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In Reply to: RE: Would that sound good? posted by Salectric on July 03, 2015 at 16:32:54
I have had really good results using a CF with a CCS on the cathode side. Better yet with Allen Wright's "Super Linear Cathode Follower". In my amplifiers, I went through a progression where I listened to a plain CF as a driver stage for several years, then added the CCS for a few years, then upgraded to SLCF. The speakers and upstream gear did not change, essentially, so I feel very confident that the improvements were due solely to these modifications. Difference between no CCS and CCS was greater than between CCS and SLCF. I guess if I did a mu-follower, I would use a dual section triode rather than transistors.
Follow Ups:
Interesting. The only time I tried a CF as a driver was my first 300B SE amp where I started with a 6SL7 direct coupled to a 6BL7 CF. It sounded pretty decent even with resistor loading on the cathode. Unfortunately I never tried a CCS on the CF driver. And since it was the first input/driver I tried for the 300B, I felt obliged to go on and try a lot of others and never went back to the first version.
On preamps with a CF the CCS made a major improvement compared to resistor loading.
Amen to that.
Lew,
My co worker, and good audio friend, used to get rid of cathode follower stages, from Audio Research SP3 A-1s, etc, and thought, into a tube amp, with short cables, the deleted stage sounded markedly superior !!
There are commercial products he told me about, it MAY have a C-J preamp series, where the only difference in the later model was an addition of a cathode follower stage, and most everyone prefers the early "simple " edition of the preamp, he tells me. We are referencing to the used market, and posted comments, after several decades of both versions' existence.
I can get the model numbers from him, if you wanna know.
Jeff Medwin
I and Salectric are both agreeing with you, that a "plain Jane" CF, at least all the ones I've heard, does impart an unpleasant coloration that is most evident when you "fix" it, at least a little bit, with a CCS. You can fix it even more, IMO, by adding a constant voltage source on the anode side of the CF, while keeping the CCS. That's the "SLCF" described by Allen Wright. If the interface requires lowering the output Z, a CF with a CCS or an SLCF is pretty darn transparent. However, I would not argue that avoiding the need for a CF is not better than any CF or variant thereof, when possible. Often that is one advantage of an "all-in-one" preamplifier, with phono stage on the same chassis as the linestage. In that case, one can usually dispense with any CF or other output buffer on the phono output.
Well posted !!! Xln't. Thanks Lew.
Jeff Medwin
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