User Manual for the Devil Fish mods to the TB-303 Robin Whittle 6 February 2015 www.firstpr.com.au/rwi/dfish/ (Modification versions 2.0 to 4.2B.
Introduction This manual is for the Devil Fish modifications to the Roland TB-303’s synthesiser. Please see separate manuals for the MIDI In System, the MIDI In and Out system and the 32 Bank Memory System. This manual covers Devil Fish versions 2.0 (1996) to 4.2B (February 2015 and to the present day). It does not cover the 18 version 1.0 and 1.1 Devil Fishes from 1993 and 1994. Starting with Version 4.
New Inputs, Outputs, Controls and Functionality This is a list of Devil Fish features with a brief explanation. The exact voltage levels etc. are detailed in later sections. CV Inputs CV and Gate inputs. The CV and Gate outputs remain available too. Two Control Voltage inputs to activate the Accent and Slide functions. The Slide input also activates the Gate function at a higher input voltage Separate CV In to drive Filter Frequency in addition to the other internal signals which drive it.
New and Changed Controls The Overdrive pot controls the level of Oscillator signal fed to the filter. This varies the amount of oscillator signal between none, through normal to heavy overdrive (66.6 times normal) which causes the filter to operate under duress. There is no danger to the filter, but the sound is big. The Slide Time pot. Normally the slide time is 60 ms (milliseconds). In the Devil Fish, the Slide Time pot varies the time from 60 to 360 ms, when running from the internal sequencer.
• Sweep Speed Fast mode: The first accent causes a strong positive output, but subsequent accents produce a smaller output. • Sweep Speed Normal mode: This is the same as the standard TB-303. The first accent causes a positive output, but when the resonance pot is fully clockwise, this sweeps upwards and some charge remains in a capacitor (C13) by the time the next accent occurs. Consequently the second and subsequent accent pulses cause a higher output than the first.
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.
Until early 2015, we installed a soldered-in cylindrical lithium battery in order to keep the memory alive for at least ten years. Since then, due to restrictions on lithium batteries in airfreight, with Version 4.
Limiting the Devil Fish to TB-303 sounds The Devil Fish’s “sound-space” is immense. A mild-mannered subset of this space is that of a standard TB-303. Some users wish to restrict themselves to that space for sacred occasions. Here are the limitations to observe. The original pot settings are specified in terms of a clock face. For instance the third line from the far left position is 9 o’clock Filter Cut Off Between about 10.30 and 3 o’clock. Resonance No limits. Env Mod Between 12 and 4 o’clock.
What Does it Sound Like? Sound samples are available at the web site’s sounds/ directory. The musical implications of all the above changes are diverse and extreme. If you are interested in solid, heavy bass sounds, idiosyncratic synthesis or weird-and-wonderful sounds you have never heard before, then I promise you that you will really enjoy the Devil Fish.
leading a healthy life . . . following simple pursuits . . . Four years engagement with the Devil Fish and this spirited artist was signing his emails . . . “mooooooo”. Please try to avoid spilling things into the Devil Fish. The basic machine, and especially the modified machine, is difficult to work on. Never spray anything inside the Devil Fish, or any other item of electronic equipment, ever. Pure water does the machine little or no harm, so don’t worry if it gets rained on.
Audio Input Voltages The two audio inputs – Filter FM (Tip of what used to be the Headphone jack) and Audio In to Filter (Mix In jack) require line level signals. Microphone or guitar signals are not high enough. -10 dBm line level signals will be OK, but you may want to drive something harder so you will need a higher level. You can’t do any damage by driving large audio signals into these inputs.
(Cut Off, Env Mod, Filter Tracking, Accent and Filter FM) plus the AC-coupled audio modulation from the tip of the old headphone socket. The filter is not a precise system and this input has a nominal 1 volt per octave response. This response is not tested or guaranteed. It may change with temperature, and with the many other things which are driving the filter frequency. A good way of driving the Filter CV In would be a 0 to 5 volt Mod Wheel output from a MIDI to CV converter.
Filter CV In for Devil Fishes prior to 2.1C With versions 2.1A and earlier, this input had an unloaded voltage of about 1.0 volts. Applying a voltage below this would lower the filter frequency. With version 2.1B, the unloaded voltage was about 3.7 volts. Any voltage below this will lower the filter frequency and any voltage above this will raise it. The 2.1B arrangement is a lot more sensitive then 2.1A – a given range of input voltages will achieve a wider variation of filter frequency.
