CTP Systems dBbox3 User manual

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dBbox3
the manual
version 4 firmware

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Introduction - version 4 firmware
The dBbox3 is an evolution of our original dBbox designed primarily for use by sound
and audio installation engineers. The unit is fitted with a powerful digital signal
processor and separate microcontroller providing huge flexibility for future firmware
updates. The unit allows monitoring, metering and generation of both stereo
analogue and AES/EBU audio from a pocket sized unit. The dBbox3 includes a simple
five button menu interface to make any test as simple as possible. With the dBbox3
you can listen to and meter AES/EBU at many sample rates, analogue line and
microphone level signals with or without phantom power. The unit can analyse
sample rate, bits, status word and errors. It can send tone at various levels and
frequencies, send microphone input to analogue line or AES/EBU output at 48kHz or
96kHz, test phantom power, test MIDI transmit and receive, read and generate
linear timecode, generate up to 80mS of delay and it even has a built in torch.
dBbox2 to dBbox3
Several ‘under the bonnet’ hardware changes have been made on the transition
from dBbox2 to dBbox3.
The unit now has a more efficient power supply for longer battery life. There is also
an auto switch off system. The accuracy of the test timecode generator has been
improved and the cable tester now also tests the XLR earth wire. Improvements have
been made to the MIDI circuitry and we have added a LED ‘torch’. We have
increased the loudspeaker volume and other improvements have been made for
more flexibility with future firmware updates.
Some general information
The battery symbol on the top right of the display shows if you have enough battery
power for the current function. A solid block is a full battery. The dBbox3 has an
intelligent battery management system that switches off all electronics not in use for
a particular test. Different functions use varying amounts of power, generating
phantom from a 9 volt battery uses a lot of power and should be avoided for
extended periods unless on external power. The unit may be made to switch off
automatically if not used for a selectable period of 1 to 127 minutes.
When on external power (via the mini USB connector) the battery symbol will
change to USB.
Press < and > together to toggle the LCD display backlight on and off.
Inserting a jack into the ¼ inch or 3.5mm headphone socket will cut the internal
loudspeaker. Press Select and the Up button for one second to switch the LED light
on. Press again for one second to switch it off.
Meter scale may be selected to either PPM or VU for analogue inputs and PPM,VU,
-18dBFS or -20dBFS for digital inputs.

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At any point in the menu system pressing Vol- and Vol+ together will return you to
the main top menu.
When the volume is adjusted a ‘slider’ display will appear with visual indication of
the current volume setting.
Using the menu system
Any menu item without > next to it is a selection. Just highlight the required line and
press ‘select’ to jump to the function.
Any menu item with a > next to it allows a selection of various parameters or
choices. Simply scroll up or down until your selection is highlighted, then press the >
key, the highlighted area will move across to the right. Press the up or down keys to
scroll through your choices, all changes are instant. To return to the main menu just
press either < or ‘select’.
For example: to listen to a phantom powered microphone on the internal
loudspeaker:
Switch on the dBbox3, you are now on the top menu. Use the up/down keys to
highlight ‘Input”. Press the > key to move the highlighter to the right of ‘Input’. Press
the up/down keys to scroll through the possibilities:
Analogue
AES BNC
AES XLR
SPDIF BNC
Off
When ‘Analogue’ is highlighted press either the < key or press “Select”. The highlight
will now move back to ‘Input’. Press select. You are now in the analogue input menu.
Press the down key to highlight “Gain”. Press the > key and the 0dB gain setting will
be highlighted. Use the up/down keys to adjust the gain setting (+70dB to -10dB in
1dB steps) . The setting will move just by 1dB then speed up if the button is held
down. Now press either < or “Select”.
Scroll down to “Phantom” and press the > key. Press either up or down to switch
phantom on. If you have plugged a phantom mic in and put in enough gain the mic
will be heard through the speaker and will be metering on the display.
To switch off the mic amp press “select” or the < key and scroll up to exit, then press
”select”. you will be returned to the top menu. Alternatively just press the Vol+ and
Vol- keys together.
The menu system really is easier to use than it is to describe.

