F6 Illustrated Build Guide

[kbergsson]

Try here:

http://www.diyaudio.com/forums/pass-labs/277850-f6-illustrated-build-guide.html#post4406647

Some folks had minor trouble with the bias adjustment range so Z1, Z2 =6.3V
and R7, R8=3.3K have been suggested

Hi Im building an F6 ( my first diy transistor amp ) and the zeners that diystore ship with the Mosfets only got me to .3V bias. Now awaiting a priority shipment of 6V8 zeners and 3K3 resistors. Cant wait to test the F6 on my Altec A5s Hope the rumors are true
Regards
Kjartan

 

[Zen Mod]

naah .......

Sissy amp .........

 

[6L6]

Don't take Zen Mod seriously. He's our Jester, after all...

The bigger zener diode should do the trick for getting your amp to bias properly. You'll love the amplifier! Please post some photos, we'd all love to see it and your system.

 

[Dennis Hui]

The rumours are true: the Mighty ZM is the Court Jester and the amp is sissy.

Seriously, I suspect this will not be your last transistor amp. Once your get a taste of
NP's designs it's hard to stop at one.

Good luck with your build.

Cheers,
Dennis

 

[kbergsson]

Thanks for the encouraging comments 6L6 and Dennis Ill post pictures once the F6 is up and running. And yes it was quite fun to build
ZM is ok, im Icelandic and we share ZM's irony and subversive humor, although ours is probably a couple of shades darker

 

[Zen Mod]

and yup , my very close sister is married for ...sson and lives on/in Iceland

so , I know everything about Berserk , from first hand

 

[kbergsson]

and yup , my very close sister is married for ...sson and lives on/in Iceland

so , I know everything about Berserk , from first hand

Lucky girl

 

[bkdog]

SISSY = Seriously Intense Sexy Sound

Niceland is a wonderful country, spend some time in Ísafjörður (but maybe not in winter...).

 

[kbergsson]

Regarding Berserkers. I was out of mushrooms so I drank some homemade mead and pulled the R7s, R8s and the Zeners last night. Good quality pcbs as I didnt destroy them in the prosess.
Yes Iceland is nice, although I live in Norway now, went back to the old country to claim back what Harald and his cronies stole back in the day

 

[kbergsson]

While awaiting components from Mouser I'll try to post pictures of my den. If you can see the pictures you'll see my A5s ( Altec 299-8g and GPA 515c with autoformer crossovers from Germany ), diy 3 armed Lenco, in progress preamp (Aikido v 6CG7s), DIY LD91 300b amp, was changing out the powersupply trafos to Hammond. The current amp is a 30w hypex with sowter input trafo ( buffer and se-> balanced). Im acclimatising from the 300B amps before testing the F6 + different stuff like boozehound phono, sowter SUTs etc..
Shared DIY - Google Photos
I have som Altec 604s on stock and have built and renovated several loudspeakers and kits although only using only precut cabinet materials as I dont have the necessary routers, table saw etc.

 

[kbergsson]

Finished

Finished the F6, quiet just a slight hiss on my effective horns. Initial impression is very positive. Dynamic, resolving but never aggressive. Im running it now at initial bias of .51V.

F6 and parts of my system

 

[kbergsson]

Quick question. Im currently running with bias of .6V and the F6 heatsinks are only lukewarm. My focus is getting the most quality out of the amps and not max effect as I have effective horns and dont need the effect. How far is it practical to push the bias?

Must say though that they are quite good amps. I can for ex. enjoy late night low volume listening and still get deep insight into the music and dynamic contrasts. The F6s dont paint as big a picture as my 300B amps but far more resolved, nuanced and relaxed.

 

[Zen Mod]

Iq - whatever you meet first - 55C on top of the heatsinks , or (say) 40W per device

if heatsinked well (under 55C) , no more than 8C difference between mosfet case and heatsink near by , you can go to 45 or even 50W per device , if using IRFP150 instead

 

[kbergsson]

Thanks Zen Mod, I need to get a good temp-meter. But how does running the transistors (mine are the std irfp240s sold by the diystore) hot influence the sound. Do they get better with more amps / higher temp (i.e. sound wise) ?

 

[6L6]

There is a slight increase in sound quality with an increase in bias. The overall tone and signature of the circuit will not change.

 

[Zen Mod]

more heat, higher temp in room , wine fumes are more effective

 

[kbergsson]

I would like to thank mr Pass for giving his designs to, and in supporting, the DYI community. Its great to be able to build/assemble amps of this quality.

The pass forum on diyaudio is also a great place with helpful and knowlegeable members. I think I cought an extremely contagious virus. Late last night I all of a sudden realised that in a moment of great weakness I had accepted a paypal payment on a site called Ed.. something

 

[silasmellor]

Back to the F6 hum question (see a few pages back), i had some time today to install the transformer in an L-bracket. Subjectively this didn't yield much difference, but the FFT shows higher overall level of 50, 100 hz and harmonics - I now see a forest of harmonics extending up beyond 2khz, where before they ended somewhere between 1-2k. Both 50 and 100 hz are up by 20dbFS, so im sure this forest is simply because the overall noise level is higher. Oh well...

I will reset the transformer configuration and next up try the DIYA rectifier PCB with some Schottky diodes instead (no snubbers). I bought these:
MBR40250TG ON Semiconductor | Discrete Semiconductor Products | DigiKey
To try. I guess 250V/40A should be a safe enough rating?

 

[drewburn]

have you looked at shielded toroidal transformers

 

[silasmellor]

I was thinking about shielded transformers as i was moving things around today Toroidy makes some nice ones i might try in the future...