The F6 Revisited

[nicoch58]

The original F6 looks to have used resistors like the 5W KOA resistor shown above.

nope production unit

 

[ranshdow]

The picture I posted was a prototype, not production. Note the SemiSouth JFETs.

 

[stretchneck]

nope, no go

xconductance easy to find in datasheet

just ggl "2sk2013 pdf"

Ah, 0.7 Siemens - that’s low. Looks like FQH44N10 is the one to go for…

 

[stretchneck]

Nice list, not sure who posted it originally:

https://www.diyaudio.com/community/attachments/power-mosfet-compare-list_02062021-pdf.956591/

HUF75639G3 is a suggested replacement for FQH44N10, but transconductance is not stated and has higher input capacitance.​

 

[stretchneck]

FQA46N15 as mentioned earlier seems good, but input capacitance is nearly double IRFP240.

Any guidelines on what input capacitance is acceptable for F6?

 

[TungstenAudio]

The HUF75639G3 appears to be intended exclusively for pulsed operation; its SOA does not include DC operation. The FQH44N10 was also suitable for pulsed operation, but it was rated for DC operation and listed for audio amplifiers.

 

[TungstenAudio]

Empirical evidence suggests that 2250 pF may be an effective upper end for input capacitance. This would be accompanied by a 68 Ohm gate stopper resistor.

Use of the IXTQ75N10P has already been covered here.

 

[stretchneck]

Thanks @TungstenAudio - that closes that one out!

 

[Donaldspace]

I just ordered PCBs from post #81 diamond buffer, from JLCPCB. Would anyone have a BOM for this build? Thanks in advance.

 

[gary s]

I made my own (hand written) from the schematic in post #1 - but TA has some specific parts for the DB build in post #48 in this thread.

 

[stretchneck]

I just ordered PCBs from post #81 diamond buffer, from JLCPCB. Would anyone have a BOM for this build? Thanks in advance.

Is #81 the latest version of the diamond buffer F6 or are these new Gerbers under review worth the wait?
https://www.diyaudio.com/community/threads/the-f6-revisited.405444/post-7544964

Not clear to me if this includes an update to the diamond version, or just verification build for the JFET buffer edition.

 

[gary s]

TA can advise specifically, but the circuit is the same, just some cosmetic changes, delete the zeners, minor spacing changes, connection for the PSU has extra lands and the transformer can now accommodate both Jensen and Cinemag transformers. See posts #'s 242,243,249 and 257 for details.

For the Diamond Buffer version, I would wait till TA has tested the new revision and releases the gerbers.

 

[TungstenAudio]

The new PCBs have identical function, but with an option for a different transformer. They can accommodate either the Jensen or CineMag quadfilar line output transformer.

 

[Donaldspace]

A couple of questions... What part number for C3,4,6,7 from Mouser? Is the R1* necessary for IRFP240 outputs? Or can it be jumpered? Is matching of the input (diamond) transistors necessary? I'm going to use the LED bias mod. I like the discrete mounting. Will leave the zener holes empty. I already have Jensens...

 

[poseidonsvoice]

A couple of questions... What part number for C3,4,6,7 from Mouser? Is the R1* necessary for IRFP240 outputs? Or can it be jumpered? Is matching of the input (diamond) transistors necessary? I'm going to use the LED bias mod. I like the discrete mounting. Will leave the zener holes empty. I already have Jensens...

Read posts 3 and 48. Post 48 has a partial BOM. R1* is a recommendation not a requirement. Matching of the diamond transistors isn’t a necessity. It’s fun.

There is a lot of variability with this design and it’s up to the builder to decide which is best. Tungsten’s research is quite helpful in that regard.

Happy New Year 🎆

Best,
Anand.

 

[gary s]

I always read the thread from the first post and printout or cut and paste relevant info from all the thread into one document for review, that way you have a handy timeline on any changes etc as the amp is tested and further developed. This method is highly recommended for potential builders, you can add screenshots of any photo's, board layouts, BOM's etc.

 

[Donaldspace]

Thankyou for the info. I've ordered parts from Mouser.com Now waiting for the goodies to arrive...
Don

 

[Monk55]

Excellent job TA & Mikerodrig27….ill wait for latest DB boards.

 

[Donaldspace]

Which alternative transformers will the new boards accommodate? I see Cinemag has CMOQ-3 and CMOQ-4 in both low -50%- and Hi -80%- nickel laminations. their pin arrangements, however, are different. What would you recommend?

 

[poseidonsvoice]

Jensen JT-123-FLPCH
Cinemag CMOQ-4LPC
Cinemag CMOQ-4HPC

Best,
Anand.