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Reviews For: dbx 286A Microphone Processor

Category: Audio Accessories for Transmitter & Receiver

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Review Summary For : dbx 286A Microphone Processor
Reviews: 3MSRP: 199
Description:
Rack-mount microphone processor normally used in pro audio, live recording, and soundstage applications.
Product is in production
More Info: http://www.dbxpro.com/286A/286A.php
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0034
W6LBV Rating: 2019-07-09
Processing your speech Time Owned: more than 12 months.
At N6PRX’s recommendation (see below), made during an eyeball QSO, I bought a dbx 286s microphone strip for use in my home station. The dbx replaced a similar Behringer mike strip then in use; that change occurred about four years ago. The dbx has been in continuous service since then.

It is true that many of the speech processing “features” built into the dbx (and similar products) are now also included in the current generation of higher-end HF transceivers. But not all of them are replicated in the radios, and not to the same functional level as with the separate microphone strips. I chose to go with the external strip for the greater degree of control it provides.

In comparison with the Behringer, the dbx product has one critical additional feature: RF filtering on both its input and output ports! Using the dbx, this filtering has produced a major improvement in the fight against pickup and coupling of stray RF energy from the station transmitters into the modulated audio, where it can create “RF feedback.”

The dbx strip contains six major processing functions in a single one “rack-unit” tall (1 3/4 inches) chassis: mike/line level pre-amp and input level control, audio compressor, de-esser (minimizes high frequency audio speech hiss), enhancer (adjusts audio frequency group amplitudes), a noise gate (fully mutes the audio output when speech is absent), and an output level control. Two of the above dbx-included functions typically are not built into modern transceivers (de-esser and noise gate). There are an abundance of front panel LED indicators to monitor 286s operation, and several useful input and output ports on the rear panel. Not included is a dedicated audio multiband equalizer function.

The instruction manual which ships with the hardware is refreshingly written in standard US English.

The dbx 286 is designed to professional audio standards: balanced audio lines (two signal conductors and an independent shield/ground conductor) and it produces somewhat larger signal voltage levels than are used for home entertainment equipment. These professional audio standards are not difficult to implement in modern Amateur stations. Manufacturers of ham transceivers are gradually moving toward adopting balanced audio line mike inputs in their newest equipment, and various simple techniques are available for conversion of the balanced line audio to the audio input formats used in older ham equipment. (See N6PRX review, below).

As has been amply demonstrated, most modern HF transmitters are capable of transmitting “really good speech audio” if they are just supplied with same. There are no longer any mystery audio circuits or special “golden microphones” which uniquely make great ham audio possible. Quality, balanced, full range transmitted speech should be today’s “everyday standard.”

Nevertheless, it is always surprising when tuning the HF bands to hear (and to see, with an audio spectrum analyzer) many on-air SSB signals with deficient, to highly-deficient transmitted speech. Undoubtedly their operators do not hear the noticeably inferior signals that they transmit, and thus never attempt to improve them. The use of a mike processor, such as the dbx 286 or its cousins, plus a $25 modern dynamic microphone could solve this in short order. There’s no need for a Shure or Electrovoice broadcast microphone just for the 0.3 to 3.0 kHz bandwidth audio used in ham service.

However, the pairing of individual operator voices with individual ham transmitters produces audio results which are specific to the pair, and this means a requirement to “tune” the speech transmission system for each voice plus equipment combination.

ARS technology moves constantly forward, and we are certainly into the era of the use of speech processing for producing quality transmitted speech. The dbx 286 can make a great improvement in the “sound” of an Amateur transmission. It’s definitely worth the cost and bother to use this kind of system.

And, not the least significant point either, the professional audio market speech gear usually is less costly then the similar “ham market only” items. I own both types of gear, and I will be continuing and expanding my work using only the professional hardware.
N6PRX Rating: 2008-10-26
Works & Sounds Great! Time Owned: 6 to 12 months.
I have been happily using the dbx 286a for nearly a year with several microphones, the favorites being the Shure SM7B and Sennheiser 421MDII. Both the microphone input and the line level output from the 286a are balanced audio. Most amateur transceivers use an unbalanced mic input with a separate ground for mic audio. Those who understand this difference know that a simple center and shield connection to the rig will not do the job of connecting a professional grade microphone or preamp to the rig properly in most cases.

