Enclosure not stated · 4 knobs
Fred Briggs Dual Band Vibrato "Bliss"
Based on the Fred Briggs Dual Band Vibrato
- Category
- Vibrato / Chorus
- Price
- see vendor
- Tags
- freestompboxes.org trace
From the vendor
The author's own design: an op-amp buffer splits the signal into a treble path (high-passed around 900Hz) and a bass path (low-passed around 1000Hz), each through a transistor phase-splitter stage with an LDR in the emitter, as in a Uni-Vibe stage. Each band gets its own LFO (phase-shift oscillator driving an LED onto that band's LDR), so depth and speed can be set per band; the overlap of the bands gives pseudo phase-shifting, from plain vibrato to an almost Uni-Vibe sound. A Mix pot blends the bands into an output gain stage.
Use two LFOs, one for each band; only one is drawn. The Mix pot can be B47K or B100K. The author likes the bass band on a slow vibrato with the treble band fast; the project was still in progress when posted.
Schematic
The schematic is in the post. Open it at Revolution Deux. No KiCad fragment has been drawn for this circuit yet.
Parts list 40 rows
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Check before you build · 3 values the reader of this schematic was not sure of
- The high-pass and low-pass filter resistors and capacitors have no values on the drawing (only the target corner frequencies, 900Hz and 1000Hz).
- The resistor above the Depth pot reads '1KB'; probably 1.8K.
- No transistor or LDR part numbers are given (all transistors high-gain NPN; any dual op-amp).
| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 16 | ||||
| R1 | 1M | 1M | to Vr; read from the schematic by eye | |
| R2 | 2.2M | 2.2M | treble band; read from the schematic by eye | |
| R3 | 10K | 10k | treble band collector; read from the schematic by eye | |
| R4 | 10K | 10k | treble band emitter; read from the schematic by eye | |
| R5 | ? | ? | high-pass at 900Hz, no value; read from the schematic by eye | |
| R6 | 2.2M | 2.2M | bass band; read from the schematic by eye | |
| R7 | 10K | 10k | bass band collector; read from the schematic by eye | |
| R8 | 10K | 10k | bass band emitter; read from the schematic by eye | |
| R9 | ? | ? | low-pass at 1000Hz, no value; read from the schematic by eye | |
| R10 | 470K | 470k | to Vr; read from the schematic by eye | |
| R11 | 3.3K | 3.3k | read from the schematic by eye | |
| R12 | 470K | 470k | read from the schematic by eye | |
| R13 | 1.8K | 1.8k | reads 1KB; read from the schematic by eye | |
| R14 | 1.5M | 1.5M | LFO; read from the schematic by eye | |
| R15 | 2.2K | 2.2k | LFO; read from the schematic by eye | |
| R16 | 10K | 10k | LFO; read from the schematic by eye | |
| Capacitors 13 | ||||
| C1 | 100n | 100n | input; read from the schematic by eye | |
| C2 | 22n | 22n | treble band; read from the schematic by eye | |
| C3 | 47n | 47n | treble band; read from the schematic by eye | |
| C4 | ? | ? | high-pass at 900Hz, no value; read from the schematic by eye | |
| C5 | 1u | 1u | electrolytic, bass band; read from the schematic by eye | |
| C6 | 1u | 1u | electrolytic, bass band; read from the schematic by eye | |
| C7 | ? | ? | low-pass at 1000Hz, no value; read from the schematic by eye | |
| C8 | 1u | 1u | electrolytic; read from the schematic by eye | |
| C9 | 1u | 1u | electrolytic; read from the schematic by eye | |
| C10 | 1u | 1u | electrolytic, output; read from the schematic by eye | |
| C11 | 1u | 1u | electrolytic, LFO; read from the schematic by eye | |
| C12 | 1u | 1u | electrolytic, LFO; read from the schematic by eye | |
| C13 | 1u | 1u | electrolytic, LFO; read from the schematic by eye | |
| Transistors 3 | ||||
| Q1 | NPN | NPN | high gain; read from the schematic by eye | |
| Q2 | NPN | NPN | high gain; read from the schematic by eye | |
| Q3 | NPN | NPN | LFO, high gain; read from the schematic by eye | |
| ICs 1 | ||||
| IC1 | dual op-amp | DUAL OP-AMP | any dual op-amp; read from the schematic by eye | |
| Potentiometers 4 | ||||
| Mix | B47K | B47k | Potentiometer | or B100K; read from the schematic by eye |
| Gain trim | 10K | 10k | Potentiometer | trimmer; read from the schematic by eye |
| Depth | B25K | B25k | Potentiometer | read from the schematic by eye |
| Speed | B10K | B10k | Potentiometer | read from the schematic by eye |
| LEDs 1 | ||||
| LED1 | LED | LED | to one of the LDRs; read from the schematic by eye | |
| Other 2 | ||||
| LDR1 | LDR | LDR | treble band; read from the schematic by eye | |
| LDR2 | LDR | LDR | bass band; read from the schematic by eye | |