F5

[John Roman]

I'm on a path to eventually bi-amp my BassZilla open baffle speakers. On a recommendation by Dick Olsher I'm considering building an F5. Nelson Pass designed this SS 25 amp heater that has been used successfully with these speakers. So I'm certainly not reinventing the wheel. It's a simple design that is well documented. So although this will be my first foray into non Bottlehead gear I'm hoping the build won't be so bad. Anyone here built an F5? Thoughts?
As always, thanks for your help,opinions, ideas, guidance, laughter common sense....... well you get the idea.
John

[2wo]

Is it happens. I got this honking transformer on hand. These heat sinks over here, are probably big enough. The PCB and FET kit was $50. So yea I am building a F5. Might be a bit OT for Doc's forum, lets ask...John

[johnsonad]

You may want to listen to one first.  I owned an Aleph 30, and a First Watt J2. There was an F5 in my system for one day only. It was a factory built unit fully broken in and about made my ears bleed. To each there own but the F5 doesn't match well with everything. Just my two cents.

[John Roman]

Hey Doc,
Nothing like asking after the fact, but is this content OK?
regards,
John

ps   Probably should have just asked for your recommendation on bi-amping my system

[Doc B.]

I don't imagine that you will get a lot of info here. You might try over on Nelson's forum on DIYAudio and you might talk to Jon Ver Halen, who works with Nelson pretty closely and has a ton of experience with his products and with the Baszilla (Jon's version sounds really, really good). Nelson is a great guy who designs great sounding, very innovative products. He happens to like a little bit different sound than I do, and it's not really appropriate for me to opine here about his designs.

In general I'll say that I would biamp with zero global feedback single ended tubes, because that's my thing. But that is a lot more challenging than single ended SS or PP tubes because we seem to have learned that the bass speaker needs to be designed with the amp's damping factor in mind to work its best, and that precludes the use of most popular speakers. Jon will know better than I how the Baszilla style woofer design fits in that scenario.

[xcortes]

I've heard two versions of Pass F5. One in my own place built by Pass. The other in a friend's house, a DIY version. I didn't like the sound of either. They sound harsh. And to me harshness is very noticeable down there.

For bass duties only I like a Gainclone better and recently I've been extremely satisified with a big McIntosh from 130hz down. Wipes the floor with any SS amp I'd tried before at such position. Deep, fast, detailed and still musical. (No, I don't like the Mc as a fullrange amp!).

[Jim R.]

Yes, it seems the F5 is the least loved of the Firstwatt amps, especially among those who prefer tubes.  F3, especially with the newer power jfets could be a better choice for SS.

-- Jim