The PCM1793 datasheet has a filtering and amplifier stage. I built this without realizing that it requires a bipolar power supply. I'd like to get it to work with a unipolar power supply. I don't have a ton of experience with analog audio stuff, so I'd like some help.

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My expectation is that I could introduce a DC bias by disconnecting the bottom end of R15 and connecting it to Vcc/2 (2.5V) created from a divider. I would then add a DC blocking cap at the output.

I don't think that's enough, though, is it? Don't I also need to reduce the gain (by increasing R12 and R15) given that half of the range is gone? Does that require recalculating any of the other passive components?

The desired goal here is line-level outputs. Would I be able to expect to have enough amplitude with ±2.5v?

The alternative to all of this is a charge pump to make -5v. The MAX1721 can make -25mA with a switching frequency of 125 kHz (so ostensibly above anything remotely audible). Is that a better plan than messing with biasing this output stage?


1 Answer 1


With +/- 2.5V or single +5V supply, the OPA2134 input will barely be able to work with your DAC output.

And if you used the datasheet example circuit, it is set to output a 2.1Vrms line level output, which is about 5.9Vpp, so if it were an ideal component, it would require at least 5.9V of supply voltage at minimum.

It might be able to drive a line input reasonably with +/- 5V.


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