Oakley 3031 - Manual (Page 2)

Introduction
The Oakley 3031, pronounced as 'thirty-thirty-one', is a heavily revised edition of the hugely
popular TB3030 project. It 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 possibilities of any mistakes in
construction.
There has been some revision of the circuitry compared to the TB3030. 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 affecting
overall volume as much. The overall output noise has been reduced too.
The more difficult to get parts have 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.
This User Guide is for issue 2 of the 3031. The new issue is identical to the original issue 1
design but for the following changes:
1. The area around the power components has been made larger to accomodate heatsinks if
used.
2. The number of ground pads has been increased from just one to three. This should help
when wiring up the board.
3. The pitch spacing for the TC resistor has been increased to reflect the larger KRL
component now supplied in the ‘odd parts’ kits.
3031 Features
1. The 3031 has an electronically balanced output. This is very useful to prevent earth loops
when connecting other pieces of equipment. Midi-CV convertors, for a good reason, use the
earth as signal ground. This can cause hum problems when you connect your analogue synth
to your mixing desk. The desk will earth the synth and so does the Midi-CV convertor. The
matters are made even worse if the synth has a safety ground. This multiple earth connection
can be bad news. One way of avoiding this is to cut the ground path in one of the leads. This
can cause tuning problems, or if the synth’s safety earth is removed, then it can be dangerous.
The best way of solving this is to use balanced connections. The 3031’s output can be
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