Knoll MA1250 - User Manual

Warranty
MA1250 Amplifier
Knoll Systems warrants MA1250 amplifiers sold in the USA and Canada by
authorized Knoll dealers to be free of defects in materials and workmanship. This
warranty extends for three full years from the date of purchase by the original
consumer. Any products returned to Knoll Systems and found to be defective by
Knoll Systems within the warranty period will be repaired or replaced at Knoll
Systems decision, at no charge. Knoll Systems will not be responsible for the
actual cost of installation or removal of the product, nor for any incidental or
consequential damages. Some states do not allow the exclusion or limitation of
incidental or consequential damages, so the above limitation may not apply to
you. This warranty gives you specific legal rights. You may have additional legal
rights that vary from state to state.
12 Channel Amplifier
Installation Instructions v1.2
Warning: To be installed and/or used in accordance with appropriate
electrical codes and regulations.
Description: The MA1250 is a member of the long line of Knoll multi-
channel amplifiers. Designed primarily for the custom install industry, it
is used to power speakers with different or similar sources in multiple
rooms. With 12 channels rated at 50 watts per channels at 8 ohms, the
MA1250 packs some serious punch. Each channel has a gain control.
The MA1250 can be turned on and off via the front panel power switch
or via the 12 VDC trigger. MA1250 channels 3-12 can be linked to
channel 1-2 individually using the link switches. MA1250 amplifiers
designed to meet the amplifier needs of custom installed systems
where high-quality sound is a specific requirement.
Specifications:
Inputs 12 Gold RCA jacks with adjustable gain
Input impedance 50k ohms
Outputs detachable plug
Output power 50 watts RMS per channel (8 ohms)
Peak output power 100 watts per channel (8 ohms)
Ideal impedance 4 - 8 ohms
Frequency response 10 Hz - 40 kHz +/- 1dB (1w)
S/N ratio over 105 dB A weighted (50 watts)
THD distortion less than 0.1% 20 Hz to 20 kHz
IMD distortion less than 0.01% 60 Hz 7 kHz 4:1 (SMPTE)
Trigger control 12 VDC 35mA on 3.5mm mono jack
Dimensions 17" x 3.5" x 11.5" (432 x 89 x 292mm)
Fan Noise quiet 26 dBA
Power 750 watts at 117 VAC or 230 VAC
Weight 21 lbs (9.5 kg)
Key Features:
1. Size efficiency. The MA1250 consists of a total of 12 power
amplifiers in one 3-1/2” high enclosure. Each power amplifier
channel can deliver 50 watts RMS into an 8-ohm load.
2. Automatic protection circuitry. Each MA1250 channel is
individually and fully protected against low impedance,
overheating, overloading, overvoltage and undervoltage. The
protection circuitry automatically restores the amplifier channel
as soon as its parameter returns to the safe operating area.
3. Individual input gain adjustment. Each channel features
an input gain adjustment pot to adjust each channel for gain
and speaker sensitivity variations. The gain adjustments are on
the rear of the MA1250 so installers normally set the gain.
Note: Specifications subject to change without notice.
4. External power on/off. The MA1250 can be turned off and
on by external controllers. To activate external power on, apply
a 12 VDC current to the trigger jack (the MA1250 power switch
is in the off position for external power control).
5. Stackable 17" chassis.
6. Link Feature. Certain installations require that some or all of
the stereo channels play the same content. Instead of using Y
cords, "link" cascades any or all of channels 2-6 to channel 1
(l/r).
Knoll Systems
145 Tyee Drive Point Roberts, WA 98281
12140 Horseshoe Way, Richmond, BC V7A 4V5
Tel: (604) 272 4555, fax (604) 272 5595
Made in Canada

Summary

Warranty and Specifications

MA1250 Amplifier Description

Details the MA1250's purpose as a multi-channel amplifier for custom installs, highlighting its power and features.

Key Features Overview

Highlights MA1250's size efficiency, protection circuitry, individual gain adjustment, external power control, stackable chassis, and link feature.

Size Efficiency

MA1250 has 12 power amplifiers in a 3.5-inch enclosure, delivering 50 watts RMS per channel.

Automatic Protection Circuitry

Each channel is protected against low impedance, overheating, overloading, overvoltage, and undervoltage.

Individual Input Gain Adjustment

Each channel has an input gain adjustment pot on the rear for custom gain settings.

External Power On;Off

The amplifier can be controlled remotely via a 12 VDC trigger input.

Stackable 17-inch Chassis

The MA1250 features a 17-inch chassis that can be stacked with other units.

Link Feature

Allows linking channels 2-6 to channel 1 for cascading stereo content without Y-cords.

Important Safety Instructions and Hum;Noise Troubleshooting

Hum and Noise Troubleshooting Steps

Provides step-by-step suggestions to diagnose and eliminate hum and noise issues in the audio system.

Suggestion #1: Cable TV Connection

Check if disconnecting the cable TV feed eliminates hum. Use a Ground Loop Isolator if needed.

Suggestion #2: Input Cables

Disconnect input cables to check if the hum originates from the cables or source device.

Suggestion #3: Home Grounding

Investigate home electrical system grounding issues. Consider AC Power Isolation Transformer.

Service, Troubleshooting, and Installation

Troubleshooting Common Issues

Provides solutions for power LED issues, sound cutting out, distorted sound, and trigger problems.

Installation Cooling Requirements

Ensure adequate convection cooling by placing the MA1250 at the top of an equipment stack with 3-5 inches of space.

Connecting Input Cables

Connect MA1250 inputs to source outputs using short, good quality RCA cables, one for each channel.

Connecting Speaker Outputs

Use good quality speaker wire (min. 16 gauge) for speaker outputs, with 14 gauge for runs over 30 feet.

Power Connection and Link Button Operation

AC Power Connection

Connect the MA1250 to a dedicated outlet supplying at least six amps (750 watts).

Trigger Input Connection

Connect a 12 VDC trigger source to the 3.5mm mono jack for remote power control.

Link Button Functionality

Explains how the Link button cascades inputs 2-6 to input 1 for synchronized stereo playback.

Knoll MA1250 Specifications