F6 Amplifier

Official Court Jester
Joined 2003
Paid Member
naah

J2 is amp for sissies .....

M2 , too
 

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(almost ) all tricks are shown

everybody can make his own F6 wannabee easily

Pa's ears are his own , not yours

These are not tricks; but core beliefs and practices by a producer of custom electronic equipment who is Mr. Pass. By the time he makes ten F6 amps [is it a mono or stereo?], Sony, Marantz and others have produced thousands for the mass market, and much cheaper too. In his younger days at Threshold Corporation, Motorola BJTs [hundreds; maybe an exaggeration on my part?] were individually tested to yield a handful of select devices which met the stringent requirements for use in his STASIS [R] amps. I believe this practice lives on.

Damn right; anybody can make a clone of F6. A certain clone has a Gmfor the upper JFEt of 9S [for example] and the bottom JFEt has a Gm of 7S [off the shelf devices]. Another amp with a Gm = 7.01S for the upper and lower JFEts [deliberately matched at a cost of time and money] will tickle your ears way better than the first one with the gross mismatch in JFET transcondutance. I hope that you agree!

Do you own a Pass amp? I own a Threshold S/150; and thus trained my ears over the past 30 years to hear what young Mr. Pass heard using his creation. I do have some of his appreciation of great sounding music [his golden ears]; do you?
 
The asymmetry in the F6 is due to the transformer winding capacitances. If you do a simulation which includes estimates those capacitances, you will see that the secondary loads are not identical and that Vout capacitively couples to the feedback node and to the gate of the lower FET.

As near as I can tell, the circlotron is the only truly symmetric (unbalanced) circuit using only N-channel FETs.

My question concerns the effect of the output fets operation on the signal. Sy stated in his Impasse article that a phase splitter was symmetrical if presented with a symmetrical load, but if the two loads were different, then it affected the tru symmetrical nature of the phase splitter. I think you see an exampl of this in the PLH. IT is a phase splitter, but i it is not driving equal loads, as you have a common drain and common source outputs summing into the load. THe transformer presents symmetrical signals out of phase to the two output fets, but they still will react differently to that signal,,, I would think.
 
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Joined 2009
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My point of view is similar to the last postings......:)

having the circuit may be 30%. Trimming the sound to the sweet spot by a good choice of the data of the semiconductors, and they are really the part with the greatest variance and uncertainty are the other 70 % of a very good sound.

And in the last part you are mostly alone.....