The Qbox Goes Digital
The original Whirlwind Qbox was developed in response to requests for a simple test device that could generate signals or listen to signals, from mic level to amplifier drive level, at any point in an analog sound system.
The Qbox does that with a built in condenser microphone or test tone generator. It also "listens" with its built-in speaker or headphone jack. There are lights to verify the presence of phantom or intercom power and it can be used as an intercom, monitor speaker, setup generator, etc.
This unit supports the "Divide and Conquer" principle of troubleshooting. By substituting a Qbox at a problem point in a system, the user can easily verify signal presence or generate signal to determine if the problem lies farther down the line.
A New "Generation"
But what do you do when transmit audio in an AES/EBU digital audio system and nothing comes out the other end? How can you verify that the sending unit is actually generating good data, that the data actually contains audio or that a receiving unit is working properly? In fact, some digital systems are so quiet that it can sometimes be difficult to determine whether the system is even on at all. So, an AES/EBU digital system presents special troubleshooting challenges.
After gathering ideas from prospective users at trade shows and through email, Whirlwind engineers designed the AESQbox.
Three operating modes are selectable with a MODE switch:
- IN/OUT: Normal Mode
- PASS THRU: The digital audio received on the input is passed through to the output at the same sample rate so that the audio content may be monitored - the AESQbox is acting like both a "wiretap" and a "repeater"
- CABLE TEST: The analog audio is delivered to the AES output where you may then test your digital cable by connecting from the output back to the AES input, which should allow the user to hear the audio. This could also be described as a "self test" mode for the unit as well as to verify the integrity of the cable.
Digital Input Section
The AESQbox recognizes digital sample rates from 32 kHz to 192 kHz. A set of INPUT SAMPLE RATE indicators shows the following sample frequencies (in kHz): 32, 44.1, 48, 88.2, 96, 176.4, and 192.
A FAULT LED indicates problems with the data stream or hardware.
The digital audio is converted to analog and may be monitored via a high quality unbalanced, 1/8" TRS stereo line/headphone output or with the built in speaker. The channel monitored by the speaker is selectable with a switch.
Digital Output Section
The SOURCE switch allows selection of MIC, TONE or AUX IN (a 1/8" TRS stereo unbalanced jack) as the analog audio source.
- The built-in TONE generator provides 440 Hz for the left channel and 880 Hz for the right.
- The built-in MIC is an electret condenser type and feeds both the left and right channels.
- The AUX IN accepts line level stereo audio.
The analog signal is converted to AES/EBU digital and output via the male XLR jack and BNC.
One of the requirements of this design is to produce high quality audio. The headphone/speaker amp circuit has superb THD and noise specs and the line output will have near pro-quality sound. The idea is that this unit can also double as a quality, portable AES-to-Line or Line-to-AES converter.
The AESQbox operates on 4 AA size batteries or with a 6V external power supply (included). A POWER indicator shows that power is on and allows the user to assess battery condition - when it gets dim, time to change the batteries.
Inputs and outputs are both DC and transformer isolated to prevent inadvertent damage to the unit.
Those are the basics but as the case with the original analog Qbox, we're sure that users will find other tips and tricks for the AESQbox that we haven't planned for.