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RCA/Rozenblit RIAA Line Amp idea

Posted by shermanr@prw.net on August 15, 2006 at 11:06:36

After seeking a reasonably priced tube phono stage, I have to admit I am not convinced about spending $250 on a Bellari after peeeking inside the chassis.

I would like to know if the following RIAA Line Amp idea holds water.

What about a combination of the popular RCA Phono Stage that is published in the RCA manuals using 2x7025 tubes married to the Line Stage that Bruce Rozenblit designed in his book beginner's guide to tube audio?

I have made a cut-and-paste copy of both schematics together sharing HV and DC Filament power. But I am afraid of posting it for fear of getting hollered at for infringing on copyright issues.

My plan is to use 2 x 125 Volt Zener diodes to piggy-back power from the Rozenblit Voltage Doubler PSU circuit for the 250 Volts required by the RCA phono stage. The 7025 filaments will also share the same DC filament supply that is floated by HV DC to make the heater cathode potential difference much less.

A 220K resistor or 250K pot will interface the two together. The potentiometere would give me the ability to vary the overall gain to better match the MM or High Output MC cartridges.

The nice thing about the Rozenblit line stage is that it has a High Impedance output 10Kohm and a Low Impedance output 800 Ohm so I can have a choice of outputs.

Is it Ok to post my copy-paste scan for you to give me opinions or suggestions?

I can build this as a two box solution, PSU in one box and the amp in the other connected by an umbilical cord.

Thanks,
Rich

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