2 threads Lima dude!!
Phono input cap to preamp
Currently reworking a Hafler DH-101. The question is regarding the input capacitor for the phono stage from the cartridge/turntable. If the phono cartridge only outputs an a.c. Signal, is a capacitor needed in that location? Is the capacitor there to prevent backfeed to the cartridge in case of failure? Currently there is an Elna 10uf 16v BP cap at c2. Seems as though one would not be needed but the interweb appears to be short of answers on this topic. Perhaps M.C. could drop a Truthbomb on this topic.
Can you reference a schematic? “C2” does not sound like the code for a series input capacitance. (I’d expect it to be C1.) Moreover if the phono load R is 47K ohms, 10uF is way overkill for maintaining a low bass response. You could get away with 2uF or even 1uF, if indeed the C is in series with the signal. On the other hand, Hafner was smarter than I in these matters.
@wturkey Measure the voltage on the output side of that capacitor. If the input circuit employs a discrete device like an FET or transistor, there may be a voltage present to bias that device properly. Getting rid of the cap could thus cause the cartridge to have a voltage across it which could mess with it and it could cause the bias voltage for the input circuit to be messed up too.
You might consider a film cap to replace that. Wima makes a little 10uf film cap rated at 35V IIRC; a little rectangular thing you can get from DigiKey.