125B · 5 knobs
ProximaOptical Compressor
Based on the Flatline Compressor· 1 other board clones it
- Category
- Compressor
- Controls
- Sustain · Sensitivity · Comp Volume · Clean Volume · Range
- Difficulty
- Easy
- Price
- $12.50in stock
From the vendor
A simple, cheap and surprisingly effective optical compressor that works great on bass or guitar.
The Proxima Optical Compressor is an expanded adaptation of the Flatline Compressor, a DIY classic originally invented by John Hollis in 2001.
There have been several community modifications and revisions during the past two decades, so while the original version only had Sustain and Volume controls, the Proxima has a more deluxe control set.
This version includes several additions: a JFET input buffer to split the signal, a sensitivity or threshold knob, a clean blend by way of separate Effect Volume and Clean Volume controls, and an output buffer to correct the phase from the mixing stage. If you like the Flatline but wish it had more flexibility, the Proxima is what you’re after.
In addition to John Hollis, we are indebted to the work of Madbean and Stompville for many of the ideas utilized in this version, and we’re hopeful that ours will in turn inspire others to take it even further.
Note: This project uses a type of capacitor that has been temporarily discontinued by WIMA. Please see our news article about the issue and the substitution spreadsheet for project-specific recommendations. We are stocking a limited supply in the mean time. The build document has not yet been updated to reflect this.
Schematic
The schematic is in the vendor's build document, page 6. Open the build document. No KiCad fragment has been drawn for this circuit yet.
Parts list 56 rows
Report a wrong parse| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 20 | ||||
| R1 | 10k | 10k | Metal film resistor, 1/4W | |
| R2 | 1M | 1M | Metal film resistor, 1/4W | Leave empty if using a BJT for Q1. See build notes. |
| R3 | 10k | 10k | Metal film resistor, 1/4W | |
| R4 | 1M | 1M | Metal film resistor, 1/4W | |
| R5 | 100k | 100k | Metal film resistor, 1/4W | |
| R6 | 10k | 10k | Metal film resistor, 1/4W | |
| R7 | 22k | 22k | Metal film resistor, 1/4W | |
| R8 | 10k | 10k | Metal film resistor, 1/4W | |
| R9 | 22k | 22k | Metal film resistor, 1/4W | |
| R10 | 330R | 330 | Metal film resistor, 1/4W | |
| R11 | 10k | 10k | Metal film resistor, 1/4W | |
| R12 | 22k | 22k | Metal film resistor, 1/4W | |
| R13 | 10k | 10k | Metal film resistor, 1/4W | |
| R14 | 10k | 10k | Metal film resistor, 1/4W | |
| R15 | 100R | 100 | Metal film resistor, 1/4W | |
| R16 | 100k | 100k | Metal film resistor, 1/4W | |
| R17 | 10k | 10k | Metal film resistor, 1/4W | |
| R18 | 10k | 10k | Metal film resistor, 1/4W | |
| RPD | 2M2 | 2.2M | Metal film resistor, 1/4W | Input pull-down resistor. Can be as low as 1M. |
| LEDR | 10k | 10k | Metal film resistor, 1/4W | LED current-limiting resistor. Adjust value to change LED brightness. |
| Capacitors 13 | ||||
| C1 | 47pF | 47p | MLCC capacitor, NP0/C0G | |
| C2 | 33n | 33n | Film capacitor, 7.2 x 2.5mm | |
| C3 | 220n | 220n | Film capacitor, 7.2 x 2.5mm | |
| C4 | 1uF | 1u | Film capacitor, 7.2 x 3.5mm | |
| C5 | 220n | 220n | Film capacitor, 7.2 x 2.5mm | |
| C6 | 100uF | 100u | Electrolytic capacitor, 6.3mm | |
| C8 | 1uF | 1u | Film capacitor, 7.2 x 3.5mm | |
| C9 | 470n | 470n | Film capacitor, 7.2 x 3mm | |
| C10 | 47pF | 47p | MLCC capacitor, NP0/C0G | |
| C11 | 1uF | 1u | Film capacitor, 7.2 x 3.5mm | |
| C12 | 100uF | 100u | Electrolytic capacitor, 6.3mm | Power supply filter capacitor. |
| C13 | 47uF | 47u | Electrolytic capacitor, 5mm | Reference voltage filter capacitor. |
| C14 | 100n | 100n | MLCC capacitor, X7R | Power supply filter capacitor. |
| Diodes 5 | ||||
| D1 | 1N5817 | 1N5817 | Schottky diode, DO-41 | |
| D2 | BAT46 | BAT46 | Schottky diode, DO-35 | |
| D3 | BAT46 | BAT46 | Schottky diode, DO-35 | |
| D4 | BAT46 | BAT46 | Schottky diode, DO-35 | |
| D5 | BAT46 | BAT46 | Schottky diode, DO-35 | |
| Transistors 1 | ||||
| Q1 | 2N5457 | 2N5457 | JFET, N-channel, general purpose | Can also use 2N5088. See build notes. |
| ICs 2 | ||||
| IC1 | TL072 | TL072 | Operational amplifier, DIP8 | |
| IC2 | TL072 | TL072 | Operational amplifier, DIP8 | |
| Opto 1 | ||||
| VACT | VTL5C3 | VTL5C3 | Optocoupler | Can also use VTL5C2, NS-32 or others. See build notes. |
| Potentiometers 4 | ||||
| SUSTAIN | 100kA | A100k | 16mm right-angle PCB mount pot | |
| SENSITIVITY | 50kB | B50k | 16mm right-angle PCB mount pot | |
| CLEAN VOL. | 100kB | B100k | 16mm right-angle PCB mount pot | |
| COMP VOL. | 100kB | B100k | 16mm right-angle PCB mount pot | |
| Trimmers 1 | ||||
| RANGE | 500k | 500k | Trimmer, 10%, 1/4” | |
| Switches 1 | ||||
| FSW | 3PDT | 3PDT | Stomp switch, 3PDT | |
| LEDs 1 | ||||
| LED | 5mm | 5MM | LED, 5mm, red diffused | |
| Jacks & sockets 5 | ||||
| IC1-S | DIP-8 socket | DIP-8 SOCKET | IC socket, DIP-8 | |
| IC2-S | DIP-8 socket | DIP-8 SOCKET | IC socket, DIP-8 | |
| IN | 1/4" stereo | 1/4" STEREO | 1/4" phone jack, closed frame | Switchcraft 112BX or equivalent. |
| OUT | 1/4" mono | 1/4" MONO | 1/4" phone jack, closed frame | Switchcraft 111X or equivalent. |
| DC | 2.1mm | 2.1MM | DC jack, 2.1mm panel mount | Mouser 163-4302-E or equivalent. |
| Hardware 2 | ||||
| BATT. | 9V | 9V | 9V battery snap | Soft vinyl type. The hard-shell type will not fit. |
| ENC | 125B | 125B | Enclosure, die-cast aluminum | Can also use a Hammond 1590N1. |
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