Why do most phono preamps lack XLR input even thought cartridges are naturally balanced?

luisma31, sorry, I got confused with initial post about TT problems.  You keep saying "unplugged from pre side" but you probably mean that shield was disconnected, otherwise what are you listening to if nothing is connected to pre?  I suspect that cable might create ground loop.  Lifting shield on pre side might still produce buzz if shield touches connector shell.  Anyway, there is very little chance that anybody can help you if Ralph couldn't.  I use XLR cable grounded at both ends between DAC and power amp and it is dead quiet.  

@kijanki I'm fine, buzz and hum are gone, the point I was making is that shield although indeed blocks RFI / EMI could create other problems which balanced lines really don't need.

There is little, if any, advantage to XLR on short runs.

danvignau

There is little, if any, advantage to XLR on short runs.

That’s a pretty broad statement and it isn’t clear exactly what you mean. As I’ve already pointed out, the use of XLR connectors does not necessarily mean that the unit is true differentially balanced.

There is great potential advantage in using differentially balanced circuitry and connections in a phono preamp. In addition to the increased immunity to noise, there’s a 6 dB increase in gain. That’s a huge advantage in a phono section!

As a counter to that cleeds, and not taking anything away, it is also true that because an RCA connection is used, does not mean that the input is not true differential.

With great gain, comes great responsibility. But seriously, w.r.t. phono, differential gives you the ability to increase gain while decreasing common mode noise, but you are still amplifying differential noise as well as noise internal to the amp. You are not getting 6db for free. You could always crank the gain 6db on a single ended connection, which again, for a cartridge, is already pseudo-differential due to the floating source.