one question arise when i look at various other designs, why there is a decouping cap at the input 9C502), i mean, why in the hell would there be a DC comming from the cartridge ? i understand the paranoia behind this for consumer market/mass production....?? but for a pure minimalist aspect and to reduce components in the audio path....
Coupling, or blocking. Not decoupling.
If you mean the first plan in the thread, the '4570 opamp is a fancy '741. The input bias current can be as high as 400nA (half a microAmp). Is this OK in the cartridge? Who knows?? The conservative thing to do is block it. The blocking cap must be "large" compared to the ~~5k of the cartridge in bass or it encourages 1/f noise (rumble).
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