Lectrosonics PA8 User Manual

PA8

8 Channel Power Amplifier

INSTRUCTION MANUAL

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PA8

Introduction

The PA8 8 Channel Power Amplifier is a unique single
rack-space solution for zoned, distributed loudspeaker
systems with eight separate power amplfiers, each with
an output power capability of 10W (4 Ohms) or 6W (8
Ohms.)

The PA8 is passively cooled, and features full short­circuit and thermal overload protection. The amplifier
outputs are muted at turn-on and turn-off to eliminate
transients

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8 Channel Power Amplifier

Contents

Introduction ..............................................................................................................................................................2

Contents ..................................................................................................................................................................3

General Technical Description .................................................................................................................................4

Bridged Output ........................................................................................................................................................4

Front Panel Description ...........................................................................................................................................5

REAR PANEL DESCRIPTION .................................................................................................................................5

Operation Note ........................................................................................................................................................5

Troubleshooting .......................................................................................................................................................6

SYMPTOM ..............................................................................................................................................................6

POSSIBLE CAUSE .................................................................................................................................................6

Specifications ..........................................................................................................................................................6

Service and Repair ..................................................................................................................................................7

Returning Units for Repair .......................................................................................................................................7

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PA8

Input

DRIVING DEVICE

PA8

GND

Output

GND

Input Output

DRIVING DEVICE

PA8

GND

GND

In 1 Out 2

DRIVING DEVICE

PA8

Out 1In 2

GND

GND

In 1 Out 2

DRIVING DEVICE

PA8

Out 1In 2

GND

GND

General Technical Description

The PA8 uses a straightforward, low parts count design
for long term reliability. The heart of the power supply is
a low radiation toroidal transformer. The toroidal trans­former generates less heat than a comparable non-toroi­dal type, and emits considerably less 60Hz energy. This
is particularly important when the PA8 is used in close
proximity to microphone preamplifiers. The input to the
PA8 is fully balanced and RF filtered. The level control
feeds a monolithic power amplifier. Each power ampli­fier is internally power limited to protect itself from short
circuits, excessively low impedances, or highly reactive
loads. Thermal limiting is also integrated into the power
amplifier, with an intelligent shutdown mode that minimiz­es thermal shock to the device under extreme operation.
Any two channels may be used in the bridged mode for
higher power (20W/8 Ohms or 12W/16 Ohms).

The block diagram of the PA8 is shown below.

Bridged Output

Two adjacent channels of a PA8 may be connected as
shown in Figure 4 to allow bridging operation. In the
bridged mode, the minimum speaker load is 8 Ohms,
and maximum power output is 20W into 8 Ohms. Note
that since the Channel Level controls of both bridged
channels will be active, they should be set to the same
level. The loudspeaker is connected to the “+” output
terminals of each channel, while the “-” outputs are left
unconnected.

Figure 5 shows bridging operation using an unbalanced
source.

Figure 2 - Balanced Input / Non-Bridged Output

Figure 1 - PA8 Block Diagram

Installation

Installing the PA8 properly is simple, and only requires
attention to a few issues. The PA8 should be used in a
grounded metal rack. One open rack space should be
provided above and below the PA8 for proper ventila­tion.

Non-Bridged Output

The standard PA8 configuration would have a balanced
output device (like the MM8 Matrix Mixer) driving each
channel of the PA8. The speaker is connected in the
non-bridged mode. Maximum output power is 10W into
4 Ohms, or 6W into 8 Ohms.

Figure 2 shows this configuration.

When driving the PA8 with an unbalanced source, the
(-) terminal is connected to the ground of the driving
signal, as well as the ground terminal of the PA8 input.

Figure 3 shows this configuration.

Figure 3 - Unbalanced Input / Non-Bridged Output

Figure 4 - Balanced In / Bridged Out

Figure 5 - Unbalanced In / Non-Bridged Out level is reached

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Front Panel Description

CAUTION

WARNING

LINE IN

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LECTROSONICS, INC.

