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

@clearthinker, contrary to your statement of 6dB reduction with true balanced which I’m not sure applies to cartridges, the designer of BAT phono has claimed that RCA offer 6dB reduction in noise over XLR with cartridges. Don’t kill the messenger.

kijanki,

When you short a oscilloscope and probe to ground, you are creating a loop antenna and creating a differential signal which is not to say that common mode noise and/or common mode voltages are not a problem in measurement. That is why Picoscope makes a differential input scope, and Tek and Lecroy sell high voltage differential probes for about $2,000/each (or more). While you are "floating" you are also a big capacitor to ground which creates a path for common mode signals. Also remember that most oscilloscopes probe grounds are also connected to chassis grounds. Floating oscilloscope inputs (battery powered or otherwise), can offer most of the benefits of differential inputs for many measurements (and tend to be much quieter).

And are you assuming the noise was common mode? Are you sure it was not differential mode?

I had TT long time ago and always had problems with low frequency hum (single ended phono stage).

Current thru this ground wire causes tiny voltage drop, seen by the input as input voltage (input is referenced to BNC GND and not to end of the cable GND).

But again, we are talking a cartridge and absent the shielding and other metal structure (and antenna effects isolated by the cartridge itself), it is a loop. Absent the shield/structure capacitance to ground, there is no other current path, whatever current flows in one wire must flow in the other, and hence whatever drop you have on one wire is cancelled by the other.

Transformers are already used for MC coils, so we know they work.

@dracule1, I'm not sure Mr van den Hul, amongst others, agrees with you.  I should like to see BAT phono's explanation of a 6dB reduction in noise using RCA single-ended.  There seems to be disagreement on the issue.

Maybe a point that needs to be made, you don't need an XLR to have a balanced input connection. You can use an RCA and still have a balanced input connection.

BAT incorporates its “Flying RIAA Network” differential circuit here, which the company claims has fewer parts yet because of ease of adjustment at the factory and dual differential common mode noise rejection, produces greater RIAA accuracy, with typical measured error of less than 0.1dB.

Hello, we are now building the first run of phono preamps with both balanced inputs and continuously variable cartridge loading (10 to 1,000) ohms, balanced outputs too.  lit will be available in a couple of weeks.  Barry Thornton, austin audio works.