Where can one buy the Leach Amplifier PCBs ? - diyAudio
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Old 14th June 2012, 07:58 AM   #1
kimbal is offline kimbal  Australia
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Default Where can one buy the Leach Amplifier PCBs ?

Hello -

I live in Brisbane, Australia.

Whilst looking for information on the Leach Amplifier, and now also learning of Prof. Marshall Leach's recent passing in 2010 ( since he supplied the PCBs) -
I am now wondering if any one knows where I can buy predrilled fibreglass PCB's for the Leach Amp design - probably the version 4.5 that is shown on the Leach Amp Website ? A local supplier of these boards would be ideal.

Additional to this - the original 1976/77 Audio Magazine articles showed the board as having an earth ground plane on the component side - so I don't know if new boards come with this feature still ?

I'm also interested in the same Leach Amplifier design, but with a higher power output > say from 250-500 watts into 4 ohms ( since I will bridge 2 modules to get even more power @ 8 ohms)< if anyone knows of PCBs being available for this.

Any assistance is greatly appreciated.
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Old 14th June 2012, 12:06 PM   #2
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I have two boards (4 channels) of the ver 4.5 boards. I purchased these from Dr Leach in 2009, but my project has never gotten off the ground. I am located in the US. If you are interested, then please PM with an offer for both boards.
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Old 15th June 2012, 12:34 PM   #3
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by kimbal View Post
Leach Amplifier design, but with a higher power output > say from 250-500 watts into 4 ohms
a 2pr output stage, the standard Lo Tim implementation will struggle, to do that reliably.
You will probably have to go to one of the clones to implement a 3pr to 5pr output stage.

2pair of MJ15003/4 or MJ21193/4 can do ~200W into 8r and possibly 250W into 4r, if kept cooler.
4pr of MJ21193/4 or MJ21195/6 can do ~400W into 8r0 and probably around 500W into 4r, again if kept cooler.
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Last edited by AndrewT; 15th June 2012 at 12:51 PM.
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Old 15th June 2012, 12:45 PM   #4
kimbal is offline kimbal  Australia
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Default About your Leach boards

Quote:
Originally Posted by WithTarragon View Post
I have two boards (4 channels) of the ver 4.5 boards. I purchased these from Dr Leach in 2009, but my project has never gotten off the ground. I am located in the US. If you are interested, then please PM with an offer for both boards.
Hi WT;

Thanks for the reply. Could you kindly send me a picture or two of your PCBs and advise if they have the ground plane on the component side.
From that I'm happy to make an offer.
My email is - kimbalsummers@hotmail.com
Regards -
Kimbal Summers ( Brisbane - Australia ).
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Old 2nd August 2012, 12:35 AM   #5
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I am also interested in purchasing a pair of Leach boards, preferably supporting outboard output xsistors
J
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Old 2nd August 2012, 06:01 AM   #6
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The more recent versions of the Leach amplifier PCBs do not have a ground plane; some years back I updated my amplifier with the 4.5 boards and was very pleased with the improvement in depth and imaging.
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Old 2nd August 2012, 08:29 AM   #7
kimbal is offline kimbal  Australia
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Default Ground-Plane On Leach Amplifier PCB's

Quote:
Originally Posted by Damon Hill View Post
The more recent versions of the Leach amplifier PCBs do not have a ground plane; some years back I updated my amplifier with the 4.5 boards and was very pleased with the improvement in depth and imaging.
So clarifying your statement -
The ground plane made quite an improvement to the overall quality of the sound ?

The boards on offer to me, have no ground plane, though being sold to their former owner through Prof Leach.
Hence, I might add aluminium foil ( or better still, see if I can bond some copper sheet-shim with drilled out oversized holes ) to the top of the PCB.

Possibly a lot of extra work for maybe very little improvement !

What have others experienced regarding this ?
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Old 2nd August 2012, 12:50 PM   #8
djk is offline djk
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"The ground plane made quite an improvement to the overall quality of the sound ?"

No, the new boards without the ground plane sound better than the old one with the ground plane.

The 4.5 sounds better because it uses more local feedback on the diff inputs, cascodes the diff inputs, and takes another feedback loop from the driver stage.
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Old 2nd August 2012, 03:36 PM   #9
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I would contact Georgia Tech and ask them. Dr. Leach's webpages are still up.

If not, then a group buy on new PCB's wouldn't be that hard to do.
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Old 2nd August 2012, 03:56 PM   #10
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I'll try contacting GT. I'm hoping to find a board(s) that support off-board output devices. I have a recently rebuilt but now defunct AR D100 I want to try to refresh. Great chassis, massive PS, but 35 yr old circuit that will cost more to repair than I am willing to risk.
If there is indeed interest in a GB for this board I'd be willing to participate- I may even be able to convince a former colleague to generate new artwork and G code in Eagle
J
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