Can good IC's be used instead of dedicated phono's

Salectric, It doesn't "figure". The gauge of the wire might make a difference, since any resistance in the ground wire would potentially allow the component to "float" at some tiny voltage above ground, which could potentiate hum, but otherwise, I cannot fathom why the character of the wire would make a difference, assuming copper or silver in the first place. Was there any difference in gauge (thickness) of the conductor? Or is it possible that when you were changing the ground wire, you did a better job making contacts between the two chassis? (That could also have an effect.)

I agree it doesn't make logical sense (at least anything that makes sense to me). That's why I mentioned it. I didn't notice any correlation between wire gauge and sound qualities. I tried about a half-dozen wires including solid silver, solid copper, and stranded copper before settling on some DH Labs 12 gauge silver-plated stranded copper. Of the ones I tried, this had the most neutral tonal balance with good dynamics and detail.

Salectric, my guess is that the different grounding wires probably made a difference in the amount and/or frequency characteristics of ultrasonic or RF energy entering the phono stage. Either by making a difference in the effectiveness of the shielding provided by the enclosure, or by differences in antenna effects.

With many and perhaps most phono stages audible differences can be expected to result from significant differences in ultrasonic or RF energy that may be sent into them, as a consequence of intermodulation, demodulation, and similar effects. One evidence of that is the number of threads we've seen here over the years in which people have reported problems hearing radio stations when listening to phono sources.

Were all of the wires you tried approximately the same length, and were they routed and positioned similarly, relative to other cables, power cords, and components (especially those containing digital circuitry) that may have been nearby?

Length differences would affect inductance, which would affect grounding effectiveness at ultrasonic and RF frequencies. Significant length differences might also result in differing antenna effects. Differences in positioning might affect pickup of ultrasonic or RF energy radiating from nearby power cords, cables, or components.

Regards,
-- Al

The wires were all about the same length---3 feet or so---and were all positioned about the same. The preamps are all on wood shelves and tables, not near any metal surfaces other than the equipment itself.

The ground wires didn't go near any power cords because I use an outboard power supply located on another shelf.

You could be right about picking up RFI but I don't hear any noise problems. In fact, my phono setup with SUT feeding a tube phono preamp is the quietest I've ever had.