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.
We go to a lot of trouble to match up the LDR's used in our optical compressors but due to the inherent variances in these devices we now offer the essence in stereo matched pairs. Ask your dealer for more detail. For more information on linking two essence units, please read this.
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.
API* 500VPR Series rack module format - plug in and play!
Advanced analogue technology - not a clone or copy of products from the past.
Powerful fully discrete hi-bias, wide bandwidth, differential Class A amplifiers.
Passive transformer coupled input, transformer coupled output
Side chain insert point
Side chain monitor selector
On board side chain EQ
Unique Differential Drive Side Chain design
May be linked to multiple essence units within one rack, more info
Switchable 10 segment VU meter
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 +/- 15-18 volts DC, as supplied by rack power supply.