As a Berning owner, I can say that few amps can match Berning amps.
However, an amp is only a part of the package, and must be paired to speakers that will match it electrically, as well as sonically.
The ZH270 has an output impedance of 1.8 ohms with normal feedback, and higher with less feedback(switchable). Therefore, choosing speakers with a "tube friendly" impedance curve, staying above 4 ohms at all frequencies would be preferred. If you desire to select less feedback, then a speaker with even higher impedance at all frequencies would be desired. For best damping factor and less strain on the amp, I'd suggest using a speaker with a nominal 8 ohm impedance, that doesn't "swing" into low impedance dips, especially at lower frequencies. Even though this ZOTL has remarkable properties for an OTL, you have to observe proper system matching to get the best from it.
However, an amp is only a part of the package, and must be paired to speakers that will match it electrically, as well as sonically.
The ZH270 has an output impedance of 1.8 ohms with normal feedback, and higher with less feedback(switchable). Therefore, choosing speakers with a "tube friendly" impedance curve, staying above 4 ohms at all frequencies would be preferred. If you desire to select less feedback, then a speaker with even higher impedance at all frequencies would be desired. For best damping factor and less strain on the amp, I'd suggest using a speaker with a nominal 8 ohm impedance, that doesn't "swing" into low impedance dips, especially at lower frequencies. Even though this ZOTL has remarkable properties for an OTL, you have to observe proper system matching to get the best from it.