Balanced outputs vs balanced design


Friends, I am looking for a balanced tube pre to mate with Halcro MC20. I have since learned that there are single ended designs with balanced outputs and fully balanced designs, like the BAT's. In a response to a thread below the author suggests that the "magic" happens in the amp and that the pre does not have to be fully balanced to benefit from the noise reduction qualitites. If so, is thre any inherent advantage to a fully balanced preanp? And more particularly for my purposes which would not run connects more than 10' from the amp. If there is no great advantage to a fully balanced pre, I can widen my search. As always, tell me about your favorite tube pres to run with this SS amp. Many thanks.
deliberate1

Showing 2 responses by eldartford

Balanced interconnects between preamp and power amp are inherently less sensitive to noise pickup in the wires...that's why the pros use them for long runs. However, in the typical home environment with relatively short runs good quality single-ended interconnects don't have a noise pickup problem.

As for balanced circuitry in the power amp the advantage over single ended is largely theoretical for well designed equipment. It is often said that balanced is quieter because the signal is twice as strong, but there is also twice the circuit noise. Common mode noise, as for hum from the power supply, will be canceled, but there shouldn't be any such noise in a good unit.

I have balanced interconnects in my system, but only because the equipment I use has this interface. I think you should select your equipment on the basis of how it sounds to you. Balanced configuration has some advantage in certain cases, but, IMHO, it is sold, at considerable cost, to audiophiles who don't need it. It mainly gives you bragging rights.
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Jmaldonado...Yes. As you say random circuit noise in each leg will appear at 1.414 amplitude at the differential output, wheras the signal will appear at twice amplitude. So there is a bit of noise reduction. S/N of my power amps is spec'd at <100 dB, and the source equipment is better. I'm not sure what another 3dB would buy me. As for distortion, there really isn't any to cancel.

The more even loading of the two rails of the power supply is a real benefit IF the power supply design is marginal.
Some amps are spec'd for power, both channels driven, with the two signals out of phase (like a balanced design amp).