Congratulations
You’ve just purchase what we believe is
the best amp on the planet! Welcome
to the growing list of artists who share
our mutual lust for tone. Now, we’d
like to better acquaint you with your
new Soul-o 45 amp.
Construction details:
1 - All components are hand soldered.
There are no quick disconnects, wire
nuts, or dipped connections and over
120 hand soldered connections on the
tubes sockets alone.
2 - All transformers are custom
designed and made exclusively for
Groove Tubes.
3 - GT S45 amps are designed to use
your choice of power tubes. Choose
from a total of 11 different tubes which
are currently available from our GT
catalog. Customized your S45 for tone
and power from 40 RMS watts to 65
RMS watts, depending on the selected
power tube!
4 - We use only double sided, double
thick PC boards with double thick
traces. We use chassis mount type
power tube sockets hand bolted, hand
soldered, and hand wired to the PCB.
This is the best of both worlds; PCB
and point to point construction.
5 - Each amps is handbuilt to order.
There are more than 18 hours of hand
labor in each Soul-o Series S45 amp!
6 - There is no particle board in any
part of our cabinetry, only solid core
American plywood.
Of course these features and
construction details cost more, but you
can really hear the difference!
The Preamp Stage
Most amp designers use a nice Gibson
or Fender guitar while developing their
design. These of coarse have magnetic
guitar pickups which are by definition
high impedance, low level output
devices. However, most players use a
foot pedal before the preamp, and
pedals are low impedance, high output
devices. The result is the pedal adds
two effects, the one you intended
(maybe distortion or chorus), and the
second effect “mush” as the pedal
overloads the amp’s preamp which
was intended to see a guitar pickup.
With this common problem in mind, we
designed the Soul-o 45 to be the first
ever
“Pedal Friendly” guitar amp,
with a preamp that will not overload
when pushed by today’s high output
pedals. This means it has “tons” of
headroom so the pedal breaths better
and remains open and transparent
sounding...and improves the punch
and tone of any pedal!
The S45 preamp stage has five dual
triodes, each performing multiple
functions in the circuitr y. The preamp
design has Gain, Bass, Middle, Treble,
and Volume. We did not design this
preamp for massive amounts of
distortion as you can get distortion and
other effects using your favorite foot
pedals. The S45 was deigned to be
pedal friendly, so the preamp will not
“mush out” no matter how hard you
play. Our design provides loads of
headroom in the preamp stage to get
the best possible results with your
pedals. However, an increase of the
Gain knob and decrease of the Volume
knob will produce a fatter, warmer tone
while the reverse produces a cleaner,
brighter sound. And when the pedals
are off, you get an amp that’s clean
and loud, yet warm and rich in
overtones.
The Passive Tone Controls
The tone controls of the S45 amp are
the Passive type, similar to those used
in older, classic tube amps. Many
amps made today instead use Active
type tone controls, which have a
separate gain section for each tone
band which literally “suck tone” from
the preamp. That’s why we don’t use
them. Passive controls use a
common tube gain stage to boost
the entire frequency range, then
divide the Bass, Middle, and Treble
with passive filters to shape your
tone. Passive tone controls are
more musical and interactive.
To get the most out of
passive tone controls,
start with all controls at
the 12 o’clock position. If
you want more bass,
either: a) crank up the Bass
control; or b) lower the
Treble control (compensate
the volume loss by
increasing Gain or Volume).
Because passive controls
share a common gain
stage, turning any one of
them fully up (or down!)
diminishes the effect of the others.
Also, our Passive tone controls are
“post Gain”, giving you a truly touch
sensitive amp that reflects your
personality. Strike the string harder,
and the gain increases into the tone
section, increasing it’s influence. As
you play harder and “push” the tone
section, the tone will brighten up. By
contrast, if you play with a lighter
touch, it gets rounder and fatter.
Lastly, remember as you play at louder
volumes, you will need progressively
less Bass level to reduce a mushy
bottom end. Experiment with this and
have some fun!
The Presence Control
This control is a part of, and interactive
with, the power amp stage. Increasing
it adds highs into the feedback loop of
the power stage and increases the
“touch” and “drive” of the amp while
also making it brighter. Use more
Presence for an acoustically dead
room, and less for live rooms. Season
to taste!
The Reverb Control
We’ve included perhaps the one effect
Groove Tubes Soul-o Series Guitar Amplifier Operators Guide
Soul-o 45
The
TM
All tube “Pedal Friendly” guitar amp with tube reverb.
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