Test Drive: Dolby SR Model 363-SR/A

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The model used for this Test Drive was the Dolby SR/A model 363. The SR/A offers both SR and A type noise reduction. This particular model might be used most in a recording studio that uses both types of noise reduction. It is easy to switch from one to the other with the flip of a switch. For broadcast purposes, the model 363-SR with two No. 350 modules is all that is necessary for installation on one stereo recorder.

A typical setup at a station wanting to use SR on all carted music would have one 363-SR in the production room or dubbing studio and at least two 363-SR's in the control room. More than one unit in the control room is necessary if you're going to segue songs -- the machines cannot decode two encoded signals simultaneously. To avoid purchasing one unit for each cart machine in the control room, you could have two "banks" of cart machines with each bank going through one 363-SR. Once the units are installed, they can be hidden away and forgotten.

If you just wanted SR in the production room to clean up spots and promos produced in-house, it would be applied either to the multi-track machine or your mastering machine. The more inexpensive route is the latter; this way, only one 363-SR unit would be needed. Otherwise, you'd have to buy one unit for every two tracks on your multi-track. Once you mixed your spot or promo to 2-track, the SR would decode the 2-track mix on the way to cart. While tape hiss would be reduced, the on-air result wouldn't be nearly as noticeable as it would if the SR were on the cart machines in the production room and the control room as described in the previous paragraph. In this case, the SR in the production room would be hooked up to the cart machine instead of the mastering machine.

The Spectral Recording process delivers greatly increased headroom as well as noise reduction. SR can also be used on microwave links to improve signal transmission from studios to transmitters. Additional applications are available in television as well. Dolby sent us a forty-three page booklet listing hundreds of locations worldwide where the SR is being used. Though one 363-SR with modules (which accommodates only two channels) lists for $2,655, analog multi-track recording studios around the world have paid the price to get as close to digital as is now possible without actually buying new and expensive digital recorders. Converting an 8-track analog recorder to an SR processed machine would take four 363-SR's or $10,620, but if you compare total cost of an analog 8-track with SR to that of a digital 8-track, you'll probably find it more cost efficient to remain in the analog domain. Dolby offers an XP series of mainframes which hold up to twenty-four modules. This eliminates purchasing several 363's, but only becomes cost effective beyond ten tracks. It is less expensive to use 363 models for any setup of less than ten tracks.

Any way you look at it, Dolby SR appears to be the most effective noise reduction process available today. Expect it to crop up in more and more stations looking for a cleaner sound from their on-air studios where carts are still the primary source of music. A recent article in Radio World (Dec. 27, 1989) reveals satisfied users of Dolby SR at KQLD-FM in New Orleans. In the article, Chief Engineer Marc Musgrove writes: "Carts are no longer the weak link in the noise floor of our facility. Dolby SR has made cart noise inaudible in our application. We've also noticed the cart audio seems to be cleaner, more transparent. This is because, in addition to noise reduction, Dolby SR offers significant audible reduction of third-order harmonic distortion and modulation noise inherent in magnetic recording. We've not heard any negative side-effects of Dolby SR and have experienced no hardware failures with any of the units in use."

All inputs and outputs are balanced XLR type. 9-pin and 15-pin connectors are available for versatile remote control of the record/play functions. Overall dynamic range is 95db (clipping level to unweighted noise level) to 105db (clipping level to CCIR/ARM noise level). Frequency response is 20Hz to 20kHz. Color is black and lights are pretty.

For more information on Dolby SR, contact Kevinn Tam, Broadcast Technology Manager at Dolby Labs in San Francisco, (415) 558-0200.

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