F6 Amplifier

[2 picoDumbs]

Modifying my F6 for the third time.
1) Offsetting PCB mounting holes on heatsink by 40mm to achieve symmetric mosfet placement over heatsink
2) Installing New/Different mosfets
3) Modifying degeneration
4) Changing bias
5) Changing feedback.
6) More capacitance
7) Dual Mono operation

Start drilling new holes tomorrow.

 

[fabrice63]

very interesting , dont hesitate to share

especially point 3 to 5

.

 

[2 picoDumbs]

After I have had a chance to measure the result.
I will notify.

 

[2 picoDumbs]

Old UMS mounting holes showing poor mosfet placement on heatsink.

 

[2 picoDumbs]

NEW Picodumb mounting holes showing much better mosfet placement on heatsink.

 

[aoc]

After I have had a chance to measure the result.
I will notify.

I found going dual mono improve the sound significantly... Still have my MOSFET in not ideal location

 

[2 picoDumbs]

... Still have my MOSFET in not ideal location

It's not too hard to install new pcb mounting holes, just offset each PCB hole by 40mm to the rear of the case.
It's only really a concern on split heatsinks though so maybe not a problem for you.

 

[aoc]

It's not too hard to install new pcb mounting holes, just offset each PCB hole by 40mm to the rear of the case.
It's only really a concern on split heatsinks though so maybe not a problem for you.

I have split heatsink.

 

[kpsthakur]

Hello all...I have just updated the chassis for my F6. Thought of giving it a test using the Bulb jig before powering on independently. Surprisingly, the bulb goes off in few seconds completely, but after 30 sec or so, it starts to glow again...this has never happened before...I could actually play the amp even while using the current delimiter. I am not sure what could be the cause, but thought of first checking with the forum.

 

[Zen Mod]

isn't a time for removing da bulb and using multimeter to poke around ?

 

[Nelson Pass]

I would expect the light to go bright charging up the caps, and then dim while the
bias voltage is developed and then glow dim when the amp is running.

 

[2 picoDumbs]

If you are using the diyaudio store power supply pcb be sure that any washers used to mount the pcb on standoffs do not also short the power supply rail to the amp chassis and to earth.
The rail output holes are very close to the pcb mounting holes (too close actually) a largish washer will make contact with the power supply rail if you’re not super careful.

 

[triode_al]

Just wrapped up 2 x F6 beasties. Excellent sounding even at break in~ 90% bias. Going to ramp them up today
Had some RIFA/Kemet PEH169 100,000uf caps that needed a home, and they got it.

These bridges - hope the current does not have to travel though iron

 

[Prologue]

Hello,


I have a 17v sec toroidal transformer, would it be a problem to use it in my F6 build ?


Thanks

 

[Zen Mod]

just go for it

volt up or down is not so important , as quality and VA of Donut

 

[Prologue]

just go for it

volt up or down is not so important , as quality and VA of Donut

Thanks !

 

[kpsthakur]

I would expect the light to go bright charging up the caps, and then dim while the
bias voltage is developed and then glow dim when the amp is running.

Thank you so much Mr. Pass. Well, too a leap of faith and started the amp directly, I was anyway using a 40W bulb which seemed reasonably less for this test, and there was almost no DC at output, the LED's looked fine...so power on, music on, everyone's happy. F6 back in business

Merry Christmas everyone

 

[BruceInOz]

Hello F6 Community & Nelson Pass,

Would appreciate your guidance on whether or not this amp would successfully drive / be a good match for my Martin Logan Ethos hybrid electrostatic speakers. The bass driver of these speakers has it's own in-built dedicated amp so the F6 would power the panels only.

I ask because the impedance curve is funky with a low 1 ohm dip albeit at 18kHz - see attached.

92dB / 2.82v /m sensitivity
nominal impedance 4 ohms

Thank you

 

[Zen Mod]

just go for it

 

[Nelson Pass]

Pretty tough load at the top, but try it anyway.