Internal Configuration And Control - Crest Audio CPA Manual

switch has been set to the 'lift' position, then the shield on balanced input lines
should be grounded at one end only (usually the signal source).
13-14. Balanced 1/4" (TRS) & XLR Input Connectors.
These connectors accept input signals on balanced TRS and XLR input plugs.
See the figure at the left for information on polarity. Connectors for each chan-
nel are in parallel; the unused connectors may be used for "loop through" con-
nection to other amplifiers.
NOTE: Unbalanced "Tip/Sleeve" plugs may be used with the balanced TRS
"Tip/Ring/Sleeve" connectors. The "ring" terminal or negative input will be con-
nected to ground internally. When using three-pole ('stereo') TRS connectors, make
sure that the ring connection is made either to the cold (–) output of the source
equipment, or to ground. Incorrect connections may cause a 6dB loss in level.
15. Fan Inlet Ports & Filters.
Cooling air enters the amplifier through the fan inlet ports located on the rear of the amplifier chassis.
Be sure not to block these ports when installing the amplifier or other associated equipment. Air must flow unim-
peded through these ports. Fan filters (removable without tools) are provided to minimize entry of dust and dirt.

Internal Configuration and Control

Input XLR Polarity
CPA Series amplifiers are supplied standard with the XLR configured as "Pin 2 hot" (+). On models , CPA400,
CPA600, CPA900 and CPA1200, an internal jumper makes it possible to alter the amplifier to "Pin 3 hot" (+).
NOTE: This jumper is NOT user configurable. Please consult your supplier or local Crest Audio service
center if you wish to have the input XLR polarity changed
On the CPA1800, an external XLR polarity switch is featured. (See Appendix E).
Input Sensitivity
The CPA Series amplifiers have a standard input sensitivity of 1.4 Volts for rated power at 8 Ohms.
Page 8 Crest Audio CPA Series Power Amplifiers
Models CPA400, CPA600, CPA900, CPA1200, CPA1800
Tip - Positive (+)
Ring - Negative (-)
Sleeve - Ground ( )
1 - Ground ( )
3 - Negative (-)
2 - Positive (+)