DRAWMER DS201 – Dual Noise Gate

The DS201 is a sophisticated dual channel noise gate incorporating a number of features pioneered by Drawmer, which are invaluable to the sound engineer, and not found on conventional noise gates.

• Variable high pass and low pass filters for "frequency conscious" gating.
• Comprehensive envelope control, attack, hold, decay, and range.
• Key input for external triggering.
• “Key Listen" facility.
• Extremely fast attack time, to preserve the natural attack of the sound.
• Balanced inputs and outputs.
• Stereo linkable.
• Can be used for "Gating" or "Ducking“.
• High audio specification.

These features and its "user friendliness" have made it the "industry standard" throughout the world.

Setting up noise gates can be tedious and unrewarding. For example, when attempting to separate a signal from unwanted noise or crosstalk that is relatively high in level, spurious triggering of the gate by unwanted components within the sound can be a serious problem. This can often be experienced in the studio when recording a drum kit. If a gate is used to clean up the snare drum sound it is quite likely that the nearby hi-hats will spill into the snare drum microphone and cause the gate to open. Increasing the threshold level may cure this problem, but then there is a very real danger that any quieter snare drum beats may not cause the gate to open at all and the performance can easily be ruined.

The DRAWMER solution to this problem is the inclusion of two variable filters, one high-pass and one low-pass, which act upon the side-chain keying circuitry. By setting the output switch to key listen the user can hear the action of the filters and adjust them to reject high frequency spillage from the hi-hats. This now enables the gate to only open on the lower frequencies present in the snare drum.

Drawmer pioneered the concept of frequency conscious gating, and the Drawmer DS201 was the first noise gate to include this feature. 

The very fast attack of the DS201 means that it can open in a matter of micro seconds, thus preserving the natural attack of whatever sound is being gated and the comprehensive envelope controls mean that the gain can be changed at whatever rate best suits the material being processed. With vocals for example, a fairly fast attack is needed so as not to clip the leading consonants but a slower release time will prevent the end of words being clipped off and will also fade out any noise gradually rather than cutting it off abruptly. This latter point is very important as the human ear is far more sensitive to rapidly changing noise levels than to a constant low level noise.

Another important role played by the gate is in the reshaping of existing sounds. An example of this might involve a simple sampling delay line used to store a sound to be re-triggered later and added to a mix. A gate can be used to impart a slower attack or faster decay to the sound and careful setting of the decay envelope can effectively hide any noise present at the end of the sample. When using a sampler or drum machine the gate can be considered a triggered envelope shaper, and the wide range allowed by the envelope controls make the DS201 ideal for this application.

The unit can be switched to accept a key input, which allows the gate to be triggered externally. An example of this would be to use a snare drum signal to open the gate on a separate ambient microphone to create a natural alternative to gated reverb.

Each channel can be individually switched from Gating to Ducking for \'voice over\' applications or the removal of \'clicks\' and \'pops\'.

The Avalon VT-737SP features a combination of TUBE preamplifiers,
opto-compressor,sweep equalizer, output level and VU metering in a
2U space.
PREAMPLIFIER
The VT-737SP has three input selections: 1. The VT-737SP features a
higher-performance microphone input transformer with +48v phantom
selection. 2. Instrument DI high source input with jack located on front
panel. 3. Balanced line input, discrete high-level Class A. The Class A
preamplifier utilizes two cascaded, dual vacuum tube triodes configured
with minimum negative feedback. A high gain switch boosts the overall
gain of the preamplifier. The four high quality tubes are configured as
singled ended anode coupled followers. A passive-variable high pass filter
and hard-wire relay bypass completes the input signal conditioning. The
phase reverse relay is available on all three inputs.
OPTO-COMPRESSOR
The opto-compressor features a minimum signal path design with twin Class
A vacuum tube triodes for gain matching. The optical attenuator acts as a
simple passive level controller. Full dynamic control from soft compression to
hard- knee limiting can be achieved with threshold, ratio-compression, attack
and release controls plus gain reduction selection on the large VU meter. Special
spectral control including de-ess is available with the dual sweep mid EQ to side-
chain switch. The EQ section can be flipped pre or post the opto-compressor
via a front panel switch for alternate effects and tone shaping. Two VT-737SPs
can be linked via a rear panel link cable for stereo tracking. The compressor
bypass is a sealed silver relay for the most direct signal path.
SWEEP-EQUALIZER AND OUTPUT LEVEL
The VT-737SP equalizer utilizes 100% discrete, Class A-high-voltage transistors
for optimum sonic performance. The high and low frequency bands provide the
smooth characteristics of an all passive design, while the dual mid bands include
variable frequency and switched Q-width selection. The enhanced range of the mid
bands is extended into the high and low bands by the use of X10 frequency multipliers.
The bypass switch incorporates a sealed silver relay for the most direct signal path.
When the EQ to sidechain is engaged, the high-low EQ remains in the audio path for
"tone enhancement“. The output level control provides a variable control of the overall
signal path. The output amplifier utilizes another dual triode vacuum tube driving a
100% discrete, Class A, high-current, balanced and DC coupled low noise output
amplifier.

