in my opinion. As mentioned in various posts, I have used this amplifier for the past 11 years. It is a factory made unit, early production and made by the Magician himself. With the two linestages I use, the differences in sound are readely apparent. And both are really musical. With the 6SN7 Supratek linestage, the characteristics of the type of 6SN7 in use as well as any change in the coupling cap are thrown into the room. With the Sylvania 5692 tube the sound is a little bit dry and clinical, kind of polite. Put in the grey glass RCA’s and one gets a more sirupy sound. The soundstage also changes according to any input differences.
Likewise, with the ba-3 linestage I built, the sound is more solid state, but very detailed and clear. Soundstage is similar; it does not have to envy the Supratek for its qualities. With the Supratek the attenuator setting is around 9 0’clock but with the ba it is around 1 0’clock, due to the gain differences in these linestages.
And this, if you do not remember or know this has to do with the fact that F4, being what it is, a special current amplifier that does not have voltage gain, reproduces exactly the sound qualities of what precedes it. One can connect to it a suitable gain linestage or even a DHT flea power amplifier, and the F4 will give you 25w of that DHT amplifier with untouched characteristics. 6 Moons Audio did dwell on this in their review of this amplifier, and according to Srajan it is a fantastic combination. I have not tried this, but thinking of doing it.
6L6, is a known fan of this amplifier as suggested and insinuated in these pages about its sound properties and especially if one gets 2 units to run them as monoblocks. I have looked into building an FW amplifier such as either the F5T or the F6, and I am also looking into the XA-25 -mucho $$$$, but it would be nice to have though-, but what the heck, the differences in sound that these options might offer, warmth, dynamics, soundstage, no-dynamics, bass, etc. one can get from the previous stage using the F4. I know that for example, the supposed bass control that the XA-25 has, might not be possible. The F4 does not have that kind of damping factor. I’m not suggesting to get a Pass Labs amplifier here, but you get the idea. So, I am considering building an F4 to have the monoblocks. But I wonder about combining a diy unit with the factory made, if there might be a big difference in their sound, and/or build two units. Have to get a DHT amp. on loan to try it with the stereo unit....
Likewise, with the ba-3 linestage I built, the sound is more solid state, but very detailed and clear. Soundstage is similar; it does not have to envy the Supratek for its qualities. With the Supratek the attenuator setting is around 9 0’clock but with the ba it is around 1 0’clock, due to the gain differences in these linestages.
And this, if you do not remember or know this has to do with the fact that F4, being what it is, a special current amplifier that does not have voltage gain, reproduces exactly the sound qualities of what precedes it. One can connect to it a suitable gain linestage or even a DHT flea power amplifier, and the F4 will give you 25w of that DHT amplifier with untouched characteristics. 6 Moons Audio did dwell on this in their review of this amplifier, and according to Srajan it is a fantastic combination. I have not tried this, but thinking of doing it.
6L6, is a known fan of this amplifier as suggested and insinuated in these pages about its sound properties and especially if one gets 2 units to run them as monoblocks. I have looked into building an FW amplifier such as either the F5T or the F6, and I am also looking into the XA-25 -mucho $$$$, but it would be nice to have though-, but what the heck, the differences in sound that these options might offer, warmth, dynamics, soundstage, no-dynamics, bass, etc. one can get from the previous stage using the F4. I know that for example, the supposed bass control that the XA-25 has, might not be possible. The F4 does not have that kind of damping factor. I’m not suggesting to get a Pass Labs amplifier here, but you get the idea. So, I am considering building an F4 to have the monoblocks. But I wonder about combining a diy unit with the factory made, if there might be a big difference in their sound, and/or build two units. Have to get a DHT amp. on loan to try it with the stereo unit....
stay with factory one
change speakers if needed
I'm perfectly happy , every day , with my Papa's Koan (F4)
change speakers if needed
I'm perfectly happy , every day , with my Papa's Koan (F4)
I'm a big fan of the F4 also for all the reasons you stated. Mine are built as monoblocks. You can just throw all kinds of different linestage circuits at it and find out what you like, it's very interesting and fun. I've had F5, BA-1 (couple of variations), F6 (both versions), and Aleph J. But what is currently in place? The F4..
I need to build this amp, have had boards for years. I too want to try with Flea power DHT on it's front end, but for reasons zenmod pointed out to me, you can't get the 25 watts out like I thought. Still a worthwhile combination I need to try. But Sissysit is first in line for next build, boards almost complete. Ditto for F7 clone. I need some Chassis!
Russellc
I pulled out my diy F4 today. Unfortunately none of my preamps have the
combination of gain/voltage swing to drive it to full output.
(I'm getting a max of about 6W into 8 ohms using my digital source)
That said, aside from the volume limitation (which is adequate for most recordings),
the sound is good.
combination of gain/voltage swing to drive it to full output.
(I'm getting a max of about 6W into 8 ohms using my digital source)
That said, aside from the volume limitation (which is adequate for most recordings),
the sound is good.
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Joined 2009
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Sony FE, choose a bias circuit, add pucks. I'm using the bog standard TL431 with thermistor.
40P50P & 40N30P, no stock of the 40N30P untill the end of April at mouser, I substituted 40N60C instead 
The Aksa Lender Preamp was designed specifically with the F4 in mind. It can drive 40Vpp to enable the full 25wrms into 8ohms. Low distortion, great harmonic profile and smile on your face and foot tapping sound quality.
AKSA's Lender Preamp with 40Vpp Output
AKSA's Lender Preamp with 40Vpp Output
40P50P & 40N30P, no stock of the 40N30P untill the end of April at mouser, I substituted 40N60C instead
Thanks kindly!
Currently using F4 with BA3FA...never went above half the volume. Will try Wayne's line stage next.
I'm liking the Burning OpAmp right now with my monoblock F4's. I have a Jensen autoformer between the two for some more gain. But there is something more to adding this signal iron than just gain. I'm not sure what it is, but I like it. Currently rebuilding my linestage to make it all more permanent. It's been just all tacked together for testing.
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