Drawmer DS404 Quad Channel Noise Gate

drawmer ds404 small image

Last Update 06-11-2015

The Drawmer DS404 is a quad channel noise gate with variable frequency detection.  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.  When I bought this one off the bay, its operation was sporatic.  I eventually uncovered a flaky power rail that was caused by a bad capacitor following the bridge rectifier.  Beware of buying used music gear on ebay!

The DS404 is a compacted version of its famous brother the DS201.  To conserve panel space some controls were omitted but this is still a useful device.  I'll reach for the DS404 first, and if that doesn't solve the problem I will reach for the swiss-army-knife DS201.  I have one of each in my studio and this has been an efficient solution for space and practicality - six channels of gates, four basic and two advanced.  So far the DS404 has worked quite well for live drums.

Tuning the gate is described on my DS201 page.  The DS404 omits the Attack and Hold controls, but internally these are automatically set in the DS404 via program-sensitive circuitry.  A simplified version of the HOLD control is offered with the GATING switch offering hard and soft gating (similar to hard/soft knees of DBX compressors).  Soft gating is optimized for vocals and wind instruments, while hard gating is optimized for drums.  The Range control is replaced by a switch offering (-)90dB or (-)20dB of attenuation when the gate is off.  (-)20dB works better for live recording and minimizes "chattering".  The DS404 omits the "ducker" function of the DS201.

Each gate channel can be slaved to the one to the left of it, meaning that the gating, threshold, and envelope characteristics are controlled by the "master" to the leftmost channel.

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.  This device has four total, adding to US$72 not including shipping and tax.  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...