To correctly interface this preamp to my TenTec Omni-VII and Icom IC-7000 I use a homebrew switching box and two Radio Design Labs model TX-1A balanced to unbalanced audio line transformers. These transformers also provide DC isolation in addition to having adjustable output levels. The 286a balanced line output is connected to the transformer inputs in parallel at 10K ohms. More rigs can be interfaced to the 286a audio output easily this way. The unbalanced audio output from each of the transformer lines can be adapted to any rig mic or back panel input without the worry of ground loop hum or level issues.

Careful attention using a line level signal generator and scope to set the 'gain chain' levels from the mic gain all the way through the transceiver into a dummy load must be done first. Next do the audio eq and processing adjustments with the microphone properly set for *your voice*, listening for the desired output while monitoring, making sure not to overdrive anything. This process resulted in unsolicited excellent audio reports. Once the preamp is calibrated in this manner, one can use the TX bandwidth adjustments of the rig itself to change the outgoing audio characteristics from ESSB ragchew to DX cutting tone very easily. One can even go further with the preamp too but that's not usually necessary if the other steps were done right.

Properly setting up studio grade mic preamps and associated signal processing equipment requires experience so this may not be the right solution for everyone. Having said that, anyone with such a desire or experience, a good ear, and the ability to monitor your outgoing signal visually and audibly will find the results are excellent for everything from ESSB to DX work even with lesser microphones. I've tried the 286a with numerous recording and live sound professional microphones from a high end Neumann to a cheap Radio Shack plastic thing. The microphone preference and characteristics is of course an individual choice but the 286a worked fine with all of them.

I have other expensive mic pres that I use for recording purposes that do sound better in the recording studio realm however the dbx 286a preamp/processor is an excellent choice with the most needed voice features for our limited amateur radio 1.8-6khz bandwidth needs and it's at a great price point under $200.

Hands down the dbx 286a is a 5 star winner.

73 from N6PRX - Marty
W6DTW Rating: 2008-06-08
Doesn't do the job Time Owned: 0 to 3 months.
I recently picked up a used dbx 286A processor from Guitar Center for about $95. I had been looking for a piece of equipment to replace my existing voice processor; Voice Shaper (a software-based voice processor) running on a Dell D410 laptop. I'm sad to say that $120 later (for the processor and cables) the 286A doesn't even come close. Here's the story:

Conditions were bad during the test; a huge clump of thunderstorms north of Iowa--and the resultant static crashes--were really hitting wiping out 80M hard all night. In a way this was good, because I knew the processors simply *had* to work. I started off trying to make contacts with the dbx 286A, but nobody was coming back to me. I swapped in Voice Shaper on the laptop and made a contact right away; San Diego came back as did Vancouver BC and Colorado. I asked them to work with me on an A/B compare, then swapped back to the dbx. Nobody could hear me. Back to Voice Shaper, and once again I was given decent reports.

Per my peak-reading wattmeter the rig was making the same amount of power in both cases; about 200 watts. Since power in single-sideband is directly related to audio level, we have to conclude that the audio levels out of the dbx 286A *must* have been set correctly. What was the different between the two processors? Same mic, same audio output levels to the radio, same output power per readings on the wattmeter.

The only difference I could see was in the spectral distribution of the transmit audio energy. Voice Shaper has a graphic equalizer which allows me to constrain audio in the "speech intelligibility" range of 300 Hz - 3.3 KHz, and it also allows me to augment certain frequencies (such as the 1 - 3 KHz range) which carry the majority of speech information. The dbx 286A has a two-band "audio enhancer" but it's not frequency-specific, and in fact the manual states that the "high-frequency" enhancer is frequency-adaptive. Therefore I have to conclude that the dbx 286A is too wideband; it's putting out audio frequencies which don't contribute to speech intelligibility and on-the-air performance.

Looks like for now my software processor is here to stay.