Sound Recipe - U2 / "Numb" Jet-Flanged Guitar

Target

The main guitar figure in U2's "Numb": short, abruptly choked low-register chord stabs turned into a metallic, vocal-like buzzsaw by a bright exciter and a slow, highly resonant flanger.

The sound should feel:

• Abrasive and mechanical, but still recognizably played on guitar
• Short and percussive rather than sustained
• Resonant rather than deeply wobbly
• Bright at the pick attack, with no glossy top end
• Dry, narrow, and embedded in the machine rhythm

Follows the house method: intention → source → performance → drive → exciter → flanger → amp → taste checks.

Useful References

• U2 — "Numb" (Zooropa, 1993); the main distorted guitar figure that enters near the opening
• U2's archive of the contemporary Time review describes the track's "lacerating guitar lick."
• Sound On Sound's Robbie Adams interview documents the guitar as part of Flood's earlier stereo band submix, but does not identify its distortion pedal or complete signal chain.
• Korg's A3 manual defines the Exciter and FLN1 algorithms; the commonly circulated SPC-01 program 62 values are preserved in this A3 settings record.

Steal the jobs: a dirty guitar source, extra upper harmonics, short-delay comb filtering, and hard performance mutes turning a riff into industrial percussion — not the exact riff.

Best For

One-note or two-note guitar stabs in electronic art-pop, an abrasive hook that must coexist with programmed drums, industrial punctuation, and a human performance that should be mistaken briefly for a synth or sample.

The Important Correction

Do not document this as "Korg A3 distortion into flanger."

The commonly circulated SPC-01 62 / JetFlng data has the A3 hard-distortion block bypassed. Its defining active stages are the Exciter and FLN1 stereo flanger. No reliable session source identifies the upstream distortion on the released recording, so the honest reconstruction is:

dirty guitar/amp tone → A3-style exciter → A3-style jet flanger

The A3 Exciter adds generated upper harmonics rather than functioning as a normal treble boost. Program 62's BLND +55 / FREQ 9.3 kHz gives the flanger a bright, complex attack to comb-filter. The distortion substitute below is chosen for the job; it is not a claim about Edge's original pedal.

Best Source

Use the Gretsch 5120 bridge pickup (TV Jones Classic Plus), guitar volume full, tone full. It is the closest owned source for a firm, compressed attack that can survive the exciter and high-feedback flange without becoming thin.

Record a clean DI through the Apollo Hi-Z input with preamp gain at minimum. The chain needs the unprocessed attack; do not print chorus, reverb, or delay on the way in.

Performance First

The stop is as important as the strike.

• Play low-register two-note fifths or compact power-chord fragments, not full six-string chords.
• Use one firm downstroke, then release fretting pressure immediately without lifting off the strings.
• Aim for roughly 80–150 ms of audible chord before the mute.
• Lightly palm-mute before the strike, then use the fretting hand for the hard stop.
• Leave clear rests. The flanger resonance should speak inside the gaps.
• Keep the timing rigid enough to interlock with the drums, but do not quantize away the physical choke.

If the dry DI does not already sound like confident percussion, processing will only make an uncertain part louder.

Fast Path

1. Gretsch 5120 bridge → Apollo Hi-Z — clean DI, short choked stabs.
2. UAD RAW Distortion — Distortion around 9 o'clock, Filter around 11 o'clock, Volume at unity. Keep it below fuzz territory.
3. Logic Exciter — Frequency 9.3 kHz, Dry Signal on, Color 1, Harmonics 20%.
4. Logic Modulation Delay — enter the locked A3 translation below.
5. UAD Ruby '63 in Paradise Guitar Studio — Brilliant channel, low gain / edge-of-breakup, boost off, 2x12 Silver Ace-style cab. Keep room and onboard modulation off.
6. FabFilter Pro-Q 4 only if needed — HPF 80 Hz; LPF 8.5 kHz; one narrow cut only if the feedback creates a painful stationary whistle.

No tempo delay. No chorus. No long reverb.

Locked A3 Translation - Logic Modulation Delay

The published FLN1 values are often misread. DPTH 8 is the modulation depth; FBAK 85 is the extreme value. The sound is a shallow sweep with very high feedback, not an 85%-deep wobble.

Lock De-Warble off, D-Mode off, Filter off, Volume Mod at zero, and Constant Mod on. Keep the LFO free-running rather than tempo-synced. The sweep should drift across the bar instead of restarting neatly with the riff.

Because Logic and the A3 are different algorithms, treat the numeric translation as the starting anchor, then judge the comb pitch and resonance against the reference at matched loudness.

Produced Path

Use the real Vox AC15HW1X for the dirty source, then recreate the A3 stages after the microphone:

1. Gretsch 5120 bridge → AC15 at edge-of-breakup; no amp tremolo.
2. SM57, 2–5 cm from the grille, aimed near the dust-cap edge and angled slightly off-axis.
3. Record short, hard-muted stabs with peaks well below clipping.
4. Logic Exciter at the locked 9.3 kHz / Color 1 / 20% Harmonics setting.
5. Logic Modulation Delay with the locked A3 translation.
6. Pro-Q only for the final HPF/LPF and one feedback-whistle cut if necessary.

This changes the historical order, which is not documented reliably anyway, but gives the real amplifier ownership of the dirt and lets the digital processing turn that recorded amp into the industrial object.

Routing and Automation

• Keep the guitar insert-based and mostly dry.
• Start with S1 Dark Plate off. Use a locked 3% send maximum only if the part feels pasted in front of the band.
• Keep the dry center intact. Do not add a widener after the stereo flanger.
• Automate track level by section, not the flanger rate. The free-running sweep is part of the unease.
• If one feedback peak dominates only on a few strikes, automate a narrow Pro-Q dynamic cut rather than lowering the whole guitar.

Taste Knobs

Exactly two:

1. Drive amount — edge-of-breakup bite ↔ serrated industrial dirt. Adjust RAW Distortion or AC15 gain, never both at once.
2. Flanger feedback — start at +85%; move within +70 to +90% to fit the chord register and avoid self-oscillation.

Lock the source, exciter frequency, LFO rate, modulation depth, 0.7 ms delay, 50% mix, opposite stereo phase, short performance envelope, and dry routing.

Common Mistake

Turning up modulation depth because the tone does not sound dramatic enough. That produces a seasick chorus sweep. The drama comes from very short delay + high positive feedback + bright harmonics + abrupt muting.

Adjustment Rules

Closest Tools I Own

Source: Gretsch 5120 bridge pickup ⭐; Apollo Hi-Z

Fast drive and amp: UAD RAW Distortion → UAD Ruby '63 in Paradise Guitar Studio ⭐

A3 translation: Logic Exciter ⭐ → Logic Modulation Delay ⭐

Produced source: Vox AC15HW1X + SM57

Cleanup: FabFilter Pro-Q 4 ⭐

Related Pages

• Guitar
• U2 / "Numb" Rewind Loop & Industrial Synths
• Creative Effects and Transitions
• Frequency and Depth Map
• Default Send Rack

Practical Summary

Play short, hard-choked low-register fifths on the Gretsch 5120 bridge pickup. Create restrained dirt with RAW Distortion, add upper harmonics with Logic Exciter at 9.3 kHz, then use Logic Modulation Delay as the A3 translation: 0.20 Hz rate, 8% modulation, +85% feedback, 0.7 ms delay, 50% wet/dry, 180° stereo phase. Finish through Ruby '63 at low gain and keep the part dry. The identity is not huge distortion or a deep sweep; it is a resonant comb filter biting into a very short guitar performance.