The Rig

The amp. All tone shaping happens here. Descended from the Fender Showman/Dual Showman preamp circuit, packaged by Ron Wickersham at Alembic in a 1U hi-fi rack format. Jerry Garcia used the earlier F-2B from the early 1970s — the FX-1 is the modern version of the same topology.

Lineage

• F-2B (1970s): Jerry's preamp. Dual-channel, dual 12AX7, Bright switch per channel, XLR + 1/4" outputs. Fender Showman topology.
• F-1X: Successor — added footswitchable channel select.
• FX-1: Current version. Single-channel with additional features.

Role in the Rig

The McIntosh MC100 is a transparent power amp — it adds zero coloration. All character comes from the Alembic. This mirrors Jerry's approach: the F-2B provided Fender-style tube warmth and EQ, and the MC2300 just made it louder.

Tube Selection

Key tube: NOS GE 5751 5 Star Gray Plate 3 Mica — gain factor ~70 vs. 100 for a 12AX7, smoother, more articulate. The classic choice for Jerry tones.

EQ Approach for the Jerry Tone

• Bass: Moderate boost — single-coil pickups need low-end reinforcement for clean sustain
• Midrange: Slightly scooped — Fender topology inherits a natural mid-scoop
• Treble: Fairly high with Bright switch engaged — clear, articulate sparkle
• Gain: Always clean — dirt comes from pedals, not the preamp

100W mono solid-state power amplifier, 1970–1974. Transistors feeding McIntosh's patented Autoformer output. The MC100 amplifies cleanly — no sag, no compression, no harmonic distortion. All tone comes from the Alembic upstream.

Why the Autoformer Matters

Speaker impedance varies with frequency. A conventional amplifier's frequency response shifts as load impedance changes. The autoformer decouples the amplifier from the speaker — identical power output and flat frequency response into any impedance tap (2Ω, 4Ω, 8Ω, 16Ω).

Jerry Context

Jerry used the MC2300 (300W/ch stereo, bridgeable to 600W mono) — same architecture and philosophy as the MC100. The MC100 is a home/small-venue version. With 103dB-sensitive JBL E120s, 100W of clean McIntosh power is more than adequate.

The speakers that defined Garcia's tone. The JBL D120F (Fender-branded), K120, and E120 were in every serious Jerry/Bob rig from the Wall of Sound era forward. The aluminum dome dust cap is the character — extended high-frequency response, wide flat frequency range, no speaker breakup.

Why JBLs

• Aluminum dome: Extended HF response. The "glassy," articulate top end.
• Flat response: No midrange honk. Equal energy across the spectrum — like studio monitors, not guitar speakers.
• High power handling: 150W each, two in parallel = 300W handling into a 100W amp. Effectively unblowabl.
• No breakup: JBLs stay clean and articulate at high volume — essential for the hi-fi approach.

Parallel Wiring

Two 8Ω speakers in parallel = 4Ω total load. MC100 set to 4Ω output tap via autoformer. Cable: Canare 4S11, 4-conductor 14AWG wired to Neutrik Speakon NL4FC (R+W conductors to Pin 1+, B+Black to Pin 1−).

Both from IO Custom Guitars (Brian White, Laramie, WY). NOS Siliconix J230 JFETs, mil-spec components, no electrolytic caps — built to the same standard as the rest of the rig.

IO Thick Air — Dual JFET Clean Boost

Two independent JFET preamp stages with dedicated footswitches and gain controls. Based on the classic Stratoblaster design, heavily refined. Adds presence, air, and a 3D sound stage without compression. Stage 1 runs at minimum gain as a permanent buffer/tone enhancer — always on. Stage 2 used as a solo boost. Right channel Air toggle lifts upper frequencies without harshness.

IO Old Dirt — Distortion

Newest pedal from IO Custom Guitars. Designed to complement the Deadhead/Jerry tone aesthetic. Placed after Thick Air — Thick Air pushes the Dirt, Dirt hits the Alembic's tube input for controllable gain staging without touching the preamp's gain control.

Gain Staging

Thick Air (buffer + subtle boost) → Old Dirt (clipping) → Alembic FX-1 (tube warmth, EQ). The Alembic should be set clean at the edge — all dirt comes from pedals, not from overdriving the preamp.

Multi-effects processor — digital reverb, delay, chorus, flanger, pitch shift, EQ. In the future state of this rig, the QuadraVerb runs in the Lehle Parallel M's loop so its A/D converters are never in the dry signal path. Used for hall/plate reverb algorithms and digital delay as an alternative to (or layered with) the Ghost Spring's analog spring reverb.

Why Parallel

Running the QuadraVerb in series means the dry guitar signal passes through its A/D and D/A converters — this compromises the transparency of the Alembic → McIntosh chain. The Lehle Parallel M puts it in a parallel loop: the dry signal bypasses the QuadraVerb entirely, and only the effect return is blended in.

Setup for the Jerry Tone

• Reverb: plate or hall, moderate decay (1.5–2.5s)
• Delay: subtle slapback or clean digital delay mixed low
• EQ: flat or slight high-shelf boost
• Mix: keep it subtle — the Ghost Spring handles the ambient spring tail

Commercial single-loop parallel mixer (~$180 used on Reverb.com). Puts the QuadraVerb in a true parallel loop — the dry signal passes through the Lehle's summing network completely untouched by the QuadraVerb's A/D converters. The effect return is blended in cleanly at the Lehle's output.

Why This Solves the QuadraVerb Problem

The QuadraVerb is a late-1980s digital effects unit. Its A/D conversion is functional but not hi-fi by modern standards. Running guitar through it in series is like routing through a 32kHz digital chain between a tube preamp and a McIntosh. The Lehle bypasses that entirely — you get the effect tails without the converters touching your dry tone.

Chain Position

Alembic FX-1 → Lehle Parallel M (QuadraVerb in loop) → Ghost Spring → MC100. The Ghost Spring sits in series after the Lehle — it's fully analog with its own Mix pot, no parallel treatment needed.

1U rack chromatic tuner. Not in the main signal path — receives signal via a passive mute switch split placed before the Alembic FX-1. When the mute footswitch is stomped, signal routes to the Sabine and the output to the Alembic is disconnected. Silent tuning with no buffer in the audio path during play.