Give your transistorized organ speaker that sweet tube sound
The MIG‑L tube preamp adds a tube‑like overdrive stage to solid‑state Leslie organ speakers, using a miniature Russian 1SH18b tube and a FET‑based overdrive circuit. It is powered from the Leslie’s existing +28 V supply and fits behind the input gain pot of the active crossover board.
The document details installation steps, wiring, adjustment procedures, remote‑switching for the MIG‑LR version, and optional modifications. It also offers advice for adapting the circuit to Leslie clones and provides component values for gain and output tuning.
| Supply voltage | +28 V |
|---|---|
| Power consumption (MIG‑LR) | ≈50 mA |
| Required input level for full distortion | ≈1 Vrms |
| Input level for full distortion on Leslie clones (MIG‑LRL) | ≈100 mVrms |
The MIG‑L is powered from the Leslie’s active crossover board with a +28 V supply.
About 1 Vrms input is needed for the MIG‑L to reach full distortion.