F4 with no preamp other than b1 is a no go. Everyone likes different stuff, but your description doesn't gel with general descriptions of amp.
I liked the F4 extremely combined with pumpkin or aleph p. B1 one was indeed too dry with F4 and unnecessary....
Normally I would say BA-3 should do it too, but my experience was that the Toshibas used in pumpkin and aleph P instead of the IRF610 were more neutral, but I liked more the slam or MosFet bloom of the 610!
So if you have an IRF pre at hand try it with the F4.
Just an idea, I will do myself, replace the Toshibas by the 610/9610 combo in the BA-3.
Normally I would say BA-3 should do it too, but my experience was that the Toshibas used in pumpkin and aleph P instead of the IRF610 were more neutral, but I liked more the slam or MosFet bloom of the 610!
So if you have an IRF pre at hand try it with the F4.
Just an idea, I will do myself, replace the Toshibas by the 610/9610 combo in the BA-3.
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Yup in the industry and here, everyone tries a tube gain with SS output.
It seems to be a perfect combo, Tube clarity and directness, with power and no output transformers! And always a disappointment, it just doesn't seem to work out that way.
But I built an Impasse tube preamp, designed by Moderator SY with high output for the F-4, and it really delivers. SY doesn't go for the extra sweet tube sound, but it has that clarity and directness of tubes and the massive power of a balanced F-4 ( I use 2 stereo F-4's in balanced mode, the Impasse is designed for balanced though it will do single ended too) ) I just love the combo!
It seems to be a perfect combo, Tube clarity and directness, with power and no output transformers! And always a disappointment, it just doesn't seem to work out that way.
But I built an Impasse tube preamp, designed by Moderator SY with high output for the F-4, and it really delivers. SY doesn't go for the extra sweet tube sound, but it has that clarity and directness of tubes and the massive power of a balanced F-4 ( I use 2 stereo F-4's in balanced mode, the Impasse is designed for balanced though it will do single ended too) ) I just love the combo!
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I was thinking that if one was not allergic to feedback, a pre-amp made out of a solid state input stage with tube output with a modest negative feedback loop allows reliable gain matching between channels and cleaner distortion profile and if designed well, less change from tube ageing.
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I have had a couple of different ideas in mind for awhile but I haven't built one yet - not having had an F4 handy being the main limitation (if I knew it'd sound pretty good in Class AB for summer use I'd put it on the active project list). Anyhow, the obvious starting point is a matched pair of p-type semiconductors in an LTP configuration driving a triode VAS with feedback from the plate to the LTP to lower the overall output impedance. I figure this would be enough to drive the high input impedance of the F4. The more linear the tube the cleaner the sound so the anode load would be best to be high impedance which also improves PSRR.
Next up you might think about a hybrid based on a simple Aleph front end. Some people prefer Singleton inputs to an LTP, which is another option here.
You need to plan out the voltages carefully, use the right tubes - and dc coupled where possible. The 6DJ8 and modern relatives might be reasonable choices and ECC99 is rumoured to be very happy with lower (by tube standards) voltages and can be very linear.
If / when I build an F4 I'll start a thread on a pre....
Next up you might think about a hybrid based on a simple Aleph front end. Some people prefer Singleton inputs to an LTP, which is another option here.
You need to plan out the voltages carefully, use the right tubes - and dc coupled where possible. The 6DJ8 and modern relatives might be reasonable choices and ECC99 is rumoured to be very happy with lower (by tube standards) voltages and can be very linear.
If / when I build an F4 I'll start a thread on a pre....
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O.K. I did the unnecessary.....
I changed the Toshibas in the BA-3 Frontend against the old 9610/610 combo.
I had to add 220R to each 5k pot to get the higher Vgs and cut some traces etc.
Distortion values were ugly higher than the Toshiba values if I checked right, but there was another problem with my setup so I am not quite sure....
But the sound rembers me very much of good old Pumpkin/f4 combo.
Because of K2 dominance more body and punch, not so detailed but you get a very natural and pleasant sound.
So can recommend to try it if you find the standard BA-3/F4 combo a bit disappointing why ever...
I will look at the distortion values and I have impression that P3 is working no more. Too much distortion in the 610/9610 combo.....?
Will inform you.....
Yes. Initial impressions are similar to yours. Bigger fets seem to be more full bodied, but I want to try to get spectra close and listen. I am also trying different loading and feedback schemes. I know you don't need the power, but balanced is the way to go, IMO hope to have pics by the weekend.
Lohk,
6l6 might be interested in those boards.
hope to have pics by the weekend.Lohk,
6l6 might be interested in those boards.
