The NDOA is an adaptation of a highly configurable German design. The op amp is a low input noise, high output current, high bandwidth performer. It is a novel, complex design quite from most discrete op amps out there -- all of it adds up to this circuit's thick, warm sound.
It can be used as a microphone preamplifier, line amplifier, a summing amplifier, a balanced differential amplifier, or in an equalizer or compressor.
The NDOA uses a twelve transistor design based on the original schematic, updated for current production transistors and fit in to the popular 2520/990 footprint.
It will work with a large power supply range (±2.5 to ±22V).