Vintage amplifier specifications

2 ohm impedance was the threshold for most designs of that vintage.  Even the original NAD 3020 would tolerate 2 ohm until driven hard and smoked.  Unsound is correct about big iron.  Include Yamaha, Accuphase, GAS and Luxman.

There were speakers of this era that really needed amps capable of delivering into low impedances, such as Apogee, Infinity, Thiel, etc..

@unsound 

As an Acoustat 2+2 and Apogee owner… I agree.

Agree with others. Solid state high current survivors just don’t struggle with speaker loads. My old Crown offers only one set of outputs but lists power specs for 16, 8 and 4 ohm loads.

My trusty Sansui AU-999 still delivers the goods. Has specs for delivering 70 watts at 4 ohm load. Drives my DLKs perfectly.