Synthesizer Accent and Accent Out The Accent function of the internal synthesizer and the Accent Out signal are both activated when any of the following are true: 1 The internal sequencer is running and an accented note is being played. 2 The internal sequencer is not running, but the last note had the accent on. 3 The Accent In socket has more than about 2.3 volts going into it. 4 The red “Accent Pushbutton” on the right of the front panel is pushed.
current could upset the Devil Fish / TB-303, but will not cause damage. This is a high gate voltage. If you need to drive a Moog or Korg active low gate, you will need a little circuit comprising of two resistors and a transistor to invert the polarity of the signal. (In my experience, Mini-Moogs are entirely unsuitable for driving from external CV and Gate, unless they are extensively modified.
Slide Slew Times The Slide Time pot gives you longer slide times than normal and can give you shorter times when running from CV In. The slide time – how long it takes for the internal CV to the Oscillator (and Filter Tracking Pot and CV Out) to slew from one level (and therefore oscillator pitch) to another – is proportional to the sum of three separate resistances. Resistance is an electrical term similar to impedance.
occur with high impedance inputs, but this may not be entirely accurate over all temperatures, or at the highest and lowest pitches Slide In Thresholds and Gate In versions 2.1C and earlier, the Slide In had a single function: to turn on the slide slew circuit. Slide In did not turn on the Gate of the synthesiser.
Accent Sweep Switch and Resonance Here is a tabular description of the two functions of this three-position toggle switch. Accent Sweep Switch Accent Sweep circuit enabled Resonance High means the filter will self resonate at mid & high frequencies when the Resonance pot is past about 2 o’clock. Use it for: 2 Yes Normal Acidee sounds with the Resonance pot fully clockwise. 1 Yes High Whistly filter sweep sounds. 0 No High Self resonant filter with no sweep on accented notes.
chaotic mess. At times, I have had this arrangement with the controls finely tweaked so that on some cycles through a pattern, the filter resonates with the spiky, “nutty” sounding intense Filter FM at about the frequency of the Oscillator, but at other times at half the rate (an octave below), or less. This is somewhat like not quite blowing a trombone into its second octave. Thus, a totally repetitive sequence can result in randomly very different sounds.
the machine reliably for 3 or 4 hours. Some machines may be more robust and others more flaky – depending on how fussy the CPU chip is. After these changes, I expect machines should run for 5 or 6 hours before the battery voltage falls to the point where the CPU may malfunction. These times are not guaranteed. The actual running times depend on the batteries, the temperature, what the Devil Fish is doing, and especially on the characteristics of the particular CPU chip.
the Devil Fish. These are the original 1980s design adaptors with a 50/60Hz mains transformer, rectification (such as with four diodes), capacitor and linear regulator. By 2011 these have been replaced by completely different adaptors with similar names: PSA-100S, PSA-120S, PSA-220S, PSA-230S and PSA-240S. All these “S” model adaptors are “switch mode” adaptors, also with proper voltage regulation.
A good adaptor will put out 9.0 to 9.5 or maybe 10 volts maximum when the Devil Fish is running from it. If the Run/Stop LED does not light fully and without fluctuation when the sequencer is running, then the external power adaptor (or the C-cell batteries if this is what you are using) are not supplying sufficient voltage. The machine may work OK with higher input voltages, for a while – but the internal regulator transistor will be asked to drop 180 mA through more than its intended 3.
The dual 10 ohm output circuit with the original, large, 1000uf bypass capacitor is capable of driving headphones hard, including headphones with impedances as low as 8 to 16 ohms. If you want to drive a small loudspeaker, please use a stereo socket and tie both the ring and the tip of your plug together, with that driving one terminal of the speaker, with the other terminal going to the ground of the plug. In general, do not plug a mono 3.
Idiosyncrasies The Devil Fish is a denizen of the catacombs of Idiosyncrasy City. Here are some of its peccadilloes. With version 2.1 and earlier, there used to be a certain amount of clicking at the start of notes and sometimes at the end of notes – even when no sound was being produced, on un-accented notes when the Soft Attack pot was fully clockwise and the Decay pot was fully anti-clockwise. Version 2.
down the Filter Tracking pot, and removing or changing the Filter CV input voltage. Another reason for not hearing any sound is the Decay pot being fully anti-clockwise whilst the Soft Attack pot is fully clockwise – but only for non-accented notes. Beware too of the waveform switch being in mid-position! Potential reliability problems In general I have been very happy with Devil Fish reliability.
