User manual

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available, just the exact knob position which provides each sound. This batch of pots has
shafts which are a little short, so we mount them on an insulating spacer to compensate
for this.
White LEDs can be used for the TB-303 front panel. This involves changing the drive
circuit for all LEDs, so if White is used, it must be for all the LEDs, except the Run/Stop,
which can be White or any other colour.
[January 2012. Starting with SN 260.] Some, many or all TB-303s have a low-level
buzz in the background, irrespective of the Volume pot setting. While this is well below
ordinary signal levels, it might be annoying. The buzz from LED activity – especially
with four LEDs on at once, such as when selecting patterns 1, 2, 3 and 4 – is apparent
when running from batteries. A higher frequency buzz, from the Interrupt oscillator, may
be audible when running from an external power adaptor. The lower frequency buzz
problem seems to be most apparent with the original LEDs or perhaps with any Red
LEDs. Blue LEDs have a higher threshold voltage and draw less current. The cause is
ground loop problems within the machine. The fix is a wire between the Output socket
ground terminal and the ACW (ground) terminal of the Volume pot.
Version 4.2A
[November 2013. Starting with SN 275, but some older machines I work on, such as to
upgrade to MIDI In and Out, will be marked V4.2A, even if they use an earlier PCB.]
This is sonically and functionally identical (apart from as noted below) to version 4.2 and
therefore 2.1D (2003-11-12). 2.1D differs only from the sonically identical Version 2.1C
(1999-05-30) due to the Slide In CV input also being able to turn on Gate.
V4.2A Devil Fishes use the 4.2 PCB – or an earlier 3.x or 4.x PCB if they become V4.2A
as part of an upgrade. All 4.2A machines have the ground level noise mod mentioned
above (January 2012). The other two changes are:
1. The pullup resistor for the Accent CV Out socket is changed from 10k in all
previous Devil Fishes to 3.3k. Assuming the machine has a healthy 6 volt supply
(it is running from an adaptor which is supplying ~9V, or its C-cell batteries are in
good shape) then this should be sufficient to pull up the Slide CV Input socket
circuit to activate both its Slide and Gate On functions. This is not guaranteed to
work if the machine is running from batteries which have a total voltage less than
about 6 volts.
2. I installed a hardware modification to the TB-303 so that the Internal Sequencer’s
Accent flip-flop is reset at power-on, to ensure it does not power up in the On
state. This caused no problems in the unmodified TB-303. It could be a problem
with the Devil Fish, due to notes being played by MIDI In and/or CV and Gate In
signals: if the Internal Sequencer has yet played any notes since the machine has
been turned on, then the Accent output of the Internal Sequencer may be On. The
workaround for this problem in Devil Fishes with version numbers 4.2 and below
is to briefly run a sequence which has no Accents.
All Devil Fishes I work on after December 2013, which have MIDI In, will have an
additional hardware modification (capacitors and resistors to ground from pins 1 and 3 of
the Sync / MIDI In socket) to combat capacitive coupling in 5 wire MIDI leads. Starting
in September 2014, when I finished the first MIDI In and Out Devil Fish, I used 0.01uF