AMT Electronics SS-11 3-Channel Dual Tube Guitar Preamp Classic Mod Fully tube-based 4 - stage overdrive channel with DUAL TUBE design (2 x 12AX7 or 2 x 6AfAe'A,AAfasA,A2AfAe'A,AAfaA,A -AfAe'A,AAfAAasAA,AAfAe'A,AAfAAasAAazA tubes) with high-voltage anode voltage (+3 V) Three separate channels: CLEAN / OVERDRIVE / LEAD Individual gain sensitivity and output level controls for clean and crunch/lead channels TREBLE SHIFT toggle switch to enter bright mode for that added punch of high end FX LOOP for external effects