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In Reply to: RE: Thank you Lew posted by Caucasian Blackplate on December 27, 2015 at 21:02:18
Did you know that the input stage of both our amps and preamps is a differential cascode with CCS? The top portion of the circuit is arranged as a CCS.
In the preamp, what this does is give us low enough noise and enough gain that even with passive EQ, only two stages of gain are needed for the phono section.
From what I have seen, the top portion of the circuit is not arranged as a CCS (I don't consider a cascode configuration to be related to a CCS since the load seen by the bottom triode is very low).
Such topology is reminiscent of Allen Wright's old circuit cookbook.
Still, you're going to get more self noise from the cascode differential pair than you would from a single cascode stage. This doesn't matter all that much in a linestage or power amp, but will start to bite you in a phono preamp.
-We've been using that topology since the mid 1980s.
Actually we've not been able to get SE implementations to be as quiet. Mind you, they come pretty close. The key to getting differential amplifiers to really work they way they are supposed to is through an effective CCS- and FWIW, most of the CCS circuits I've seen really don't perform all that well, leaving a lot of performance in the actual amplifier on the table.
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