Summing two stereo signals before monitors
I am currently using ITB gain adjustments for level matched A/B comparisons. However, I would like to do this in the analogue domain if possible, to allow me to keep the mastered track at its exact volume rather than attenuating it. I have a spare DAC with an output level control (Benchmark DAC1) available, and I can easily handle switching between the two signals ITB, and both my monitor DACs have independant volume controls, so all I really need to do is sum the two signals before my monitors.
Is there a simple, off the shelf product that accomplishes this with minimum loss of fidelity? It's my understanding that a simple Y Split cable would be a very bad idea. I could always buy a Coleman monitor controller, but it seems overkill when I would only really be using it to sum two signals together - I would not need any of the other functions at all.
I don't want to go DIY - is there something cheaper than a Coleman that accomplishes what I want and maintains signal accuracy?