DC Servo MOSFET Amplifier

[still4given]

I like this amp so I went ahead and built another F100 PSU/protection board too. Here is a pic of them hooked together.

This is a nice amp. I running it now on +-60vdc. It is very powerful so such a small footprint. I have to clamp a heatsink to that angle of course. One note, for those who may want to build this. The trimmer has only two holes so the center pin must be bent and soldered to one of the other pins before being fitted to the board in place of the 4k7. As I said earlier, 4k7 is not enough to bias the amp. It needs at least 3k. I am running them at 2k7 and I will probably replace the trimmer with a 2k7 resistor just to be safe.

Blessings, Terry

 

[still4given]

I reworked the layout to replace R22 with a 5k trimmer. I hope this helps someone interested. You still need to attach Q6 with wires and mount on top of one or the outputs.

 

[Bonsai]

Very nice Terry!

 

[apexaudio]

I reworked the layout to replace R22 with a 5k trimmer. I hope this helps someone interested. You still need to attach Q6 with wires and mount on top of one or the outputs.

Nice pcb... you can add 2R2 resistor from power GND to signal GND...

 

[vargasmongo3435]

Nice pcb... you can add 2R2 resistor from power GND to signal GND...

Something like this mister Mile

the highlighted area is power GND to feed 2R2 to SGND connection

Best Regards
Juan

 

[still4given]

Something like this mister Mile

the highlighted area is power GND to feed 2R2 to SGND connection

Best Regards
Juan

I used a slightly different approach and fit it into the center. Let me know if one way is better

 

[still4given]

OK Juan showed me how to fit the 2R2 ground lift resistor without the jumper. So Here is the file for iron transfer. If someone can check it for mistakes that would be helpful.

Blessings, Terry

 

[apexaudio]

OK Juan showed me how to fit the 2R2 ground lift resistor without the jumper. So Here is the file for iron transfer. If someone can check it for mistakes that would be helpful.

Blessings, Terry

It is OK and you can remove SGND pin
Regards

 

[still4given]

It is OK and you can remove SGND pin
Regards

Done. This should be final version. Happy building.

 

[apexaudio]

Done. This should be final version. Happy building.

Thank you for this pcb design, only one suggestion.
Regards

 

[still4given]

Hi Mile,

Easily done, For my learning, what is the difference?

Thanks, Terry

 

[still4given]

For those who want to mount the outputs vertically here is a layout for that.

Also, I'm not sure if Thimios is still building APEX amps but just in case I am attaching a photo sense file too.

Blessings, Terry

 

[vargasmongo3435]

Good work Terry I hope mister Mile like it

Best Regards
Juan

 

[apexaudio]

MPSA42 and MPSA92 can be use instead BF420 and BF421.

 

[still4given]

I used KFC1845/A992. BF420/421 are ecb like the KSA. MPSA are ebc.

 

[apexaudio]

I used KFC1845/A992. BF420/421 are ecb like the KSA. MPSA are ebc.

There is many pairs instead BF420/421, F100 is very old design newer version use MPSA42/92 but you can use any modern pair for FX100.

 

[thimios]

For those who want to mount the outputs vertically here is a layout for that.

Also, I'm not sure if Thimios is still building APEX amps but just in case I am attaching a photo sense file too.

Blessings, Terry

Thanks Terry,banks in my country are under capital control so we can't order parts .....

 

[still4given]

Sorry, I remember seeing that. Any end in sight?

 

[still4given]

There is many pairs instead BF420/421, F100 is very old design newer version use MPSA42/92 but you can use any modern pair for FX100.

I moved things around a bit so MPSA can be used. Please check the layout.

 

[thimios]

Sorry, I remember seeing that. Any end in sight?

i can't see such a thing