The 576 Blue Stripe is a FET compressor in API 500 format, built by IGS Audio on the UREI 1176 Revision A topology – the original "Blue Face" version with its blue front panel, widely regarded as the most aggressive and characterful of the entire 1176 family. Unlike the Alter 500, which targets later 1176 revisions, the 576 Blue Stripe aims specifically at the Rev A circuit: Carnhill transformers on both input and output, and a pure Class A output stage. The input transformer contributes the dense, characterful low-midrange colour associated with transformer-coupled FET compression on the original Rev A hardware. Attack time: 20 µs – 800 µs. Release: 50 ms – 1.1 s. Stereo link via the 500-series power supply rail (PSU). Needle VU meter. Relay bypass.
Carnhill transformers and Class A output – where Rev A differs from later 1176 revisions
The original UREI 1176 Revision A used an input transformer in the circuit (later revisions removed or simplified it) and a different output stage configuration. The Carnhill input transformer in the 576 Blue Stripe contributes galvanic isolation and the tonal character of a transformer-coupled FET topology – slightly more body and density in the low-midrange compared to direct-coupled designs. The pure Class A output stage without AB switching maintains lower distortion at normal operating levels and a more linear harmonic profile. Input impedance 2.4 kΩ, output impedance 600 Ω via Carnhill transformer. SNR –99 dBA. Maximum gain 36 dB, maximum gain reduction 20 dB.
Six ratio positions and SLAM – the full dynamic range in one module
The 576 Blue Stripe provides the five ratio positions of the original 1176 (4:1, 8:1, 12:1, 20:1) extended by an additional 2:1 not present on the original hardware, plus SLAM mode (All-Buttons-In). The 2:1 ratio opens the compressor to applications where the 1176 circuit character is desired but the amount of compression needs to remain subtle – acoustic guitar, vocals in delicate arrangements, instrument sub-buses. SLAM activates simultaneous engagement of all ratio buttons, producing the non-standard, heavily coloured operating mode with aggressive dynamic behaviour valued on drums, electric bass, and full groups. Attack is adjustable from 20 µs (maximum speed, full transient control) to 800 µs (slow, transients pass through). The Attack knob follows the original 1176 convention: counter-clockwise is slow, clockwise is fast.
KEY FEATURES
- FET compressor 1176 Rev A-style, API 500 format, mono
- Inspired by the UREI 1176 Revision A ("Blue Face")
- Carnhill transformers on both input and output
- Pure Class A output stage
- Ratio: 2:1 / 4:1 / 8:1 / 12:1 / 20:1 / SLAM (All-Buttons-In)
- Attack time: 20 µs – 800 µs
- Release time: 50 ms – 1.1 s
- Needle VU meter
- Stereo link via 500-series PSU rail
- Relay bypass
- 3-year manufacturer warranty
TECHNICAL SPECIFICATIONS
- Type: FET compressor/limiter (1176 Rev A-style), API 500, mono
- Gain control element: FET (field-effect transistor)
- Output stage: Class A
- Transformers: Carnhill input and output
- Input impedance: 2.4 kΩ (balanced)
- Output impedance: 600 Ω (balanced, Carnhill)
- Ratio: 2:1 / 4:1 / 8:1 / 12:1 / 20:1 / SLAM
- Attack time: 20 µs – 800 µs
- Release time: 50 ms – 1.1 s
- Maximum gain: 36 dB
- Maximum gain reduction: 20 dB
- Operating level: +4 dBu
- Maximum input level: +20 dBu
- Maximum output level: +22 dBu
- SNR: –99 dBA
- Bypass: relay
- Stereo link: yes (via 500-series PSU)
