The Sunn Beta Lead is quite a capable amp. It is rated at 100watts RMS with a 4 ohm speaker load. The two channels can each be used individually, but it is really designed for a single instrument - that is, both channels are not completely independent of each other. Both channels are also in phase with each other.
The sound of the amp, especially the distortion sound, is created at the front end and centered around the drive control. The drive control itself is a dual pot arranged to control the amount of negative feedback - hence the gain around a circuit consisting of a couple of op amp stages, with about 4 or so "CMOS inverter" stages in between, each with their own feedback resistors, cascaded into each other.
A CMOS inverter is an extremely high gain FET circuit primarily used in digital equipment. It is sometimes called a "not gate", because in digital terms, the output signal is the inverse of the input. A digital "1" will come out as a "0" and vice versa.
Digital circuits don't use feedback... but by applying feedback the extremely high gain of these devices can be substantially reduced to allow them to be used in analog circuits - it can be made into a controlled gain stage.
As these gain stages are used in the Beta series... the sound can go from crystal clear to extreme "metal style" distortion, just by a turn of the gain control. Inbetween settings can allow various levels of "touch controlled" distortion... suitable for blues or even country.
Quite a versitle amp... and the number of accessory in-out jacks on the back panel allow effect units to be located per channel, or both. The separate channel master volumes and an overall master volume control is a great idea.
Plugging into both channels... well almost any distortion sound can be created. One of my favorites is to have one channel with higher gain settings but to cut off the treble, and the other channel with a lower gain setting and cut off the bass. The sound is almost a dead ringer to the early Clapton with Cream - where the distortion comes from the low gain marshall amp turned up - fuzzy bass and clear trebles.
I paid $200 for mine about 10 years ago and have never had any problems with it. If I found one for $120, I would pick it up as a spare.
I should mention one thing. The channel switching IC is quite rare to find a replacement for... and when it goes bad, if it ever goes bad... it can take either or both channels out with it. I normally use both channels together and if that ever happened with mine, I would come up with an alternative to keep both channels on.
Hope this helps!!
