Drawmer 1961 Vacuum Tube Equaliser - Manual (Page 6)

1961 OPERATORS’ MANUAL 4
INTRODUCTION
The Drawmer 1961 is a hybrid, vacuum tube/semi-conductor, dual-channel equaliser
designed to combine the tonal qualities of classic tube circuitry with the low noise
and high reliability associated with contemporary circuit design.
A simple linking facility is included which allows the 1961 to be used in conjunction
with the Drawmer 1960 tube compressor/preamplifier where it may be used either in
the side-chain ( for de-essing, de-popping and so forth ) or in the main signal path for
conventional equalisation.
In addition to tube circuitry being used in each of the four main equaliser bands, a
further tube amplifier is included in the output stage which may be deliberately
overdriven to achieve the warm, detailed sound of vintage classic tube designs.
The filters are based around a specialist adaptation of the gyrator 'virtual inductor'
circuit which faithfully recreates the essential characteristics of a vintage LC
(coil/capacitor) network without incurring the penalties of noise, instability or
susceptibility to magnetic interference. Rather than employ a continuously variable
resistor as a means of frequency control, the 1961 utilises the same rotary 'step'
switching system used in vintage designs. This enables the component values for
each frequency band to be optimised for uncompromising performance across the
entire audio spectrum and also makes setting up more accurate, especially when
treating stereo signals.
The 1961 has numerous applications in studio recording, live sound, location
recording, post-production and as part of a musician's rack system. It has the benefit
of being both simple and intuitive to use and shares the traditional Drawmer styling
adopted for the rest of the product range.
In addition to the four parametric equaliser sections in each channel, the 1961
incorporates both high and low pass, 12 dB per octave shelving filters providing the
user with a very precise means of controlling the cutoff frequency at both ends of the
audio spectrum. All filter bands, including the high and low-pass filters, have
independent Bypass controls and a further Master Bypass switch is provided which
switches the entire equaliser out of circuit making A/B comparison straightforward.
There are six, dual-stage tubes in the audio signal path with low noise microcircuits
used in the input and output balancing stages as well in certain other noise-critical
areas of the design. The input stages feature extremely low noise, balanced input
circuitry which may be switched on the rear panel to accept either -10dBV or +4dBU
signals while a five-section, three-colour LED meter monitors the input signal level (
whether it is fed from the input XLR or the 1960 Insert linking jack ). An Input gain
control provides up to 20dB of further gain and a red peak overload LED warns when
clipping is imminent; a yellow soft-clipping LED shows that the tube circuitry is being
driven to the level where it is producing musically useful harmonic distortion.