Reason SM20 amp
The SM20 amp is a combo and was fashioned after it’s
bigger brother, the SM40. It features independent Normal and Bright
channels, each voiced to deliver wonderful vintage tones in
“plug n’ play” fashion. Additionally, it
delivers a third channel or mode, called StackMode™.
The StackMode™ feature on this amp sets it apart from any
other amp on the market. Using StackMode™ will allow you
access to a broad range of sounds including some that are simply not
possible on other vintage voiced amplifiers. Furthermore,
StackMode™ allows you the ability to adjust unique parameters
through its simple control set and interactive features.
Reason SM20 Specifications:
- Output: 20 watts RMS @ 10% THD
- (2) EL84 output tubes, in Class A Cathode Biased
configuration
- (2) 12ax7 preamp tubes
- 5U4 Rectifier tube (GZ34 may be suited for higher plate
voltage)
- 3 way Stack switch - Normal, Stack, Bright
- Normal channel – Volume, Tone
- Bright channel – Volume, Tone
- StackMode™ – Bright & Normal
channel controls are active, Stack Volume & Hi-Cut
- Oversized extra capacity power supply
- Harmonics Switch - works in the final output stage to
change the harmonic structure of the overdrive.
- Power Switch
- Standby Switch
- Independent output jacks for 4,8, 16-Ohm operation
- Footswitch access to all three channels/modes
Inputs – Inputs High/Low sensitivity. This traditional input
arrangement allows for a wide variety of
tones and loading options. Careful selection of the input will maximize
response from the guitar. For
example, overly bright single coil pickups may benefit from the loading
of the low sensitivity input as
highs will be reduced slightly. Humbuckers can be used in the Low
sensitivity input to gain more
clean headroom. In either case, the High input will yield more gain and
high frequency response.
Normal Channel – The Normal has a classic vintage voice that
is British in flavor, while still retaining
a personality that is unique to the SM40.
Tone – Functions as a hi-frequency roll-off when Normal
Channel is engaged. Settings of 2-3
on the tone knob will provide the flattest frequency response curve. As
the knob is increased
from 2-3 onward, more mids and gain are added to the sound. From 8 to
its maximum setting,
the bright capacitor is fully engaged and the Reason amplifier will
achieve “glassy” highs. The tone
knob has maximum effect at lower settings of the volume knob and
gradually less effect at
higher volume control settings.
Volume – Controls volume of amplifier when Normal Channel is
engaged. Gain is increased
in higher settings.
Bright Channel – This channel is identical to the Normal
Channel, but has some extra high
frequencies built in. Additionally, a larger bright capacitor allows
more high mids to come through,
making the Bright Channel more cutting and aggressive when the Bright
Channel Tone control is at
maximum setting.
Bright Channel Tone – Functions as a hi-frequency roll-off
when Normal Channel is engaged.
Settings of 2-3 on the tone knob will provide the flattest frequency
response curve. As the
knob is increased from 2-3 onward, more mids and gain are added to the
sound. From 8 to its
maximum setting, the bright capacitor is fully engaged and the
amplifier will achieve “glassy”
highs. The tone knob has maximum effect at lower settings of the volume
knob and gradually
less effect at higher volume control settings.
Bright Channel Volume – Controls volume of amplifier when
Bright Channel is engaged.
Gain is increased in higher settings.
StackMode™ – Reason’s proprietary
StackMode™ feature is a switching circuit that allows you to
select between two independent channels (Bright & Normal) in
the typical fashion. Additionally, you
can select the “Stack” setting, where both channels
are then arranged in series. In the “Stack”
setting, use of the Bright & Normal channel controls are
retained.
Stack Volume – Controls the overall volume of the amplifier
while in StackMode™ and is in
design, a post phase inverter master volume. At maximum setting, this
control is taken out of
the signal path and the amp essentially becomes a non master volume
amp.
Stack Hi-Cut – Active only while amplifier is in
StackMode™, the Stack Hi-Cut is the amps
final tone control and works in the power section of the amplifier.
Maximum high frequencies
attenuation is achieved at maximum setting (clockwise.)
Harmonics Switch – The harmonics switch works in the
amplifiers phase inverter section by
changing the structure and drive level being fed to the output tubes.
The effects of this control are
more noticeable at higher volumes.
When set to “Even”, the control suppresses the
higher order odd harmonics, thus accentuating even
order harmonics. Conversely, when set to “Odd”, the
control does just the opposite. It drives the
tubes hard and clips them symmetrically for maximum harmonic richness.
