basic passive preamp

Yes the McCormack Micro line drive is a great potentiometer based passive, with an active stage that can be switched in as well, if your source has low output voltage, <1v. 
Trouble is the active stage is just a  Analog Devices AD712 dual-op-amp chip, not the best of audio opamps, that would be better replaced for dual OPA627's per channel on Browndog adapter boards.
And I think it's only available s/h, long discontinued now.

http://www.stereophile.com/solidpreamps/521/#jMEKhFqoSfSA6o7j.97

Cheers George           

Thank you George for the heads up on the op amps and if a upgrade there is still available it would be worth looking into.  Let me pull a statement from Stereophile worth repeating: "The task of the designer is to come up with a preamp circuit that does the least damage to the audio signal, then add the necessary preamp functions in such a way that the purity of the signal is not compromised".

Gents - I see Luminous Audio offers an XLR equipped version of the Axiom, can anyone tell me if that represents a true balanced design?  Hoping it's not a completely ignorant question.  My very basic understanding is that just because a piece of gear is equipped with an XLR connector does not mean the design is actually balanced.  Thanks in advance.  

I wrote to Tim Stinson at Luminous Audio. He replied that the design of the XLR equipped Axiom II is fully balanced.

You might also think about a used Placette Audio passive. Their bigger one has 3 inputs, uses vishay S102 resisters, has remote control, consistent input impedance.