AVALON VT-737SP FEATURES
Vacuum tube triode signal path, transformer balanced microphone input, high-voltage
circuits for maximum headroom to +30dB, low noise -92dB, internal discrete power
supply with toroidal transformer, soft-start tube life extender, stereo link for compressors,
all discrete Class A equalizer with musical passive filter design, sealed silver relays for
signal routing, large control knobs with professional conductive plastic potentiometers,
VU meter for output level monitoring and compressor gain reduction.

VT-737SP SPECIFICATIONS
Circuit topology Four dual triode vacuum tubes (Sovtek 6922), high-voltage discrete
Class A
Gain Range Microphone: Transformer balanced 850/2500 ohm, 0dB to +58dB Instrument:
Unbalanced 1 meg ohm, 0dB to+30dB Line: Balanced Class A 20k ohms, -27dB to 28dB
Maximum input level and connector types Microphone26dB@25Hz, +30dB@1kHz balanced
XLR Instrument+30dB unbalanced front panel jack socket
Line +36dB balanced XLR
Maximum output level +30dB balanced 600 ohms, DC coupled, discrete Class A
Output type and gain XLR connector, output trim gain -45dB to20dB
Noise 20kHz unweighted -92dB
Noise microphone EIN -116dB, 22Hz to 22kHz unweighted
Distortion THD, IMD 0.5%
Frequency response -/2.5dB 10Hz to 120kHz input filter included
Frequency response -3dB 1Hz to 200kHz line in-out
VU meter and gain reduction High quality illuminated OVU =+4dB and gain reduction to -20dB
High cut filter Variable 6dB per octave 30Hz to 140Hz
Compressor type Optical passive attenuator incorporating twin vacuum tubes and stereo link
Threshold - Ratio Threshold variable -30dB to +20dB, ratio-compression variable 1:1 to 20:1
Attack - Release Attack variable 2mS to 200mS, release variable 100mS to 5 seconds
Equalizer type Discrete Class A, variable active and switched passive design
Frequency bands (4) Treble - switched 10kHz, 15kHz, 20kHz, 32kHz, +/- 20dB range, shelf
High mid - variable 200Hz to 2k8Hz and 2kHz to 28kHz, +/- 16dB range, hi-lo Q Low mid -
variable 30Hz to 450Hz and 300Hz to 4k5Hz, +/- 16dB range, hi-lo Q Bass - switched 15Hz,
30Hz, 60Hz, 150Hz, +/- 24dB range, shelf
AC power Internal toroidal 100v to 240v, 50-60Hz selectable, 75 watts maximum
Dimensions 19 x 12 x 3.5 in (482 x 305 x 89mm)
Weight 22lbs (10kg)
Dimensions-shipping carton 21 x 18 x 8 in (533 x 457 x 203mm)
Weight-packed 26lbs (11.8kg)

Shure DP11EQE Dynamics Processor Specification:

