A true balanced amp processes the inverted and non-inverted components of each channel of each balanced input through seperate circuits (including discrete volume control sections). The amp responds to the difference in signal across the inverted and non-inverted components.
SET amps are just that - single ended. By definition they cannot process seperate inverted and non-inverted signal components since there is only one signal path. To properly (note the word "properly") handle a balanced input an SET would have to supply fron end circuitry to invert the inverted component and add it to the non-inverted component to yield a single ended signal for the remainder of the SET to process. This circuitry would be more complex than the SET itself and is most easily implemented by an op amp, though it could be done with tubes. Either way you've lost the minimalist philosophy that is one of the appeals of these amps.
If you must use balanced inputs then use an adapter. Typically these connect only the non-inverting signal component to the single ended input, thus destroying the key technical advantage of balanced connections: interference rejection.
SET amps are just that - single ended. By definition they cannot process seperate inverted and non-inverted signal components since there is only one signal path. To properly (note the word "properly") handle a balanced input an SET would have to supply fron end circuitry to invert the inverted component and add it to the non-inverted component to yield a single ended signal for the remainder of the SET to process. This circuitry would be more complex than the SET itself and is most easily implemented by an op amp, though it could be done with tubes. Either way you've lost the minimalist philosophy that is one of the appeals of these amps.
If you must use balanced inputs then use an adapter. Typically these connect only the non-inverting signal component to the single ended input, thus destroying the key technical advantage of balanced connections: interference rejection.