Technical data

www.asti-usa.com ASTi DACS: Operation & Maintenance Manual (Version 4, Rev. B.1)

Line Level Device Connection: For most standard line level devices such as a tape player or

VCR, the audio output of these devices can be connected directly to the Waveform Synthesizer

input. Check the specs of the equipment, for the maximum output level of the equipment. Even if

the maximum output level is higher than the RIU or Waveform Synthesizer maximum input volt-

age, the actual audio output signal may never reach this level. Some equipment provide output

level adjustments which can be used to reduce the output signal level. External pads can also be

used to reduced signal levels. In most cases this will not be required. The use of isolation trans-

formers is recommended between the RIU and the line-level device.

Microphone Connection: In general there are four types of microphones which the user may

encounter. These include dynamic, ampliﬁed dynamic, condenser, and electret microphones.

Dynamic Mics: Dynamic microphones typically require 40 - 60dB of gain to bring microphone

signals to a suitable input level. When connecting directly to a Waveform Synthesizer the user will

need to set the channel preamp gains. Each Waveform Synthesizer input provides a preamp stage

with gain adjustment from 0 - 60dB allowing direct connection of the microphone to the DACS.

To set the preamp gain values, commands are inserted in the Model Builder start-up conﬁguration

ﬁle. Gains can also be set temporarily from within the Model Builder software runtime environ-

ment. Consult the Model Builder Reference guide for input gain setting command information.

RIUs have adjustable gains via jumper blocks on the RIU circuit card. Gains from 0dB to 60dB

may be set by installing the appropriate jumper. See the RIU conﬁguration procedure found in

chapter 5 or the conﬁguration information supplied with your RIU.

For long microphone cable runs (50 feet or more), a preamp may need to be installed close to the

microphone to boost the mic signal early and maintain a good signal to noise ratio and help avoid

cross talk problems. This often depends on the installation. Use of good shielded, twisted pair

cabling, with proper grounding can extend the cable length.

Ampliﬁed Dynamic, Condenser, and Electret Mics: These microphone types require “phantom

power”, which is a DC voltage level supplied on the microphone signal line. The current provided

is used for microphone element operation, preampliﬁer power or both. Microphone signal levels

for these microphones is typically much higher than that of dynamic mics. In some cases, little or

no additional pre-ampliﬁcation may be necessary.

Direct connection of these types of microphones to a Waveform Synthesizer input is not possible

as the card does not provide a phantom power source. For DACS with Waveform Synthesizers

only, the user will need to either provide the phantom power source, or install a commercially

available mic preampliﬁer with appropriate phantom power. ASTi’s AIU may also be used to pro-

vide phantom power.

RIUs (version 4.1 and later) have a limited phantom power capability. Resistor packs are used to

set the voltage level available to the microphone. The user may also use other commercially avail-

able phantom power adapters.