Gainclones or Gaincards use a high power op amp chip to power the speakers. Unlike a conventional amplifier that uses transistors like mosfets or bi-polars..etc. There are roughly 9 parts in the signal path of a gain clone or Gaincard. The signal paths are also some of the shortest for an amplifier..only a few millimeters long.
This equates to a very pure sound. These amplifiers don't hide the source at all. If the source is sub par you'll know it.
Most aren't designed to power tough loads. They run out of steam quickly if pushed too hard.With properly matched speakers the sound is fluid, pristine and grain free. Op chip amps sound like neither SS or tubes... IMO it falls some where between.
The Gaincard was the original op chip amp. It is just the name of an op chip amp like the Patek.
Scott Nixon also makes mono block op chips amps...they sound great!
There's an agon member who builds these to order. From his feedback..he knows what he's doing and the prices are very reasonable.