General Technical Description - Lectrosonics DSP4/4 DUAL Operating Instructions And Troubleshooting Manual

4 in / 4 out digital audio processor; dual 4 in / 4 out digital audio processor

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Table Of Contents

Table of Contents

The DSP4/4 is a 4in/4out audio signal processor that uses a state-of-the-art 32-bit floating point DSP (digital signal

processor). The unit provides powerful and flexible audio processing for all types of sound systems. Superior audio

quality is ensured by the use of 24-bit A/D and D/A converters.

The ADFE system on the DSP4/4 can find and eliminate feedback on each of the four outputs individually, allowing

multi-channel distributed sound systems to have the benefit of ADFE economically. The ADFE system works by

detecting feedback frequencies in the range of 100Hz to 5.6kHz. It places a 1/5 octave notch filter on the offending

frequency with 1/10 octave accuracy. The initial notch depth is 6dB, but is changed to 12dB if the same frequency is

still found to be feeding back.

Figure 1 shows the simplified block diagram of one channel of the DSP4/4. The gain for each input is individually

controlled. Following the input gain control is a 4 x 4 matrix with fully adjustable crosspoint gains. Each of the four

matrix outputs has a complement of 12 user-adjustable filters, a full function compressor, a limiter, audio delay, and

individual output gain control.

13 programmable pin connections on the rear panel allow control of a variety of functions on the DSP4/4. Set up as

"inputs," external pots or switches can be connected to provide input and output muting and/or level control, or used

to recall of any of the 8 available preset memories. 8 of the 13 pins can also be programmed as "outputs," which are

used to drive external indicators to signal the state of a programmable input. For example, a programmable output

can be used to light an LED as an indication of whether an output is muted or unmuted.

An RS-232 port is available to allow almost all of the functions of the DSP4/4 to be controlled either by a computer or

a dedicated control system (such as AMX or Crestron systems).

Input Channel (1 of 4)

Balanced Input