Time
Delay length before repeats.
- Turn up Longer echoes.
- Turn down Shorter slap / quick repeats.
Pedals / BBD delay + chorus/vibrato
Memo Man
BBD delay + chorus/vibrato · play-tested
seth — fish
seth@ninevolt:~$
Knobs
In the TUI each knob runs from low (left / 0%) to high (right / 100%). Start near noon, then nudge while you play.
Feedback
Number of repeats.
- Turn up Longer trails, more wash.
- Turn down Fewer repeats.
Blend
Dry versus delayed/modulated sound.
- Turn up More effect.
- Turn down More dry guitar.
Rate
Speed of the chorus/vibrato modulation on the delay.
- Turn up Faster wiggle on the echoes.
- Turn down Slow or nearly still modulation.
Depth
Amount of that modulation.
- Turn up Wobblier, more seasick echoes.
- Turn down Straighter delay with little pitch wiggle.
Inspired by
Electro-Harmonix Deluxe Memory Man — MN3005 BBD delay with an LFO modulating the clock for chorus and vibrato, plus Feedback and Blend. EH-7850 service calibration (David Morrin / Howard Davis): chorus LFO <1 Hz with ~10% delay-period swing at max; vibrato ~4 Hz; MN3005 compander + recovery filtering. Distinct from DM-2 pure echo (Ana Echo) and from mod-only chorus (Nano Chorus — see TIME_MOD_COMPARISON.md). Edge/U2-era ambience; shoegaze modulated repeats.
Signal path
| Step | What it does |
|---|---|
| LFO | Rate < 0.5 → chorus (~0.12–0.8 Hz); Rate ≥ 0.5 → vibrato (~1.6–6 Hz). Nano DMM: ~9 o'clock chorus, ~2 o'clock vibrato. |
| BBD clock × Depth | LFO swings virtual CD4047 clock ±10% at full Depth (clk = 1 + depth × 0.10 × sin). |
| Clock-modulated write | clk > 1 → duplicate samples into line (pitch up); clk < 1 → skip writes / sample-hold (pitch down). |
| Read fixed stage offset | Tap always Time samples behind write — fixed MN3005 stage count; effective delay ms scales as 1/clk. |
| Recovery LP ×2 | BBD darkening; cutoff tracks effective delay (clock-linked bandwidth). |
| Feedback | Feedback knob; soft-limited when hot (NE570-class compander on feedback path). |
| Write sum | Full-level input + compressed feedback → anti-alias LP → BBD saturate → clocked writes. |
| Blend | Dry/wet mix — center blend + depth = lush chorus; full wet + depth = vibrato wash. |
How we modeled it
Ana Echo BBD comb core plus LFO-modulated BBD clock. Depth at 0 = pure delay (one write per sample, clk = 1). Depth up runs a virtual CD4047: faster clock duplicates samples into the line (pitch up + shorter effective delay), slower clock skips writes (pitch down + longer delay). Read tap stays a fixed stage offset behind write, like MN3005. Blend center + moderate Depth = classic DMM chorus; Blend high + fast Rate = vibrato wash.
Simplifications
- Virtual BBD clock at host sample rate (not analog CD4047 waveform / duty cycle) - Mono — no dual-BBD stereo spread - Single sine LFO (no triangle/square Chorus waveform switch) - No Level / overload LED modeling