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RE: Unity Gain Control Amp

The tweaked RCA phono setup I'm associated with will drive a recording device. ;>)

The tweaks address 2 of the 3 weaknesses in the RCA original. Grid leak biasing the 2nd gain block lightly loads the EQ network and improves bass extension. The MOSFET source follower deals with the original's very poor drive capability. See RCA's remarks. The 3rd weakness is the high CMiller of the 'X7 triode, which can adversely interact with some carts. and SUTs. Dealing with that requires a tube and EQ network change that I didn't want to get involved with. The 6GK5 is (IMO) an obvious candidate for the alternative 1st gain block role.

FWIW, those who have built the tweaked setup have been pleased. Check the archives.

Eli D.

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