Field Report: Airtools 6100
Nov 1, 2005 12:00 PM, By Robin Cross
At KCUR we produce two one-hour live call-in talk shows every weekday. When I started in January 2004, I was surprised to find that they operated with no profanity delay. I immediately suggested that we purchase and install one. Because we are an NPR station and had operated for nearly 20 years with no delay, it was thought that we weren't in real danger. Then the famous Superbowl half-time show occurred and people realized that the FCC fines could put a serious dent in our budget. Then my suggestion was taken seriously. We tried a software-based option. It worked OK, but was problematic in that it depended heavily on the stability of the PC hardware. We started looking for alternatives. There were two products available that met our requirements. We needed to keep our air chain all digital. We selected the Airtools 6100.
It is a 1RU device with an IEC ac cord. There is no wall-wart.
The front panel interface is easy and I would say almost intuitive. The alphanumeric and bar graph display works with three buttons and a knob. The three buttons are labeled Previous, Next and Home. These navigate through the circular, single-level menu. When the Home button is pressed this display reverts to a bar graph of the audio passing through the unit. The knob selects the various choices for each menu entry. There is a numeric display of the delay time. In addition, on the front panel are the familiar switches for Exit, Start, Cough and Dump. When any of these functions are engaged on the front panel or remotely via the DB-25 remote control and indicators connector, the appropriate switch flashes. A bypass switch is the last switch on the front panel. This is a mechanical bypass relay in case of disaster.
Performance at a glance 24-bit audio
As many as 40 seconds of delay
User-selectable delay algorithms
Automation control interface
AES3 and analog I/O
The rear panel is a busy place because of the 1RU form factor. Three TC89 time code BNC connectors, a DB-9 RS-232, an RS-485, the previously mentioned remote control and indicators DB-25, an automation DB-25, a BNC word cock in connector and six XLR connectors for stereo audio in and out and AES3 in and out are all on the rear panel.
The 6100 was easy to install and interface with our Enco DAD system. Contact closures from the DAD wired directly to the remote control and indicators connector. This allows the delay to be entered on a time basis programmed by the DAD system. We enter the delay 10 minutes before the talk show starts. This allows the algorithm to have a full six-seconds delay by the time the show starts. The 6100 can be set for any delay from zero to 40 seconds in 0.1 second increments. We selected the Gap Detect and Catch Up algorithm, which for our format was the most seamless. The choices are Gap Detect, Gap Detect and Catch Up, Continuous, and Pitch Shift. The best way to select the algorithm is in the air chain. We used the AES3 inputs and outputs but also wired the analog input as a backup.
There are four user programmable SPDT form C relay contacts available. For complete control, there is a description of the functions available, protocols and syntax in Appendix D of the users guide. Because this has an embedded processor this is one powerful unit.
ParameterSettingInput Sourceanalog or AES/EBU Nominal Input Level-10dBu, +0dBu, +4dBu, +8dBu Nominal Output Level-10dBu, +0dBu, +4dBu, +8dBu Digital Input Syncinternal 48Hz, word clock, AES/EBU Delay Time0.0 to 40.0 seconds (in 0.1 second increments) Dump Lengthfifth, fourth, third, half, whole Algorithmgap detect, gap detect and catch up, continuous, pitch shift Delay Ratio10:1 to 40:1 * Bar Graph Modepre-delay, post-delay Automation Trim�300ms from Early to Late in 30ms increments Rear Serial PortRS-232 (DB-9) or RS-485 (3-pin euro) Serial Port Baud9600, 19200, 38400 Unit Number ID1 through 255 *- ratio controls the balance of delay build/exit speed vs. overall audio quality
Things that must be said
This is a professional unit and it has XLR type balanced connectors. It can be wired and the levels set for unbalanced wiring. It also uses AES3 connections. There is no provision for S/PDIF digital audio. The input source must be selected but the AES3 and analog outputs are always active. We used the analog output as the source to drive our mono analog line that backs up our T1.
With all the setup and connections, I cannot imagine a situation where it could not be configured. At KCUR it was easy to install and configure. Earlier versions of the firmware had some problems, but the latest version seems to be bug free.
There is an additional use for the unit. It can be used as the audio delay for HD Radio for the air chain. Because the delay can be set in 0.1 second increments, the delay can be precisely timed for the required HD Radio delay. This eliminates the need to route the AES3 audio through the HD Radio exciter.
We view this device as insurance. We hope that we never need to use it but we know that it is there when we need it.
Cross is the chief engineer of KCUR-FM, Kansas City.
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