• Just click on the image below to download a PDF of the schematic and stripboard assembly details •
The schematic above shows the relay version of the interface circuit.
This is the (slightly) more complex of the two versions. The Vent remote socket and the YC61 sustain input jack are isolated from the electronics - and from each other - by the use of a G5V2-H1 12V DPCO relay.
A current of around 10 mA flows through the relay coil when it is energised.
The relay controls 2 x volt free 'changeover' contacts which - in conjunction with the selectable links D,E, F and G - allow both outputs to be configured as 'normally open' or 'normally closed' contacts.
When used with a 'normally closed' Yamaha sustain pedal and a Vent - and using output 1 to control the Vent - links E and F would be fitted.
Q1 and Q2 allow for function inversions, so that the Vent speed control is always activated when the input footswitch is pressed. This applies when used with either a normally open or normally closed sustan footswitch.
In addition, the relay is only ever energised when the footswitch is actually being pressed, regardless of the input footswitch polarity.
For a normally closed input footswitch, links A and C are fitted.
For a normally open footswitch link B is fitted.
R1 and R2 serve to provide DC bias to the bases of Q2 and Q1 respectively.
The unit only draws about 1mA of quiesent current, until the relay is activated by pressing the footswitch, where it rise to c.10mA.
D3 is fitted to protect against any damage that may occur, if a DC power supply of the wrong polarity (tip -ve) is connected in error.
It's important to note that the Vent 2 output jack socket MUST be a stereo (TRS) type. Connections are made to the RING and SLEEVE terminations.
(The TIP connection is not terminated on the Vent 2 output socket).
Both input and output footswitch jack sockets can be either mono or stereo, as they both only require connections to the TIP and SLEEVE terminals.(Note that the schematic shows stereo sockets fitted for all three jacks).
To see details of how to assemble the stripboard for this version, just click on the schematic image at the top of the page for assembly details...
This relay version provides more comprehensive linking options, to allow for both polarity selections on all inputs and outputs.
The circuitry is more complex than the opto version (but only marginally!) and the unit does provide for 2 isolated volt free changeover contacts, to cover most requirements.