CRATE STEALTH GT50 Lee Jackson

CRATE STEALTH GT50-H - CH2 (DISTORTION) PREAMP - V2 =================================================== WHAT IT IS ---------- A Neural Amp Modeler capture of the Lee Jackson- designed Crate Stealth GT50-H distortion channel (CH2) PREAMP. *** Preamp only. NO cab, NO power amp. This is a DI capture - stack your own guitar cab IR after it (a 4x12 V30 works well). *** Built from the real factory schematic (Crate drawing 07S292), reverse-engineered stage by stage in LTspice and dialed in by ear against a recording of a real Stealth head. Signal chain: V1B 12AX7 -> TL072 IC1A (freq-shaped, mid-hump voicing) -> IC1B (inverting, 1N746 back-to-back zener soft-clip, +-4.5 V) -> GAIN 1 pot -> MPSA13 transistor stage with 1N914 hard clip -> IC2A -> a preamp-gain / drive stage -> V2B 12AX7 recovery -> Marshall FMV tone stack -> master -> V2A 12AX7 output. WHAT'S NEW IN v3 --------------- - The 1N746 soft-clip is now wired back-to-back (+-4.5 V) as the schematic shows. Earlier builds had it anti-parallel, which clamped at +-0.6 V and choked the gain structure - it read as "low gain / no headroom." This is the fix; the diode stages now actually work. - Added the CH2 PREAMP gain stage (the real amp has GAIN 2 / GAIN 1 / PREAMP; earlier captures only had GAIN 1). The Stealth is Lee Jackson's hot-rodded JCM800 - "the tone you get by adding another 12AX7 to a stock 800." Tight, bright, forward mids, medium- high gain that stacks well with a boost. SETTINGS CAPTURED ----------------- One fixed snapshot of the circuit, controls at (0-10): - GAIN 1 (CH2) ................. 8 - PREAMP (CH2) ................. low (~3) - CH2 VOLUME .................. 4 - BASS ....................... 6.5 - MID ........................ 4.5 - TREBLE ..................... 5 - MASTER ..................... ~6 Not in the capture: - PRESENCE - it's a power-amp NFB control, not preamp. Add a gentle high-shelf downstream if you want the top rolled back. - GAIN 2 - on the demo head it did nothing; left out. RECOMMENDED USE --------------- - Run it RAW (loudness normalize OFF). - Input calibration: +12 dBu (the usual default). Feed a normally-tracked DI at its natural recorded level - it tracks pick dynamics, digs in when you do. - An overdrive / boost in front is fine and the amp likes it (tightens the low end, sharpens attack). - Stack a 4x12 V30 cab IR after it, then your usual post EQ / bus chain. DIALING NOTES ------------- - Too bright? High-shelf cut around 3 kHz (this is your "presence down"), or a darker 57 IR. - Want it heavier / more saturated? Boost in front, or push your power-amp sim - a big part of the real amp's cranked grind is the 6V6 power section + speaker, which a preamp capture doesn't include. - Responds to the guitar volume knob - roll it back for crunch. CREDITS ------- - Circuit source: Crate / SLM Electronics factory schematic, drawing 07S292 (L. Jackson design; 1992) - Early LiveSPICE traces used to get started: MARKTHERENCE - Circuit modeling, voicing, NAM training: edgiljr5 ===================================================