More on XLR vs RCA considerations?

I've never heard of a single ended triode preamp, but maybe that's just something else I've never known about until now? 

@immatthewj Most tube preamps are single-ended and triode. Its the rare one that isn't!

Since my preamp and amp are single ended triode design, I can never use a balanced cable between them.

@drbarney1 You could if you wanted. All that's needed is a set of line transformers at either end of the interconnect.

True balanced topology imposes twice the circuitry into the signal path.

@perazzi28 This is a common myth. Differential amplifiers are not 'twice the circuitry' at all. Another common myth is balanced lines are only good for longer lengths; the reality is there is a benefit even if the cable is only 6" long.

How on earth do we know if our gear supports AES48?

@billpete You could ask the manufacturer.

Perhaps if the circuitry (caps etc.) becomes equal between the two, there is not much advantage to XLR? Not sure, myself. I like to have the option even though I've never used it, just makes me feel good, knowing it's there if I ever decide to use it. Long wire runs seems to be the main reason. Are there others? I heard, lowers noise floor with higher gain. OK.

@billpete There's a lot of confusion in high end audio about balanced operation. My company has been doing balanced line longer than anyone else in high end audio so I might be able to clear some things up.

1) Long cables is not the only reason to run balanced. The goal of balanced lines originally was to eliminate ground loops and interconnect cable coloration (if you've ever compared two cables side by side and heard a difference, this is what I'm talking about). But to do that the equipment must be designed to support the balanced line standard, known as AES48. So the benefits are available even if short cables are used.

2) because a lot of high end audio equipment does not support the standard, in some cases the RCA output may actually sound better. That is not the fault of balanced operation, just that the standard is that important to getting the cables to sound right. In such cases you might get a 6dB increase in gain if running balanced. If the equipment supports AES48 this doesn't happen.

3) the equipment does not have to be balanced internally. Transformers can be used to interface between balanced lines and single-ended circuits. That is how it was done in the 1950s and 1960s.

4) quite often a preamp that has a balanced output can convert single-ended sources to balanced no worries.

5) Phono cartridges and tape heads are examples of balanced sources. The reason to run them balanced isn't so much for lower noise (although that is possible); the main reason is to avoid colorations from the tonearm cable. If this is done properly, there's no need for that 'ground wire' that accompanies most tonearms since that is handled by the shield of the balanced cable instead.

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