Audio ground with single supply LM358 non-inverting

[boylesg]

If I am creating a non inverting amplifier with a single 12V supply and I am biasing the audio input at 9V, so that it swings between 12V and 6V, then what should I be connecting the audio input GND line? Should it be GND in my op amp circuit or 9V?

 

[KlausST]

Hi,

if your supply is 0V/12V, then it´s usual to connect audio GND with 0V of the supply.

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...so that it swings between 12V and 6V...

Mind that LM358 common_mode_input_voltage_range is 0..V+ -1.5V. So if V+ = 12V then it can only operate with input voltages less than 10.5V.

Why that unsymmetric? Why not 12V/2 = 6V?

Klaus

 

[boylesg]

I am inputing it to a 555 CV pin and i read that it was biased to 2/3 Vcc or 9V in my case.

So 9V should be my 0V for the audio signal, and it should swing from 12V to 6V.

So I biased the audio signal at 1/3 of 12V = 9V.

So it had me thinking for a moment whether or not input audio ground should be 0V or 9V.

With audio from my desktop PC audio plug x11 amplification seems to work well with a speaker attached via a TCC4422 and a FET.

The sound quality seems very good for a crude setup. It has not been as successful when my input audio was biased at 0V or what ever.

 

[D.A.(Tony)Stewart]

THe COntrol pin is biased at 2/3 or 9V in your case and the modulation should be limited to 10% above and below 9V, so it should NOT be used as an audio ground for a single supply source.
The Threshold input should also be centered in this range.