Musical Fidelity X10D schematic

[andrew_whitham]

Has anybody ever tried setting this thing up as a true buffer, that is, with no gain? Stock, R104 is 8K2 and R106 is 1K5, so the gain is 1.18x or 1.44 dB. (My unit has these resistors and the schematics in this thread show the same.)

I can clearly hear the extra gain when this is switched in/out of my preamp's tape loop. I might just bypass R106/R206 (and C103/203) with wire links.

Hi Eric,
Did you (or anyone else) try this? Fitting one to a CD player as a switched thing, really would prefer gain to be 1
Andy

 

[andrew_whitham]

Also at the risk of being ridiculed. Its been a while since I looked at valve circuits

Valve 'b' has the grid at 0v relative to the cathode both at -30? that can't be right (?) it obviously works. Am I missing the forest for the trees here?

Question:
Why is C102 even there? Is it because the voltages are insufficient and the full ~60v is required across both tubes? Seems to me there is an opportunity to set DC conditions on V2 with a resistive level shifter and use the feedback ratio to compensate for what I imagine will be some attenuation?

Appreciate I'm digging here

Andy