My speakers have a sensitivity rating of 99 db. I have an old stereomour with ac filaments but hum is not an issue. I have to put my ear up next to the speakers to hear hum. I never hear any hum while the music is playing even during parts of the music when there is complete silence. Other than hum what other advantages are there in dc filaments?
That's pretty much it. It's not important to everybody, so it's not in the basic kit; the upgrade will be available for those who really want or need it - some of our customers have 110dB speakers! This way the price of the basic kit stays low. One other application: subwoofers can be more easily taken from the speaker outputs, which almost always gives better integration with the main speakers. Hence there are no second preamp outputs (another cost saving).
The original Stereomour does not have enough filament power available to make DC heaters (I tried); the new power transformer fixes that. (It's also the power transformer for the Seductor.)
We already make two dedicated headphone amps (Crack and Mainline) and a combination amp (SEX) so we neither considered headphone performance nor added the cost of additional wiring and jacks to Stereomour II.
The Stereomour II uses two 12AT7 tubes as drivers, using half of each tube. This makes it possible to have an upgrade kit that uses the other half as a hybrid shunt regulator for that stage, bringing it closer to the Paramount sonics.
Going to separate volume and balance controls allow for the possibility of the BeeQuiet type stepped attenuator, the best sounding option we've found - without adding much cost to the basic amp.
It retains the OT-2 output transformer, which has been quite successful. That means the impedance switch upgrade kit will also be available.
Hope that clarifies a few questions.
