A standard RCA/XLR converter plug may not work, as these typically short XLR pin 3 to ground.... As suggested by Lewm, if in an RCA configuration cartridge negative phase and shield to RCA barrel share a common wire, then grounding the shield to pin 1 or chassis will have the effect of shorting out and eliminating one half of the balanced signal.
Actually, that is not correct. The phono stage will see the same signal amplitude whether or not pin 3 is grounded. There will be the same difference in voltage between pins 2 and 3, as generated by the cartridge, either way. The cartridge will not "care" whether those lines are referenced to the phono stage's ground, or are floating.
The difference will be, as I said in my post immediately above, that the impedances of the two signal lines relative to ground will be unequal if pin 3 is grounded. That will severely degrade rejection of common mode noise, but will not affect the amplitude of the signal that is processed through the phono stage.
Essentially, it would convert the balanced input stage into a single-ended input stage, but with no change in signal amplitude.
And again, to be precise, it is one polarity, or one of the two signals in a balanced pair of signals, that is shorted to ground, not one half of a signal. Each of the two signals comprises a complete waveform containing all of the signal information, and the waveforms on the two signal lines are identical except for being inverted relative to each other.
Best regards,
-- Al
