Bright Switch; Boogie Channel Controls - Mesa/Boogie Subway TT-800 Owner's Manual

BRIGHT SWITCH:

rising response at higher frequencies much like the "bright" switches found on many popular classic tube amps. Engaging this filter
can bring some "sizzle & bite" into the tone.
BOOGIE CHANNEL:
GAIN CONTROL:
This control determines the gain (drive level) of the BOOGIE CHANNEL's 12AT7 (or 12AU7) vacuum tube
gain stages (V2A & V2B). Overdriving these gain stages may be a desirable tonal characteristic of your playing style, to increase the
amount of overdrive beyond what the range of this control allows, simply switch the INPUT GAIN SWITCH to the high gain position.
Note that the BOOGIE CHANNEL is already a higher gain channel than the SUBWAY CHANNEL. When using significantly overdriven
tones, you may find it helpful to back down on the TREBLE EQ a little bit to reduce harshness and also to reduce the BASS EQ (and/
or increase the frequency on the high pass filter) to increase the clarity and impact. These tube gain circuits draw inspiration from ele-
ments of our legacy amps, primarily the Bass 400/400+. If it's your tone, this tube gain stage is designed to be overdriven, so give it a
try, but it's also monstrous when run clean. When employing heavier overdrive, it's generally more pleasing reduce the tweeter level if
your cabinets have tweeters. Note that the GAIN control operates in a linear fashion, an increase in gain continues linearly throughout
the entire rotation of the control. The amount of overdrive is increased by turning the GAIN CONTROL up beyond the clean area of
operation, and the overall volume will be controlled by turning the CHANNEL VOLUME down as needed.
HIGH PASS FILTER:
maintaining control over the extreme low end (especially under high drive conditions). This precision two pole variable filter is adjustable
from 25Hz to 125Hz. While HPF's have been standard fare within the pro audio industry for decades, this feature has only appeared
in bass guitar amplifiers within the past few years (with some notable exceptions). This filter provides additional mechanical protec-
tion to the speakers from over-excursion by reducing the power to the speaker below the frequency range that the speaker cabinet
provides adequate acoustic loading to the speakers. This is one of the primary (and preventable) causes of premature speaker failure,
especially with compact speaker cabinet products that are driven very hard. A second use for this filter is to roll off the very low end
when overdriving the amp. This prevents the signal from becoming muddy, and preserves the naturally musical growl and grit of the
overdriven signal. A third use is for rolling off the extreme low end when boosting the bass eq control, allowing for some unique low
mid voicings, and a fourth use is for reducing the sub-bass frequencies that can get out of hand in a boomy room. Experimentation
will be helpful in all of these applications. This control sweeps between a linear scale between the labeled endpoints. The 12:00
position equates to ~75Hz.
BOOGIE TONESTACK EQ:
back to Randall's earliest days, hand building amps in a Lagunitas mountain shack (a converted dog kennel). Starting with the Mesa
450, the path was set, and along with Doug, Mike, Jim and Dan, all still with us today, the rest is history. All of these legacy amps
have this tonestack in common, and this amp takes this tonestack to a new level with more refined and smoothly operating BASS-
MID-TREBLE controls plus a new sweepable MID FREQ (MID SHIFT) control which provides expanded range and Q of the mid
portion of the circuit. Even though this is a "passive" tone network, additional makeup gain circuitry makes it even more usable and
toneful than before by reducing inherent losses through the passive network. These are evolutionary steps in our path, evolution
being something that we have done continuously over the past 50 years.
BASS CONTROL:
This control is shelving type filter, responsible for the amount (or volume) of low frequencies present in the
signal, relative to the rest of the spectrum. Low frequencies (<80Hz) are responsible for the "depth", "bottom", "roundness", and "feel"
of the tone. The HIGH PASS FILTER control, combined with the BASS CONTROL adds another dimension of tone sculpting by rolling
off the extreme low end when boosting the bass eq control, allowing for some unique bass and low mid voicings.
MID CONTROL:
This control is responsible for the amount (or volume) of midrange present in the signal, relative to bass and
treble. There is an inherent mid dip present (in this design around 500Hz), which is characteristic of this style of tone stack eq, so
for a stronger, flatter response you will find this control set between the 1:00 and 4:00 positions will get you there. The midrange is
responsible for the articulation and perception of pitch, especially in the lowest octave of the instrument, because of how the harmonic
spectrum is distributed in the output of a bass guitar's signal.
This switch (and its associated blue "tally" or "indicator" LED) engages the BRIGHT filter, which causes a
This control sets the low frequency roll-off point of the amplifier channel, and is an important feature in
This eq section is based very much on the legacy Bass 400/400+ tonestack, but also stretches
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