The Crown EQ 2 Graphic Equaliser brought two complementary forms of frequency adjustment into a single unit. Each channel contained eleven active equaliser filters alongside a separate shelving tone-control section. The shelving controls adjusted broad portions of the bass and treble response, while the individual equaliser bands addressed more localised peaks and dips. Both sections had their own cancellation switches for each channel, allowing their effects to be assessed independently without disturbing the control settings.
The equaliser’s nominal centre frequencies extended from 20 Hz to 20 kHz. With the frequency adjustment controls centred, the eleven bands were positioned at 20 Hz, 40 Hz, 80 Hz, 160 Hz, 320 Hz, 640 Hz, 1.25 kHz, 2.5 kHz, 5 kHz, 10 kHz and 20 kHz. A separate rotary control for every band moved its centre frequency by up to half an octave in either direction. This allowed the operator to position a correction between the marked frequencies rather than being restricted to fixed octave centres.
Each vertical equaliser control was a stepped slide switch operating through a resistor network. Boost and cut were adjustable in 1 dB increments between flat and ±6 dB, with additional positions at ±8 dB, ±12 dB and ±15 dB. This provided closely spaced settings around the flat position and larger adjustments towards the ends of the control travel. The two banks of eleven sliders displayed the selected boost and cut settings, while the corresponding frequency controls occupied the lower part of the front panel.
The bass and treble sections provided up to 20 dB of boost or cut, using shelving characteristics with 6 dB-per-octave slopes. Each had separate level and hinge-point controls, allowing the operator to adjust both the amount of tonal change and the frequency at which it began to take effect. These controls operated separately for the two channels, so broad response adjustments could be made independently of the eleven-band equaliser settings.
Internally, the Crown EQ 2 used eleven tuned amplifiers per channel, each incorporating an active resistor-capacitor filter. Their outputs were combined through summing circuitry. Crown described the equaliser section as a half-octave, constant-bandwidth system with variable Q and adjustable frequency centres. The shelving section preceded the individual equaliser filters in the signal path.
The two channels could also be cascaded for mono operation. With their frequency settings arranged appropriately, this configuration provided a 22-band, half-octave mono equaliser. The same unit could therefore serve as a two-channel equaliser with nominal octave spacing or provide more closely spaced control over a single signal.
Transformerless balanced inputs and separate unbalanced inputs supported different system connections. The balanced input circuitry offered a choice of unity gain or 10 dB gain, while the unbalanced input operated at unity gain. Rear-panel input attenuators controlled the signal level for each channel and affected either input connection.
Normal and inverted unbalanced outputs were provided for each channel. Used together, these could form a balanced output with a specified output impedance of 600 Ω. The normal output impedance was 300 Ω. The Crown EQ 2 could be connected between a preamplifier and power amplifier or inserted into a preamplifier’s tape-monitor loop, where the monitor selector enabled comparison between equalised and unequalised reproduction.
Separate overload indicators monitored the two channels. The detection circuitry sampled four internal points, allowing overload to be indicated at several stages within the signal path. A reed-relay muting circuit suppressed the Crown EQ 2’s switch-on transients at its outputs.
With all controls set flat and an IHF load connected, the Crown EQ 2 was specified within ±0.1 dB from 20 Hz to 20 kHz and within ±0.3 dB from 10 Hz to 100 kHz. Rated output was 2.5 V RMS, with a specified clipping level of 10 V RMS under the same flat-control loading conditions. Intermodulation distortion was below 0.01% at rated output, and hum and noise were 90 dB below rated output over a 20 Hz to 20 kHz measurement bandwidth.
The enclosure supported rack installation or mounting in an optional Crown wooden cabinet. Its front panel combined satin-finished aluminium with a suede Lexan inlay. Original supplied accessories included a test record, connecting leads, mounting hardware and a Plexiglas front-panel cover.
Features
- Two independent channels with eleven active equaliser bands per channel.
- Nominal octave-spaced centre frequencies covering 20 Hz to 20 kHz.
- Individual centre-frequency adjustment of ±½ octave for all 22 bands.
- Stepped boost and cut controls providing up to ±15 dB per band.
- Separate bass and treble shelving controls with adjustable hinge points and up to ±20 dB adjustment.
- Independent tone-section and equaliser-section cancellation switches for each channel.
- Cascaded operation for 22-band, half-octave mono equalisation.
- Transformerless balanced inputs and separate unbalanced inputs.
- Selectable unity or 10 dB gain for the balanced inputs.
- Individual rear-panel input attenuators.
- Normal and inverted outputs that can be combined for balanced operation.
- Separate channel overload indicators monitoring four internal circuit points.
- Reed-relay output muting to suppress switch-on transients.
- Rack installation or mounting in an optional wooden cabinet.