Drawmer DS201 Dual Channel Noise Gate
Last Update 06-11-2015
The Drawmer DS201 is a dual channel noise gate with variable frequency
detection and transient control. It is designed to improve
signal-to-noise ratio of
particularly noisy signals such as live vocal mics or the neighboring
mics
on the toms of a drum kit. Another one of those bargains I found
in a music
store that I frequent but if you buy a used one be warned that the
3-way OUTPUT switches go bad with age and frequent use (see
below). Drawmer dynamic processors are very
transparent high fidelity devices and are desireable pieces in the pro
audio industry, so it's not every day that you find used Drawmer gear
in mom-n-pop music stores. A gate can be a real handy tool for
cleaning up mixes - a live drum kit often has drum heads that are
resonating at sympathetic frequencies ("ringing"), and reducing these
ringings go a long way to keeping the mix from getting muddy.
There's a pretty comprehensive set of controls for
each channel. Configuring a gate is known as tuning and involves
adjusting the trigger, then
the envelope, then the transition. The best approach
is to auto-loop a section of interest, especially with wide dynamic
response (in the case of a live show, a stagehand repeatedly plays the
instrument during soundcheck), and play each channel in isolation while
alternating between bypass and active (and hence the reason why the
OUTPUT switches go bad). Start with the threshold
at 0dB, Key Source switch to INT, LF Key Filter at minimum, HF Key
Filter at maximum, attack at minimum, range at (-)60dB, and release at
one second. Set the OUTPUT switch on KEY LISTEN so you can
monitor the source going through the Key Filters. The status of
the gate is illuminated by the "traffic light" red-yellow-green LEDs,
red meaning gate is closed (audio is attenuated), green meaning gate is
open (triggered and fully passing audio), and yellow meaning transition
between open and closed. If the gate doesn't open while audio is
playing, then lower the threshold.
Now we're ready to adjust the trigger. The DS201 includes
frequency
conscious gating, which is essential if you want to gate only on
selected spectrum of a crowded signal. While listening to the KEY
LISTEN, rotate the LF KEY FILTER clockwise. You will notice that the
bass is gradually rolled off - this is the filter in action. As
you continue rotating clockwise, more bass rolls off and eventually the
gate stops triggering (the yellow/green LEDs either briefly illuminate
or not at all). This means you've gone too far, now go
counterclockwise until the gate works again. Then repeat the
adjustment with the HF KEY FILTER, only rotating the opposite
direction. The HF filter rolls off high frequencies.
Optimum settings of these filters will help isolate neighboring
instruments that have leaked into the microphones. Once you
dialed in the filters, then play with the THRESHOLD control for
consistent triggering of the gate.
While you are doing all this, toggle between bypass and active to
verify that the gate isn't prematurely cutting off (toggle OUTPUT
switch between BYPASS and KEY LISTEN).
If the internal Key Filters aren't doing the job, you can use the rear
panel Key Input with the filter or processor of your choice. A
dedicated key
input on the back panel via a 1/4" jack is normalled to the audio input
and is configured as a TRS with ring carrying send for the source
material and tip carrying return signal. You use this as an
"insert" where you can EQ the sidechain audio. The Key Source
switch needs to be set to EXT.
Sometimes a neighboring tom drum will cause a false trigger that no
amount of fine tuning will fix. Either you live with it or you
re-record the part with better mic placement.
With triggering done, we move to adjusting the envelope. When the
gate is no longer triggered, the gate holds open by the time specified
by the HOLD setting, then closes at the time rating by the RELEASE
setting. You want to listen to the bypassed source to make sure
that the Hold and Release settings generate nearly the same release
tail of the original. You are of course free to define your own
release tail. The yellow LED indicate that the gate is in HOLD
transition. For tom drums these controls go a long way to masking
the gate operation, for you don't want it too obvious that the gate is
opening and closing. The ATTACK control governs how fast the gate
opens, this can give some extra control for really crowded
signals. With the envelope settings in place, you can see the
"traffic light" LEDs operating in kind.
