Drawmer DS201 Dual Channel Noise Gate

pic of drawmer dl231

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.