Taken from the NAD site
http://www.nadelectronics.com/hifi_amplifiers/c370_framset.htm
"The C370 also benefits from NAD's proprietary Impedance Sensing Circuit (ISC) topology, now well established and used in many NAD models including the highly reviewed C320 and C340.
The ISC topology allows the C370 to deliver maximum performance under virtually any circumstance, independent of the loudspeakers it is driving. The circuitry automatically recognises the impedance characteristics of the loud-speaker and will then adjust its power supply settings to best cope with that specific load. With ISC topology, the relationship of voltage to current is kept at an ideal proportion, eliminating the current limiting distortion common in lesser designs. This also gives it an unusual characteristic compared to traditional amplifiers when measuring its continuous output power; the RMS out- put power remains the same at 120 Watts with either an eight or a four ohms load.
We take exception to mindless "brochure power" specifications, which don't give a realistic indication of an amplifier's true capabilities. Instead, the ISC topology is a practical approach to enable an amplifier to easily deal with musical dynamics and difficult speaker loads. More meaningful in the real world are the C370's dynamic capabilities; up to 450 Watts into 2 ohms and up to 70 amps current capability into 1 ohm! "
