|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.