phono line stage project

[kevinkr]

Eli, what's the point/purpose of running the second stage at zero bias?

Second stage employs grid leak bias, purpose here I suppose is to provide a very high input impedance to avoid loading the EQ network.

 

[rongon]

Yeah, the input impedance of the Yamaha is about an order of magnitude too low for good performance with this circuit.

Eli's circuit is the one with the MOSFET source follower on the output. You could use a tube (maybe a 12AT7 or 6DJ8) as a cathode follower, if you're more comfortable with that. The follower is an output buffer, which lowers the output impedance to a point low enough to effectively drive the low input impedance of your Yamaha solid state amp (or receiver). It seems to me that you need to do this.

Handmade Electronics used to sell a pcb for the RCA RIAA circuit (from the old tube manuals). I stuffed one of those boards and stuck a cathode follower on the end, using a 12AV7 (because I had a sleeve of 'em, but you can use 12AT7 just as easily). It worked out pretty well. Kind of surprised me.

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