Each channel has an independent gain control with

40 detents for accurately setting and matching the gain between channels. The gain controls are calibrated in dB (from off to 30) and in volts (with indications of 1V, 2V, and 3V).

Six discrete LEDs are used

to indicate signal level for each channel, including a signal present LED, indicators at –20, –9, –6, and –3dB below full power, and an overload LED to indicate when the output has reached the clipping point.

Outputs.

The M•1200 and M•1400 differ in their output connector configurations. They both come with heavy-duty 5-way binding posts, which can accept standard double banana plugs, spade lugs, or bare wire (Export versions will not accept banana plugs due to European safety requirements). The M•1200 also has 1/4" TS phone jack outputs in parallel with the binding posts. The M•1400 comes with Neutrik brand Speakon® connectors in parallel with the binding posts.

Stereo, Mono and Bridge modes.

The amplifiers can be operated in one of three modes. In stereo mode, the amplifier operates with two inputs and two outputs. It accepts separate channel 1 and 2 input signals, and outputs separate channel 1 and 2 signals.

In mono mode, the ampli-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

so it doesn’t

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

degrade the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

audio signal in

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

any way.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

T-Design

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Constant

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Gradient

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cooling

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Tunnel.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Most amplifi-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ers have a fan

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

in the back that

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

blows air (along

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

with dust and

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

other contami-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

nants) into the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

inside of the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

amplifier, across

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

the heatsinks
fier operates with one input

as well as all the other inter-

nal components, and finally

and two identical outputs. It
out through the front.
accepts an input signal through

These designs are cheap to

channel 1, and outputs the
implement, but not very
same signal at both channel

efficient.

 

 

 

 

 

 

 

1 and 2 speaker outputs.

 

 

 

 

 

 

 

Others use a cooling tun-

In bridge mode, the ampli-

nel with the fan at one end.

fier operates with one input

The problem with this design

and one output. It accepts an
is that the heat from the
input signal through channel

first transistors warms the

1, and combines the power

air so that by the time the

of both output sections into

air reaches the end of the

a single output, using the

tunnel it’s too hot to provide

channel 1 positive and
sufficient cooling.
channel 2 positive speaker
Our T-Design Constant
output terminals.

 

 

Gradient Cooling Tunnel
Clipping eliminator.

offers a much more efficient

Mackie Designs power
method of providing cool
amplifiers use a method of

air to all the transistors with-

protecting the amplifier and

out blowing contaminants

the speakers from clipping

all over its insides. A dual-

that doesn’t affect the low

speed fan is located in the

impedance capablility of the

center of the amplifier, direct-

amplifier. A defeatable limiter

ing air from the front of the

circuit is em-

 

 

 

 

 

 

 

 

 

amplifier

 

 

 

ployed that

 

 

 

 

 

 

 

 

 

through a
reduces the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

large intake
input signal

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

manifold into

 

 

 

when the out-

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

the cooling
put of the

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

tunnel. The

 

 

 

 

 

 

 

 

 

 

amplifier ap-

 

 

 

 

 

 

 

 

 

cool air is
proaches the

Cooling tunnel airflow

 

 

 

 

 

 

evenly dis-
clipping point.

 

 

 

 

 

 

tributed

 

 

 

 

 

 

 

 

 

The moment the output

from the middle of the tun-

level drops below clipping,

nel to each end, where the

the limiter turns off and iswarm air then exits the
effectively “out-of-circuit,”amplifier on either side.

3