Test Drive: Radio Systems RS2 Noise Reduction/Phase Correction System

The decode modules contain the phase correction circuitry as well as the Dolby S decode circuitry. The encode modules obviously provide the encode circuitry. Both modules incorporate control circuitry utilizing a 500Hz cue tone which is recorded onto Dolby encoded carts and then detected by the decode module. In the "automatic" mode, this allows the unit to automatically switch back and forth from an "on line" state to a "bypass" mode, thus enabling the mixing of encoded carts with regular, non-Dolby recorded carts in the same cart deck. The RS2 engages the decode circuitry when the 500Hz tone is detected, and bypasses the decode circuitry once a cart is removed, stopped, or fast-forwarded, depending upon how it is installed.

The front panel of the encode card consists of nothing more than a bypass switch, input/output level controls for each channel, and LED level indicators for input and output. Two lamps indicate whether the unit is in the Dolby mode or bypassed. The front panel of the decode card has the same controls with the addition of an Auto Detect button which, when turned on, places the unit in the automatic Dolby detect mode described above.

Also on the front panel of the decode module is an on/off button for the phase correction system. This particular system uses single-ended technology and analyzes common channel material to detect a phase shift between left and right channels. The phase correction system will correct up to 90 degrees of phase error at 5kHz in real time. A green LED phase meter indicates the amount of phase correction occurring. If the center LED is lit, this indicates no phase correction. As the LEDs further to the left and right of center illuminate, this indicates phase correction up to plus or minus 90 degrees.

One final item on the front panel is a row of six LEDs connected to the power supply. These illuminate when the power supply is working properly and go out when there is a problem -- nothing more than a handy tool for troubleshooting.

The back panel of the RS2's mainframe is bare with the exception of the power cord and a fuse. All audio and control connections are on the backs of the encode and decode modules. All audio ins and outs are managed with a standard 9-pin connector, one for the stereo input and one for the stereo output. A third port, a 15-pin connector found on both modules, handles the connections to the cart machine's cue tone audio input and output for recording and detection of the 500Hz cue tone. This connector also handles several other control functions which enable the RS2 to function properly with cart machines.

We connected the RS2 to an ITC99B cart machine. Setup was very quick and simple. As with the 363-SR unit we reviewed a couple of years ago, we found the new S-type noise reduction to work exceptionally well. At normal listening levels, the tape hiss essentially disappeared. We conducted A/B tests with some voice tracks as well as some classical music and found no reduction in the crispness of the audio nor any audible distortion of any kind when playing back the Dolby encoded versions. We then handed the unit to our trusty technical advisor, Paul Strickland, and asked him to check out the specs on the unit. After a while, he returned and said, "it does just what they say it does!"

Speaking of specs, the ins and outs are balanced. Frequency response (encode - decode back to back) is 20Hz-20kHz. Overall harmonic distortion is at .5% maximum at Dolby level. Typical dynamic range using 7.5 ips tape is 90-95dB. Crosstalk between channels is better than -75dB, 20Hz to 20kHz.

As of Feb. 1, Radio Systems has dropped the price of the RS2 significantly. The mainframe, which houses the power supply and holds up to three encode/decode modules, dropped from $695 to $495, and the encode modules went from $695 to $595. The decode/phase modules remained the same at $595 each.

Yes, there are a lot of digital cart machines on the market now and in use at many stations. But the number of analog cart machines still in use is a much larger number. For many stations, the prospect of "going digital" is still in the distant future. Many stations are now playing CDs in the control room, but the commercials, promos, IDs, etc. are still being played from carts. In this case, a system like the RS2 is ideal for getting your promos, jingles, spots, etc. up to par with the music you're playing. For those stations still carting music, especially FM stations, noise reduction like the RS2 is practically a must. Furthermore, as we get closer to digital broadcasting, you'll HAVE to do one or the other -- go digital or bring in the best noise reduction money can buy.

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