Lectrosonics DM84 User Manual download pdf (Page 7)

DM84 Installation Guide

Rio Rancho, NM

Microphone Number 2:

From Speciﬁcation Sheet: V

(min) = 9 V

mic

(max.) = 2 mA

= 15 V - (1k)(.002A)

= 15 V - 2V = 13 V

Since the calculated Vph is greater than the Vph from

the microphone speciﬁcation sheet, this is an accept-

able situation.

Audio Outputs

All outputs are a balanced differential conﬁguration, and

include an attenuator to reduce the signal to mic level.

NOTE: Using a Line Output with digital attenuation

applied with the Control Panel to achieve Mic Level

will result in added noise.

When the DM84 output is connected to an unbalanced

input, wire it as shown here.

DM Out

Destination

DM Out to Unbalanced Input

(2-Wire)

Shield

DM Out

Destination

DM Out to Unbalanced Input

(3-Wire)

Shield

Phantom Power

The DM84 supplies +15 VDC phantom power to the

audio inputs via a programmable switch and two 2 k

resistors.

+15V

Phantom On/Off

(from Micro Controller)

Gain Control

(from Micro Controller)

0, 10, 20, 30, 40, 50 dB

RF Filter

and

AC Coupling

2k ohm 2k ohm

To CODEC

Pin 2 or 4

Pin 1 or 5

Pin 3

PGA

Chassis GND Analog GND

Programmable Gain Preamplifiers with

Software Switchable Phantom Voltage

+15 VDC

PGA

Equivalent Circuit

Phantom On/Off

However, the true phantom power available at the

microphone may be less due to voltage drop across the

microphone itself (source resistance). In some cases,

the voltage drop may be enough to result in marginal

performance.

The following formula can be used to determine how

much phantom power will be available to a particular

microphone.

= 15 V - (1k)(I

mic

)

Where:

= the actual voltage available at the microphone.

(Microphone speciﬁcations list this as the mini-

mum recommended phantom voltage value. To

minimize problems, the calculated Vph should

exceed this value.)

mic

= the current draw of the microphone. (Refer to

individual microphone speciﬁcations for this

value.)

Examples:

Microphone Number 1;

From Speciﬁcation Sheet: V

(min) = 11 V

mic

(typical) = 4 mA

= 15 V - (1k)(.004A)

= 15 V - 4V = 11 V

Since the calculated Vph is equal to Vph from the

microphone speciﬁcation sheet, this is a marginal situ-

ation.

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Lectrosonics DM84 User Manual Page 7

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