Driving 1 ohm

If they were Apogees or Kappa9's, a rugged SS amp would be the way to go but for ESL's, Ralph is right.

Another option is "monostrapping" or parallelling an identical pair of stereo amps. That would double the current and wattage and halve the output impedance. Some manufacturers don't approve of this method.

Rwwear, in the real world, people want to use OTLs with low impedance speakers. If you use an autoformer to do this, you often meet with success. The fact of the matter is that the autoformer has bandwidth that is wider than most amps, tube or solid state, which is only possible because its turns ratio is so low.

IOW, using the ZERO would not be practical if you did not already have a low output impedance and no DC at the output. So that could be an OTL, but it could also be a transistor amp. Its already been shown that a transistor amp will sound better driving 4 ohms or less if it does so through a set of ZEROs rather than direct.

So the argument holds regardless of the amplifier technology, which inherently includes OTLs.

For $2000, the H2O Audio Signature 100 can drive a 1 ohm load with no sweat. Hell, they can handle the vaunted Apogee Scintilla with absolute ease. There aren't too many (great sounding) and truly affordable power amp's that can make such a claim.

If I take the aforementioned Apogee Scintilla as a reference (straight 1 Ohm throughout the frequency spectrum) these are some of the amps that will drive them:

- Classé 400
- Krell 250
- Hafler XL600
- BAT VK-60 triode tube amps
- Sphinx Project 16
- Sphinx Project 26 mono amps

There are probably many more amps that will drive these kinds of loads, like the big Thresholds/Pass amps etc.

The Scintilla does not need a lot of power. We drove it very easily with a set of MA-1s and a set of our Z Music autoformers (we no longer make that product, but something similar is sold under the name ZERO). Its not normally a load that you would put on a tube amp but it worked great!