Crown D-150 - Page 41

APPLICATION NOTE 3
PA ADAPTER PANEL INSTALLATION
FIGURE 1.
FRONT VIEW OF P-A ADAPTER PANEL
REAR VIEW OF P-A ADAPTER PANEL
The PA adapter panel is used to connect the aripiifier to obtain a
monaural 50-voilt balanced output line (see schematic, Figuie 4).
This is achieved by a precision push-pull transformer (inverted
signal to Channel 1). This results in over 150: watts of 50-volt
balanced output from the two output terminals in 16 ohms, over
250 watts wien tenninated- 8 -ohms.
The adapter pariel provides balanced inputs of 150 ohins, 600
ohms CT, and 5000 ohms bridging. Sensitivity is -Sdbm, 600
ohms.
Two switches are provided on the front panel for insertion ofhi-cut
and lo-cut filters. The characteristics of these filters may be al-
tered by changing internal capacitors in accordance with Figure 3.
The.P-A adapter. comes wired for. an amplifier input impedance of
10K. Therefore it will be necessary to parallel the 18K resistors
Gurmished with the adapters) across the arnplifier inputs as
described on a note with the resistors.
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_ FIGURE 3.
P-A ADAPTER FILTER RESPONSE
The output circuit contains a roll-off capaciter (C 101) which
should be used if matching transformers are ised on the output
line. This will. prevent large. low-frequency currents from flowing
into their-primaries.
matching transformers are not used, and the low-frequency in-
pedance (DC resistance) of the load is 6 ohms or greater, the
system nay be directly coupled to the amp output terminals, by-
passing C 101. Otherwise, use the output terminals on back of the
adapter panel.
To ensure maximum output (without premature clipping) both
amplifier jevel controls.must be full- CW.
FIGURE 4,
P.A ADAPTER SCHEMATIC