    GENERAL:
        Frequency Response: 20 to 20k Hz +/- 1.0 dB re 1 kHz
        Dynamic Range: 104 dB minimum, A-weighted, 20 Hz to 20 kHz
        Sampling Rate: 48 kHz
        Digital-to-Analog, Analog-to-Digital Conversion: 20 bit resolution
    Voltage Gain:
        1 dB +/- 1dB (power off)
        12 dB +/- 2 dB (input 10 dBV, output +4 dBu)
        12 dB +/- 2 dB (input +4 dBu, output 10 dBv)
        0 dB +/- 2 dB (equal input and output sensitivities)
    Impedance:
        Input: 47 kilohms +/- 20% actual
        Output: 120 ohms +/- 20% actual
    Input Clipping Level
        +18 dBu minimum (at +4 dBu setting)
        +6 dBV minimum (at 10 dBV setting)
    Output Clipping Level
        +18 dBu minimum (at +4 dBu setting)
        +6 dBV minimum (at 10 dBV setting)
    Total Harmonic Distortion
            LED Signal Indicators
        Signal: 40 dB
        Clip: 6 dB down from input clipping
    Propagation Delay from Input to Ouput
        0.8 ms (all filters flat, no dynamics processing, 0 ms delay), up to 2.1 ms (all processing enabled)
    Polarity
        Input to output: inverting optional (default: non-inverting)
        XLR: pin 2 positive with respect to pin 3
        1/4-inch TRS: tip positive with respect to ring
    Operating Voltage
        DP11EQ: 120 Vac, 50/60 Hz, 50 mA max
        DP11EQE: 230 Vac, 50/60 Hz, 25 mA max
        DP11EQJ: 100 Vac, 50/60 Hz, 50 mA max
    Temperature Range
        Operating: 0 degrees to 60 degrees C (32 degrees to 140 degrees F)
    Fuse
        DP11EQ: 120 Vac. Fuse: 100 mA, 250V time delay
        DP11EQE: 230 Vac. Fuse: 50 mA, 250 V time delay
        DP11EQJ: 100 Vac. Fuse: 100 mA, 250 V time delay
    Dimensions
        219 mm x 137 mm x 44 mm (8-5/8 in x 5-3/8 in x 1-3/4 in)
        Weight: 930 g (2.05 lbs)
    DYNAMICS PROCESSOR
        Gate and Expander:
        Threshold: 72 to 1 dB, 0.5 dB resolution
        Attack: 1.0 to 200 ms
        Decay: 0.05 to 1 second
        Gate Hold Time: 0 to 0.5 seconds
    AGC Leveler
        Threshold: 72 to 1 dB, 0.5 dB resolution
        Attack: 0.2 to 3 seconds
        Decay: 0.5 to 5 seconds
        Hinge: Threshold to 1 dB, 0.5 dB resolution
    Compressor and Limiter
        Threshold: 72 to 1 dB, 0.5 dB resolution
        Attack: 1.0 to 200 ms
        Decay: 0.05 to 1 second
        Knee: Hard or Soft selectable
    No Overshoot Peak Limiter
        Propagation delay: 1 ms
        Threshold: 72 to 1 dB, 0.5 dB resolution
        Attack: 0 msDecay: 100 ms
    PARAMETRIC EQUALIZER
        Parametric Filter Frequency Bands
        Up to 9 bands, variable frequency, variable Q
    Boost/Cut Range
        +6 dB to 18 dB per band
        Q Range
        1/40-octave to 2 octave
    High and Low Shelf/Cut Filters
        Shelf, +6 to 18 dB per filter
        Cut, 12 dB per octave nominal
    DELAY
        Up to 1.3 seconds, 21 microsecond resolution

The DPR-504 is a 4-channel noise gate.

Each channel features:
A parametric key filter with key filter listening.
Simultaneous key level and threshold metering with average and
peak metering.
A gate status LED.
A RELEASE/HOLD control (hold tracks proportionally with release
times).
Attack switchable auto/fast (auto tracks signal dynamics for optimum
setting).
Link (links two channels together).
Key source allows external triggers.

The Range switch selects between 7OdB and 2OdB gating depth to
provide alternative release profiles.
The unit features electronically balanced inputs and outputs. 

The Multicom Pro-XL MDX4600 gives you 4 channels of first-class dynamic
control in a single rack space. With a multitude of new features like the
advanced program-adaptive expander gate, extensive metering plus a variety
of configuration options, the Multicom Pro-XL puts a lot of dynamic processing
power in your rack.

Features
Switchable IKA (Interactive Knee Adaptation) program-adaptive compression
circuitry combines the advantages of hard-knee and soft-knee characteristics
IRC (Interactive Ratio Control) expander/gate circuitry for virtually inaudible noise
suppression
Switchable dynamic enhancer for brilliant, lively audio even with heavy compression
IGC (Interactive Gain Control) peak limiting circuitry combines clipper and program
limiter for reliable and inaudible protection against signal peaks
Switchable low contour filter prevents "pumping" due to low-frequency dominated
compression
Stereo couple function selectable for channels 1/2 and 3/4
Ultra low-noise 4580 operational amplifiers and state-of-the-art THAT¬ VCA's
Separate 8-segment LED meters for input/output levels and gain reduction
Selectable operating level (+4 dBu/-10 dBV)
High-quality detented ALPS¬ potentiometers and illuminated switches
Servo-balanced inputs and outputs with ? in. TRS and gold-plated XLR
connectors
Manufactured under ISO9000 certified management system