Quote:
Originally Posted by markmaxx  My MPX3 has the supra transformer and 400V out put for the 6BL7GTs I am not sure whats inside? Is it a SE? I belive it was the first MPX3 with 400V. out put stage.
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There are a couple of other SP amps with raised operating plate voltages (Va), like yours, but they never got a name.
The
Supra 398, however, did, which too was build with the 6BX7GT and 6BL7GT in mind.
Interestingly, Supras, at least in the beginning, actually had a lower Va than the MPX3 with the aim to extract more detail and definition from 6SN7 tubes; the early 6SN7GT's in particular
(note not the 6SN7GTA or GTB). That was the main idea behind the Supra model. An even larger power-supply than the MPX3, with finer capacitors, sought to compensate for any possible loss in dynamics. Correct me if I am wrong there. The plate effect, i.e. dissipation, was, however, unchanged between the MPX3 and Supra because of a raised plate current. For the record, it would be very interesting to know what operating points the first SDS' had, considering the size of the power capacitor silos.
Stand up, the usual suspects.
To the point. Is your 400 Va MPX3 a "SE"? Probably it has to be concluded - no. It does aim to accomodate the 6B(X,L)GT tubes, just like the
Supra 392, but it does not have a
switchable Va. Yours seems to be a model in the pioneer era towards non-6SN7 tube sets in SP amps.
So - pls tell us, what does it sound like? "OK"?
Good to hear!
