Please note: Ready made units and PCBs for this project are no longer available.
This was a heavily revised edition of the hugely popular TB3030 project. The 3031, pronounced as 'thirty-thirty-one', is designed to be built into a 1U 19" rack. All the thirteen knobs, the four switches and the four LEDs are designed to be mounted directly onto the printed circuit board. This simplifies building and reduces the possibilites of any mistakes in construction.
There has been some revision of the circuitry too. Gone is the old 4013 based sub-octave circuit. In its place, a new 'all discrete' divider and waveshaper. You now have the choice of triangle or sawtooth waveforms with a front panel switch. This results in a much more musical sub bass than the old digitally generated square waves.
The Overdrive circuitry has been revised to allow changes in 'overdrive' level without drastically affecting overall volume. The overall output noise has been reduced too.
The more difficult to get parts have all been replaced with current devices. Careful selection of the replacement parts have led to the new circuitry yielding the same TB sound we all love.
The VCO circuitry is easier to tune and set up, and space is now provided for the more accurate wirewound temp co resistors.
The PCB itself, as well as being a different shape, has been laid out for minimum noise and ease of construction. The legending has been made clearer and its easier to interface to the tbDAC too. The size of the PCB is 15.7" (399mm) x 4.1" (104mm).
A close up of the VCO, waveshapers and filter section of the 3031's sound engine.
For those of you not familiar with my original TB303 clone, the 3031 includes, a balanced output, an overdrive/distortion circuit, filter FM, a sub octave generator, VCA decay control and an accented decay control.
The unit also incorporates a circuit that allows a velocity CV to control slide and accent. This means that computer sequencer users can simply control accent and slide by velocity values. MC-303/505 owners with a midi-CV convertor will be able to get complete control of the 3031 by using the four velocity pads on the MC's front panel. This is a very powerful feature that can be used by computer sequencer users and keyboard players too.
A closer view of the left hand side of the front panel. Here we can see the VCO and filter control surface.
I have made the 3031 fully compatible with traditional gate and CV. It does not have MIDI. You will need a midi-CV convertor to use a computer sequencer or modern keyboard controller.
The gates are any positive voltage up to 15V. The velocity CV can be driven up to 15V but it will not respond to anything higher than 10V. The velocity CV control is split into four bands. Low values of velocity CV will give no accent or slide. With slightly higher values, accent only is triggered. Higher values still will produce slide only. And higher values still will produce slide and accent, should you need it. The sensitivity of the velocity CV input can be easily controlled by a trim pot on the board. When played with an ordinary midi keyboard, the results can be quite confusing at first. But you will soon learn how to get control of your sounds.
A view of the rear of the front panel. This shows the PCB mounted pots, switches and LED. This makes the boards much easier to build than the previous TB3030 design.
The design is to be powered from a AC wall wart with an output of 12V or 15V at 200mA. An internal mains transformer may be fitted by more experienced builders. The onboard power supply has been designed to able to run many other additional circuits if needed.
For a suitable MIDI to CV convertor you can use any good quality commercial midi-CV unit such as the Kenton Pro-Solo or Pro-2000.
Please note: The 3031 does not contain a sequencer.
Project Downloads
Use 'save as...' button to download and view the file. IE users need to right hand mouse click and then choose 'save as'. Links to schematics are available to purchasers of the PCB or module and will be sent via e-mail when the board(s) are shipped.
Schematics and PCB data
Ready made PCBs are no longer available. However, schematics, gerber and drill data can be purchased for non commercial use. The schematics are 4UKP, and the gerber plots are an additional 5UKP. All data is provided as downloadable files only.
Schematics and any other data is provided for non commercial use only. You may build as many PCBs as you wish but the EULA forbids any PCB to be sold for commercial gain.
E-mail us here to purchase any of the schematics for any of the discontinued projects. See the prices page for ordering information and payment methods.
Front Panel Database
I have also a database for Schaeffer-Apparatebau panel design software for one 3031 in a 1U rack available for free. The database for my panel design can be found here: 3031.fpd To read this file you will need a copy of 'Frontplatten designer' from Schaeffer. The program also features on-line ordering, so its now even easier to buy your panels from Scheaffer. The company are based in Berlin in Germany and will send out panels to anywhere in the world. Delivery to the UK normally takes around ten days. For North American users you can also order your Schaeffer panels from Front Panel Express.
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