In Reply to: RE: " better EMI/RFI rejection " is it really an issue for speaker cables ? posted by rick_m on February 12, 2015 at 07:35:40:
Hi Rick,
I'm having a little trouble wrapping my head around this:It has little to do with gain, a lot to do with effective aperture: Speaker wires and power lines are great antennas! The junctions in your output bugs are rather directly connected to the speaker wires, especially if the design doesn't use a Zobel network, and your amplifier becomes an amplified crystal set.
For a typical solid state amplifier with low output impedance, and a similarly low impedance speaker cable, I presume the output stage should effectively become a sink for any induced noise currents at frequencies within the bandwidth of the output stage, just as it is a sink for back-EMF. In other words, it is close enough to an ideal voltage source within its bandwidth that the speaker only sees the noise induced voltage differential across the cable.
Assuming a typical push-pull output stage, I don't see how it could behave like a crystal set because one side or the other is always conducting so there would be no rectification.
I hadn't given much thought to noise frequencies outside of the bandwidth of the output stage, but wouldn't they just be shunted through stray capacitance?
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Follow Ups
- RE: " better EMI/RFI rejection " is it really an issue for speaker cables ? - Dave_K 12:18:54 02/12/15 (1)
- RE: " better EMI/RFI rejection " is it really an issue for speaker cables ? - rick_m 14:26:42 02/12/15 (0)