Technical data

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

Audio Outputs

Waveform Synthesizer audio outputs are low impedance (<100!), single ended (unbalanced) out-

puts. Maximum analog output levels are approximately 6Vp-p into 600! or larger loads.

RIU audio outputs are low impedance (0.1! into an 8! load), differential (balanced) outputs.

Each channel is capable of supplying 1W RMS into a bridge-connected 8! load. If a single-ended

8! load is connected, the RIU will supply 250mW RMS.

Line Level Device Connection: As with the analog inputs, standard line level devices such as a

tape player or VCR, the audio input of these devices can be connected directly to the Waveform

Synthesizer output. Check the specs of the equipment, for the maximum input level allowed by

the equipment. Remember that the actual audio output signal from the Waveform Synthesizer or

RIU may never reach this level depending on gain levels set in both software and hardware. To be

safe however, the user may wish to scale the output gains by setting scaling factors in their sound

model itself. External pads can also be used to reduced signal levels. In many cases this will not

be required.

Headset and Speaker Connection: Headset impedances vary widely from headset to headset. In

general the Waveform Synthesizer and RIUs can drive a 600! headset directly, however, dynamic

range may not be satisfactory. Headsets down to 150! or below can also be driven, but generally

not to full scale.

As an example, most military headsets are very low impedance (typically 10 -20!) and require

ampliﬁcation. Users may also require headset amps if higher headset volume levels are desired.

Some users may ﬁnd that some of the commercially available 150-300! headsets are adequate

without ampliﬁcation. ASTi offers a headset evaluation service to assist customers with their

audio interfacing requirements.

Speaker channels will also require ampliﬁers between the audio output and the speaker. Good

quality, commercial stereo amps are excellent for this application. Audio outputs can be hooked

directly to most speaker ampliﬁers. To minimize ground loop problems, be sure to use balanced

inputs or utilize the ground lift capability on your ampliﬁer if available.

Audio Interface Unit

This device is no longer available as a production item, but supporting documentation can be

obtained by calling ASTi at 703-471-2104 or sending email to:

support@asti-usa.com

Cabling

For minimum noise, individually shielded, twisted pair cable should be used for all audio lines.

Shields should be tied at a single point to a good earth ground and in general should not be con-

nected to audio ground.

Of utmost importance is using a shielded twisted pair on the microphone line. Microphone lines

usually carry a very small signal and typically run next to the headset line which typically has a

much larger, higher current signal. The potential for additional noise and crosstalk is greatly

increased if proper cabling techniques are not used.