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Doc Q7.0
NEG FDBK
– This controls the amount of negative feedback, or damping, in the power amp simulation.
Higher values give a tighter and brighter sound but can sound harsh at very high master volume levels. Lower
values give a loose and gritty sound and feel. Like many other power amp parameters,
NEGATIVE FEEDBACK
is
set to an appropriate value whenever you change the amp
TYPE
, but it can then be changed as desired. For
example, you might dial in some negative feedback on a “Top Boost” to give the power amp a more
“American” sound while still retaining the preamp voicing.
MASTER VOLUME
– The almighty
Master Volume!
This is a very important control. It determines the
distortion and dynamics characteristics of the power amp simulator, and its setting is central to an amp’s
sound. As the Master is turned up, the tone controls will have less influence, and the sound will have more
“bloom” and touch sensitivity. Settings for
MASTER
don’t necessarily correspond to knob positions on the amp
being modeled. With a little experimentation on your favorite Axe-Fx II amps, you will learn to appreciate the
different
DRIVE
and
MASTER VOLUME
settings and how to enjoy different combinations.
When you select an amp
TYPE
, the
MASTER
will change to an appropriate/typical setting for that amp. If a
real amp doesn’t have a Master, the “correct” setting for
MASTER VOLUME
is 10.0.
At high Master settings, less drive is usually required, especially for high-gain types.
Amps designed for preamp distortion will typically sound great with the
MASTER VOLUME
set low to
prevent the tone becoming muddy or noisy. This includes the USA Lead types, SOLO 100, and others.
Amps with negative feedback (damping greater than zero) tend to have a “crunchier” power amp
distortion, which can get “raspy” if driven too hard. You can experiment with the interactivity of
DAMPING
(see
Advanced Parameters
, below) and
MASTER VOLUME
to achieve desired distortion timbres.
Setting
SAG
(see below) to zero will
disable
Power Amp simulation, at which point the
MASTER
becomes a
simple level control with 40 dB of range.
If more power amp gain is desired, the
MASTER VOLUME TRIM
) can be used
for increased range.
OUTPUT LEVEL
–
This is a copy of the
LEVEL
control on the MIX page for easy volume adjustment without
page turning. This only affects volume. It has no effect on tone! For many people, this is the “go to” parameter
for setting the output level of a preset.
Amp Speaker Page (“SPKR”)
5.1.4
These parameters shape the virtual speaker impedance curve and the resulting resonances in the virtual power
amp. Amp/Speaker interaction elicits an increase in power amplifier response at certain frequencies, affecting the
tone. Note that the power amp frequency response will not equal the speaker impedance if the
NEGATIVE FDBK
is
greater than “0” (because negative feedback
flattens
the response curve).
LOW FREQ, LOW Q, LOW RES
– Guitar loudspeakers have a low-frequency resonance, typically about
100 Hz. This shifts up slightly when the speaker is mounted in an enclosure.
HI FREQ, HI RES
– A loudspeaker voice-coil presents an inductive load to the power amp at high
frequencies. This inductive load, in conjunction with the output transformer capacitance, creates a high-
frequency resonance at the specified frequency.
XFRMR LF, XFRMR HF
– These set the output transformer bandwidth.
