1316 Chapter 34
grammed and adjusted exactly the same as the first DSP.
If you suspect an all-in-one DSP, try patching from the
mixer directly into the system power amplifiers. Keep
the level down on the mixer and insert the mixer’s
input-channel high-pass filters to avoid damaging HF
loudspeakers. This is a crude method but should provide
some insight into the problem.
A second problem with DSP troubleshooting is that
the trouble may be improper DSP programming or
adjustment. For example, if a graphic equalizer module
has several adjacent filters reduced by several dB, it
may be necessary to increase the gain in the following
module to compensate. Then, if a high-level signal
occurs that’s outside the frequency range of those
filters, it may overdrive the following gain stage. It’s
not easy to troubleshoot this kind of problem because
you can’t insert real test equipment between the DSP
modules. However, many DSP units now include meters
and signal generator modules that can be patched into
system nodes for troubleshooting.Figure 34-80. Troubleshooting Part 2. Assumes that the problem is distortion or interruption of signal and the block diagram
flow is from left to right. Method is use of signal generator and tracer (a tape deck and powered loudspeaker may suffice) to
locate the faulty component.
Select signal source
and tracer.Move tracer farther right,
or go to 10.Yes Symptom is intermittent,
or problems are to the right
of the tracer.Is the
symptom
gone?Move source about half way
through system (to right),
inject signal, monitor with tracer.NoMove source farther left,
inject signal,
monitor with tracer.Yes Is the
symptom
gone?Move source farther right,
inject signal
monitor with tracer.NoYes
10Throw up hands.Replace or patch around
faulty component.Don't
care!
Go to 10.NoConnect source at system
input (far left), inject signal
connect tracer at system
output (far right), monitor
signal.Has the faulty
component
been found?