are some phono stages more resistant to hum?

thanks to everyone for the responses. It is definitely hum, and not tube or other noise. I suspect that Dhl93449 correctly diagnosed a ground loop. How to solve it, in an apartment with exceptionally noisy wiring (even a flourescent light on the same circuit) and few outlets, is an open question.

Noise issues with phonostages are often quite unpredictable and hard to figure out.

While it might be the case that certain gear is generally more susceptible to noise problems, it can also be the case that it is only more sensitive in certain applications; e.g., sometimes the problem can be cured by moving the location or orientation of the phonostage or interconnect cables.

I have a preamp with a built in phonostage that, in my setup (preamp on a shelf two levels below my turntable) I have hum issues, whereas that same preamp in another system is dead quiet with a phono cartridge that has a .05 mv output (my problem is evident with a .30 mv cartridge).

Hum generated from the power supply of the phonostage itself might be a bigger issue with tube linestages, but, again, when things are right, tube stages can be essentially dead quiet (like my stand-alone phonostage).

I have heard both solid state and tube units that had noise issues. I don't think "type" tells you that much about proclivity to be noisy--one has to actually try the unit. In any given application, a unit that is otherwise known to be quiet may behave badly. For example, a friend's very expensive Boulder phonostage buzzes badly from over the air interferene (from lighting) where a tube unit we tried is quiet (Boulder is NOT known to be prone to ANY kind of noise problems).

You have to reference the input voltage to somewhere, and for phono inputs its the shield (-). If you could get a cartridge with a true balance output (like a center tapped transformer), with the split (or center tap) connected to the analog ground/shield, then you can have a true balanced input. Some microphones are wired this way. But phono cartriges are not.

All phono cartridges made today are balanced sources. None are single-ended. You don't need a center-tap to be balanced- that is a common myth. I don't know of any microphones that have such a thing- my Neumann U-67s sure don't. Neither do Shure SM-57s- these are mics at far extremes of cost and performance.

Any tome arm that has 5 connections (stereo signal + tone arm ground) can be run balanced by replacing the interconnect cable between the arm and preamp.

To clarify my comments, phono carts are ISOLATED devices, but are not inherently balanced. A true balanced voltage source would produce a symmetric V+ and V- signal referenced to common.

However, I agree they can be run in a balanced configuration with the correct wiring configuration and true differential input phono stages.

Sorry Lewm if I misread your original post. Its just that true differential phono stages are very rare, and neither of the OP preamps have true differential inputs, so using balanced wiring with these single ended input stages converts the system to single ended with little to no CMR advantages.

The OP asked whether one or another different types of phono stage might be more or less susceptible to hum. In responding, I brought up the fact that true balanced phono stages are much more immune to hum. Then we got off on this tangent. I don't think the discussion was out of line with the intended subject of the thread, but it was prolonged by your insistence that a cartridge is not a balanced source. Anyway, it's all good.