The Qbox Goes Digital
The original Whirlwind Qbox was developed in response to requests for a simple
test device that could generate or listen to signals, from mic level to
amplifier drive level, at any point in a 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 the total lack of hum and hiss can sometimes make it 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.
Following is a brief description of the AESQbox and it s functions. For a detailed description, you may download a detailed white paper
here.
MODE Selections
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 he 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.
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The built-in TONE generator provides 440 Hz for the left channel and 880 Hz for
the right.
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The built-in MIC is an electret condenser type and feeds both the left and
right channels.
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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.
Quality Audio
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.
Other Stuff
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.