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SPEAKER OUT LINE IN

MADE IN U.S.A.

TO REDUCE THE RISK OF FIRE
OR ELECTRIC SHOCK, DO NOT
EXPOSE THIS EQUIPMENT TO

RAIN OR MOISTURE.

TO REDUCE THE RISK OF FIRE,

REPLACE ONLY WITH SAME TYPE

3A, 250V "SLO-BLO" FUSE

120V AC

300 WATTS

SPEAKER OUT

POWER
AMPLIFIER

CH 5CH 6CH 7CH 8

CH 1CH 2

CH 3CH 4

E

POWER AMPLIFIER

POWER

OUTPUT LEVEL OUTPUT LEVEL

CH 8CH 7CH 6CH 5CH 4CH 3CH 2CH 1

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LECTROSONICS

R

POWER SWITCH - Turns AC power on and off.

POWER LED - Indicates the presence of AC power to

the PA8.

CHANNEL LEVEL 1-8 - Controls the volume level of
each channel.

Figure 6 - PA8 Front Panel

8 Channel Power Amplifier

REAR PANEL DESCRIPTION

LINE INPUTS 1-8 - Accepts balanced or unbalanced
signal. Fully balanced differential input, RF filtered.

SPEAKER OUTPUTS 1-8 - Drive minimum 4 Ohm
loads non-bridged, and minimum 8 Ohm loads bridged.

AC POWER RECEPTACLE - Accepts standard de­tachable 120VAC power cord.

AC POWER FUSE - Accepts a 3A, 250V (1.5A, 250V
when wired for 230VAC operation) Slo-Blo fuse.

Figure 6 - PA8 Front Panel

Figure 7 - PA8 Rear Panel

Operation Note

Remember that the PA* expects a loudspeaker load
without a matching transformer at the speaker.

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PA8

Troubleshooting

SYMPTOM

No sound from system

Specifications

Line Input
Type: Electronically balanced and RF

filtered
Impedance: 20k Ohms, Balanced or
Unbalanced
Input Level for Rated Output: -2dBu (615mVRMS) at maximum
level
+15dBu (4.36VRMS) at mid level

Output Power: 10 Watts into 4 Ohms, 6 Watts into
8 Ohms
20 Watts into 8 Ohms with bridged
monoconfiguration

Output impedance: 4 Ohms minimum
Maximum System Gain
Line Input to Speaker Out: 20dB (x10)

POSSIBLE CAUSE

1) Channel Level control not turned up

2) Channel input incorrectly wired

3) Power switched off

4) Fuse may be blown

Signal-to-Noise Ratio: 88dB relative to 10W at 4 Ohms
System THD: Less than 0.1%, 20Hz to 20kHz

(10W into 4 Ohms)
System IMD: Less than 0.1%, 60Hz/7kHz (10W

into 4 Ohms)

Slew Rate: 12V/uS
Power Consumption: 200 Watts max at 120VAC

Euro Version*: 200 Watts max at 230VAC

Weight: 8 lbs, 9 ozs
Dimensions: 19” wide x 1.3/4” high x 8 1/4” deep

*Euro version, I-PA8 is CE marked and runs on 220VAC.

Specifications subject to change without notice

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8 Channel Power Amplifier

Service and Repair

If your system malfunctions, you should attempt to correct or isolate the trouble before concluding that the equipment
needs repair. Make sure you have followed the setup procedure and operating instructions. Check the interconnect­ing cables and then go through the Troubleshooting section in this manual.

We strongly recommend that you do not try to repair the equipment yourself and do not have the local repair shop
attempt anything other than the simplest repair. If the repair is more complicated than a broken wire or loose connec­tion, send the unit to the factory for repair and service. Don’t attempt to adjust any controls inside the units. Once
set at the factory, the various controls and trimmers do not drift with age or vibration and never require readjustment.
There are no adjustments inside that will make a malfunctioning unit start working.

