I'm curious about the status of the amplifier boards. If I ever recover financially I want to build a more professional looking Leach amplifier using plastic flatpack output transistors, ideal the Thermaltrak devices. The board should ideally mount directly on the heatsink with the shortest possible leads.
In a fairer world, I might have tried being a source for the original Leach boards, but real life hasn't been like that. :/
In a fairer world, I might have tried being a source for the original Leach boards, but real life hasn't been like that. :/
I actually have recovered some versions.... let me know what your are looking for.
\\\Jens
Last GB was for the board that can have either 6 or 12 output transistors.
Is that what you are after - I have the GB data.
\\\Jens
Hi Everyone,
It's time to have a new Leach Amp Clone PCB group buy by Mr JensRasmussen.
Before this starts, can the DIY-ers who have built these amps before give some comments for further improvements.
I want to have two versions of the PCB, 3pairs and 6pairs of output devices.
Regards
Arthur
It's time to have a new Leach Amp Clone PCB group buy by Mr JensRasmussen.
Before this starts, can the DIY-ers who have built these amps before give some comments for further improvements.
I want to have two versions of the PCB, 3pairs and 6pairs of output devices.
Regards
Arthur
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the PCB has fuses, but the onboard capacitors are quite high value.
Fuses feeding high value capacitors are a complete waste of PCB space. They achieve nothing.
Make sure you implement IV protection and not the simplified I protection proposed by Leach.
Retain the separate supply route for the front end for those that wish to use it.
Make sure you implement the NFB route from the OUTPUT and not from the junction between the emitter resistors.
Add the protection diodes across the on board Signal Ground to Power Ground resistor.
I recommend that 4 diodes (1n4004) be used to help protect the amp from abuse.
One each across the supply rails to power ground and one each from output rail to supply rails.
And an extra pair from front end supply rails to Power Ground for those that separate the supplies.
Have a look at using TT transistors. Use four to implement Leach's tempco.
That leaves 2 spare, if a 3 pair. One could be used to trigger an over temp warning/alarm.
Roender found very good tempco using 5 TT diodes running at very low Id. That uses up the sixth.
Fuses feeding high value capacitors are a complete waste of PCB space. They achieve nothing.
Make sure you implement IV protection and not the simplified I protection proposed by Leach.
Retain the separate supply route for the front end for those that wish to use it.
Make sure you implement the NFB route from the OUTPUT and not from the junction between the emitter resistors.
Add the protection diodes across the on board Signal Ground to Power Ground resistor.
I recommend that 4 diodes (1n4004) be used to help protect the amp from abuse.
One each across the supply rails to power ground and one each from output rail to supply rails.
And an extra pair from front end supply rails to Power Ground for those that separate the supplies.
Have a look at using TT transistors. Use four to implement Leach's tempco.
That leaves 2 spare, if a 3 pair. One could be used to trigger an over temp warning/alarm.
Roender found very good tempco using 5 TT diodes running at very low Id. That uses up the sixth.
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