!USER GUIDES - DISCONTINUED PRODUCTS
12/8/2 and 16/8/2 Series 2 Six-Four-Two Series 2 12/2 and 16/2 Series 2 SLM 82 Stereo Line Level Mixer
DNG-One Dual Noisegate AB-1 Active A-B switchbox
12/12/8/2 and 16/16/8/2 Series 3
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12/8/2 and 16/8/2 Series 2
SLM 82 Stereo Line Level Mixer
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DNG-ONE
Dual Noise Gate - User Guide
In it's simplest form, a noisegate is an automatic on/off switch which will mute a signal when the volume falls below a preset level, reducing or eliminating unwanted background noise like hum, hiss, leakage from adjacent sound sources, etc. It has no effect at all on the sound when the gate is open, passing the signal and any background noise equally (when the noise will probably be masked by the music), but as soon as the wanted signal stops, the gate will close.
The DNG-ONE has a full complement of controls allowing flexible and sophisticated gating, and will provide excellent results in applications including live multitrack recording, sound reinforcement, broadcasting, live gigs and multi-microphone public address installations.
Connections
Power: Connect
the Eurolead mains cable into a suitable power supply - in the UK,
230 volts, 50Hz - and plug in the other
end
into the rear panel eurosocket.
Inputs: These
are unbalanced mono jack sockets, 20kOhms impedance, connect to the
signal source to be gated with a
screened
lead.
Outputs: Unbalanced
mono jack sockets, connect to a load of 600 ohms or more for maximum headroom.
Key:
Unbalanced mono
jack sockets, 10kOhms. This input allows the DNG-One's detector
circuit to respond to a signal
source
other than the audio that is being processed.
A noisegate would typically be used with a mixer, connected to and from a channel insert point (breakjack), across the stereo output, between a reverb unit and an auxiliary return, in line between an instrument and an amplifier, and so on. An internal signal flow diagram is printed on the top cover.
Controls and Operation
1) Threshold:
The gate
decides what is useful audio and what is noise by comparing the input
level at any one moment with a user-determined Threshold level.
Signals louder than the Threshold will be passed to the output,
signals not reaching the Threshold will be reduced or muted
(according to the Floor setting, see 5).
Turning the control left increases
the sensitivity, lowering the Threshold point; turning to the right
decreases sensitivity. In use, set the knob fully left, and
rotate to the right until the background noise no longer opens the
gate. This adjustment must be made with some care - if the Threshold
is too high, the start of the wanted signal may be clipped off.
Note too that increasing the level of the signal fed into the
gate has the same effect as lowering the Threshold.
2) Attack: This
control determines how quickly the gate will open once the input
signal exceeds the Threshold. A fast attack usually suits short
percussive sounds like a snare drum, handclaps, etc, and can enhance
the effect by adding extra emphasis to the very start of the signal.
Slower attack times are used with
programme material with a naturally slow 'rise time', like strings or
flutes. Special effects like a 'bowed' sound from a guitar can
be achieved by using an artificially slow attack, similar to riding a
guitar's volume control with the little finger.
3). Hold: This
can keep the gate open even after the input signal has fallen below
the Threshold level: only when the entire Hold time has elapsed will
the gate begin to close. If the input level rises above the
Threshold again during the Hold cycle, it will reset and start
counting once more from zero.
Rather than having the gate
chopping in and out again between, for example, every phrase of a
vocal or a solo, a longer Hold time may result in more natural
sounding gating by only closing the gate during long pauses. 2½
seconds of Hold time is available.
To achieve an effect like gated
reverb, the gate is triggered by it's external Key input fed by the
dry signal, with only the reverb signal passed through the gate.
By setting a shortish but noticeable Hold time (say 300msec)
and a very fast Decay time (see 4), the dry signal is followed by a
burst of reverb and then silence, just before the next signal sounds.
See also Floor (5).
4. Decay: When the Hold cycle is completed, the gate will close at a speed determined by the Decay control. Again, this should be set for the most natural effect when the gated signal is listened to in the context of the complete mix. As a total of 32 seconds of decay is available, automatic and repeatable fade-outs of complete stereo mixes are possible, with greater smoothness and precision than can be achieved when pulling faders down by hand.
5. Floor: It is not always a good thing to mute background noise completely, since a very noisy signal switched quickly on and off may sound more irritating and confusing than if it were left on all the time. So, adjust the floor control to allow a little of the natural ambience through whenever this will give a more natural result. The range covers -70dB (total shutdown) to -1dB (almost completely open). Start at -70dB, and slowly rotate the control until the best result is obtained. Gated reverb can also benefit from allowing a little reverb to remain.
