Certon M21 User manual

User’s Manual
for
Certon M21
Power Amplifier

Certon M21 User’s Manual
2
Safety Instructions
Do not use near water
Do not expose to rain or moisture
Clean only with dry cloth
Do not block ventilation
Do not place on a soft surface
Do not operate near a heat source
or in a confined area
Do not use with a damaged power
cord
Use main plug to disconnect from
power grid
Do not remove cover
A lightening bolt triangle
is used to alert the user of
the risk of electric shock.
An exclamation point
triangle is used to alert the
user of an important
operating or maintenance
instruction.

Certon M21 User’s Manual
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Getting Started
Thank you for purchasing the Certon M21 monaural power amplifier. The M21 features
patent awarded technology for achieving powerful high-fidelity sound from a small enclosure.
The M21 is typically used in a stereo or multi-channel set-up. Each channel requires its own
power amplifier. Simply connect each M21 in a set-up to its respective loudspeaker. The M21
has loudspeaker output binding posts that accept bare wire, banana plugs or forks. Pay
attention to the polarity of the loudspeaker. Make sure the wires are firmly attached, and are
not short-circuiting the outputs of the amplifier. Connect the RCA-type phono or XLR input
of the M21 to the audio output of your pre-amplifier, home-theater processor or other similar
audio equipment. Make sure the audio source toggle switch in the back is in its corresponding
position. Attach the power cord to the power inlet of the amplifier, and to a power grid outlet.
Turn on the power switch at the back of the M21, and press the on/off push-button on the
front panel. Your M21 should be ready for operation in a few seconds, in which case a steady
light from a LED on the push-button would indicate this.

Certon M21 User’s Manual
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Controls
1. On/off mains switch
2. Loudspeaker terminals
3. RCA audio input
4. XLR audio input
5. Bal./unbal. Switch
6. Trigger in
7. Trigger out
8. Power inlet
9. On/off push-button
10. Clip indicator
11. Protection indicator
9
2.
10
3
11
5
4
1
8
2
6
7

Certon M21 User’s Manual
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Installation
Place the M21 on a stable surface. The unit has a self-resetting heat-switch, however:
Do not place the amplifier on a thick cloth or carpet, as ventilation would
be obstructed. Do not place in a confined area. Clearance should be allowed for heat
dissipation on the top and sides of the enclosure.
The M21 is equipped with a mains power switch (1) at the back of the unit.
During installation, keep the power switch in the “off” position.
Firmly attach all wires. Attach the loudspeaker cables to the positive and the negative
loudspeaker binding posts (2) of the M21. Pay attention to the phase. In general, the positive
terminal of the loudspeaker should be connected to the positive binding post of the amplifier,
and the negative terminal of the loudspeaker should be connected to the negative binding post
of the amplifier. Tightly secure the terminals. The M21 is non-inverting.
Do not short-circuit the loudspeaker terminals. Protection circuitry within
the amplifier will protect the unit from most overload conditions, but short-circuits
may seriously harm your M21. It is recommended not to use loudspeakers with a
nominal impedance of less than 4 ohms.
It is advised not to use highly capacitive loudspeaker cables, as this reduces
the phase margin of the amplifier and may potentially cause failure.
M21 has both RCA-type and XLR inputs. Attach an RCA-type or XLR signal cable between
the audio input (3,4) of the M21 and your pre-amplifier, home-theater processor or
corresponding unit. The RCA-type connector offers unbalanced operation, while the XLR
connector offers balanced operation. Be sure to put the toggle switch (5) in its appropriate
position.
Do not connect both RCA-type and XLR cables simultaneously, as this may
harm your pre-amplifier, home-theater processor or corresponding unit.
Be sure not to connect the audio input of the M21 to a line output. Doing so
may cause damage to your loudspeakers and your hearing.

Certon M21 User’s Manual
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M21 has a 12 VDC trigger input (6) and output (7). You may daisy-chain several amplifiers.
Simply connect a trigger output of one unit to a trigger input of another unit. Doing this
enables all units to be powered-up by control from your pre-amplifier, home-theater processor
or corresponding unit.
Attach the power cord between the power inlet (8) of the amplifier and a power grid outlet.
Turn the power switch at the back of the M21 to the “on” position.
Operation
Your Certon M21 is now responsive to a 12 VDC signal on the trigger input (6), and to the
actuation of the on/off push-button (9) on the front of the unit. Either or both take the M21 out
of stand-by mode, provided there is no fault condition.
The unit should be ready for operation within a few seconds. A blinking operation mode
indicator at the center of the push-button indicates that the unit is starting, while a steady light
indicates that the unit is ready for use.
Removing the 12 VDC signal and/or pressing the on/off push-button again takes the amplifier
back to stand-by mode.
When the unit switches on or off, a discrete click, pop or chirp may be heard in the
loudspeaker. This is normal for the M21, because of the absence of a relay in the audio signal
path.
The amplifier has a clip indicator (10). The clip indicator is an instrument to determine an
operating condition called clipping. Frequent clip-indicator blinking (e.g. less than a second
apart) or a steady light is generally indicative of extensive clipping that may seriously harm
your loudspeakers. Subjecting your loudspeakers to extensive clipping may void warranty. A
low wattage amplifier like the M21 is more prone to clipping than a high wattage amplifier,
and may thus be more harmful to loudspeakers at a specific loudness than a high wattage
amplifier.
Immediately turn down the volume or halt playback in the event of a
frequently blinking or steady clip-indicator light.
Maintenance
It is recommended to use a dry non-abrasive cloth to clean the amplifier.
Do not use detergents or other strong chemicals to clean your Certon M21
amplifier.

Certon M21 User’s Manual
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There are no user-serviceable parts inside the enclosure. Opening the cover
exposes high-voltage surfaces that may cause electric shock.
Your Certon M21 has a DC protection circuit through which DC faults are detected. In the
event of a malfunction within the unit, or in another component of your audio system that
leads to a DC offset, the M21 shuts down. A LED indicator (11) indicates that a DC fault has
occurred. This may be a single event or a persistent condition. Try to reset the amplifier by
turning it off, and then back on. If the problem persists, try a different pre-amplifier (or
completely turn off the pre-amplifier) and reset the M21 once more. If this does not rectify the
problem, your M21 may require servicing by a qualified technician.
Do not repeatedly reset the M21 without taking consecutive action to try to
resolve the problem with DC offset, as this may subject the amplifier to unnecessary
stress. In the event of loud thumps, clicks or pops from the loudspeaker at reset, do
not proceed but seek assistance from a qualified technician.
There is a heat switch inside the enclosure. The heat switch protects the amplifier against
excessive and potentially harmful temperatures that may result e.g. from loud listening for
prolonged periods at elevated ambience temperatures. When the heat switch trips, the
amplifier turns off. As soon as the temperature is safe again, the amplifier is ready to be
turned on again.
Specification
Power (8 Ohms)
25 Watts RMS
Damping factor (8 Ohm)
>450 @ 100 Hz
Input impedance (RCA/XLR)
40 kOhm/80 kOhm
Input voltage (at full power) (RCA/XLR)
1 Volt RMS/0.5 Volt RMS
THD+N
< - 60 dB
Output binding posts
WBT
Audio input jack
RCA phono type (cinch) and XLR
Remote trigger voltage
12 VDC (either polarity)
Remote trigger connector
3.5 mm. tele jack (mono)
Enclosure
Steel
Weight
2.8 kg (6.2 lb)
Size of enclosure: (width x depth x height)
205 x 200 x 120 mm. (8.1 x 7.9 x 4.7 in.)
Mains voltage
AC 110 - 230 Volts, 50 –60 Hz