OK, I think I understand most of that.
I was just thinking that one supply would make for a less complicated setup, even if it required sacrificing some "audiophile-ness".
I was just thinking that one supply would make for a less complicated setup, even if it required sacrificing some "audiophile-ness".
I agree, one supply would definitely be much more convenient. So that means we'll be using some coupling caps on the input.
EDIT
There is one way to get around the coupling caps but involves the use of a center tapped secondary power supply. With a center tapped secondary we can provide both the 24V supply and a ground reference for the op amp and the input signal. One thing I forgot to mention is that the offset voltage of the op amp increases as the output common mode voltage gets closer to the rail voltages. 24V/8=3V above the negative supply pin of the op amp, which won't be great for the offset.
EDIT
There is one way to get around the coupling caps but involves the use of a center tapped secondary power supply. With a center tapped secondary we can provide both the 24V supply and a ground reference for the op amp and the input signal. One thing I forgot to mention is that the offset voltage of the op amp increases as the output common mode voltage gets closer to the rail voltages. 24V/8=3V above the negative supply pin of the op amp, which won't be great for the offset.
Would a virtual ground circuit work instead of a center tapped transformer? I assume it will.
I have used the "Sijosae discrete rail splitter" on a headphone amp and I like the way it works. The 12v rails of the amp never fluctuate more than 0.5v at full power.
http://i13.tinypic.com/2exsc9c.jpg
There are tons of 24v SMPS supplies on the market and they can usually be had for much less than a transformer.
I have used the "Sijosae discrete rail splitter" on a headphone amp and I like the way it works. The 12v rails of the amp never fluctuate more than 0.5v at full power.
An externally hosted image should be here but it was not working when we last tested it.
http://i13.tinypic.com/2exsc9c.jpg
There are tons of 24v SMPS supplies on the market and they can usually be had for much less than a transformer.
A rail splitter COULD work depending on how your other equipment is earthed and whether or not the output of the switching supply is floating. If you use a 24V SMPS with its output ground terminal also connected earth ground and a rail splitter to get a virtual ground, and then try to connect your preamp whose output is also connected to earth ground, you could have problems. I mention this because a lot of SMPSes have their output ground also conencted to earth for safety reasons. The way to get around that is to disconnect either the source ground or the supply ground from the earth ground.
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