MASTER VOLUME AMPLIFIERS MARK II SERIES(1976-1990)
The Master Volume was introduced in 1976 in response to the
demands of guitarists who wanted an overdriven sound at more
controllable volume levels. The Master Volumes were a direct
offspring of the Standard series and are nearly identical
aesthetically. However, Marshall had been working on crude Master
Volume designs and gained experience with this type of circuitry
prior to 1976 when performing preamplifier and gain modifications
to Ritchie Blackmore's 200watt Majors (Doyle, 1990). 'The
preamplifiers are cascaded (wired in series) by removing one
channel and connecting that channel to the remaining one so that
an increase in gain (sensitivity) is created which may be
adjusted by using the two volume controls as a preamplifier and
Master Volume controls" (Doyle, 1990, p. 22). So was born
the definitive heavy rock amplifier.
Although the Master Volume series filled a need for many players,
"many feel that much of the guitar's sound quality is not
quite up to that of their Standard counterparts and the warmth of
those amplifiers tends to be lost in the blaze of distortion.
This observation, though, is not confined to Marshall amplifiers
as it is a problem generally associated with all Master Volume
type designs" (Doyle, 1990, p. 11).
Regardless, the Master Volume design was a natural and logical
step in the evolution of Marshall amplifier design. This basic
format of preamplifier/master volume controls appears on most
amplifiers, Marshall and others, that have a built-in overdrive
effect to produce distortion. The Master Volume series quickly
outdistanced the Standard series in popularity, so much so that
the latter was eventually dropped from the Marshall line at the
conclusion of the JCM 800 series and only are available in
reissue versions. The Master Volume remained relatively unchanged
until the radical redesign of the current and powerful JCM 900
Mark III High Gain series.
The design of the Master Volume is almost identical to the
Standard series, except in appearance, and very similar in
circuit design, except for the input section, preamplifier
section, and minor internal changes. Except for the power/standby
switches on the front panel and the smaller input section, the
front panel looks identical to the original Standard series.
The back panel features are very similar also and show only
aesthetic changes in comparison. The Mark II Master Volume series
remained almost unchanged throughout its 15-year history.
The capabilities of the Master Volume models, like the Standard
series, are a by product of their design. The whole idea behind
the Master Volume was to provide minimum to maximum overdrive at
any volume level through a preamplifier
control on the front panel of the amplifier.
This feature is in direct opposition to the Standard amplifiers
which only distorted
when operated at high volumes or with external booster boxes. The
Master Volumes have the advantage of having the overdrive effect
built directly into the amplifier circuitry and allow infinite
control of the preamplifier gain with the preamplifier gain
control.
The input jacks allow for a wide variety of tones similar to the
Standard amplifier. Replacing the Standard amplifier's two-channel,
four-input design, the Master Volume simply had two inputs: one
for high gain and one for low gain. The high-gain input was used
for distortion sounds and the low-gain input for clean sounds.
The high-gain input sends a strong, hot signal to the
preamplifier section, while the low input provides a soft, padded
sound. The major capabělity advantage the Master Volume has over
the Standard series is its ab ' ility to produce full-blown,
distortion sounds at the lowest of volumes. The distortion
produced in the Master Volume's preamplifier, however, is
significantly different from the power amplifier distortion
produced by the Standard series. The debate goes on endlessly
about whether preamplifier or power amplifier. distortion sounds
better, yet from a practical standpoint, Master Volumes are a
more logical choice for those players seeking the overdrive
effect wěthout highvolume levels.
The major disadvantage with the preJCM 800 Master Volumes is
their inability to patch internally or link with other amplifiers
like the Standard series. All these funetions must be done by an
external patching and switching system (see Chapter 11). JCM 800
models did, however, have a direct input (DA.) output for linking
to external destinations. All 50-watt heads will power two-speaker
cabinets (the 100-watt models only carried the four-cabinet
capability for a few years and dropped this feature in favor of
the two-cabinet format).
Master Volume amplifiers are very versatile, probably even more
so than Standard amplifiers because of their lowvolume overdrive
capability. Master Volumes, both old and new, can be found
everywhere from clubs and recording studios to arena rock
concerts. I highly recommend them, especially the pre-JCM 800
models which have a warmer sound than their JCM 800 successors.
(The High-Performance Marshall Handbook by John"Dutch"Boehnlein)