3.7 Set Input Sensitivity; 3.8 Set Ground Lift Switch; 3.9 Connect to AC Mains- Page 9

Micro-Tech Series 

Power Amplifiers

page 9

Operation Manual

3 Setup

3.7 Set Input Sensitivity

The three-position input sensitivity switch is 
located inside the amplifier behind the MT-XLR 
module (Figure 4.2 letter “I”). The switch is set 
at the factory to a sensitivity of 0.775 volt for 
standard 1 kHz power into 8 ohms. (Factory 
setting for International versions is 1.4 V.) If 
desired, the sensitivity can be switched to 1.4 
volts for standard 1 kHz power into 8 ohms, or 
a voltage gain of 26 dB. The 26 dB gain setting 
is equivalent to a sensitivity of 2.1 volts for the 
Micro-Tech 600, 2.5 volts for the Micro-Tech 
1200 and 3.2 volts for the Micro-Tech 2400. 

To change the input sensitivity:

1. Remove the back panel cover plate (or 
input connector accessory).

2. Locate the access hole for the sensitivity 
switch inside the chassis opening (Figure 
3.7).  The sensitivity switch will not be vis-
ible because it is mounted below the hole. 
Use your little finger to reach it.

3. Set the switch to the desired position 
noted on the label beside the access hole.

4. Replace the back panel cover plate (or 
input connector accessory).

3.8 Set Ground Lift Switch

The 

ground lift switch

 (Figure 3.7) is located 

on the back panel and can isolate the input sig-
nal grounds from the AC (chassis) ground. It 
affects only the phone jack inputs and has no 
effect on accessory input connectors. Sliding 
the switch to the left isolates or “lifts” the 
grounds by placing an impedance between the 
sleeve of each phone jack and the AC ground.

The Micro-Tech 2400 has two 

reset switches

for its high-voltage power supplies. Refer to the 
Troubleshooting Section in the unusual event 
of a tripped breaker.

3.9 Connect to AC Mains 

Connect your amplifier to the AC mains power 
source (power outlet) with the supplied AC 
power cordset.  

WARNING: The third prong of the power  
connector (ground) is an important 
safety feature. Do not attempt to disable 
this ground connection by using an 
adapter or other methods.

Amplifiers don't create energy. The AC mains 
voltage and current must be sufficient to deliver 
the power you expect. You must operate your 
amplifier from an AC mains power source with 
not more than 10% variation above or below 
the amplifier's specified line voltage and within 
the specfied frequency requirements (indicated 
on the amplifier's back panel label). If you are 
unsure of the output voltage of your AC mains, 
please consult your electrician.

3.10 Startup Procedure

Use the following procedure when first turning 
on your amplifier:

1.

Turn down the level of your audio source. 

2.

Turn down the level controls of the ampli-
fier.

3.

Turn on the “Power” switch. The Power 
indicator should glow. 

4.

Turn up the level of your audio source to 
an optimum level.

5.

Turn up the Level controls on the amplifier 
until the desired loudness or power level is 
achieved.

6.

Turn down the level of your audio source 
to its normal range.

If you ever need to make any wiring or installa-
tion changes, don't forget to disconnect the 
power cord.

For help with determining your system's opti-
mum gain structure (signal levels) please refer 
to the Crown Amplifier Application Guide, 
available online at www.crownaudio.com.

0.77 V

26 dB

SENSITIVITY SWITCH INSIDE ACCESS HOLE

1.4 V

UNBALANCED

INPUT WIRING

BALANCED

INPUT WIRING

+

–

TIP

RING

SLEEVE

GND

+

TIP

SLEEVE

GND

THIS AMPLIFIER IS EQUIPPED WITH SELECTABLE INPUT SENSITIVITY. REMOVE COVER PLATE (ABOVE) TO ACCESS SENSITIVITY SWITCH.

CH-2

INPUT GROUND LIFT

(AFFECTS PHONE INPUTS ONLY.)

(MONO)

INPUT

GAIN

CH-1

INPUT

GAIN

LIFT

0

1

2

3

4

5

6

7

8

9

10

11

12

0

1

2

3

4

5

6

7

8

9

10

11

12

GROUND LIFT SWITCH

Figure 3.7 Input Sensitiviy and Ground Lift Switches