Originally Posted by Aflac
Ari, your transformer thing is very interesting. So basically it steps up what impedance the source sees from the headphones? If there's no increase in power from the transformers, how does this affect the output of the headphones? Admittedly I don't know very much about impedance/impedance matching. Is there a basic schematic for your device? (on a somewhat unrelated note I wish I could go to the Philly meet so I could hear this thing in-person and hear you explain it...)
Yes, the power through a transformer is roughly constant. 1mW in gets you 1mW out. This works to your advantage with SS gear here the same way it does with a tube - the output stage of your source can probably output a little power, just not into a low impedance. By using a transformer you give the source the high impedance load it works best with and you can save a bunch of active circuitry and all the nastiness associated with that.
The impedances are a tricky point here. In a tube amp the output impedance of the tube makes a transformer a totally obvious solution. In SS even a junky opamp or simple circuits with 1 transistor as voltage follower can achieve a ~0ohm output impedance easily so the transformer got passed over by the world to save a few bucks. The problem is that when you MUST have an op amp driving the load (as is almost always the case in ultra-small portables where you dont have physical room or adequate battery power for a real buffer) they dont work as well into low impedance loads as high. Some do better than others, but for the troubles associated with "almost stable" ultra-fast high current op amps why bother when you dont even need gain to run IEMs or even many full size headphones?
Impedance matching is a weird point. Multi-driver IEM's want the source to have a very low output impedance so the crossovers work the way they were designed. Im not sure what the limits are, but since nobody has complained about certain portables with 22ohm output resistors screwing up the sound from their headphones the single digit output impedance from a transformer should be totally cool.
Single driver IEM's are much less critical of amplifier output impedance. I really like my Ety ER4p on my transformers.
I pretty much always have the transformer with me at meets, ask the next time you see me.