I don't like balanced operation and only use it when I have to.
I do supply balanced inputs and outputs on some of my preamps, but only because people want them, and because sometimes you have no choice.
Balanced operation comes from the pro-audio world, music venues etc, and is used to cancel out noise that is caused by very long cables, and less than ideal electronic applications.
It doesn't cancel all the noise but does a pretty good job of making it inaudible.
But balanced operation doesn't do a better job than a properly designed and implemented unbalanced design in normal hi fi home situation, if you are using 200 metre long cables you need another house!
Balanced operation in hi fi situations is a clever marketing ploy based on fashion.
Below is a simplified circuit of a cascaded tube preamp.
The round circles are tubes, the squiggly lines are resistors and the parallel lines are capacitors.
It's very simple and very effective, has nice harmonics , good phase response, all you need really.
If it has a good power supply, is designed and constructed properly it will be very quiet with very little, if any, hum and noise.
Below is the same circuit in balanced mode.
Note how there are double the components , two different phases and operating in differential or push pull operation.
It wont be audibly quieter than the above unbalanced circuit, unless you want to drive 200 metre long cables. Harmonics aren't as nice as single ended and there's no guarantee it will be perfectly balanced between tubes and components.
After many years of building both balanced and unbalanced preamps, I've still to hear a balanced circuit sound better than a simpler unbalanced circuit.
To my ears there's always a slight veiling, a lack of cohesion and clarity with balanced operation.
Yes there are plenty of good sounding balanced power amps , but I've never heard a good balanced preamp.
The perfect place to use a balanced circuit would appear to be with moving coil phono cartridges. The voltages from MC cartridges are minuscule , around 0.5 mV , that's half of a thousandth of 1V!
Using tubes to get the required gain of 5000 is tricky , as the noise floor is also amplified, so balanced operation makes sense in this situation.
I built hundreds of differential balanced phono-stages and never heard one that sounded as good as a really well built single ended phono stage.
Yes they are quieter but a well built single ended phono will be quieter than the noise floor of a vinyl record anyway, so there's really no point.
Below is how Supratek preamps provide balanced operation.
The Single ended circuit remains but I use transformers to accept the balanced input and provide balanced outputs.
Good quality transformers, brands like Lundahl , Jensen and Magnequest provide perfect phase splitting and combining- without any of the complications of a doubled-up balanced circuit.
Nice even harmonics are maintained throughout the circuit , and it can be easily switched for balanced or non balanced operation.
Its a win-win, gives true balanced output, there's no price to pay, no compromises and sounds as good as balanced gets.
