McIntosh MA6400 Owner's Manual page 22

power transistors for the output power produced. The amplifier uses large area heat sinks to
TECHNICAL
efficiently dissipate the transistor heat. Natural convection air flow is sufficient for safe cool
DESCRIPTION
operation.
sensors will turn off the speaker relays. When the problem is corrected and the amplifier cools
to its normal operating temperature, the speaker relays will turn back on.
channel. POWER GUARD eliminates the possibility of ever over driving the amplifier into
overdriven amplifier can produce both audible and ultrasonic distortion levels approaching
40%. The audible distortion is certainly unpleasant, but the ultrasonic distortion is also
of conservative design. You will never experience the harsh and damaging distortion due to
microprocessor is programmed with exclusive Mclntosh software. It receives data from the
second microprocessor decodes the CD1 Control commands.
ELECTRO-MAGNETIC SWITCHING
MAGNETIC switching is an old an proven technology that has been upgraded with modern
materials and manufacturing techniques.
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If the cooling air is blocked, or the amplifier operating temperature is forced too high, thermal
POWER GUARD
The MA6400 includes the unique patented Mclntosh POWER GUARD circuit on each
clipping. Clipping occurs when an amplifier is overdriven past its output design capabilities. An
undesirable, since it can damage tweeter loudspeakers. The Mclntosh POWER GUARD circuit
acts as a waveform comparator, monitoring both the input and output signal waveforms. Under
normal operating conditions there are no differences between these waveforms. When an
amplifier is overdriven beyond its maximum distortion free output, there will be a difference
between the two signal waveforms. If the difference exceeds 0.3% (equivalent to 0.3% harmonic
distortion), the amber POWER GUARD indicator will light. If the difference continues to increase,
the POWER GUARD circuit controls an electronic attenuator at the input of the amplifier to
reduce the gain just enough to prevent any further increase in distortion. Distortion will not
exceed 2% with as much as 14dB overdrive. Without POWER GUARD, the distortion could
easily reach 40% for the same operating conditions.
A Mclntosh power amplifier with POWER GUARD will always deliver its maximum distortion
free output. This power is always well above the rated power due to the Mclntosh philosophy
clipping when using a Mclntosh MA6400 amplifier with POWER GUARD.
LOGIC DRIVEN CONTROL
All Inputs, Outputs, CD, and Data Ports are controlled by logic circuits in the MA6400. This
logic is changed by front panel switches or by the microprocessor IR decoder. This
MA6400 front panel IR sensor and provide the command signals for all switching functions. A
The logic circuits activate Electro-Magnetic switches for the final step in all signal switching.
All signal switching in the MA6400 is done by ELECTRO-MAGNETIC methods. ELECTRO¬