You may have better results with a lower stepdown ratio. If the transformer has a 16 or even 32ohm tap, for example, try that. You wont get as much voltage at the output, but you dont really need that. As much as the STAX mafia likes to talk about freakishly high voltage swing, nobody uses much more than 100vrms in real life. It is not uncommon to see electrostatic headphones singing proudly with only 5-10v.
Transformers are not perfect devices. They do not (generally) work as well as one would hope backwards. Yea, a theoretically perfect device would work exactly the same forwards or backwards, but you know.
The lower stepdown ratio would appear as a higher impedance to the amp, which is nice. Lower step down ratio transformers are said to work better (I dont know why) than their higher ratio brothers. The higher impedance primary (well, really the secondary wired backwards...) would show a higher DCR to the amp AND show a higher inductance - both of these things are niceeee here.
You mentioned the Ciuffoli article - the transformers he used *only* had a voltage ratio of 1:14.4 which is an impedance ratio of ~1:207 - a FAR cry from 1:1900(impedance). Again, you don't really need as much voltage as many people like to say and 1:14.4 (voltage) gets us ample output voltage with even a relatively low voltage input. 2.6v from the amp (which is basically nothing for any reasonable SS speaker amp) becomes ~37.5v at the output - which is a bit more thana more than we really need - with WAY more voltage available from the amp and also through the transformer.
Regarding stability - The vast majority of solid-state speaker amps will be stable driving 32ohms. They will be stable driving 300ohms. They will be stable just swinging voltage with no load at all! Some amps do have output protection, but I would never count on it. Shorting an amp (or even showing it a load impedance BELOW some acceptable limit) is a surefire way to kill it. Don't worry that you are not "loading the amp down" - that is leftover BS from certain tube designs. Put another way I would worry FAR more about shorting the amp out than I would about "underloading" it. There are no doubt exceptions, but they are insanely rare.
Edited by nikongod - 5/30/14 at 12:25pm