Infinity 310a User manual

Reference Series
310a
311a
1 CHANNEL POWER AMPLIFIER
SERVICE MANUAL
Infinity Systems, Inc.
250 Crossways Park Dr.
Woodbury, New York 11797 Rev2aa10/2005

- CONTENTS -
SPECIFICATIONS ………………………………….……..1
FEATURES/TEST CONDITIONS……..…………………2
CONTROLS/CONNECTIONS………….……..…...…..…3
INSTALLATION………………….……...……..…...…...…5
BASIC TROUBLESHOOTING..…….…….………………7
TYPICAL SYSTEM WIRING..…….…….……………..…8
EXPLODED VIEW/PARTS LIST…….….….…………....9
MECHANICAL PARTS LIST……………..…………......10
AMPLIFIER BLOCK DIAGRAM…………………………11
P.C.B. DRAWINGS….…………………………………….12
ELECTRICAL PARTS LIST ……………………………. 15
REF 311a ELECTRICAL PARTS LIST ADDENDUM….…….….18
IC/TRANSISTOR PINOUTS..…………………………….19
REF 310a SCHEMATICS………..……….…….………..22
REF 311a SCHEMATICS………..……….……….……..24
PACKING…………………….…………………………....26
Reference 310a/311a Specifications
Output Power: 116W RMS x 1 channels @ 4 ohms; ≤1% THD + N
(14.4V supply) 312W RMS x 1 channels @ 4 ohms; ≤1% THD + N
Signal-to-noise ratio: 81dBA (reference 1W into 4 ohms)
Dynamic power: 347W @ 2 ohms
Effective damping factor: 6.398 @ 4 ohms
Frequency response: 17Hz – 302Hz (–3dB)
Maximum input signal: 6.0V
Maximum sensitivity: Reference 310a - 250mV
Reference 311a - 75mV
DC Offset <50mV (-50%)
Output regulation: .05dB @ 4 ohms
Idle Current 800mA
Input Impedance 22kΩ
Max Current Draw 24A @ 4 ohms
40A @ 2 ohms
Dimensions: 12 x 11 7/16 x 2 11/16” (L x W x D)
(305mm x 290mm x 68mm)
Fuse: 30A
Infinity continually strives to update and improve existing products, as well as create new ones. The specifications and details in
this and related publications are therefore subject to change without notice.
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Power Amplifier Reference 310a/311a

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•
If the amplifier’s fuse must be replaced, use
only the same type and rating as that of the
original. Do not substitute another kind.
The Reference amplifiers are capable of
delivering high power levels, and require a
reliable connection to the vehicle’s electrical
system in order to perform optimally. See
Figure 1 for connection location. Please
adhere to the following instructions carefully.
GROUND CONNECTION
Connect the amplifier’s Ground (GND) terminal
to a solid point on the vehicle’s metal chassis,
as close to the amplifier as possible. Refer to the
chart below to determine minimum wire-gauge
size. Sand away any paint from this location; use
a star-type-lock washer to secure the connection.
POWER CONNECTION
Connect a wire (see chart at right for appropriate
gauge) directly to the vehicle’s positive battery
terminal, and install an appropriate fuse holder
within 18" of the battery terminal. Do not
install the fuse at this time. Route the wire to
the amplifier’s location, and connect it to the
amplifier’s positive (+12V) terminal. Be sure to
use appropriate grommets whenever routing
wires through the firewall or other sheet metal.
Failure to adequately protect the positive wire
from potential damage may result in a vehicle
fire. When you are done routing and connecting
this wire to the battery and to the amplifier,
you may install the fuse at the battery.The
fuse value should be selected based on total
amplifier-current draw; see chart at right.
REMOTE CONNECTION
Connect the amplifier’s Remote (REMOTE)
terminal to the source unit’s RemoteTurn-On
lead using a minimum of 18-gauge wire. If your
source unit does not have a remote turn-on
connection, connect the amplifier’s (REMOTE)
terminal to the vehicle’s accessory circuit.
WIRE-GAUGE CHART
Amplifier Maximum Minimum
Model Current Draw Wire Gauge
AWG
AWG
310a/311a 40A #8 AWG
AWG
AWG
These recommendations assume 7' – 10' wire
runs. If your installation differs markedly, you
will need to adjust the wire gauge accordingly.
SPEAKER CONNECTIONS
Refer to the application guides on the pages
that follow. Speaker connections should be
made using a minimum of 16-gauge wire.
NOTE: When using the low-level or high-level
inputs, the AUX outputs can be used to pass a
full-range line-level signal to another amplifier.
POWER CONNECTIONS
Figure 1.Terminal-connection end plate.
Power Amplifier
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Reference 310a/311a

The Reference subwoofer amplifiers are
single-channel amplifiers.There are two sets of
terminals to make it easy to connect multiple
woofers. Either set of (+/–) terminals may be
used when connecting woofers.
To the right are two application diagrams to help
plan your subwoofer system installation. Figures
3 and 4 show how to configure the Reference
subwoofer amplifiers
1210a).
NOTE: For simplicity, Figures 3 and 4 do not
show power, remote and input connections.
NOTE: Minimum speaker load is 2 ohms.
APPLICATIONS – 310a/311a
Figure 3. Reference subwoofer amplifier with two woofer connections.
Figure 4. Reference subwoofer amplifier with one woofer connection.
Power Amplifier
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Reference 310a/311a

