ToTo Man
the band not the dog
I posted about this last year so apologies for the deja vu but I'm still no closer to solving the problem.
I am using this passive RCA switch to route the line output from my amplifier to one of two tape decks (my amp doesn't have tape loops) but am finding it is adding 50Hz noise to the signal on the LEFT channel.
i have measured the internal noise of my ADC (Focusrite 4i4), the noise of my amplifier connected directly to the ADC, and the noise of my amplifier connected to the ADC via the 2-way switch.
Can someone please explain why a passive switch would cause in a huge increase in 50Hz and its harmonics, and why only in the left channel?
NOTE: I have amplified each recording by +75dB to make the noise easier to see. (This really equates to a boost of +65dB because the ADC records a 2Vrms input at -10dBFS instead of 0dBFS so you need need to boost it by +10dB for unity playback level).
ADC internal noise:
Amp (off) -> ADC:
Amp (on) -> ADC:
Amp (off) -> switch -> ADC (switch set to ADC):
Amp (off) –> switch -> ADC (switch set to other output):
Amp (on) -> switch -> ADC (switch set to ADC):
Amp (on) -> switch -> ADC (switch set to other output):
I am using this passive RCA switch to route the line output from my amplifier to one of two tape decks (my amp doesn't have tape loops) but am finding it is adding 50Hz noise to the signal on the LEFT channel.
i have measured the internal noise of my ADC (Focusrite 4i4), the noise of my amplifier connected directly to the ADC, and the noise of my amplifier connected to the ADC via the 2-way switch.
Can someone please explain why a passive switch would cause in a huge increase in 50Hz and its harmonics, and why only in the left channel?
NOTE: I have amplified each recording by +75dB to make the noise easier to see. (This really equates to a boost of +65dB because the ADC records a 2Vrms input at -10dBFS instead of 0dBFS so you need need to boost it by +10dB for unity playback level).
ADC internal noise:
Amp (off) -> ADC:
Amp (on) -> ADC:
Amp (off) -> switch -> ADC (switch set to ADC):
Amp (off) –> switch -> ADC (switch set to other output):
Amp (on) -> switch -> ADC (switch set to ADC):
Amp (on) -> switch -> ADC (switch set to other output):
Last edited:
This site contains affiliate links for which pink fish media may be compensated.