Two Rock Studio Pro 22 Combo Black ~ Secondhand

This amplifier is 22 watt, 1x12'' all-tube amplifier combo that features spring reverb, effects loop and a WGS British Invasion Speaker

Best described as a "portable" Classic Reverb/Custom Clean hybrid, the Studio Pro offers ample clean headroom, dynamics, and a variety of tone shaping options.

Two-Rock have added a pickup loading feature, which optimizes pickup balance between single coil and humbuckers.
The stellar reverb circuit with send and return controls, contour control, and full buffered effects loop are standard on this amp.

•22 watts, 2 x 6V6
•Pull Bright control
•Active Buffered Effects Loop
•Spring Reverb with Send and Return Controls
•Contour
•Small chassis design
•Pickup Loading Feature
•Combo dimensions 15" L x 18" H x 10" D / Weight: 39 lbs

Pickup Loading feature control has 5 settings.

In the first position(fully counterclockwise), there is no additional pickup loading, with 4 additional settings available.
Fully clockwise(last position) is full loading.
Loading the guitar pickup(s) to varying degrees changes the impedance relationship between the pickup and the amplifier's first gain stage.
Loading reduces inductive "ringing" in the pickup coils.
The effect is a more controlled high frequency response and a reduction in high frequency artifacts produced when a pickup's magnets and coils feed back with each other, usually at or near the pickup's saturation point.

The damping effect will also reduce the gain, which is normal.
Tonally speaking, reducing these artifacts results in a cleaner waveform and an apparent lack of harshness in the upper frequencies.