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Re: Berning ZH270 or Seigfried compared to Atma-sphere MA60

I don't mean to cast aspersions on David Berning's ingenious circuit or to deny his basic claims for its capabilities, which in my estimation, include removing the typical tube amplifier output transformer nonlinearities while adding the capability to respond down to DC and retaining the ability to transform the voltage/impedance between 'primary' and 'secondary'.

It's just that the means by which this is accomplished will presumably add its own sonic characteristics, and that the tendency is, since it is encouraged to generically refer to it as an 'OTL', to casually assume that no transformer at all exists in the signal path between output stage and load. But you have made reference to this already.

Btw, I've designed a 'conventional' OTL that indeed does repond down to DC (as in amplifying a DC voltage presented at its input - I deliberately rolled it off to unity gain at DC to minimize voice coil mayhem, however) with output offset referenced to ground in the tens of millivolts or less without any solid state devices in the signal path whatsoever and without resorting to the use of a feedback servo, and with some tweaks to the input and driver stages, could also respond flat to 200khz (as is, my prototype measured 3db down somewhere past 100khz into 8 ohm).


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