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* The two wires from the AGND and DGND pad must be brought back separately to the one
G1 pad on the 3031. The two wires will fit into one pad quite nicely. The 3031’s accent, filter
and slide pads are left unused.
The midi IN and THRU connections must be made to the tbDAC as detailed in the tbDAC’s
User Guide.
CV, Gate and Audio Connections
If you have fitted the tbDAC you need only one audio connection. This is your output. If you
are building a completely analogue unit you need five 1/4” sockets to interface to your system.
These are: audio output, pitch CV, velocity CV, modulation CV, and gate.
The audio connection is a balanced output but it is simple to wire up. Some people have used
an XLR-Cannon socket for this, but this is costly and the large hole makes for a difficult
exercise on sheet metal working. You can simply use a stereo or two pole 1/4” jack socket.
Most mixing desks use this sort of connector for pro level signals. These type of sockets are
sometimes called TRS or tip-ring-sleeve. Use twin screened cable to connect the socket to the
board. This is the type that has two cores and one screen surrounding the pair. Its sometimes
called microphone cable. You can use a twisted pair instead if you wish. This is just two wires
tightly twisted together to form a simple cable.
Connect the tip connection of the jack socket to the OUT+ pad on the PCB. Connect the ring
connection of the socket to the OUT-. If you have used screened cable then connect the
screen at one end only to the sleeve or earth connection of the jack socket.
If you are not fitting the tbDAC then all your interfacing must come through separate sockets.
I would use 1/4” sockets as these are much more reliable for CV and gate than those horrible
3.5mm types. Plastic types are recommended in this case as they will be insulated from the
case.
All the CV and gate sockets will be two pole, or mono, 1/4” sockets. Each socket has two
connections. One is the tip, and this will carry the signal. The other, the sleeve, is the common
ground or earth. The ground tags of each socket must all be connected together by a single
piece of wire. I often use uninsulated wire for this purpose. This commoned connection now
needs to be connected to the main ground on the PCB. Do this with a single wire. This should
connect to the G2 pad on the TB3031 PCB. Thus all the ground lugs are now connected to
the TB3031’s main ground.
The signal lugs of the sockets, the tip connection, should then go to the relevant pad on the
board. Pitch CV to KBD, Gate input to GATE etc.
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