Guidocorona, as I mentioned, there is no "true balanced" designs. Why balanced sounds better to many is because both phases are eventually added at the end - the speaker. Just like paralleling multiple devices (DACs, components, etc.) you are getting the sum of them which results in better sound. Wheter you are going to parallel two single ended stages or use balanced design, the end result (sonically) should be the same when it comes to home applpications. Of course, the balanced design rejects all kinds of common signals making it suitable for Pro requirements. To design a "true balanced" I will have to use two triodes driving the output transformer. This will create all kinds of problems due to tubes mismatch. Even if you get exactly matched tubes, they will deteriorate differently over their life span. This can be somewhat compensated by NFB but I don't like this idea. With the component-less single ended to balanced conversion, you will get exactly the same benefit of the so called "true balanced" designs (sonic-wise).
Regards,
Alex
Regards,
Alex