they have most almost most opposite signatures in FW family 
. Nelson mentioned this earlier. F5 is very clean and holographical, with a great soundstage. AJ is more sweeter, a little bit of a sweet coloration. With an outstanding dynamics! I would go for AJ if you ask me, but it needs bigger heatsinks.
. Nelson mentioned this earlier. F5 is very clean and holographical, with a great soundstage. AJ is more sweeter, a little bit of a sweet coloration. With an outstanding dynamics! I would go for AJ if you ask me, but it needs bigger heatsinks.
Aleph 3 is still the bestest
The game changer! Also the best looking!!! Hot Spiney Stuff
(TO-3 Fets = better sound than TO-247)
photo:milan's pages
The game changer! Also the best looking!!! Hot Spiney Stuff
(TO-3 Fets = better sound than TO-247)
An externally hosted image should be here but it was not working when we last tested it.
photo:milan's pages
they have most almost most opposite signatures in FW family
not so opposite as F5 vs. F1 , 2 , 3
regarding heatsinks - F5 and Aleph J are pretty much in same ballpark ..... meaning - juice is your choice , as long you're above Klunk! area
(not that J will give much above Klunk!)
Shame on me, newer made those
No way!regarding heatsinks - F5 and Aleph J are pretty much in same ballpark ..... meaning - juice is your choice , as long you're above Klunk! area
(not that J will give much above Klunk!)
Well, maybe i newer set up bias according to the specs 
The Amp Camp Amp has the characteristic that the 1W distortion raises slightly at high frequencies. 0.7% at 1KHz and below, 1% at 10KHz, 1.4% at 20KHz. I attribute this to the input capacitance of the IRFP240. I changed the IRFP240 to an IRF520 and that reduced the high frequency distortion. This softened the high end, graphs are posted in the ACA sticky thread. In listening tests I turned the tweeters up a couple of clicks, probably closer to flat with the !RF520 version. Overall the differences are small. Do other Pass amps do this?
My thinking was that it might make those full range drivers sound "better". I have no experience with those. Nelson's designs seem more focused on creating a pleasant experience for the listener rather than technical specifications.
The devil is in the details. Forget the SIT1 for a second. The amount of detail a 2SK82 SIT can produce is rather amazing. There is a quality to the sound of a SIT is like, "How the heck is that possible?". It's a real, "That's what I have been looking for..." moment.
Resurrecting an oldie here..You may not be able to name a favorite child, but a parent always has an
opinion about the characteristics.
I always keep in mind that someone else's experience will not duplicate mine.
Speaking strictly of the the FW amplifiers, my listening is generally restricted
to 90+ dB sensitivity and no tough loads, as the amps are low power and
typically low damping factor.
F5: Dynamic, accurate, a little unforgiving. On speakers with peaks in the
top end, it will reveal as too bright and annoying. On speakers with a slightly
diminished top end, it adds a little sparkle, this in spite of being flat out at
high as 500 KHz. Good control - if your speaker is a little boomy, it will tend
to tighten it up. Overall, probably the most neutral of the FW amps. It will
drive 4 ohm loads without particular issues. Oh, and it does sound very good.
J2: A more relaxed version of the F5. Decent bottom end control, a warm
midrange, excellent depth. Overall, one of the most popular pieces. Still
in production, it best hits the mainstream taste of the FW audience, probably
because it delivers a consistently pleasant sound. Not intended for 4 ohms
unless the speaker is particularly efficient, which is rare.
F3: An even more relaxed version of the J2. Not much power or control. Popular
with Avant Gardes and other horn drivers, and does smooth out the peaks in
the tops of a lot of full range drivers. Used to be my favorite for the
Feastrex and Lowthers over the F5, now has to compete with SIT-1 and
SIT-2 for that spot.
M2: Some people just like the sound of push-pull output stages, transformers
and no feedback, and this is what the M2 delivers. Limited bandwidth and
control, but a pleasant sound, and it will drive 4 ohms. Has a bit more noise
than the other amps due to hum pickup on the input transformers, although
nobody seems to mind very much.
SIT-1: Broke the mold in the ability to play with the load line of a no-feedback
Common Source amplifier that still has any damping factor. A very unique
harmonic signature that can be dialed in to taste - Lots or little of 2nd
harmonic of either phase. Literally the sound of one transistor clapping -
without the input buffer (which no one seems to use) there is only 1
transistor in the amp. Has tremendous clarity and depth, depending on
setting, spectral consistency with warmth and detail. It allows you to focus
on a single instrument in an ensemble, almost to the exclusion of all else if
you want. This is the amp that convinced me that absolute phase is not
such a subtle factor.
SIT-2: A SIT-1 with a constant current source load instead of a stack of
power resistors. More efficient but similar to the SIT-1, it is set at a single
load line setting, so is not quite as flexible or fun.
Sony SIT amp (the big one shown at CES): This is a push pull VFET follower
output stage. Dynamic, high power, good control, drives the crap out of 4
ohms. It was voiced around AR-1's, and shows them to good advantage. It
is primarily 3rd harmonic in character, so the aspect is a little different than
the single ended SIT designs, but it is very impressive, detailed and easy to
listen to.
You realize that the original VFET (SIT) designs from the 70's were not
Class A and had more complex gain paths. I speculate that things might have
turned out a little different if they had gone for simple Class A designs that
play more to the strength of these parts.
Of course tastes have changed over time.
Mr Pass, How would the F6 and the Aleph J compare to the other amps you summarized in the post quoted above?
Thanks,
Kevin
Aleph J is reasonably close to the J2. I don't recall noting a lot of difference, but
the edge goes to the power Jfets which deliver the goods with less feedback.
For some reason the F6 is not so popular with the public. Probably would have
been if I had used the power Jfets, but I have a particular affection for it -
simple elegant topology with no degeneration, little feedback (via the step up
transformer), very stable thermally. It also can be dialed in for arbitrary 2nd
harmonic character.
One of my favorite concept amps, and I do have the power Jfet version here also...
the edge goes to the power Jfets which deliver the goods with less feedback.
For some reason the F6 is not so popular with the public. Probably would have
been if I had used the power Jfets, but I have a particular affection for it -
simple elegant topology with no degeneration, little feedback (via the step up
transformer), very stable thermally. It also can be dialed in for arbitrary 2nd
harmonic character.
One of my favorite concept amps, and I do have the power Jfet version here also...
That would be my favorite FW amp as well. I tried it with both jfets and mosfets and I can't say which one I like better. Mosfets have more sparkle on the top and jfets are more realistic in midrange... Bad thing I played with adjustable version when I was in that point of my life... looking for a lowest THD, so missed some sweetness most likely
I was thinking of revisiting maybe, but it will never happen as too many projects. Thinking of making B1 korg, that might give me what I need. Stay safe guys!