Hey Ralph. Here's my chance to zero in now that you've chimed in. My
experience has been that there's no free lunch. What is the compromise
in implementing the ZEROs? It seems you would lose extension one way or
another, no?
Because the ZERO does not have to block DC, and also because you need an amplifier that already has a low output impedance, the result is a very low turns ratio with low distributed capacitance. Translated that means it has a very wide bandwidth- wider than our amps (which is quite a bit different from the usual output transformer which is often the limiting factor in tube amplifier frequency response); about 2Hz to 2MHz!!
So, 'no', you don't loose any bandwidth at all. What you loose is a bit of voltage gain as the transformer steps down the voltage.
How it seems to work is if the ZERO creates sonic compromise, you probably don't need it.
I have never seen it as a band-aid as George puts it; prior to the ZERO we actually made a similar product called the Z-Music autoformer, which did pretty much the same thing (ours also allowed for one ohm operation, allowing Steven Stone in a TAS review 25 years ago to have a set of our MA-1s drive a set of Apogee Full Range loudspeakers with very convincing results to my ears).
The simple fact is that four ohms is not good for **any** amplifier made regardless of the technology, and this is easy to see in the amplifier's specifications. Distortion is always higher, and the distortion is of a type that is easily heard as brightness and hardness. This is why Steve McCormick sent a letter to Paul Speltz (who makes the ZERO) stating that his amps sound better driving 4 ohms through the ZERO rather than directly. The amp has lower distortion and you can hear it right away.
That's not a band-aid so much as its a fix for a problem; the problem being speakers that cause amps to make increased audible distortion.
This being high end audio and all, distortion **bad**, music **good**!