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Audio Inputs
Access to the various facilities will be described as for example:
Input> Analogue Gain > Where analogue input is selected and we are
dealing with the gain settings.
Analogue Inputs, metering and monitoring
On the analogue input page it is possible to listen to and meter mono or stereo
analogue signals using PPM or VU metering (as selected in Setup) with a stereo
phase meter and, for testing microphones, to apply phantom power.
Input> Analogue Gain > Gain range -10 to +70dB
Input> Analogue Phantom > Phantom power (both inputs) on or off
AES/SPDIF Inputs, metering and monitoring and analyzing
All digital inputs are essentially the same apart from the connector in use, voltage
levels and impedance. They all use the same display page so will all be described
together. Input metering may be 18dBFS, 20dBFS, PPM or VU and includes a stereo
phase meter. The unit will auto switch sample rates in the range 32kHz to 96kHz.
Input> AES BNC
Input> AES XLR
Input> SPDIF BNC
The examples will use AES BNC.
Input> AES BNC Listen > Select to listen to left, right or both
Audio channels.
Input> AES BNC Errors This lists any errors that may occur on the
Digital signal. Checks are made on:
CRC Q subcode
CRC channel status
Unlock
Data validity
Biphase encoding
Parity
With no signal input some of these errors may still show as “OK’ as there is no signal
to analyse or compare.

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Input> AES BNC Errors type> loop or sticky
When set to “Loop” any errors
are continuously monitored so a brief error may not be noticed. When set to
“sticky” an error once set will be continuously displayed even if the signal has
recovered from the error.
Input> AES BNC Ch.Status Shows the channel status of the
AES signal. Possible readings are:
Sample rate Sample rate is calculated directly from the incoming clock.
Possible displayed values are 32kHz, 44.1kHz, 48kHz, 64kHz,
88.2kHz, 96kHz, 176.4kHz and 192kHz. Any other sample rates
will be displayed as ‘???’.
Audio bits Possible readable values 16 bit, 20 bit, 24 bit.
Emphasis On or off.
Generation Original or Copy
Copyright Yes or No.
Format Possible data types PCM, IEC61937, DTS_LD, DTS_CD.
Only while reading channel status some sample rates may sound distorted through
the loudspeaker or headphones as it’s necessary to switch off some synchronising
functions to efficiently calculate the sample rate.
Input> AES BNC Stat.word
This displays the first five (and most important) bytes of the AES status word in
binary format.

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Audio Outputs
All available output signals are the same for analogue, AES and SPDIF signals so will
be described together. Analogue signals go up to +12dBu and digital signals up to
0dBFS.
Output> Analogue
Output> AES BNC
Output> AES XLR
Output> SPDIF BNC
Audio Output Menu
Tone Access the tone menus
Int.Mic Output the built in mic.
Noise Gen. Output pink or white noise
Frame Rate> This item will only show if digital output is
selected. Set to 48kHz or 96kHz as required.
These examples will use AES BNC.
Output> AES BNC Tone Type> Various types of tone output are
available:
Steady Continuous tone both channels.
GLITS Graham’s Line Ident Tone System. Used extensively for
Stereo line identification by the BBC amongst others.
EBU Cyclic break on the left channel, steady on the right.
Sweep Tone rising in frequency from 20Hz to 20kHz. Press Vol- or
Vol+ to start the sweep.
Left Left channel only
Right Right channel only

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Output> AES BNC Tone Level> Sets the output level of the tone from
-60dB to +12dB in 1dB steps. Settings
will be retained in memory.
Output> AES BNC Tone Frequency> Sets the frequency of the tone in third
octave steps from 50Hz to 20kHz.
Output> AES BNC Tone OP listen> Switch to ‘on’ to enable the internal
speaker and volume control for
confidence monitoring.
Output> AES BNC Int.mic Enables the user to speak to
analogue or digital outputs using
the built in microphone.
Output> AES BNC Int.mic Gain> Sets the internal mic gain
or effectively the level on the
outputs.Available settings +12dB,
+6dB, 0dB, -6dB, -12dB
Output> AES BNC Int.mic Limiter> Sets the threshold of the
limiter on the outputs.
Possible settings +12dB, +6dB,
0dB, -6dB, -12dB
Output> AES BNC Int.mic Output> Select to left, right or both
outputs.
Output> AES BNC Noise Gen.
Generates pink or white noise with a frequency range of 20Hz to 20kHz
Output> AES BNC Noise Generator Type> Set output of the noise
Generator to Pink or
White noise.
Output> AES BNC Noise Generator Level> Set output level of the
noise generator from -
60dB to +12dB in 1dB
steps. Setting will be
retained in memory.