Figure 13. Control end panel.
SETTING INPUT SENSITIVITY
1. Initially turn the INPUT LEVEL control(s) to
minimum (counterclockwise).
2. Reconnect the (–) negative lead to the vehi-
cle’s battery. Apply power to the audio system
and play a dynamic music track.
3. On the source unit, increase the volume
control to 3/4 volume. Slowly increase the
INPUT LEVEL control(s) toward three o’clock
until you hear slight distortion in the music.
Then reduce the INPUT LEVEL slightly until
distortion is no longer heard.
NOTE: After the source unit is on, blue LEDs (on
the top panel) will light, indicating the amplifier
is on. If not, check the wiring, especially the
remote connection from the source unit. Also
refer to “Troubleshooting” on the page 7.
INSTALLATION AND SETUP
REMOTE LEVEL CONTROL (OPTIONAL)
All three Reference subwoofer amplifiers and
the 5760a amplifier have inputs for an optional
remote level control (100rc).This will allow the
subwoofer level to be adjusted from the listening
position. Connect the optional remote level
control using the RJ-11 jack on the side of the
amplifier. Install the control module in the front
of the vehicle within easy reach of the driver.
Both the underside of the dash and the center
console are suitable locations. Refer to the
mounting instructions accompanying the 100rc.
AUX OUTPUT
Reference amplifiers are equipped
with full-range outputs that can be used to
connect additional amplifiers.
NOTE: When using the low- or high-level inputs,
the AUX outputs can be used to pass a full-range
line-level signal to another amplifier.
Power Amplifier
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STATUS LEDs
Clip: Indicates the amplifier is being overdriven,
and your speakers may be in danger.This
should blink only on musical peaks, and not
be on constantly.
Power: Indicates the amplifier is on.
Protection: Refer to “Troubleshooting” for specific
indications.
Figure 15. LED status.
SETTING DBO™
The Dynamic Bass Optimizer (DBO) is used to
enhance low-frequency reproduction in a vehicle.
Conventional bass-boost circuits only increase
bass at a fixed frequency, and cause the amplifier
to consume considerable power.The DBO allows
you to adjust the frequency (20Hz – 80Hz) as well
as the boost level (up to 12dB; see Figure 14),
allowing you to fine-tune the bass in your system
to optimize performance.
For sealed enclosures, the DBO can be used
to enhance the lower bass region of sealed
enclosures.
For bigger/fuller bass, adjust the HP FREQ
between 35Hz and 45Hz; adjust the BOOST
control according to your preference.
For tighter-sounding bass, adjust the HP FREQ
between 45Hz and 55Hz; adjust the BOOST
control according to your preference.
For vented enclosures, the DBO should be used
as a subsonic filter to reduce overexcursion
of the woofers. Set the HP FREQ control 10Hz
below the tuning frequency of the enclosure
(e.g., 25Hz for a box tuning of 35Hz); adjust the
BOOST control to taste.This will conserve
amplifier power typically wasted on frequencies
below the tuned frequency of the enclosure.
For infinite-baffle applications, set the HP FREQ to
the speaker’s Fs value (reducing overexcursion of
the woofer); adjust the Boost control to taste.
Figure 14. Frequency-response curves show
typical DBO control ranges.
INSTALLATION AND SETUP (CONT.)
-9
-6
-3
0
-12 20 80 Freq. (Hz)
dB
DBO HP FREQ Control
(adjusts cut-off
frequency)
HP FREQ
100Hz20Hz
-6
0
6
12
-12 20 80 Freq. (Hz)
dB
DBO BOOST Control
(adjusts boost amount
at cut-off frequency)
BOOST
MAXMIN
Power Amplifier
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• PROBLEM:
No audio (POWER LED is off).
CAUSE and SOLUTION:
No voltage at BATT+ and/or REM terminals, or
bad or no ground connection. Check voltages
at amplifier terminals with VOM.
• PROBLEM:
No audio (PROTECT LED flashes every
4 seconds).
CAUSE and SOLUTION:
DC voltage on amplifier output. Amplifier may
need service; see enclosed warranty card for
service information.
• PROBLEM:
No audio (PROTECT LED is on).
CAUSE and SOLUTION:
Amplifier is overheated. Make sure amplifier
cooling is not blocked at mounting location;
verify that speaker-system impedance is within
specified limits.
• PROBLEM:
No audio (PROTECT and POWER LEDs flash).
CAUSE and SOLUTION:
Voltage less than 9V on BATT+ connection.
Check vehicle charging system.
• PROBLEM:
No audio (PROTECT LED is on).
CAUSE and SOLUTION:
Voltage greater than 16V or less than 8.5V on
BATT+ connection. Check vehicle charging
system.
• PROBLEM:
Distorted audio.
CAUSE and SOLUTION:
Input sensitivity is not set properly, or amplifier
or source unit is defective. Check INPUT LEVEL
setting, or check speaker wires for shorts or
grounds.
• PROBLEM:
Distorted audio (PROTECT LED flashes).
CAUSE and SOLUTION:
Short circuit in speaker or wire. Remove
speaker leads one at a time to locate shorted
speaker or wire, then repair.
• PROBLEM:
Music lacks “punch.”
CAUSE and SOLUTION:
Speakers are not connected properly. Check
speaker connections for proper polarity.
TROUBLESHOOTING
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