1590B · 2 knobs
Chroma (Legacy)
Based on the Boss SP-1 Spectrum· 2 other boards clone it
- Category
- EQ / Filter· Parametric EQ
- Controls
- Balance · Spectrum
- Difficulty
- Intermediate
- Price
- see vendor
From the vendor
The Chroma Equalizer project is a clone of the BOSS SP-1 Spectrum, one of the three original BOSS compact stomp boxes released in 1977. (The other two were the OD-1 OverDrive, which is available as the Corona project, and the PH-1 Phaser.) It was discontinued in 1981, and due to its extreme rarity, it routinely sells for $500 or more on eBay.
The SP-1 Spectrum is a parametric equalizer with only two knobs. The frequency knob sets the boosted frequency between 500Hz and 5 kHz, and the balance (or mix) knob adjusts the dry-to-wet signal ratio. The gain and Q (frequency width) are fixed. It only boosts frequencies—it doesn’t have the ability to cut. Its function is very similar to a fixed wah, and you would hear a wah-like effect if you turn the Spectrum knob while a signal is being passed.
Schematic
The schematic is in the vendor's build document, page 4. Open the build document. No KiCad fragment has been drawn for this circuit yet.
Parts list 34 rows
Report a wrong parse| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 16 | ||||
| R1 | 1k | 1k | ||
| R2 | 470k | 470k | ||
| R3 | 10k | 10k | ||
| R4 | 10k | 10k | ||
| R5 | 1k | 1k | ||
| R6 | 10k | 10k | ||
| R7 | 18k | 18k | ||
| R8 | 10k | 10k | ||
| R9 | 22k | 22k | ||
| R10 | 10k | 10k | ||
| R11 | 10k | 10k | ||
| R12 | 10k | 10k | ||
| R13 | 470R | 470 | ||
| R14 | 100k | 100k | ||
| R15 | 33k | 33k | ||
| R16 | 33k | 33k | ||
| Capacitors 12 | ||||
| C1 | 47n | 47n | ||
| C2 | 4u7 | 4.7u | elec | |
| C3 | 4u7 | 4.7u | elec | |
| C4 | 100n | 100n | ||
| C5 | 3n3 | 3.3n | ||
| C6 | 3n3 | 3.3n | ||
| C7 | 1uF | 1u | ||
| C8 | 4u7 | 4.7u | elec | |
| C9 | 47pF | 47p | ||
| C10 | 1uF | 1u | ||
| C11 | 47uF | 47u | ||
| C12 | 47uF | 47u | ||
| Diodes 1 | ||||
| D1 | 1N4002 | 1N4002 | ||
| ICs 1 | ||||
| IC1 | RC3403A | RC3403A | ||
| Potentiometers 3 | ||||
| BALANCE | 10KA | A10k | Potentiometer | |
| SPECTRUM | 100KB | B100k | Potentiometer | |
| RPD | 1M | 1M | Potentiometer | |
| LEDs 1 | ||||
| LED1 | into | INTO | ||
Other boards based on the Boss SP-1 Spectrum
- Chroma Aion FX · 125B · $12.50
- SP-1 Spectrum PCBWay: Glory to Ukraine