Sound of transformers in preamps?

Also, wether or not a transformer coupled preamp sounds best etc... I have no idea. I think a skillfully designed transformer or capacitor coupled preamp will yield beautiful results. The transformer quality as well as the cap quality in that position is vitally important. I do know this :-)

Transformers have two primary (pardon the pun) issues if used in the signal path, which can be mitigated but not entirely eliminated:

bandwidth limitations
additional distortion

The bigger the transformer the more limited the bandwidth. In preamps where the transformer is fairly small this usually can mean a loss of bass impact. If you consider that you have to have bandwidth to 2Hz in order to reproduce a tone at 20Hz correctly, then the issue is clear. Most good signal coupling transformers are specced to 10Hz; the best are set 5Hz. That means that in the best cases you will have artifacts up to 50Hz.

Distortion is the other issue. Transformers will 'ring' (distort) like any inductor if not properly loaded at the output. There is a point called 'critical damping' where in the inductor is loaded at its optimal point. This is the point of least 'overshoot', but to say there is no overshoot (distortion) would be inaccurate. Anytime distortion is added, you can count on it to obscure detail/transparency.

This is why transformers have usually been avoided in preamps, although cost has something to do with it too. However there seems to be a cult of sorts associated with transformers in the Asian rim and we are seeing products appear here that are influenced by that. IMO the slight overshoot, which is adding a 2nd harmonic, is adding some lushness. That is nice for CDs which are often dry sounding, but not that great if you play analog and like all the detail that if offers.

To degradations of sound quality using transformers in signal path (of preamp or output stages of DAC's) are well described by Athmospere. I will add also mismatch impedance effect on the sound. If your output sstage is passive and transform based you MUST use ultralow capacitence interconnects.

Also, to "Anytime distortion is added, you can count on it to obscure detail/transparency " I wish to add that you are loosing musicality i.e. emotional connection with music which for some of us isTHE most important in interactions with (even reproduced) music.

DOWN WITH DISTORTIONS OF ALL KIND !!!!

well then, what is the significant advantage since there has been quite a number using transformer for volume switching and output coupled? do resistors has unstable impedance and cause freq response fluctuation due to feedback from amp? Thanks

The VRE1 manual is available online. On page 6 under Design Highlights Steve McCormack claims a couple of advantages. He says that the input transformer confers a tube like musicality. He also states that it also gives great noise rejection and isolation from DC voltage levels. I can understand the electrical advantages but I am confused what he is talking about with the tube qualities. Maybe he is talking about the second harmonic distortion that Atmasphere talked about. Maybe there are other effects of transformers that give the tube like musicality too like saturation and hysteresis. I don't know.

Bob