This 20 watt amp was only made for one year, which isn't surprising since it was meant for accordion. It sounds great for guitar, much better than I expected. The accordion input is quite sensitive so it is easy to get the amp to distort. The tremolo and reverb are also really useful.
Power Amp: 2 x 7591
Preamp: 1 x 12DW7, 1 x 6U10, 1 x 12AX7
Rectifier: Solid state
Speakers: 1 x 12" Eminence
Controls: Volume, tone, speed, intensity, dimension.
This amp is very similar to a GA-40 but with a different speaker configuration. You don't really need a GA-40 with this amp around though. It sounds great! It is loud and clear with good distortion when you turn the treble knob all the way up. These amps with 5879 preamp tubes are always quite enjoyable. The tremolo has a lot of variety. It can be very slow and warbly, or fast and choppy.
Power Amp: 2 x 6V6
Preamp: 1 x 12AX7, 1 x 6SQ7, 2 x 5879
Rectifier: 1 x 5Y3
Speakers: 4 x 8"
Controls: Bass, Treble (for both channels). Microphone channel - Depth, Intensity, Volume. Instrument channel - Volume
A rare find, this Ampeg Jupiter II has two separate preamps that can be used in stereo. Very clean and loud even with its 20 watt rating, but that is fairly normal for an Ampeg. Despite still retaining its original Jensen P12R speakers and tubes, the tone is surprisingly bright, as in "piercing pinch harmonics with a Les Paul" bright. The vibrato isn't functioning yet but hopefully it is a simple fix.
Power Amp: 2 x 6L6
Preamp: 3 x 12AX7, 1 x 12AU7, 1 x EF86, 1 x 6SL7
Speakers: 2 x 12" Jensen P12R
Controls: Speed, intensity. Channel 1 - volume, treble, bass. Channel 2 - volume, treble bass.