Gotta love Nelson Pass

chakster I’m sure that i don’t need an active gain in my system, because even with B1 buffer preamp i only use 10-20% of the volume control.

If that’s right B1 has no gain, you don’t need any gain,
BUT! your FW F2J is only 2kohm input impedance this doesn’t bode well for any passive or tube preamps, even your B1 has 1kohm output impedance, which is not a good look either into the 2kohm of the F2.

You really need a low gain preamp with an output impedance that’s below say 250ohm output impedance for this amp. You could look at the Schiit Ferya low gain with solid state output is 75ohm and the tube output is 210ohm, forget the passive output. Remote, excellent volume pot, cheap! and you can return it.
http://www.schiit.com/products/freya
Cheers George

I ended up with original First Watt B1 buffer preamp

No problem the B1 buffer is unity gain, which Nelson 1st designed to be a (no name), buffer for my passive "Lightspeed Attenuator" preamp so it could drive one or two very low input impedance amps of his which some of my Lightspeed owners had, this worked a treat for them.

Latter Nelson released it and called it the "B1 Buffer", and designed a diy around it on DiyAudio forums, and also I think a ready made retail unit First Watt B1 preamp.

Still to me if all is good between passive pre and the amp, no buffer is the best buffer whether it’s got gain or not.
And that’s why Nelson says "you suffer the effects of active circuitry only when additional gain is necessary" on the Aleph L, meaning passive sounds better on it up to 3 o’clock on the volume control after which the active buffer with gain comes in, then it’s not quite as good.

Cheers George

Yeah the MkI was straight passive all the way, the MkII was passive all the way till 3 o’clock, after which it slowly became active.
Nelson introduced this MkII for very low gain amps like some of his, and very inefficient speakers <84db, that need more gain from the preamp.
But as he said you paid the penalty if used passed 3 o’clock because it’s now becomes an active preamp with added distortions/colouration’s.

Cheers George

One of Nelson's favourites it seems that he thinks highly of, was the Aleph L preamps, really different because it takes the best of both worlds and joins them together. 
It's a quality passive pre, but as the volume goes higher once it gets to 3 o'clock or higher it slowly turns into active pre for more gain if you need it for low gain poweramps or inefficient speakers. I've had searches out for a used one, but none of the owner ever sell them.

Nelson Pass
" I don't know why this invention didn't bring me fame
and fortune, but who can explain it.....
 At the 3 o’clock volume control position, the Aleph L offers a direct path from input to output.
The only component in the signal path is wire and switch contacts.
At positions below 3 o’clock, the volume control functions as a precision passive attenuator using discrete resistor ladders.
Above 3 o’clock, active gain is added to the output signal in 2 decibel increments, for amaximum of 10 dB.
As a result, you suffer the effects of active circuitry only when additional gain is necessary."

Cheers George

Youtube interview with Dennis Had (I have one of his Firebottle HO amps) where he laughs off the fuse thing

Like to see this wolf, got a link, might need some backup Ordnance one day.

 
Cheers George

mikexxyz

 He is an impressive guy. I love the fact that he routinely shows up at forums and discusses projects and donates designs to DIY'ers.
I am always amused at the wanna be engineers that try to redesign his products with after market products like PC, fuses, and other nonsense. If Pass Labs thought that these “mods” improved the sound of their audio they could incorporate them at a fraction of the “retail” price. But they don’t. I suppose he has to leave something to the bottom feeders.

This needs to be posted up at the voodoo or shillers fuse forum
https://forum.audiogon.com/discussions/the-new-synergistic-research-blue-fuses

Cheers George

His 1977 A20 driving Quad ESL57's made me a believer, so much so, I morphed that amp into a massive 2 man lift pure 150w Class-A, that was water cooled, own pump, radiator, and cooling fan.

 http://www.firstwatt.com/pdf/art_classa_20.pdf

Cheers George