There have been only two versions of the Effect Gizmo. You can tell the difference easily - the old Effect Gizmo does not have an XLR MIDI jack on the front panel, and the newer version does.
The differences between the two versions are fairly minor, but the 2nd version has small improvements to audio quality and build quality.
The differences are as follows:
Effect Gizmo V1
- No front panel XLR jack
- Audio circuitry runs at 9V
- 1st generation Click Stopper circuit
- Red LEDs (usually. There are a very small number of units with blue LEDs)
- Brushed aluminum or silver painted front panel
Effect Gizmo V2
- Front panel XLR MIDI jack
- Audio circuitry runs at 30V
- 2nd generation Click Stopper circuit, includes a 2nd buffer
- Blue LEDs
- Silver or black painted front panel (there were also a small number of units in other miscellaneous colors)
- Voltage monitor circuit, which warns when the incoming voltage is too low for reliable operation
- More durable chassis