TOA D-901 US User Manual

Digital Mixer

D

Perfect to take the important audio role in AV-based presentation systems,

the D-901 Digital Mixer features a compact,

modular design with a 12 in/ 8 out configuration for

a variety of source equipment, with automixing,

feedback suppression, equalization, 16 memory presets and

full remote control capability.

-

901

High-resolution sound quality and rem
all-in-one modular digital mixer.

D-901

Ready for any requirement.

The new TOA D-901 Digital Mixer is a fully modular, cost-effective
digital mixer featuring a 12-input, 8-bus, 8-output channel
configuration (12 x 8 matrix) with easy operation that can be
expanded as applications require.

All-in-one design.

The compact D-901 is just 3U-sized but incorporates several of
the most important functions. These include a digital mixer,
feedback suppression, auto mixing, parametric EQ,
compression, delay and echo. Its remarkable operational scope
allows it to do the work that conventionally requires several
different pieces of equipment, providing a cost-effective solution
that is perfect for any requirement.

Feedback suppressor.

This sophisticated and TOA proprietary function automatically
processes feedback at certain frequencies through constant
monitoring then automatically attenuates only the precise
problematic frequencies, keeping the audio sounding natural.

Automatic mixing function.

The D-901's automatic mixing function adjusts input level
automatically to make operating easier. It features smart Number
of Open Microphones (NOM) attenuation that sets the gain for
all microphone inputs according to the number of microphone
inputs utilized. This allows satisfactory levels to be set without
feedback problems. A "Ducker" function operates when an input
channel is open, to enable that channel's priority to initiate the

low channel signal that will attenuate the other channels.

Sound processing.

As a full-featured digital mixer, the D-901 incorporates several
useful built-in functions to ensure maximum performance without
needing other equipment. A compressor can be switched in to
reduce the dynamic range between the smallest and largest
signals, preventing amplifier clipping at high levels. The flexible
crossover function allows setting speaker crossover points and
filter slopes to optimize multichannel speaker systems. Full
equalization and filter setting configurations can be saved in up to
sixteen memories for instant recall. The time delay function
can be used to align remote speakers.

Ergonomic control layout.

Convenient front panel controls and display make it easy to
perform all functions and confirm parameter settings without
requiring a PC. Another advantage is the ability to store up to 16
sound parameter setting configurations in memory for instant
recall when required. These include crossover, EQ, filter slope
settings, time delay and other parameters. Control settings can
also be locked to prevent unauthorized tampering.

Wide application scope and remote control
ability.

The D-901 can be externally controlled with an external signal
trigger or the RS-232C port on the back panel which enables the
D-901 to easily interface with external equipment.

Note: The D-901's heatsinks and aircooling are located at the bottom of the unit,

requiring a perforated ventilation panel to placed directly below the unit
when rack-mounting is desired.

ote control capability in a compact,

Compression

All audio below a selected threshold is allowed to pass while
audio above the threshold is compressed, reducing the dynamic
range of the loudest sounds. This prevents signals from clipping

and distortion.

Feedback Suppression

Conventional suppression

Manual cancellation of feedback is
imprecise as filtering problem
frequencies affects neighboring
frequencies as well. This tonally
impacts the signal and often results in
audio that does not sound natural.

TOA feedback suppressor

This proprietary technique works by
automatically detecting the frequencies
where acoustic feedback is occurring.
Once these frequencies are detected,
the suppressor automatically sets
precise notch filters that drastically
attenuate just those those frequencies
with accurate pinpoint filtering.

Audio signals are therefore minimally
affected because only the problem
frequencies are attenuated to negligent
levels through the suppressor's action.

Gain is increased

Level at which

Gain

Microphone gain is increased to induce
feedback so that feedback susceptible
frequencies can be located.

Gain

Microphone gain is automatically raised
till feedback is induced.

Gain

Using a continuously variable filter
makes it possible to insert filters at
different frequencies.

feedback is likely
to occur

Gain is increased

Level at which
feedback is likely
to occur

Feedback points

273Hz

Frequency

Frequency

734Hz

Frequency

(feedback most likely to occur point)

Gain

Feedback is filtered and eliminated as
soon as it starts. The intensity of filtering
required will impact tonal characteristics
resulting in altered sound.

Gain

When feedback is detected, do not increase
gain. Staying at the same gain setting, start
to look for other feedback-susceptible points
across the entire frequency range.

Gain

For example, accurate pinpoint filters
are set at frequencies of 273 Hz and
734 Hz.

level

Input signal

First peak

Level at which
feedback is likely
to occur

First filter

Searching for the points at which

feedback occurs.

Filter insertion

273Hz

Frequency Frequency

Level at which
feedback is likely
to occur

Frequency

734Hz

Frequency

level

threshold

level

time

Repeat

As microphone gain is increased and
feedback occurs, a filter is inserted at
that point.
This step is repeated as many times
as the number of filters required to be
inserted to eliminate feedback.

Setting filters

Level at which

273Hz

feedback is likely
to occur

Frequency

734Hz

Frequency

Gain

Because filters are simultaneously
inserted at all detected feedback points,
there is minimal impact on tonal
characteristics.

Precise elimination of feedback

frequency components.

Gain

Since dividing filters are not used,
sound quality does not deteriorate.

Output signal

Resulting characteristics

Original acoustic characteristics

of the room

Gain

A space’s acoustic characteristics
that have been altered by filtering

The acoustic characteristics are now
radically different from the original,
resulting in sound with little resemblance
to the original sound.

Resulting characteristics

Original acoustic characteristics

Gain

Flat equalization eliminates acoustic
anomalies to allow clear PA reproduction.

time

of the room

Flat response

Frequency

This method has the
least effect on audio

quality and allows

more natural-sounding

audio.

D-901 PC Software

The D-901 comes standard with dedicated
software to assist in D-901 system
configuration, parameter setting and general
setup using a PC. The software features
menu-driven operation with an easy to
understand GUI. The software offers
comprehensive control over virtually every
possible function. For set up these include
crossover slopes, combinations, and storing
crossover configurations. For operation,
menus offer dedicated pages for viewing and
adjusting matrix, trim, EQ, compression,
automix, gating, filtering, delay, echo and
feedback suppression settings as well as
mic/line input modules and many others.
Presets can configured and stored for
immediate recall when desired. In addition, the
software allows determining user level as well
as preparing the D-901 for remote control.
Lastly, a full assortment of protection functions
can be utilized.

*Download installation program from TOA's homepage

(http://www.toa-products.com/international/) and save it
to the desktop.

Input/output Gain Compressor/Limier/Noise Gate

Crossover Delay