I have not calculated the 47pF.
I chose it for it's low value and ability (low inductance due to being very small) to shunt VHF to ground.
This is an extra filter to supplement the main RF filter at the PCB.
It's value is not critical but it can form a 2pole filter with the inductance in the interconnect and thus must be small enough not to attenuate the audio signal
I chose it for it's low value and ability (low inductance due to being very small) to shunt VHF to ground.
This is an extra filter to supplement the main RF filter at the PCB.
It's value is not critical but it can form a 2pole filter with the inductance in the interconnect and thus must be small enough not to attenuate the audio signal
Ah, thank you sir.
220pF seems to be doing okay in mine, so I'll leave it be.
Adding that cap really transformed the performance of my amps. Went from harsh and bass-light to really quite nice. I don't know if that's an indication I've messed up elsewhere in the build, though.
Cheers.
is there an RF filter at the input of the amplifier?
Internally generated EMI requires attenuation.
It may be that the EMI is passing back down the input cable to be attenuated at the RCA socket. I would much rather have it as close to the input amplifier components as possible.
Most amplifier front ends like to see a low source resistance. Adding the 220pF, even though it is remote, will reduce the apparent HF impedance seen by the amplifier input.
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