F5 V3

[McQuaide]

What is the ideal gain of a preamp before the F5?
My DAC output is on the low side, 1.3V.
Playing a 0dbFS 1khz .wav file, I measure 8.3Vrms on the F5, which is ~6x or 15dB which is up to spec of the F5.

Is it correct that the F5 would need 2.35V input signal to reach 25W output to 8ohm?
((2.35V * 6)^2 / 8) = ~25W ?

I don't know the measurements but I find a BA-3 or AV receiver pre-out has enough gain.

 

[b4bz]

I using an AS-3220 - 300VA 20V Transformer, can I use this and the Universal power supply to power three F5 boards? All caps on the power supply are 22,000uF, if that matters. Bridge rectifiers are oversized, at 1KV 50A. If so, what fuse should I use? Thanks. Also, can someone please give me a link to the posts/article talking about tuning the pots?

 

[6L6]

If capacitors are 35V or greater, all your parts will work beautifully. Bias adjust is in the F5 guide in my signature.

 

[b4bz]

If capacitors are 35V or greater, all your parts will work beautifully. Bias adjust is in the F5 guide in my signature.

Check, and check. Thanks!

 

[McQuaide]

Consider what happens when the bolt holding the MOSFET heats up. It's going to get longer.

Three things could happen at that point:
(a) the transistor case could swell even more, keeping everything nice and tight
(b) the Keratherm could un-compress a bit, but still be compressed enough to maintain excellent thermal conduction
(c) the transistor could be come loose, causing thermal conduction to plummet

For those of us using mica or a ceramic pad you're down to one of (a) or (c).

Since (c) is not good, I like to have some sort of spring washer in there: preferably a Belleville washer or failing that a wavy washer. I'll even use a split washer if I really have nothing else.

Wavy washers acquired from the local Ace and installed. OK, now what do I do for the other 23 hours and 55 minutes of this day? Play music I guess.