The Photon 500 is an optical compressor/limiter in API 500 format, built by IGS Audio on the classic opto-electronic topology first used in the LA-2A limiter and later in the LA-4. The compression element is an opto-coupler that introduces negative feedback into the audio path – this is the mechanism that gives opto compressors their characteristically smooth and musical response, different in speed and character from VCA or VCR designs. The input is electronically balanced with an API 2520-compatible op-amp in the gain stage; the output runs through a Carnhill transformer at 600 ohms. All front-panel controls are switches or stepped selectors – the 12-pole stepped Output knob for makeup gain ensures full session recall without relying on unmarked pot positions. Three-year manufacturer warranty.
London / New York – two compression characters from one module
The London/New York switch is the key differentiator between the Photon 500 and simpler opto clones. London mode models a smooth, gentle compression curve with a slower envelope response – analogous to an LA-2A working on a vocal, acoustic guitar, or full mix where the compressor coheres the material without audible pumping. New York mode activates a more aggressive curve shaping, closer to using compression as an effect: pronounced gain reduction, more evident transient shaping, more audible action on drums, bass, or electric guitar. The side-chain highpass filter at Flat/60/120 Hz prevents low-frequency content from triggering unintended compression – particularly useful on bass-heavy tracks, drum buses, or mix groups where sub-bass energy would otherwise drive the detector continuously.
Ratio and gain staging – flexibility without panel complexity
Three ratio positions – 2:1, 4:1, and 12:1 – cover the range from transparent dynamic cohesion (2:1 on vocals or piano) through standard tracking compression (4:1 on instruments and groups) to near-limiting behaviour (12:1 on kick drum or as a safety limiter on a mix bus). The Peak Reduction knob controls the gain of the side-chain detection circuit, which translates directly to the depth of gain reduction – maximum GR is 20 dB. The 12-pole stepped Output handles makeup gain with full repeatability. Maximum gain is 30 dB; maximum input level +24 dBu, output +32 dBu; THD up to 0.5%; frequency response ±0.2 dB across 8 Hz – 20 kHz.
KEY FEATURES
- Optical compressor/limiter (opto-coupler), API 500 format, mono
- Inspired by LA-2A and LA-4, negative feedback via opto-coupler topology
- Electronically balanced input with API 2520-compatible op-amp
- Carnhill transformer output, 600 Ω
- London mode (smooth compression) / New York mode (aggressive curve)
- Ratio: 2:1 / 4:1 / 12:1
- Side-chain HPF: Flat / 60 / 120 Hz
- Output: 12-pole stepped makeup gain
- Maximum gain reduction: 20 dB
- Hard-wire bypass
- 3-year manufacturer warranty
TECHNICAL SPECIFICATIONS
- Type: optical compressor/limiter, API 500, mono
- Compression element: opto-coupler
- Input: electronically balanced, API 2520-compatible op-amp
- Output: Carnhill transformer, 600 Ω
- Input impedance: 10 kΩ
- Output impedance: 600 Ω (Carnhill)
- Ratio: 2:1 / 4:1 / 12:1
- Side-chain HPF: Flat / 60 Hz / 120 Hz
- Maximum gain: 30 dB
- Maximum gain reduction: 20 dB
- Maximum input level: +24 dBu
- Maximum output level: +32 dBu
- THD: max. 0.5%
- Frequency response: ±0.2 dB, 8 Hz – 20 kHz
- SNR: above 99 dB
- Operating level: +4 dBu
- Power supply: ±16 V
- Current consumption: 110 mA
- Dimensions (H×W×D): 133×37×180 mm
- Weight: 700 g
