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How to get low level from high (audio)


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Hi Stuee,
Maybe the line out of your head unit is low-impedance and can drive many amps that have a high input impedance. Their spec's will say.

If one amp feeds the other amp, you won't have the advantages of having separate amps:
1) If you feed the 2nd amp from the output (attenuated) of the 1st amp, you lose the ability to separately adjust the levels of the amps.
2) If the 2 amps are the same, the output of the 2nd amp would have twice the noise and distortion of the 1st amp.
3) If the 1st amp clips, the 2nd amp would also reproduce the severe clipping distortion, even if the 2nd amp is turned down.

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Hi John,
That's a nice attenuating "balun" circuit.
But it provides a signal that is out-of-phase. While investigating swapping its inputs to swap the phase, I wondered what a null would sound like. Complete cancellation? Just distortion?
So I changed your resistor values and came up with this circuit that will provide an attenuated signal in-phase, a null and a signal out-of-phase. Normally you would use a ganged pot. If the pots are separate, you can have the channels in-phase or out-of-phase with themseves or with its output:

post-1706-14279141874968_thumb.jpg

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Hi John,
I am assuming that the car radio's amps are bridged without a transformer, with a + non-inverting amp and a - inverting amp for each speaker. Each amp's common is ground, not floating.
Since your circuits have the lowest value resistor in the - inverting side, their outputs are also - inverting, which is out-of-phase.
My revision of your circuit also adjusts the volume, but as an addition allows you to adjust for a + non-inverting or a - inverting output for a choice of phase, with a null position for extreme attenuation.

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