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Output> AES BNC Noise Generator Output> Select to left, right or
Both outputs.
Output> AES BNC Noise Generator OP listen> Switch to ‘on’ to enable
the internal speaker and
volume control for
confidence monitoring.
Phantom power measurement
Phantom
Connect your phantom mic cable to Ana Out L. Phantom power will be measured on
both live and neutral (XLR pins 2 and 3) with a tolerance of +- 1 volt.
Four Wire Box
4 Wire Box
This feature is analogue only.
The dBbox3 will act as a four wire box using the internal microphone and speaker or
headphones. Listen to incoming audio and adjust the volume using Vol- and Vol+.
Up. If the speaker is in use it will cut on talk to prevent feedback, the headphones
will not.
Press the down arrow to speak on the internal mic. The microphone passes through
a limiter, the threshold of this limiter is set by
Output> Analogue Int.mic Limiter>
Signal conversion
In/Out/FX
This page allows conversion of audio signals with the addition of a limiter, gain
adjustment and equalization. Note that only 48kHz AES signals may be used in this
menu.
In/Out/FX Input> Available inputs Analogue, AES BNC, AES
XLR and SPDIF.

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In/Out/FX Output> Available outputs Analogue, AES BNC, AES
XLR and SPDIF
In/Out/FX Gain> Gain range will be +70dB to -10dB when on
analogue input (to allow for microphone
levels) and +12dB to -10dB when on digital
inputs.
In/Out/FX Phantm> Phantom power on/off. This item may only
be changed in on analogue input, else it will
Be forced to off.
In/Out/FX Limit> Switches the limiter on or off.
In/Out/FX Lim Th> Adjusts the limiter threshold.
Possible settings +12dB, +6dB,
0dB, -6dB, -12dB.
In/Out/FX HF> High frequency equalization. Range
-12dB to +12dB in 1 dB steps.
In/Out/FX Mid> Middle frequency equalization. Range
-12dB to +12dB in 1 dB steps. Centered around
1kHz.
In/Out/FX Low> Low frequency equalization. Range
-12dB to +12dB in 1 dB steps.
MIDI
The MIDI menu is broken down into two selections, MIDI analyse and MIDI notes.
MIDI Analyse
This is used to analyse incoming MIDI data and will display the MIDI channel number
(where applicable) , the MIDI message and the associated data.
The mode or type is shown as a text description (ie. ‘system common’) and as data in
blocked characters. MIDI signals may be passed through the unit so MIDI may be in
use while being analysed.

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MIDI Analyse Format> Selects MIDI data to be displayed in
hexadecimal or decimal.
MIDI Analyse Clear> Clears the screen
MIDI Analyse Oneshot> When the cursor is put over ‘oneshot’ the word
will change to ‘Waiting’. When the next MIDI
message is received it will displayed on the
screen and all following messages will be
ignored. This is useful for analysing a single
message when many messages may be passing
through. Press ‘select’ to clear the screen and
wait for the next message.
MIDI Notes
The MIDI notes page incorporates a MIDI transmitter and a MIDI receiver, they may
be used at the same time.
MIDI Notes Channel> Selects the MIDI channel to transmit
the note on. Range 1-16.
MIDI Notes Note> Selects the MIDI note number to be
transmitted. Range 0-127.
MIDI Notes Veloc.> Selects the velocity of the transmitted MIDI
note. Range 0-127.
MIDI Notes Send On Highlight this and press select to transmit
your MIDI note with ‘note on’ information.
MIDI Notes Send Off Highlight this and press select to transmit
your MIDI note with ‘note off’ information.
MIDI Notes Clr RX This will clear all data from the MIDI RX
Display ready for the next received data.
The MIDI RX area will display MIDI channel, note number and velocity of the last
received MIDI data. It is also displayed at the bottom of the page in hexadecimal for
analysis purposes.