This is an Avalon AD2044 Stereo Opto Compressor in excellent, lightly used condition. Included is the B2T Power Unit and cords. There are some small marks from rack mounting.SONIC EXCELLENCEThe Avalon AD2044 Pure Class A opto-compressor is the most transparent, low noise optical-compressor available today. Designed to optimize absolute signal integrity and musical performance, the AD2044 combines advanced electronics with sonic excellence unequaled by lesser designs. The AD2044 is the perfect solution for two buss music-program compression, mono bass and instruments and  mastering applications.Features include state-of-the-art, balanced 100% discrete, Pure Class A signal amplifiers, practical "real-world" user features and rugged hardware designed to deliver true high performance audio for many years. LINEAR OPTICAL COMPRESSIONCustom manufactured, high speed linear opto elements provide the non invasive passive attenuator system for invisible gain reduction. The AD2044 incorporates a unique external control loop and current monitored optical driver for smooth control plus the benefits of traditional vintage LDR compression.MINIMUM SIGNAL PATH DESIGNAvalon's advanced true symmetry design offers high-voltage, large headroom, extended bandwidth and very low noise. The use of 100% discrete, Pure Class A signal amplifiers offer the serious music professional unlimited sonic character and a natural harmonic detail that enhances the program material and becomes one with the music itself.The AD2044 can be found in the world's leading recording studio's, mastering facilities and artist/producers outboard racks. These professionals rely on the AD2044 daily to help them complete their "sonic signature" and turn recordings into musical masterpieces.Smooth musical detail and sonic excellenceMinimum audio signal pathPure Class A, 100% discrete designDual mono or Stereo operationTransparent, non-invasive compressionVery low noise -94dBHigh headroom +30dBFully balanced inputs and outputsLong lasting, stainless steel hardwareExternal 150W Toroidal power supply100% discrete power supplies for audio pathAll signal routing w/sealed silver relaysExternal side-chain access XLRLow distortion less than 0.5% THD and IMDWide bandwidth -3dB 1Hz to 450kHzLarge accurate professional VU metersVariable threshold, ratio, attack & releaseDC coupled, no transformers in audio pathFully balanced inputs and outputsCircuit topology: High-voltage 100% discrete, balanced and symmetrical Class AOutput Gain Range: Variable -10dB to +10dB, center detent 0dBMaximum Input Level: +30dB balanced XLR pin 2 hotMaximum Output Level: +32dB balanced 600 ohms, DC coupled, high-current discrete Class AInput / Output Type: XLR type, pin 2 hot balancedNoise 20kHz Unweighted: -94dB (compressor in)Distortion THD, IMD: 0.5% (typical 0.05% at +6dB 1kHz)Frequency Response: -3dB: 1Hz to 450kHz (input band limited)Gain Reduction Meter: Illuminated gain reduction meter 0dB to -20dB rangeOutput Meter: Professional moving coil type -20dB to +3dB (0VU=+4dB)Compressor Type: Optical passive attenuatorBypass: Hard-wire relay bypass for compressor in-outLink Switch: Large illuminated push switch for stereo L-R linkingMake Up Gain: Variable 20dB range (-10dB to +10dB)Threshold: Threshold variable -24dB to +20dBRatio: Ratio-compression variable 1:1 to 20:1Attack: Variable 0.5mS to 150mSRelease: Variable 80mS to 5 seconds for 12dB releaseSide-Chain: XLR type, pin 2 hot balanced (switch/relay selectable from front panel)AC-DC Power: External AC supply, 150w toroidal transformer, 4 pin cable 90v isolated, (B2T Power Supply Included) 100-240v selectable 50/60Hz, 150w maxDimensions: 19 x 3.5 x 12 in (482 x 88 x 305mm)