The sockets I use seem to be robust and have plenty of spring-pressure on the contacts. I don’t know of any other “better” sockets and the problem is so rare I cannot reproduce it – so I have no means of being sure I have entirely eradicating it. The problem is occasional, since there have been only a few reports from users and one instance with a newly modified Devil Fish I was testing.
when the mains voltage is rather low (say 110V or 220V AC) then the same power supply, when cool, unloaded and running from a higher mains voltage (120 volts or greater than 240 volts) is bound to put out significantly more than 9 volts. The question is: what voltage is the adaptor putting out in practice, when loaded by the Devil Fish? 10 or perhaps 11 volts is probably OK. Anything above this risks overheating Q45, and so causing damage soon or in the long-term.
Small pots and toggleswitches in the Devil Fish board There have never been any problems with the seven beautiful little ALPS pots used in the Devil Fish. Likewise the C&K 8125 switches used beneath the Accent button (and in the memory system) seem to last forever, unless something smashes against the button. There have never been any failures of the 6mm sockets used in the TB-303 (Filter In, Filter Out/FM and Audio Out) – these are remarkably reliable sockets. There have never been any failures of the 3.
this problem, and the fact that the shafts of these 2006 to 2009 Resonance pots are too large (I drilled out the knob’s splined hole) we are very fortunate that Technology Transplant has gone to the trouble of having these pots manufactured. In late 2009 and early 2010, there was a new batch of pots from Technology Transplant. There is still this minor problem with the Resonance pots being “log” on both ends.
Applications It was quite a few years before the idiosyncratic personality of the TB-303 was fully recognised. Most of the things you do with the Devil Fish will be unique because the combination of your music and the new sounds have never been tried before. There is a great deal to be done, just with the machine as it stands, playing from its internal sequencer, synched up to other equipment.
Version History Version 1.0 and 1.1 [April 1993 to April 1994, serial numbers -001 to 016.] There is no musical or functional difference between these versions. Version 1.1 used a more convenient value for the Accent and Normal Decay pots, which simplified the modification a little. In Version 1.0, I had to use different pots while I waited for the right ones to arrive from Japan. Some of these machines had the Sweep Speed switch retrofitted. All version 1.
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.
the DAC in the standard TB-303) which causes any pitch difference between the notes to be audibly slewed. (Normally, without Slide, C35 is driven by the IC11B op-amp, which follows the DAC voltage directly.) In MIDI there is no formal concept of a slide.
Version 3.0 [February, March and August 2004, SNs 162, 163 and 164.] This is sonically identical to version 2.1D. There are two changes: 1. The printed circuit board is a fresh design, integrating the changes listed above which were done as modifications to the 2.1 boards. 2. I pack the six small TB-303 knobs (Tuning to Accent) with a small insert, which together with the “Blu-Tack” which helps stop the knob from coming adrift, causes the knobs to be about 1.5mm higher. This makes them easier to turn.
they reduce the voltage drop between the four C-cell batteries and the CPU, enabling the machine to run from a lower total 4 x C-cell voltage. The standard TB-303 draws about 85 mA, or more depending on the number of LEDs illuminated, whether the headphone amplifier is on, and what signal it is driving into the headphone load. The Devil Fish draws more current, depending on the three new LEDs it may be turning on – Gate and either the Normal or Accent Decay LED.
3. A 1 amp silicon diode 1N4004 is wired across the lower current D2. This reduces the voltage drop to the CPU from about 612mV to 545mV – a drop of 67mV. The silicon junction voltage drop is intentional in the design, since (apart from the drops in Q44 and R168 above), D2 is the only mechanism for providing the CPU with its proper voltage. Since four fresh alkaline batteries can provide as much as 6.
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.
capacitors in parallel with 33k resistors, to ground, for both the Clock and Run/Stop pins of the Sync socket. The reason for this is explained is the following paragraphs: There can be coupling between the two MIDI signal wires (for pins 4 and 5 of the 5 pin DIN socket – the intermediate pins) and the two outside pins (1 and 3) which are for DIN Sync, if the cable has all five pins connected.
Document history o 1996-09-13: Initial version of “Release notes” o 1996-10-04: Updated to reflect the availability of patch sheets and polycarbonate face-plates. o 1999-06-01: For V2.1C.; 1999-02-05: For V2.1B.; 1997-09-22: For V2.1A. o 2000-03-09: Added a section on “Known Reliability Problems”. o 2000-04-12: Added to the “Known reliability problems”: Discussion of the CV input socket problem. An update on the 32 bank memory system C-cell battery problem.
