buzzaudio REQ-2.2

A stereo inductor based recording and mastering parametric equalizer, that operates and sounds like no other!

the resonance factor

The REQ-2.2 equalizer utilises parallel resonant circuits in a clever configuration whereby the bandwidth (Q) of the circuit can be adjusted like an active filter, but without any complex relay switching. The inductor/capacitor resonant "tank" eq circuit runs at a low internal signal level which avoids any inductor saturation effects. The overall result is the sound of real choke based filters with a big open sound, but without the limitation of only a few - or no bandwidth selections as found on traditional choke eq's.

audio path quality

As you would expect, the REQ uses our BE40 True Class A circuits developed for the MA-2.2 microphone amplifier for the best possible audio performance that mastering engineers desire. But sometimes you might need a bit more color, so we have included a saturation section that introduces measured amounts of low frequency harmonic distortion via a steel audio transformer driven by a single ended tansistor amplifier. The High Pass Filter is placed in the beginning of the eq chain and the Low Band eq section is placed last in the chain. This layout produces the best overall equalizer coherency.

operational beauty

The large knobs and positive feel of the switching make the REQ a pleasure to operate and everything is visually clear when mounted into a console. In total there are 72 frequency choices per channel with overlapping selections across the four bands so you can always find the centre frequency you are looking for. A looping line XLR input and two parallel XLR outputs provide flexible connection options in the mastering control room. Finally, the brushed aluminium low glare rustic silver finish and retro Elma knobs give the REQ an impressive look in your rack!

controls and functions

Each eq band has a 12 position switch to select the Frequency and another that selects the Bandwidth of the bell shape curve (Q) which is adjustable from 1/3 octave to 2 octaves wide. On the High and Low bands, the Bandwidth control reverts to shelf Slope control when Shelf mode is selected via the push button switch (not with the Active Low Band option). The Low and High Mid bands frequency range is changed to alternative selections when the Freq x2.5 mode is selected. Each band also has an in/out switch. The mastering version Boost/Cut control is a 23 postion Elma switch with a range of +/-8dB. The recording version is fitted with a Alps center detent pot with a range of +/- 15dB.

On the right side of the front panel are the High Pass Filter and Saturation controls with their own in/out switches. The overall System in/out controls and the power switch complete the picture. The channel A and channel B push button switches in this section can be grouped by holding down any switch for 5 seconds. This means for stereo work you only need to push either the channel A or B switch to change both channels simultaneously. (This feature only applies to units with serial number Q1110 and up).

The REQ equalizer is available in a mastering or recording version with different boost/cut ranges as noted above. The High Pass Filter section of the mastering version has a softer slope (12dB/oct) compared to the recording version (18dB/oct) and the cutoff frequencies are more applicable to the mastering process.

We are now offering an option for the Low Band section of the REQ. This option replaces the Choke based eq filter with an Active filter which provides a "tighter" bass sound. This option has come about from requests from some users who work with modern music styles in mastering. The only operational difference between the Active and Choke filters is that in Shelf mode, the Bandwidth control does not work as a slope control and is disabled.

Ordering model numbers

• Recording version with choke filter low band - REQ-2.2
• Recording version with active filter low band - REQ-2.2A
• Mastering version with choke filter low band - REQ-2.2ME
• Mastering version with active filter low band - REQ-2.2MEA

frequency chart

specifications

Frequency Response measured with all eq bands on and set flat, Saturation and HPF off = 5Hz to 125kHz +0.2/-3dB 
Harmonic Distortion at +10dBu signal level;
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
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 output level (A weighted) 
Power requirements 115V/230V selectable on rear panel 
Dimensions 4U rack mount, 300mm deep 

Specifications are typical of a production unit and are subject to change without notice. 0dBu reference = 0.775 volts RMS.