Posted by Ferrstein on September 20, 2004 at 09:09:30:
In Reply to: Re: Re: Re: Re: Hello, Question on Operating Voltages posted by Lew on September 17, 2004 at 13:03:38:
Well... these amps do sound good on the Acoustats. I would imagine that they would need some changes to the equalization circuitry in order to work well on the Soundlabs. There is a segment in the input section of the Acoustat Servo amps for the high frequency, mid frequency, and bass equalization. All of it is passive. There were revisions to these areas of the circuit throughout the lifecycle of the Acoustat speakers, so I would imagine that these amps could be adapted to the Soundlabs in terms of tonality.
As far as using the high voltage amps for the audio and the Soundlab backplates as a bias supply, I have actually done just that with Acoustat's transformer interfaces. When I first got the Servo amps for my Acoustat model 3s, I had been using them with their transformer interface/bias supply. At the time, I was under the impression that it was a bad idea to switch the bias supply on and off all the time. Since the interfaces used a constant-on bias supply, I decided to have them supply the continuous bias, and I ran the amps for just the audio signal. For this setup, I just left the bias output of the amp unused. It worked fine! I later found that the 5kV supply coming from the servo amps sounded just fine, regardless that they were not constant-on. It is important for both the bias supply and the amps to be on the same ground plane. This should happen if correct 3-prong power cords are used for everything.
I am hearing that the Acoustat Servo’s may be a bit low on output for the audio signal anyhow. They should be able to do about 5kV peak to peak. When I set the clipping symmetry on the amps, they are right around 2.6kV per side. I do know that all the components are specified for that voltage, and it would be very difficult to get more out of them.