Analog audio has always been easy to check. There are hundreds, if not thousands, of types of test equipment to listen to and verify the quality of analog audio. Many of these devices are small and portable. When the audio changes to AES3 or S/PDIF digital audio, the quantity of easy-to-use, rugged and portable test equipment declines greatly. This is why I was glad that Whirlwind decided to introduce a digital version of its Qbox.
The AES Qbox is loaded with features that make it user friendly. It is also built to stand up to continuous use. Whirlwind designed the control surface to be easy to use, and it allows for quick and easy testing of AES3 or S/PDIF audio and cabling.
The AES Qbox has XLR and BNC inputs and outputs. It allows for three modes of operation. The in/out mode is the normal mode for the unit, and it simply allows audio to be received, analyzed and monitored. When in this mode the system locks the output to the sample rate of the input. The equipment can also generate AES3 or S/PDIF audio at multiple sample rates in this mode. Another mode is a pass through mode, which allows the unit to be used as a wiretap and placed in-line to monitor audio. The third mode is the cable test mode, which does exactly what the name implies. This mode also provides a quick method to test the AES Qbox itself. By simply connecting a short cable between the input and the output all the features of the unit, such as tone generation, the condenser mic and the internal speaker can be tested and verified.
Performance at a glance
Audio tone generator
Built-in speaker and condenser mic
Tests XLR and BNC digital audio inputs
Input sample rate from 32kHz to 192kHz
Operates on AA cells or power supply
Signal fault and sync indicators
When the unit is first powered on it runs through a self diagnostic check. The fault indicator, sample rate indicator and lock indicator will sequence on and off and then all the LEDs will flash on and off twice to indicate that the test is finished.
The unit can be powered from an external 6Vdc wall wart or four AA batteries. Battery operation makes the device totally portable and the battery life is respectable. In my experience, batteries have lasted four to six hours for continuous use. The one disadvantage is the lack of a rechargeable battery, but knowing this I carry some spare AA batteries when using the system at remote sites.
The unit supports sample rates on the input section from 32kHz to 192kHz. There is an easy-to-read LED display to indicate the incoming sample rate as well as a fault light to indicate any faults in the AES3 or S/PDIF stream.
The unit can generate audio at sample rates from 44.1kHz through 192kHz. The audio generator can provide three output signals. A stereo tone can be generated with 440Hz in the left channel and 880Hz in the right channel, the line-level stereo aux input can be routed to the outputs, and the unit also contains a built-in condenser mic that can be routed to the outputs. For monitoring audio, the device features a built-in speaker with a volume control. If better fidelity is needed, headphones can be connected to the 3.5mm TRS stereo line/headphone output.
Making the grade
The AES Qbox really proved its value as a helpful tool during some of the HD Radio builds that I have been involved in recently. The unit's ability to generate a tone is useful when testing a line before the programming chain is complete. The ability to generate audio with various sample rates and to monitor digital audio truly allows for complete testing at any point in a project.
I have also been using the system for troubleshooting. Digital audio chains are often so quiet that you are hard pressed to know if there is a problem. Even if no audio exists but AES sync is present, the visual indicator shows that the circuit is good because the sync lock lights.
The equipment also supports the “divide and conquer” principle of troubleshooting. By inserting a Qbox at a problem point in a system, the user can verify signal presence or generate a signal to determine if the problem lies farther down the line. I have also found the built-in condenser mic useful when I needed something other than tone to send down the line.
A manual provides clear explanations of the operating controls and their functions.
The AES Qbox continues to prove itself to me; I have used it extensively for a few months. It has been thrown in tool bags and used in some challenging environments, yet still works like it was new. I would recommend it to anyone who manages a digital facility and needs a simple yet effective way to install, test and maintain AES3 or S/PDIF cables.
Smith is president of JRS Broadcast Engineering, Monroe Twp. NJ.
Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.
These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.
It is the responsibility of Radio magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.