Trace Elliot GP12 SMX schematic

[MarkusBass]

I'm looking for schematic of Trace Elliot GP12 SMX bass amp. I'm looking for the schematic of the power amp with 2SK135/2SJ50 MOSFET transistors. On the power amp board there is also a fan control circuit.

Mark

[Jazz P Bass]

Trace Elliot GP12 SMX Schematic

Here is what I have.

[MarkusBass]

Thanks but this one uses BUZ900/905 and has different schematic. The preamp schematic is OK but the rear board and the power amp are completely different.
PS: I'm looking also for bias procedure. Does anyone know what should be the quiescent current in this amp?


Mark

[Jazz P Bass]

Trace Elliot GP12 200W Schematic

Maybe this will help.

K135/ J50 output section.

[doctor]

There are also GP12 schematics of 300/400W and 600W using SK135/J50 transistors that can be replaced with BUZs.

If so, let me know.

[MarkusBass]

Can you post it? The power amp is almost as the one posted by Jazz P Bass. The difference is that the fan control circuit is missing. Maybe the stronger version has it. Although the amp has only two pairs of 2SK135/SJ50 and it has about 100W but it is really very loud. This was achieved most probably with very high power supply +/-75V.

Mark

[doctor]

Can you post it? The power amp is almost as the one posted by Jazz P Bass. The difference is that the fan control circuit is missing. Maybe the stronger version has it. Although the amp has only two pairs of 2SK135/SJ50 and it has about 100W but it is really very loud. This was achieved most probably with very high power supply +/-75V.

Mark

May be this schematic will be more useful.

[MarkusBass]

Yes, this is exactly what I needed. Thank you very much. Now if I only knew how to set up the bias.

Mark

[doctor]

Yes, this is exactly what I needed. Thank you very much. Now if I only knew how to set up the bias.

Mark

Biasing of the MOSFET amps is very simple:

1. Check the power supply when the power amp is disconnected.
2. Connect the power amp without load back to the power supply.
3. Connect an amperemeter (use for the beginning range 10A DC)
in series with a drain of one of the MOSFET.
4. Connect the power supply to the mains through a variable transformer.
Power of the variable transformer should be about 130-150% of the amp’s power.
5. Slowly increase voltage by means of variable transformer so that Vdrain
increases up to 50 VDC. Simultaneously monitor amperemeter readouts.
Continuously adjust the trimmer so that the drain current does not exceed
the 50-70mA.
6. When Vdrain will be equal to its nominal value adjust drain current to the
70mA (this is the value for the each pair of the 2SK135+2SJ50 or BUZ900+BUZ905).
7. Connect load back to the amp and repeat clauses 5-6.
8. Finally adjust the trimmer for the minimum crossover distortions at the output at 1KHz.