Blue tooth adapter for Rega Planar 1 plus

[BF-Bert]

Probably something used, probably a 160. I could probably fix the electrics for the motor as long as it’s windings etc are operational, bearing true along with the platter. I would then look to simply gut the tone arm electrics to expose MM/MC balanced outputs for a RIAA tube stage (like a differential Borbely style amp). A travesty but balanced common mode noise cancellation is far better than single ended RCA.

Is there any benefit to having balanced outputs on a turntable?

 

[NickK]

Is there any benefit to having balanced outputs on a turntable?

Yes. In essence it provides a lower noise floor and that can be quite is large difference. Now how much that depends on the record noise.. but if you’re trying to reduce noise other than what the stylus picks up then it’s worth it. There in lies the Achilles heel - lower noise floor will show up your stylus, the setup state and the state of the record.

MM and MC (even lower) both are lower signal strength compared to line levels. So being a balanced between the cartridge and phono preamp is a big win. So if we just took the left channel for a second, as the two wires are close any noise appears on all both wires. Compared to a single ended earthed cartridge where the noise is signal (no way to differentiate) plus you get ground noise injected.
Any good phono amp is heavily shielded given the low signal levels involved.

A differential preamp (balanced) would then output a differential output to the main amp. Again, any noise occurring on both wires for the channel can then be cancelled out at any stage however that is typically continued in a fully balanced stereo through to the bridged speaker.

Now balanced won’t stop noise that is not common, other techniques can help with that but it does help with the more digital world imposing it’s broadcast noise into your stereo.

Balanced isn’t mythical and you can benefit is different ways. A balanced connection simply means noise rejection in transport. Balanced amps mean noise rejection in amplification. And a bridged output (or balanced headphones) simply means noise rejection in the speaker cable (includes amp). Combining all of those means waiting till the last possible instant when all the noise cancels out.

note that’s the extreme. It’s possible to switch between balanced and single ended at will, only the SE section will not be able to reject common mode noise. If the SE section is ultra quiet then that may not matter and so you can just use balanced wheee you find noise interference.

 

[BF-Bert]

Yes. In essence it provides a lower noise floor and that can be quite is large difference. Now how much that depends on the record noise.. but if you’re trying to reduce noise other than what the stylus picks up then it’s worth it. There in lies the Achilles heel - lower noise floor will show up your stylus, the setup state and the state of the record.

MM and MC (even lower) both are lower signal strength compared to line levels. So being a balanced between the cartridge and phono preamp is a big win. So if we just took the left channel for a second, as the two wires are close any noise appears on all both wires. Compared to a single ended earthed cartridge where the noise is signal (no way to differentiate) plus you get ground noise injected.
Any good phono amp is heavily shielded given the low signal levels involved.

A differential preamp (balanced) would then output a differential output to the main amp. Again, any noise occurring on both wires for the channel can then be cancelled out at any stage however that is typically continued in a fully balanced stereo through to the bridged speaker.

Now balanced won’t stop noise that is not common, other techniques can help with that but it does help with the more digital world imposing it’s broadcast noise into your stereo.

Balanced isn’t mythical and you can benefit is different ways. A balanced connection simply means noise rejection in transport. Balanced amps mean noise rejection in amplification. And a bridged output (or balanced headphones) simply means noise rejection in the speaker cable (includes amp). Combining all of those means waiting till the last possible instant when all the noise cancels out.

note that’s the extreme. It’s possible to switch between balanced and single ended at will, only the SE section will not be able to reject common mode noise. If the SE section is ultra quiet then that may not matter and so you can just use balanced wheee you find noise interference.

Thanks for that. I rather suspect that the noise coming out of the cartridge will far exceed any noise picked up between the cartridge and the phono stage.

 

[NickK]

Thanks for that. I rather suspect that the noise coming out of the cartridge will far exceed any noise picked up between the cartridge and the phono stage.

MM is 3-5mV signal and MC can be 0.16mV to 1.6mV. Compare that to consumer line level of 447mV 0dB and 3.16V +20dB (3.16V=3160mV)

100mV of common mode nose isn’t going to worry a balanced connection unlike a on RCA. However you’re right - if there’s 2mV of noise on the record or created by the stylus itself interacting with dust etc.. then there’s less return given it’s 50% of the sound you’re hearing.

 

[BF-Bert]

MM is 3-5mV signal and MC can be 0.16mV to 1.6mV. Compare that to consumer line level of 447mV 0dB and 3.16V +20dB (3.16V=3160mV)

100mV of common mode nose isn’t going to worry a balanced connection unlike a on RCA. However you’re right - if there’s 2mV of noise on the record or created by the stylus itself interacting with dust etc.. then there’s less return given it’s 50% of the sound you’re hearing.

A cartridge shouldn't have common mode noise as it has no ground reference.

 

[NickK]

A cartridge shouldn't have common mode noise as it has no ground reference.

Any interference coupled to both wires is common mode noise, be it LED lights, mobile or switched supply RF or power.
Even if the shield is connected to ground at one end, a shield offers an attenuation of noise coupled to both the signal and shield, just as the shield is low impedance it provides an easier route for the energy so it attenuates the interference before it gets to the signal wire(s). You will still get some dB on the signal wire (albeit purposely very low in most designed cases).

Sorry I used “common mode” wrt to RCA meaning the same coupled noise that is affecting in both differential and single ended cases. That should be “coupled noise”.

A cart attached to a step up transformer can have no ground ref, and that by it’s nature is differential to the transformer (or op amp) However it’s also possible to ground one end and use it single ended..but not ideal but can be cheaper to produce.
I’d expect the modern internal preamp for thorens and RP to be opamp based with differential inputs into the op amp but single ended out to the external RCA.
The issue here (for me) is that differential signal is not exposed to bypass the internals. I assume the “thru” switch simply sets the opamp amplification to unity (ie the signal still goes through it by it has no gain) which is why “thru” is still single ended except on the top end models.