Alesis Matica 900 - User Manual

Other manuals for Alesis Matica 900

Reference Manual20 pages

Questions and Answers

R
Richard FrancisJul 26, 2025
What to do if my Alesis Amplifier has no power?
- M
  Maria GibsonJul 26, 2025
  If your Alesis Amplifier has no power, meaning no LED and no fan, it could be due to a tripped or faulty breaker. Try resetting the breaker first. If that doesn't work, the breaker might need replacement. Other potential causes include a faulty transformer, which would require replacing the transformers and retesting, or an issue with the A.C. Be sure that a 30 amp service is available without significant voltage drop.
T
Tammy BrooksAug 3, 2025
What to do if Clip LED is on Alesis Matica 900 Amplifier but there is no output?
- K
  kkellerAug 3, 2025
  If the Clip LED is on but there's no output from your Alesis Amplifier, this could be due to a blown output section. In this case, replace all active components following the diver I.C. (U2-channel A U3 channel B) in the blown channel. Also, replace any out of tolerance resistors in the output section. Another cause might be poor solder on the large power supply capacitors, which causes ground reference to drift, so troubleshooting and repair would be necessary. Also check if J1 or J14 are loose, if so, reseat the cable and apply hot glue to prevent re loosening.
A
April HallAug 13, 2025
Why Alesis Matica 900 Amplifier has no output, no LED, but Fan running full on?
- S
  Sarah AndersonAug 13, 2025
  If your Alesis Amplifier has no output, no LED, but the fan is running full on, it could be due to a disconnected fan board or main harness. Try reconnecting and retesting. It could also be a faulty +15V regulator, which would require troubleshooting and repair.

Summary

Theory of Operation

Input Section

The input stage is made up of a dual Signetics 5532A op amp. This is a low noise selected version of the 5532.

Pre-Amp Section

The pre-amp section also uses the Signetics 5532A op amp. The circuits of the pre-amp are of opposing signal polarity.

Main Amplifier Section

The main amplifier is composed of four sections: The monolithic front end. A complimentary voltage gain stage or transconductance stage.

Output device protection is accomplished with a relatively simple circuit. The protection circuit is broken up into Q17 that protects the NPN output devices and Q18 that protects the PNP output devices.

Bias Circuit

The bias circuit is more that just a single device Vbe multiplier seen in many audio amplifiers. The circuit consists of an active shunt regulator.

Speaker Protection

There are two sections to the speaker protection circuit. A section made up of a quad comparator with a low pass filter before it and a discrete bipolar transistor circuit.

Fan Speed Control

The fan circuit has three modes of operation in which it varies the speed of the fan depending on demand or condition.

Thermal Management System

The large extruded aluminum heat sink in the center of the chassis is the heart of the amplifiers heat dissipation scheme. It is a forced air cooling system.

Updates and Corrections

Stripped Heat Sinks

Occasionally when tightening down the heat sink clamps one of the screws will strip the threads out of the heat sink itself.

New Case Bracket Insulator(s)

It was found that it was possible for the insulation on the wires from the main power transformer(s) could over time be cut by the case bracket(s).

Transformer Insulators

These foam insulators were added for two purposes: Electrical Isolation, Added resistance to mechanical shock.

Troubleshooting

Alesis Matica 900 Specifications

General

Type	Power Amplifier
Channels	2
S/N Ratio	> 100 dB
Input Connectors	XLR, 1/4" TRS
Dimensions	19" x 3.5" x 15.5"
Power Output	900 W (bridged 8 Ohms)
Frequency Response	20 Hz - 20 kHz, +0, -0.5 dB
THD	< 0.03%
Input Impedance	20k Ohms
Output Connectors	Binding Post
Cooling	Variable speed fan