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Re: Impedance of MP-1 phono section?

Posted by Dave Garretson (A) on February 9, 2007 at 13:11:51

In Reply to: Re: Impedance of MP-1 phono section? posted by Ralph on February 9, 2007 at 11:45:18:

Thanks, Ralph. There is a fellow named George in Australia who builds an optocoupler-based standalone passive under the Lightspeed name, using Silonex NSL-32SR2S optocouplers. Using a 5V control voltage manipulated by a dual 100K pot, his passive design measures around 20K input impedance. By going down in control voltage, one should be able to bring input impedance up into the 50-100K range as I would think would be appropriate for a volume control in an active pre. But I believe that distortion in these devices increases with impedance, and they need to be carefully matched for the diff balanced application, so we'll see. Reportedly the Silonex is more reliable than devices used in the Porzilli volume control of the defunct Melos MA333 preamp.

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