LECTROSONICS’ Service Department is equipped and staffed to quickly repair your equipment. In warranty repairs
are made at no charge in accordance with the terms of the warranty. Out-of-warranty repairs are charged at a mod­est flat rate plus parts and shipping. Since it takes almost as much time and effort to determine what is wrong as it
does to make the repair, there is a charge for an exact quotation. We will be happy to quote approximate charges by
phone for out-of-warranty repairs.

Returning Units for Repair

For timely service, please follow the steps below:

A. DO NOT return equipment to the factory for repair without first contacting us by email or by phone. We need

to know the nature of the problem, the model number and the serial number of the equipment. We also need a
phone number where you can be reached 8 A.M. to 4 P.M. (U.S. Mountain Standard Time).

B. After receiving your request, we will issue you a return authorization number (R.A.). This number will help speed

your repair through our receiving and repair departments. The return authorization number must be clearly shown
on the outside of the shipping container.

C. Pack the equipment carefully and ship to us, shipping costs prepaid. If necessary, we can provide you with the

proper packing materials. UPS is usually the best way to ship the units. Heavy units should be “double-boxed”
for safe transport.

D. We also strongly recommend that you insure the equipment, since we cannot be responsible for loss of or dam-

age to equipment that you ship. Of course, we insure the equipment when we ship it back to you.

Lectrosonics USA:

Mailing address: Shipping address: Telephone:

Lectrosonics, Inc. Lectrosonics, Inc. [phone]
PO Box 15900 581 Laser Rd. [phone] Toll-free
Rio Rancho, NM 87174 Rio Rancho, NM 87124 [phone] Fax
USA USA

Web: E-mail:
www.lectrosonics.com [e-mail]

Lectrosonics Canada:

Mailing Address: Telephone: E-mail:

49 Spadina Avenue, [phone] Sales: [e-mail]
Suite 303A [phone] Toll-free Service: [e-mail]
Toronto, Ontario M5V 2J1 (877-7LECTRO)
[phone] Fax

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PA8

581 Laser Road NE • Rio Rancho, NM 87124 USA • www.lectrosonics.com
[phone] • [phone] • fax [phone] • [e-mail]

LIMITED ONE YEAR WARRANTY

The equipment is warranted for one year from date of purchase against defects in
materials or workmanship provided it was purchased from an authorized dealer. This
warranty does not cover equipment which has been abused or damaged by careless
handling or shipping. This warranty does not apply to used or demonstrator equipment.

Should any defect develop, Lectrosonics, Inc. will, at our option, repair or replace any
defective parts without charge for either parts or labor. If Lectrosonics, Inc. cannot
correct the defect in your equipment, it will be replaced at no charge with a similar new
item. Lectrosonics, Inc. will pay for the cost of returning your equipment to you.

This warranty applies only to items returned to Lectrosonics, Inc. or an authorized
dealer, shipping costs prepaid, within one year from the date of purchase.

This Limited Warranty is governed by the laws of the State of New Mexico. It states the
entire liablility of Lectrosonics Inc. and the entire remedy of the purchaser for any
breach of warranty as outlined above. NEITHER LECTROSONICS, INC. NOR
ANYONE INVOLVED IN THE PRODUCTION OR DELIVERY OF THE EQUIPMENT
SHALL BE LIABLE FOR ANY INDIRECT, SPECIAL, PUNITIVE, CONSEQUENTIAL,
OR INCIDENTAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THIS EQUIPMENT EVEN IF LECTROSONICS, INC. HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES. IN NO EVENT SHALL THE LIABILITY OF
LECTROSONICS, INC. EXCEED THE PURCHASE PRICE OF ANY DEFECTIVE
EQUIPMENT.

This warranty gives you specific legal rights. You may have additional legal rights which
vary from state to state.

May 18, 2009

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