Studio Technologies 220 2013 User Manual

Page 39

Model 220 User Guide

Issue 5, February 2013

Studio Technologies, Inc.

Page 39

associated printed circuit board to the

enclosure. The interconnecting cables are

then used to link the card with the Model

220’s main printed circuit board assem-

bly. One end of the ﬁrst interconnecting

cable is plugged into the card’s 3-position

header that is labeled MIC. The other end

of this cable is plugged into the 3-position

header associated with the microphone

input connector, labeled P5, located on the

main printed circuit board assembly. One

end of the second interconnecting cable

is plugged into the card’s header that is

labeled RELAY. The other end of this cable

is plugged into the header associated with

the auxiliary relay, labeled P9, located on

the main printed circuit board.
After the direct microphone output card

has been installed, one conﬁguration step

must also be performed. Using the con-

ﬁguration switches, located on the bottom

of the Model 220’s enclosure, the auxil-

iary relay control mode must be set to the

“follows main output status” position. This

provides the on/off (muting) control of the

direct microphone output signal. Should

the auxiliary relay’s conﬁguration be left

in the “relay disabled” position, the direct

microphone output will always be in the off

(muted) state. It’s interesting to note that

the recommended auxiliary relay conﬁgura-

tion assumes that the direct microphone

output will be used in place of the Model

220’s main output. However, for other

applications there is certainly no reason

why the direct microphone output can’t

be conﬁgured to follow the status of one

of the talkback buttons. Special situations

may beneﬁt from having a microphone

signal that is active only during “talkback.”
Using the direct microphone output is

essentially the same as connecting

directly to a microphone. An interface cable

should be wired so that signal high (+ or

hot) is connected to pin 2, signal low (– or

cold) is connected to pin 3, and shield is

connected to pin 1. When connecting a

condenser microphone it’s recommended

that the Model 220 provide the source of

phantom power. In this way the micro-

phone will stay active whenever the Model

220 is operating, even if the connection

made to the direct microphone output is

broken. By ensuring that the microphone

remains active, the talkback functions will

continue to operate correctly.
Two slight differences between connecting

to a stand-alone microphone and connect-

ing to the Model 220’s direct microphone

output should be noted. The ﬁrst is that

pin 1 on the direct microphone output’s

3-pin male XLR connector is electrically

isolated from pin 1 on the Model 220’s

3-pin female XLR microphone input con-

nector, as well as the Model 220’s signal

common/chassis connection. This is in-

tended to minimize the chance of “ground

loops” being created. Contact the factory

should assistance in this area be required.
The second difference is that while the

circuitry between the microphone input

and direct microphone output is entirely

passive, it will still impact the microphone

signal. The impact is benign but is still

worthy of description. The circuitry asso-

ciated with the Model 220’s microphone

preampliﬁer and phantom power supply

is always connected across (“bridged

onto”) the microphone input. This adds

a 2 k ohm essentially resistive load to the

microphone, something that should have

no sonic impact. In some cases this may

reduce the microphone signal level by

less than one dB. Also, two 150 ohm resis-

tors are electrically connected in series

between the microphone input connector