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| INSTALLATION
PDM
PDM Operator's Manual Version 2.4a • September 2019
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When PDM first powers up, it looks for a signal on its digital input jack. If it sees one
at 48 kHz, it uses that sample rate to compute delay and ramping times. If it sees one
at 44.1 kHz—or doesn’t see a valid digital signal at all—it uses 44.1 kHz.
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If you’re processing a 48 kHz input signal, be sure PDM’s digital input has a 48
kHz signal
before turning the unit on
. Or power-cycle PDM once the signal is
available. This assures that PDM’s delay and timing displays remain accurate.
Under extreme circumstances, an intermittent digital input can cause erratic audio behavior.
If this happens, power-cycle PDM.
Digital Output
The digital output is always active on XLR-equipped units, letting PDM act as your digital-
to-analog converter: feed it an analog input signal, and use the digital output.
When set to AES/EBU via the
Audio
menu, this output conforms to IEC 958 Professional
(5v p-p, 110
Ω
balanced) on XLR connectors. Output is 16-bit PCM linear.
When set to s/pdif, the voltage and impedance switches to IEC 958 Consumer (.5v p-p, 75
Ω
unbalanced): connect signal to pin 2 and shield to pin 3 only. Do not connect pin 1 for s/pdif
operation.
If there is no signal on the digital input jack, PDM provides its own low-jitter clock at a 44.1
kHz sample rate. When there is a valid 44.1 or 48 kHz signal at the digital input jack—even
if analog inputs are selected—the internal clock and digital output are locked to it. But see
the warning about digital clocking above.
Analog Inputs
Information about input and output levels is on
page 27
. Unbalanced operation is not
recommended.
These are electronically balanced XLR female, pin 2 hot, with a load of 20k
Ω
: this makes
them compatible with all modern electronically-balanced outputs. If fed from a transform-
er-balanced output, we recommend bridging a 680
Ω
resistor between pins 2 and 3.
Analog Outputs
These are electronically balanced XLR male, pin 2 hot, designed to feed a load of 600
Ω
or greater.
PDM uses advanced algorithms to process signals in true stereo, with no smearing or vari-
ation in the stereo field during time compression. So while the analog outputs (and analog
inputs) are labeled
CH1
and
CH2
on the back panel, we assume you’ll be using them for the
left and right channels of a stereo pair and that’s how we’ve written this documentation.
However, you can also use PDM for dual, identical processing of two mono signals. There’s
no cross-talk.
Summary of Contents for PDM
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