AMT Electronics SS-11A 3-Channel Dual Tube Guitar Preamp (Classic Mod A) Pedal w/ 3 Cables Fully tube-based 4 - stage overdrive channel with DUAL TUBE design (2x12AX7 or 2x6?2?-?? tubes) with high-voltage anode voltage (+300 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.