User manual

6
The Filter FM pot frequency-modulates the filter frequency with the audio output of the
VCA. So the output signal of the filter passes through the VCA (which includes the Muffler
on its output) to the Filter FM pot, which feeds none, some or a lot of this signal back into
the filter frequency. This gives edginess and complexity dependent on the signal level
coming out of the VCA – so it is stronger on accented notes. At higher settings, the results
approach chaos.
A three position Muffler Switch is provided. This affects the output of the VCA and
provides two types of muted clipping. This distortion is unique to the Devil Fish and is only
roughly comparable to fuzz clipping. It softens the loudest extremes of the sound and
introduces a moderate level square wave clipping buzz, whilst allowing the bass to pass
largely unaffected. The Muffler affects sounds which are louder than usual – those resulting
from high levels of Accent or Overdrive or high level external audio input signals. It has
little or no effect when the signal level at the VCA output is low.
New Functionality
Bass response is improved. In the TB-303, 32 Hz was down by 5 dB. Now it is down by 1
dB.
In the TB-303, the start of the audible note was between 1 and 5 ms (typically 4 ms) after the
start of the gate signal. In the Devil Fish, notes start within 0.5 ms.
In the TB-303, the decay at the end of an unaccented note was about 16 ms – 8 ms of normal
volume and 8 ms of linear decay. In the Devil Fish, this is now a more natural logarithmic
decay which starts immediately after the gate signal ends.
The range of the filter’s Cut Off Frequency pot has been increased so it goes higher and
lower. The maximum resonant frequency of the filter, with no Env Mod or Filter Tracking,
is approximately 5 kHz. This is an octave above the typical maximum for the TB-303.
The Env Mod pot range has been tripled and made to include no Envelope Modulation.
There is an on/off LED to show when the Gate is active. This LED is located in the ‘e’ of
the Devil Fish logo.
Two LEDs show, by their brightness, the output voltage of the Main Envelope Generator
(MEG). One is for the normal notes and the other is for accented notes. These are located
adjacent to the Normal Decay and Accent Decay pots which control the MEG.
The maximum cut off and resonant frequency of the filter is limited to approximately 20
kHz. This is to reduce the likelihood of oscillations at extreme frequencies which may cause
undesirable outcomes with digital audio ADCs, loudspeaker systems and canines.
Within the limitations noted above, regarding bass response and starting and ending of notes
(which are generally not perceptible), the Devil Fish can still sound exactly like the TB-303.
Details of restricting it to the TB-303 subset of its sound potential are in the next section.
The battery arrangements for retaining memory contents in Devil Fishes are discussed
in detail in a separate manual: DF-Memory-Backup.pdf. (Devil Fishes with the
Quicksilver 303 system need no batteries for their non-volatile pattern, track and
configuration memories.) The following is a summary of the options.