Now we move to adjusting the transition. The RANGE control
governs how many dBs the gate is attenuating when it is closed.
You can set it all the way to (-)60dB for nearly complete pinchoff of
audio, but if your other settings aren't optimized this can result in
"chattering" which is rapid open/close of the gate. Sometimes you
need to re-adjust the HOLD setting to eliminate chattering. You
don't always need 60dB of attenuation, as smaller amounts may work
fine. Adjust to taste.
Set the OUTPUT switch to GATE, and you'll hear the result.
The DS201 can also be used as a ducker, whereby inserting a second
audio source into the rear panel KEY INPUT jack will close the gate in
the presence of signal. This is good for public broadcast, where
the DS201 is used inline with the main audio playing background music,
then when an announcer starts talking the "ducker" automatically drops
the background music in level. In the studio you can also duck
other instruments at will. Haven't yet tried this.
Don't expect one setting to work for every song. You'll have to
re-tune the gate if the drummer replaces or re-tunes or wears out the
heads on his toms (and make a note on the track sheet for post
processing!). If the gain or level changes at the insert jack of
the console channel, you'll have to re-set the threshold. If a
player changes instruments during the track (IE alto sax with tenor
sax) then the gate settings may not work for the entire song.
Gating vocals during live performance is not recommended. Live
performance is a jungle of spurious signals leaking into vocal
microphones (especially if the mic is not in a fixed position), and the
singer(s) aren't focused on mic performance (especially after a few too
many drinks) as
they are in the studio.
You will be chasing audio gaps from non-triggering gates all night long.
If the DS201 is used inline with main stereo program material, the
Stereo Link switch optimizes dual gate operation to reduce "phasing"
artifacts when one gate is prematurely cut off.
Inputs and outputs are
electronically balanced +4dBu XLR
jacks, no -10dBv 1/4" jacks here.
These boxes do have one achilles heel - the 3-way OUTPUT toggle
switches will
lose their contact integrity with age (translated: the audio cuts in
and out, and wiggling the switch handle confirms the fault). I
had to
replace them on my unit. Unfortunately these are a custom switch
available only from Drawmer. They are a two pole switch, but not
the
on-off-on action - in the center position one pole is shorted to one
throw, but the other pole is shorted to the opposite throw. And
these
are PC board mounted switches so the replacement must be an exact
fit.
They are basically emulating the action of 3-way slideswitches.
You're
bloody unlikely (Drawmer is british, mind you) to find these switches
on any low quantity electronic supply vendor because of their custom
operation, and I can't find ANY OEM marking on the case of these
things. So Drawmer referred me to an authorized service center
here in
the states, which quoted me US$18 PER SWITCH not including shipping and
tax. This device has two total. Disassembly to get
to these switches is a bit of a PITA in that you have to disassemble
the front panel (including all knobs and mounting nuts/washers), then
you have to spread the sides of the case to get the switch assembly
clear of the unit. Not fun...
The DS201 has earned its place as the gate that gets the job
done. Almost every studio has a set of them, and they are the
gate of choice for professional sound reinforcement. These were
introduced way back in 1982 - very
few outboard effects last this long on the market, a testament
to how effective they are. This is the
"swiss-army-knife" of gates in that it offers (nearly) every control
for effective gating, and is one of the few gates that actually
works. Here's how well it worked: I don't have separate rooms in
my project studio so if I record a live band I have to deal with
leakage. You can only minimize it so much by exploiting the nodes
in the mic patterns. When the trumpet player wasn't playing, the
rest of the band could be heard in his microphone. I didn't want
phase issues to muck up the mix so I gated the trumpet mic using the
DS201. I use the four channel DS404 for simpler gating and
reserve the DS201 for the more problematic sources. The other
channel gated the kick drum, because you could hear the rest of the kit
even though the mic was inside the kick drum shell. It was a
challenge to gate but the DS201 did the job. Once you dial it
right, the DS201 gate is flawless.
Drawmer offers a single channel version in the API 500 format and a
simplified quad channel version called
the DS404.
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