@songmic In saying that the ZDS is the best you've heard with the Utopia, does this take the ECBA into consideration as well? What made you consider the ZDS over the BA during the time you got yours? Why does the ZDS seem to be more popular than the ECBA (even when the ECBA was still available before)?
Simple. I haven't heard everything, and ECBA is one of the myriad of amps I have yet to have the pleasure of listening to.
According to people who have heard the BA whose ears I trust, it seems like a better choice than ZDS if I were listening to HD800(S) only as the BA is apparently the warmest and the tubiest sounding of the EC tube amp lineup (not that EC amps are tubey sounding in general, especially compared to overly lush amps such as Woo Audio). At that time, however, I wanted an amp that could drive both HD650 and HD800 equally well, and the BA/HD650 is not really a good match as it might be too warm and lush.
The BA with its Cinemag transformers is said to be superior to ZDS in terms of technicalities, but its warm/lush tone limits its use to neutral-to-bright cans like HD800, and to an extent, Utopia. The ZDS is more popular because it is more versatile, and also more affordable than BA. It is EC's longest-running, signature product after all.
I have a feeling that the BA will also drive Utopia wonderfully too, but resulting in a sound that is warmer, more laid-back and polite than ZDS/Utopia. The ZDS/Utopia's tonality is perfect IMO; not too bright nor dark, not too aggressive but has just the right amount of bite.
I would take ZDS or BA over Studio if my primary headphones were Utopia.
