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Reviews Categories | Microphone Equalizers & Transmit Audio Accessories | dbx 286A Microphone Processor Help


Reviews Summary for dbx 286A Microphone Processor
dbx 286A Microphone Processor Reviews: 2 Average rating: 3.5/5 MSRP: $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
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N6PRX Rating: 5/5 Oct 26, 2008 17:14 Send this review to a friend
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: 2/5 Jun 8, 2008 03:29 Send this review to a friend
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.
 


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