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Loaded Phantom Voltage
When you plug a microphone into a phantom
power supply, the supply voltage drops due
to the load of the microphone. The higher the
current drain of the microphone, the more the
voltage drops.
The loaded phantom voltage is the phantom
voltage available when a microphone is plugged
into the phantom supply. You can calculate
the loaded phantom voltage for the PH-1A as
described below:
For AC powering, the loaded phantom voltage
is:
E
= E
- RI
L
U
where
E
= loaded phantom voltage
L
E
= unloaded phantom voltage (30.7V with
U
Crown PS-24 AC/DC adaptor)
R = 983 ohms (typical internal resistance of PH-
1A when used with an AC/DC adaptor)
I = current drain of microphone in amperes.
For battery powering, the loaded phantom
voltage is:
E
= E
- RI
L
U
where
E
= loaded phantom voltage
L
E
= unloaded phantom voltage (18V with two
U
9V batteries)
R = 743 ohms (internal resistance of PH-1A
when used with battery powering)
I = current drain of microphone in amperes.
Architects' and Engineers' Specifi cations
The model shall be the Crown PH-1A. It shall be
a single-channel, battery or AC powered, 17- or
24-volt phantom power supply for condenser
microphones.
With AC power, the supply shall provide 24V
DC nominal loaded voltage on pins 2 and 3 with
respect to pin 1 of the microphone input con-
nector. With battery power, it shall provide 17V
DC nominal loaded voltage.
The supply shall include suffi cient hum fi lter-
ing for extremely quiet operation, and shall be
transformer isolated. If AC power fails, the bat-
teries shall automatically take over. The Crown
model PH-1A is specifi ed.
Warranty
Crown professional microphones are guaran-
teed against malfunction for a period of three
years from date of original purchase. See
enclosed warranty sheet for additional informa-
tion.
Service
If the unit fails to operate, plug your AC/DC
adaptor into a 120V AC power outlet and mea-
sure its DC output voltage between the tip and
sleeve of the
inch (3.5 mm) phone plug. You
1/8
should measure at least +24V DC on the phone-
plug tip with respect to the phone-plug sleeve.
If the AC/DC adaptor is working correctly, plug
it into the phantom supply. Measure the DC
voltage between pins 2 and 1 of the microphone
input connector. With no microphone plugged
in, you should measure at least 24V DC. If not,
return the PH-1A to Crown's Service Dept.
PH-1A
If both the AC/DC adaptor and phantom supply
are working correctly, check your microphone
cables and batteries.
Also check your microphone data sheet under
"operating voltage" to make sure it will operate
on the voltage supplied by the PH-1A.
If service is required, return the unit in its origi-
nal packaging to: Crown Factory Service, 1718
West Mishawaka Road, Elkhart, IN 46517-
9439. A Service Return Authorization (SRA) is
required for product being sent to the factory
for service. An SRA can be completed online
at www.crownaudio.com/support/
factserv.htm.
For further assistance or technical support call
800-342-6939.
Crown International
1718 W. Mishawaka Rd.
Elkhart, IN 46517-9439
TEL: 574-294-8000
FAX: 574-294-8FAX
www.crownaudio.com
®
©
2008 Crown Audio
, Inc. Specifi cations subject
to change without prior notice. Latest information
available at www.crownaudio.com. Crown and
Crown Audio are registered trademarks of Crown
International. Printed in U.S.A.
6/08
103292-9
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