One of the advantages of working in a major market is that equipment manufacturers come to you to show off the latest products. Recently, the team from Symetrix/Air Tools visited Chicago to demonstrate the latest offerings in IP-controlled products. One particular item that caught the eye of the Clear Channel engineering department was the Air Tools 6200 dual voice processor. We were already familiar with the venerable 528E microphone processor — we have several of them in each of the 28 studios at our facility — so we were acquainted with the favorable performance-to-cost ratio of the Air Tools products.
A unique application
At the time of the demonstration, Clear Channel Chicago was heavily involved in launching HD Radio on each of our seven stations. We were looking for products to process an audio side-chain so that the jocks could hear a pre-delay simulation of what was going to air. The general consensus among the engineers in attendance was that the 6200 product was worth a try. Though it is specifically designed with microphone processing in mind, there was no reason it could not work as a stereo program processor. We liked the fact that it could be configured over the LAN using the provided software. We also liked the idea that the front panel controls, and there are not many, could be locked so that little fingers could not play.
A 6200 arrived just in time for the launch of one of the HD Radio stations, so I set it up and was able to quickly configure an IP address using the software supplied, a laptop PC and a USB cable to the front-panel USB port. General setup is possible using the front panel, but the USB was quicker. Once the IP address was set to an existing subnet on our LAN, I used the LAN to connect. John Boehm, Clear Channel Chicago's transmitter supervisor, assisted with the processing, and was quickly able to make the 6200 sound close to the PD's settings on the main processing. We did notice a bit of inconsistency from song to song, but that was to be expected when comparing a single band processor with a multi-band processor. The DJs, however, never noticed when we switched the 6200 online to their monitors. The product was a hit, so we ordered several more for the other stations. I will admit that we are not using the 6200 on all the stations, because aggressive main processing on two of them was hard to match using the single band AGC of the 6200. In those instances, we were forced to opt for a more expensive multi-band solution from another manufacturer.
Back to its roots
Performance at a glance
Dual-channel, single-band AGC processing
Real-time configuration via multiple means
Analog and AES-3 I/O
Recently, a staff addition to one of the stations necessitated the ability to day-part program the microphone processing in the studio. Everyone has his own idea of how he wants his voice to sound, and every voice is different and needs to be processed differently, especially when those involved have differing levels of mic technique. As I mentioned, we are using 528Es in the air studios, and they serve us well, but they are not programmable to change parameters on the fly. They also require security covers to keep the jocks from playing with the knobs. Enter the 6200. Because we were already familiar with the product, a quick order was placed for two units to handle the four microphones in the studio. Once again, Boehm was called on to do the setup. He was able to do a quick off-site configuration, once I placed the two units on the LAN, and the next day we installed them in the studio. While jacked into the 6200 USB port, with headphones on and sitting in the studio, it was a simple walk-through process to make a change. Before long, the smiles on the DJs faces told us that the settings were right. This procedure was followed for the balance of the day, and the following day we fine tuned it while Boehm was at one of the transmitter sites and on the phone with the studio. The front panel controls were then locked out, and the settings archived to a PC for later reference.
Software and connections
The 6200 truly is a software-defined product. The designer software comes on a CD and is also available at the Air Tools website. Configuration is accomplished by using a graphical interface. Configurable parameters include preamp gain, phantom power, output levels and a series of DSP modules. These modules may be rearranged by dragging and dropping the graphical block diagram in the desired order. Typical DSP modules include symmetry, high- and low-pass filtering, a shelving filter, a four-band parametric EQ, expander, compressor and AGC. Once a configuration is defined, it can be saved and loaded into a daypart scheduler to change to a different processing preset at a fixed time of day. The clock in the 6200 can be set manually or via a time server on the network.
Audio connections on the back panel include stereo (or dual mono) analog in and out, AES out 1 and AES out 2. Because the primary function of the 6200 is microphone processing, AES inputs are not provided on XLR connectors, but they can be accessed on a special RJ-45 jack called the Homerlink. This link can transmit four AES-3 mono channels and receive two AES-3 mono channels over a CAT-5 link. Specific applications are for integration with the Air Tools Studio Matrix system for crosspoint routing. Also on the back are RS-232 and Ethernet (10 Base T) ports for programming. A midi port is available for use with the optional Air Tools RC-1 controller, and a TC89/TC90 port for time code input. A Euroblock connector allows for RS-485 control using third-party products, hardware contact closure for remote bypass and two software-definable analog ports for connecting external 10kV pots for physical control of DSP functions. Finally, there is a standard IEC three-prong jack for power input (110Vac to 240Vac, 50Hz to 60Hz).
What can be improved
In configuring the units for microphone processing, we discovered that even though the front panel is software locked, the right combination of actions can unlock the panel. This is not documented, and I will not do so here because I don't want the jocks finding the secret. Although I understand the reason for this backdoor, I would like to see it a bit less easy to open. Also, I would like to see a software capability to disable the front panel USB port. I do not discount certain jocks from trying to crack the system by plugging their laptop into the port. Password enabling the software interface would provide the same level of security.
Overall, we are impressed. The unit sounds good as a voice processor, is configurable and provides enough presets to easily day part our processing. In addition, its versatility allowed us to use it in an unconventional application for pre-HD Radio delay processing for fake air fold back.
Wright is senior studio engineer at the Clear Channel stations in Chicago.
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