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BrianGT 17th June 2002 06:42 PM

redesign of leach amp pcb for integrated TO-247 output devices
Ever since I finished my leach amp, I have been thinking of ways to improve the design. I have decided to redesign the pcb in order to use TO-3P (TO-247) devices that will be integrated into the pcb, and effectively eliminating a lot of external wiring for the amplifier (12 wires to be exact).

I have the pcb layout mostly worked on paper, and have about half done on the computer. Here are a few pictures of my progress:

Feel free to add comments to the pictures in the gallery.

The preliminary board specs will be these:
4" x 6" dimensions (dimensions might approach 3" x 6" if possible)
2 layer pcb
0.093" board thickness
2 oz copper on both sides
soldier mask on both sides
silkscreen on top layer

Preliminary parts list with dimensions:

I most likely will use the MJL3281A/MJL1302A (more linear) devices instead of the MJL21193/MJL21194 output devices, but since I currently have some MJL21193/MJL21194 devices, I will use them for prototyping.

Any comments/suggestions on this project would be appreciated. I will update the pictures of my layout, as I near completion. I should finish the layout soon, and get some prototype boards made in august, then if everything works good, get a large batch of production quality boards made for myself and some friends, possibly opening up room for others, but this is a couple of months off, so I will discuss this later.


BrianGT 26th June 2002 12:01 AM

I have the pcb layout just about done, and have posted the new board layout, also with a component view without the traces, and a parts list.

If anyone is interested in building one of these Leach Amps with the new boards, let me know.

If you want to see pictures of my first leach amp, using the 4.5 boards, go here:


jleaman 26th June 2002 12:13 AM

Brian what is the price and what is the power out put of a leach amd that you have just made pcbs for..?

i might be interested


please email me back thanks

BrianGT 26th June 2002 12:22 AM

It is no different from the normal Leach amp, which outputs around 120w per channel.

I am not getting boards made until August, as I am in France studying for the summer (Georgia Tech has a campus here).

As for the price, I am not sure yet. I am just wondering if there is enough interest for me to order a batch of pcbs. They should cost no more then $50 for a pair including shipping inside the US, if I order a high enough quantity. They will be double sided with soldier mask, silk screen, 2 oz copper, and 0.093" thick board.

Does anyone who has built and modified a leach amp have any suggestions for any modifications to the design?


Kevinbd 26th June 2002 09:54 AM

Leach Circuit Diagrams

Could anyone point to a link with the Leach schematics. I have heard it is a good amp but have never seen the diagrams.



Geoff 26th June 2002 10:12 AM


Go to the front page of Scroll down to where it says links. Select amplifier projects. Move to page 2. The fifth entry down is entitled "The Leach Amp". Click on this link.

Alternatively, do as the rest of us do and use Google, AltaVista, Lycos or whatever is your preference.

BrianGT 26th June 2002 10:12 AM

Leach Amp webpage:

Leach Amp circuit diagram (pdf)


shadow 27th June 2002 06:24 PM

Brian you know this site?

BrianGT 30th June 2002 05:04 PM

Yes, but his board was for integrated TO-3 devices. I have a similar goal to his, but I want to use the newer case devices, which are much easier to use with heatsinks.

Comparison of devices:

The metal ones are the old to-3 output devices and the plastic case ones are the TO-247 (also called TO-3P).

By the way, the board design is done:


EJ 1st July 2002 03:23 AM

does it have to be two-layer board?
It will be difficult for most diyers to make the board by themselves
if it is not single-layer. I think one of reasons why Leach Amp is
so popular is that the board is quite easy to make. :D

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