Specifications

YOU ARE PROTECTED FROM
LISTENING TO AMPLIFIER
PRODUCED DISTORTION
WITH MCINTOSH
POWER GUARD
Plus:
• Mclntosh Output Autotransformer delivers full
power output. Multiple feedback loops assure
lowest distortion at all power levels and all
speaker impedances
• Mclntosh engineers developed a unique output
stage circuit arrangement that is completely
temperature accurate, that delivers clean output
power at any level without crossover distortion
• Mclntosh life testing of components permits com-
ponent selection for trouble-free performance; ad-
ded care in production engineering and manufac-
turing results in long product life
• Mclntosh designed "turn-on/mute" circuits pro-
vide positive protection from "turn-on transients"
and other potentially damaging noises
• Mclntosh POWER GUARD assures maximum
amplifier power without clipping distortion
Higher power demands on amplifiers have
presented music listeners with a form of unpleas-
ntness in listening, amplifier overload (hard clipping)
that looks and acts like square waves. Clipping is
caused when the amplifier is asked to produce more
power output with low distortion than it can deliver.
Clipping of a complex wave form is largely compos-
ed of odd order harmonics and intermodulation pro-
ducts. High order odd harmonics and intermodula-
tion products are dissonant and are not musically
related to the signal being amplified. They are heard
as great and disappointing discordance and distor-
tion.
In most acoustical events we may listen to sur-
prisingly low average power output but the peak
power requirements can be very high. Consider
these graphs of the power demanded of an amplifier
reproducing the piano, the pipe organ, and the bass
saxophone. The charts show that the peak power de-
mand is almost 1000 times (30 dB) the average power
demand. Since it is necessary that these short inter-
val power spikes be reproduced with low distortion,
it means the average power output of the power
amplifier must be limited to 1/1000th of its capability
or the listener must accept the discordant distortion
of clipping.
Amplifiers when driven to clipping are capable of
delivering up to twice the heat load to the
loudspeaker. In addition, they can have more than
40% harmonic distortion. The extra heat energy con-
tent of the clipped signal will damage most
speakers. Mclntosh leadership in engineering has
developed a new circuit that...(1) dynamically
prevents power amplifiers from being overdriven in-
to hard clipping. ..(2) which reduces the heat
developed in the loudspeakers. ..(3) assures that the
amplifier will produce its maximum output without
increased distortion. That circuit we call "POWER
GUARD."
20 100 1K 10K
HERTZ
-30
0
30
PIANO
PIPE ORGAN
30
0
-30
20 100 1K 10K
HERTZ
BASS SAXOPHONE
30
0
-30
20 100 1K 10K
HERTZ
3