User manual

32
Version 2.1C
[30 May 1999] This is the same printed circuit as 2.1, but with further changes to
achieve:
1. Filter CV in is now about 1 volt per octave (exponential response). In 2.1A and
earlier it was a linear arrangement – a certain number of Hertz per volt. In 2.1B it
was linear up to about 4.2 volts and above that, a more sensitive linear response.
2. Internal adjustment to ensure that the maximum resonant filter frequency (no Env
Mod, Filter Tracking or external CV In) is 5 kHz – an octave above the standard
frequency of the TB-303. Previously component variations caused this frequency
to vary somewhat from one Devil Fish to another.
3. The Filter Tracking circuit has been altered to give more tracking at lower settings
of the pot. The maximum tracking remains unaltered.
4. A small internal change to stabilise a voltage in the filter driver.
Starting with serial number 070 [19 November 1999] I added a resistor across TM6 to
make it easier to adjust the 5.333 volt voltage correctly. This has no effect whatsoever on
the sound – it is just to make it easier to calibrate. Sometimes the voltage cannot be
calibrated properly with this resistor, so I remove it or replace it with a higher value.
Starting with serial number 081 [4 April 2000] I altered the battery supply arrangements
for the 32 bank memory system to avoid potential problems when C-cell batteries are
installed. See discussion above on known reliability problems.
Starting with serial number 084 [13 April 2000] I bent the fixed contact of the CV In
sockets a little to increase the pressure the spring contact makes on it. See discussion
above on known reliability problems.
Version 2.1D – a new Slide In arrangement
[11 November 2003, starting with serial number 157.] All subsequent Devil Fish
modified TB-303s have the same sound as with this version of the modifications. The
later versions involve some other changes regarding LED brightness, CV inputs and
outputs etc. – but these do not affect the sound it makes.
Version 2.1D is the same as 2.1C, but with updates to the Slide In and Gate in circuit as
described above and below. This was to make it compatible with version 3.0. which is a
new printed circuit design which embodies all these features which previously were
modifications to the 2.1 circuit boards. Therefore, version 2.1D is functionally identical
to version 3.0.
The musical concept of a slide is for one note event (in terms of triggering envelopes) to
begin at one pitch and to transition to another pitch with an audible slew between the two
pitches. In the TB-303 sequencer, this is achieved with two or more notes (that is a pitch
with a timing value of one or more steps) where the first one or more notes has the Slide
bit turned on. The result is that what would otherwise be two note events, with two
pitches, and two separate activations of the envelope generators, is turned into a single
longer note event, starting at the start of the first note and ending at the end of the second.
Thus, Slide in the TB-303 sequencer ties two notes together in time to become one, whilst
turning on a “slide slew” circuit (IC11B following C35 driven by the 100K impedance of