The Diamond Pedals CPR-1 is an analog compressor pedal made by Diamond Pedals. Diamond described it as "a dynamics and tone shaping tool for live and studio use - with low-noise, ultra-linear signal buffering, smooth opto-based compression, and a versatile 'tilt' EQ that musically shifts overall frequency balance"1. The design concept came from recording studios, where rackmount "vocal channels" combining a preamp, compressor and EQ are used as a front end for vocal recording1.
RockBoard's PedalPedia describes the CPR-1 as inspired by rackmount studio "vocal channels," the mic preamp, compressor and EQ units that recording studios often use all in one as a front end for vocal recording1.
How it works
The CPR-1 is an optical compressor. Like other optical compressors, it used an optocoupler for dynamic gain reduction, the method behind its smooth compression character2. Alongside the compression, the pedal carries low-noise, ultra-linear signal buffering1.
The controls: Comp, EQ and Volume
Diamond kept the pedal to a user-friendly three-control package: just Comp, EQ and Volume1.
| Control | What it does |
|---|---|
| Comp | Sets the amount of optical compression1 |
| EQ | Tilt control that musically shifts the overall frequency balance1 |
| Volume | Sets the output level1 |
The EQ is a tilt control, an adaptation of the "Tilt" control from the Quad Model 34 hi-fi preamps of the 1980s. Aion FX describes it as similar in usage to the bass/treble pivot of the Big Muff tone control, but refined so it has a truly flat frequency response in the middle position2.
Power
Diamond's design concept for the CPR-1 draws on studio practice: recording studios often use rackmount "vocal channels," a mic preamp, compressor and EQ all in one unit, as a front end for vocal recording1.
History and the BCP-1
Diamond conceived the CPR-1 with studio practice in mind: recording studios often use rackmount "vocal channels," a mic preamp, compressor and EQ all in one unit, as a front end for vocal recording1.
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Questions
Is the Diamond CPR-1 an analog compressor?
Yes. Diamond listed the CPR-1 as an analog compressor pedal, and it works on the optical principle: an optocoupler handles the dynamic gain reduction, which gives the smooth, transparent style of compression the pedal is known for. It also includes low-noise, ultra-linear signal buffering alongside the compression.
What power supply does the Diamond CPR-1 need?
Diamond's specification calls for 9V DC, center negative. A review at Ovnilab notes that the CPR-1 can also take up to 18V DC, which gives players some headroom when pairing it with a supply that offers a higher voltage option.
Does the Diamond CPR-1 have an EQ control?
Yes. Alongside Comp and Volume, the CPR-1 has a tilt-style EQ control adapted from the Quad Model 34 hi-fi preamps of the 1980s. It shifts the overall frequency balance musically rather than working as separate bass and treble bands, and is designed to be flat in the middle position.
Is the Diamond CPR-1 still made?
No. Diamond Pedals ceased operations in 2020 and all of its pedals, including the CPR-1, were discontinued. SolidGoldFX, which bought the Diamond brand, relaunched new compact versions of Diamond's most popular circuits in 2023.
What was the Diamond BCP-1?
The BCP-1 Bass Compressor was a bass-specific variant of the CPR-1 released in 2009. It added a 900 Hz/250 Hz pivot toggle and a more sensitive envelope detector, and it was Diamond's first pedal designed specifically for bass instruments.
Sources (2)
- CPR-1 by Diamond Pedals, RockBoard PedalPedia, 2026
- Quartz Optical Compressor / Diamond Compressor, Aion FX, 2024-04-19
