Goes from pristine clean to hot and jangly to smoky, slightly ragged overdrive, with a 2-band eq that is voiced just right. Transparent when bass and treble are at noon and plenty of flavours available including mid scoop, mid hump, bright, dark, thin, and fat.
All that is followed up with an optical compressor circuit designed to emulate a sagging GZ34 tube rectifier, a saturated output transformer, and over-loaded voice coils & speaker cones for that ultimate small combo experience.
The Rubber Soul takes the classic "normal" channel and blends it in with the "bright" channel just like most folks would probably tend to use the old amps with those two channels: jumpered and blended. So you get the cutting presence of the bright channel but with a bit of the beef and fullness of the normal channel added in--just not so much that it turns to mud at high gain.
The Rubber Soul responds very much like a tube amp would to your pickup volumes and to the impact of running other effect pedals in front of it.