
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Quote:
Originally posted by AndrewT
Hi Gold, no, it doesn't.
Leach has a signal ground connection from PCB to audio ground and correctly runs a power ground connection from the PCB to audio ground.

These two routes could be quite long, so he has added a short route, with lower and consistent impedance, on the PCB between signal ground and power ground.

There is a mistake in the PSU schematic where he shows the same symbol for the safety earth and the PSU 0volt. This implies these should be connected. Don't.

Keep the safety earth separate from the audio ground.

Run a wire from PSU 0v to audio ground.

Run a wire from safety earth to a disconnecting network and then a wire from the other side of the disconnecting network to audio ground.
Hi AndrewT
Yes the question was the resistor between ground signal and
power ground (or output ground) R51 82Ohms
http://users.ece.gatech.edu/~mleach/lowtim/

Schematics link http://img166.imageshack.us/img166/8651/ampleachfq5.gif

bye.

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