aion VULCAN Manual - Page 6

Browse online or download pdf Manual for Music Equipment aion VULCAN. aion VULCAN 11 pages. Effect type octave fuzz; based on foxx tone machine; a classic untamed fuzz from the 1970s that adds an octave-up overtone

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BUILD NOTES, CONT.

Tone control modifications

Midrange switch

The Tone Machine's tone control is reminiscent of the Big Muff in its topology, but missing a resistor to

ground on the treble side to complete the filter, and with a very low value for the treble capacitor, which

makes it a little harsh on higher settings. By changing the capacitor to a higher value, the frequency

range is increased and the treble side of the control becomes a lot more usable.

Big Muff resistor

As mentioned previously, the tone control is one resistor away from a Big Muff tone control. An optional

resistor, RX1, has been added in case you want to experiment to see how it sounds. Start with 22k as a

value. R17 and C13 can be adjusted as well to match a Big Muff variant.

Minimum bass value resistor

R18 sets the minimum value for the bass side of the knob rotation, setting it approximately 10% higher

than a standard Big Muff tone section. If you want more bass (especially if using modified filter values to

be more like a Big Muff) then you may want to jumper this resistor to give the control more range.

Octave switch

The octave in this effect is generated by splitting the signal into two, one in-phase and one out of phase,

and then rectifying the signals to cancel out half of the waveform of each. The signals are then combined

back together which emphasizes the octave overtone.

The octave switch lets you disable half of the phase splitter to cancel out the octave effect. However, the

non-octave signal still passes through a series diode (D2) which introduces something called "crossover

distortion". While this crossover distortion is part of the sound of the Tone Machine, it sounds very good

without it as well and justifies having its own setting.

As a result, the octave switch has been modified to have Octave, No Octave (original) and No Octave

(modified) settings.

R23 resistor

In Version 1.1 of the Vulcan, a new resistor (R23) was added to one half of the octave generation path.

This is a counterpart to R10 that ensures that both sides of the octave signal are held at the same DC

voltage.

The vintage Tone Machine units were missing this resistor, so they had a pop when switching the octave

on and off. This can be considered a design flaw in the original units. There is no change to the tone by

adding this resistor since it only impacts the DC voltage, not AC (signal), but it can be omitted if you

want it to be 100% stock.

VULCAN OCTAVE FUZZ