Our MP-1 has a low output impedance- it has a patented direct-coupled output and can drive 32 ohm headphones quite well.
It was intended to support the 600 ohm balanced line standard. You may already know this, but the low impedance standard was created to eliminate interconnect cable problems and differences, and to allow long connections without degradation. That's how the record labels like RCA and Mercury were able to produce recordings that are still revered today- 50 years later- while running as much as 150 feet between the microphones and the input of the tape recorder.
Our original MP-1 was the world's first balanced line all tube preamp for home audio, introduced in 1989. Traditionally tubes were coupled to low impedance balanced lines using an output transformer, but we were making OTLs already, so it seemed the logical thing to do. With that it appears that we introduced high end audio to balanced line operation. Sorry to sound like an ad but that's the history.