6. Bypass: Use this switch to get an instant a/b comparison of the processed and unprocessed signals. When in the 'out' position (button pressed) the audio signal is routed directly to the outputs.
7. Key: The input detector is normally triggered by the signal being gated. Alternatively, it can be made to respond to an external signal, thus allowing the main signal to be turned on and off by another, independent signal (one that may have nothing to do with the sound being gated). As an example, a bass drum track could be replaced by a synthesiser sound by putting the synth through the gate, and using the bass drum signal to trigger the gate via the Key input; in other words, the bass drum is 'playing' the synth. Ragged bass guitar and bass drum tracks can be tightened up in a similar way by having the bass drum keying the bass guitar. White noise could be added to a snare drum, using the snare signal as the key. Gated reverb also makes use of the Key facility.
8. Key Filters: Quite
often a gate can be triggered erratically because the mic used is
picking up rather a lot of other ambient noise - like hi-hat on a
snare mic, guitar on a vocal mic, traffic noise in an outdoor
recording, for example. The solution to this is to tailor the
response of the detector to not respond to unwanted sound by using
the Key filters.
For normal gating the two filters
should be set fully left and fully right (25Hz and 34kHz), which
allows the complete signal to pass through. Settings other than these
(see 9) allow you to define precisely the audio band in which the
wanted signal is located, and thereby to exclude other parts of the
sound that might cause erratic gating. To take one of the above
examples again, setting the filters to only pass frequencies from,
say, 30Hz to 250Hz on the bass drum will prevent almost all of the
other sounds from the drum kit from interfering with the bass drum.
It is important to appreciate that the gated signal itself
will not be equalised by the filters in any way - only the detector
circuit hears (and responds to) the equalised sound.
9. Monitor: To hear what is happening when the filters are used, or to listen to an external Key signal, select 'Key' on the monitor button.
10. Link: When the gate is used on a stereo signal, such as a stereo keyboard or gating the output of a stereo reverb unit, press the Stereo Link button to prevent image shifting and to ensure perfect stereo tracking. When linked, both channels are triggered by channel 1, and whichever channel has the more sensitive settings (mainly the Threshold), will become the master channel.
11. Status: These leds give a visual indication of when the gate is open or shut, illuminating during the 'shut' mode.
Specifications
Input impedance: 20kOhms. Key
input impedance: 10kOhms. Output impedance:
600 ohms. Frequency response: 15Hz-20kHz ±
0.5dB @ 0dB. Max input level: +20dB (+22dBm) ref 1
kHz. Distortion: 0.02% ref 1 kHz @ 0dB. Noise:
open -85dB unweighted, closed -86dB unweighted. Low
key filter: 25hz-3.6kHz, 12dB/octave. High key filter:
200Hz-34kHz, 12dB/octave. Threshold: -44dB to
+20dB. Attack: 10 microseconds to 200 msecs. Hold:
8msecs to 2.5 secs. Decay: 10msecs to 32 secs. Floor
range: -70dB to -1dB. Connections: ¼
inch jacks, unbalanced. Power: 240V AC, 50-60Hz,
14 watts. Dimensions: 482w x 240d x 44h (mm). Weight:
4.5 Kilos.
Active A-B Switchbox
User
Guide
The AB-1 is a device for switching an incoming signal, usually from a guitar or keyboard, to one of two separate outputs. The re-routing is effected by stepping on the switch, but the audio signal itself is switched electronically, resulting in a near silent changeover.
All signal sockets are mono jacks. Plug your instrument into the Input socket, and connect the two Output sockets A and B to two channels of a combo, two different combos, two chains of effects pedals, etc.
The unit runs on an internal PP3 9 volt battery (not supplied), accessed by removing the lid. It is switched on and off by inserting a jack plug into the Input socket. Remember to remove the jack plug after use to conserve battery life. The DC input can also be used to connect an external 9 volt DC supply, this should be a regulated model to avoid hum and must be centre pin negative. It is not necessary to remove the battery, but, if a battery is not fitted, we recommend that the plastic sleeve supplied is left over the battery terminal clip to prevent possible shorting.
The led on each output will permanently indicate which channel is selected, and the 'low battery' led will glow when a battery change is needed.
Specifications
Frequency response: 20Hz-20KHz
±
3dB Input/Output
Impedance: 100Kohm/33Kohm
Channel Indicators: two led's Signal/Noise: -103dBu
Power: 9vDC battery or DC
input 9v, 100mA, neg. centre pin
Low
battery led: Indicates @ approx. 4.5v
MTR Ltd, Ford House, 58 Cross Rd, Bushey, Herts,
WD19 4DQ UK
Tel: +44-(0)1923-234050 Fax: -255746
e-mail: mtrltd@aol.com www.mtraudio.com
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