The essence is a True Class A Optical Compressor designed to fit the API* 500 VPR Series rack frames offering a great feature set in a compact package. The essence will find application with those seeking a musically transperant compressor for all tracking and mixing tasks, and it sounds particulary outstanding when processing voice and bass tracks. The essence - the Heart 'n' Soul of your next recording!

The essence control circuit design is based on the Buzz Audio SOC-1.1 Stereo Optical Compressor but the main audio path utilises our BE40 and BE50 True Class A amplifiers along with high spec Lundahl* input and output transformers. The input transformer is directly coupled to the Buzz proprietary Opto gain reduction element (completely passive input), amplified and then balanced via the output transformer - a very simple but gutsy signal path!

The essence control circuitry utilizes the Differential Drive Side Chain (DDSC) topology that was developed for the SOC-1.1. This system, which processes positive and negative audio waveform in seperate paths, provides the incredibly musical characteristic you will hear with this unit. The DDSC design also provides for a much faster attack time compared to most other LDR based optical compressors.

Simple side chain equalizers have been provided to allow the user to adjust the sensitivity of the compressor at high and low frequencies. In addition, a side chain insert point is provided for more complex EQ and compressor 'keying'.

The essence consumes 2 slots within a 500 Series rack. The input/output (I/O) connectors associated with the first slot carry the main audio path. The I/O connectors associated with the second slot are used for a side chain insert point (send and return). The insert can be switched in/out of circuit and monitored via front panel switches.

Rack Compatibility

The essence power consumption of 120mA is higher than other 500 series modules, but because this demand is spread over two slots (60mA each) it should work fine in all available racks.

features

• Frequency Response with no gain reduction = 14Hz to 107kHz, +/ 1.5dB
• Maximum Input Level = +25dBu
• Maximum Output Level = +27dBu
• Total Harmonic Distortion
• Measured at 0dBu input, no gain reduction, make up Gain 0dB
• 100Hz = 0.1%, 1kHz = 0.015%, 10kHz = 0.002%
• Measured at +10dBu input, 20dB gain reduction, make up Gain +15dB, Attack AUTO, Release 16
• 100Hz = 0.1%, 1kHz = 0.015%, 10kHz = 0.005%
• Residual Noise = 95dB A wtg, 150ohm source Z, make up Gain 0dB
• Make up Gain Range = 0dB to +15dB
• Maximum Available Gain Reduction = 25dB
• S/C HI EQ Boost/Cut = 8dB @ 10kHz
• S/C LO EQ Boost/Cut = 8dB @ 100Hz
• Main Audio Input Impedance = 20k ohms, bal or unbal
• Main Output Impedance = 100 ohms bal or unbal
• Sidechain Send Output Impedance = 100 ohms unbal
• Sidechain Return Input Impedance = 44k ohms bal or unbal
• Sidechain Max Input/Output Levels = +22dBu
• Size = (3'Wx5.25'H). Fits 2 spaces in API 500VPR Series rack format
• Power requirements = 120mA +/ 1518 volts DC, as supplied by rack power supply.