I’m not sure if I’m stupid or if it could be this simple:
RCA hard splitters on the phono outputs, with the second ones inverted (with a transformer or…?), connect those to XLR out signal pins, and use the RCA ground for connecting to the XLR out ground pin, then use a proper XLR cable for transmitting especially an MC signal as is seemingly recommended?
Of course with a balanced phono preamp.
I’m asking because a friend has a balanced (only balanced) phono pre, but has a self-built turntable with RCA outs. He uses XLR converters to connect with XLR cable and I’m assuming this has the benefit of shielding the MC signal somewhat since while the XLR ground is only connected at the preamp end, I’m guessing it’s a half-way shield right? Or just superfluous, I dunno.
Why doesn’t your friend simply change his RCA on the TT to XLR?
Is it that straightforward, how does it connect from the TT such that the other signal leg is inverted?
I’m tired, might be I’d understand this straightforward when rested, but doesn’t a cartridge output a single-ended signal? Actually might be that I don’t really understand turntables yet.
Most cartridges simply have left and right coils like voice coils on speaker drivers. Therefore they are not truly balanced where there are two polarities referenced to ground. However, if the four connections are separate and not referenced to ground, one can use a balanced phono input tying the ground pin to the shield in most cases. Right now all he is doing is using the non-inverting half of the balanced amp. He should try it both ways and use the one that sounds the best with lowest noise.
How exactly? Could you describe this more elaborately, for some reason I can’t visualize this. (covid wrecked my brains apparently)
You would need a multimeter using its ohms setting to measure between the two - pins between the channels and between each - pin and the turntable ground. Each reading should be >1MOhm for you to use this configuration. Otherwise the TT needs to be modified internally.
So I don’t fully understand how the cartridge outputs could be made balanced without surplus circuits since there’s a signal and ground leg for both channels, isn’t that essentially single-ended? Or did you mean that I could connect the channels’ + and - to XLR out pins 2 and 3 and connect the turntable’s discrete ground lug to pin 1?
And the channels’ return leads should have very significant resistive separation to the discrete TT ground?
No surplus circuits are needed, the output of the cartridge is in fact balanced. It is not referenced to ground, it is floating. The positive pin of the cartridge (typically right is red and left is white) is connected typically to pin 2 of the balanced cable and the negative pin of the cartridge (typically right is green and left is blue) is connected typically to pin 3 of the balanced cable. The ground wire of the balanced cable will be either left floating at the turntable end or connected to a ground terminal on the turntable (VPI has this, I can’t speak for any other turntable brands). At the phono pre-amp end the ground is connected to the ground of the pre-amp. See the image below. I should note that I use the term “typically” to indicate these are the common pin assignments, but you need to verify this is how your cartridge and phono pre-amp are wired. One note on the image below, the ground they show goes to the cartridge, I’ve never seen a ground terminal on the cartridge. The ground will be on the turntable itself.