Buzz Audio REQ-2.2 MEA – Active low band section (ALB) version

The REQ is a combination of passive filter circuits and active amplifier stages. Parallel resonant chokes and capacitors form the frequency selective part of each band and these are coupled into the amplifier stage via the boost/cut control. The resulting equalisation is best described as “surreal” and it never sounds hard or harsh. The low frequencies remain tight and powerful with the high frequencies clear and well defined.

Many other equalizers using passive filters have limited centre frequency choices, but the REQ boasts 72 different frequencies split over four bands per channel. The high and low bands can be switched to bell or shelving mode and the two bell mid bands have two centre frequency ranges. Each band has a bandwidth (Q) control and if the high or low bands are switched shelf mode, this control reverts to a shelf “slope” control. In addition a passive high pass filter and a variable “saturation” module are provided. The saturation module converts the REQ into a more “vintage” sounding unit by adding harmonics to the signal via the use of a steel audio transformer driven by a “single ended” old style Class A amplifier (see distortion specs below). The low frequency response is also altered by the saturation control, depending on the position of this switch.

All other controls on all versions are switched for repeatability. The high pass filter of the mastering version offers smaller steps and varying filter slopes to that on the recording version.

Taking a look inside the REQ chassis you will discover a vey high level of engineering and build quality with modular construction for easy serviceability, high quality controls, single point power supply wiring, discrete power regulators for each band – the list goes on and on. Click on the images on the left to see inside the Resonance Equalizer and discover for yourself why this product is truly unique and an investment you will never regret!

Applications

• No other equalizer like it in the world.
• Fully discrete hi-bias wide bandwidth differential Class A amplifiers.
• Real choke and capacitor resonant circuits that sound fantastic.
• 72 frequency choices per channel.
• Individual discrete power supply regulators for each EQ band.
• Large easy to adjust knobs.
• High quality long life switches and potentiometers.
• Modular internal construction for easy future servicing.
• Mastering and recording versions.
• Unique transformer saturation module.
• Overall and individual band bypass switches.
• High-end balanced input and output amplifiers.
• Input connectors with loop through.
• Two output connectors on each channel.
• Rugged chassis construction.

Specifications

Frequency Response
Measured with all eq bands ON set flat, Saturation and HPF OFF 5Hz to 125kHz +0.2/-3dB

See graphs in side bar above for typical eq and HPF frequency response measurements.

Harmonic Distortion
At +10dBu, Saturation OFF 100Hz 0.007%…1kHz 0.004%…10kHz 0.007%…100kHz 0.013%
Saturation ON POS-1 20Hz 1.5%…100Hz 0.07%…1kHz and up 0.01%
Saturation ON POS-2 20Hz 1.5%…100Hz 0.14%…1kHz and up 0.01%
Saturation ON POS-3 20Hz 1.5%…100Hz 0.16%…1kHz and up 0.01%
Saturation ON POS-4 20Hz 1.6%…100Hz 0.17%…1kHz and up 0.01%
Saturation ON POS-5 20Hz 1.7%…100Hz 0.18%…1kHz and up 0.01%
Saturation ON POS-6 20Hz 2.0%…100Hz 0.22%…1kHz and up 0.01%

Maximum Input Level +25dBu
Input Impedance approx 20k ohms

Maximum Output Level +32dBu balanced…+26dBu unbalanced
Output Impedance approx 70 ohms

Input Common Mode Rejection (ref 0dBu) 100Hz -65dB…1kHz -65dB…10kHz -60dB

Noise all bands ON set flat -110dB below max input level A weighted

General
Power requirements 115V/230V selectable on rear panel
Dimensions 4U rack mount, 300mm deep