Zeppelin Design Labs VPM-1, Owner'S Manual

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A WORD ABOUT DIGITAL POTENTIOMETERS: The expression upgrade comes with two different
digital potentiometer IC’s (integrated circuits). The digital pot that is installed on the board is labeled
MCP41050, which is a 50K ohm pot. The other IC is labeled MCP41010, which is a 10K ohm pot.
We provide the optional 10K pot because some newer pedals will perform better with this value. If you
would like to replace the digital pot on your expression board please see “APPENDIX 3: REPLACING
THE DIGITAL POTENTIOMETER” on page 25. Please fully read and pay close attention to the
information about static discharge so that you don’t damage your ICs!
STEREO UPGRADE
The stereo upgrade board gives the VPM-1 the ability to control a stereo audio signal. This upgrade
board has a second set of optocouplers on it and all the related circuitry to control the second audio
path. Both sets of optocouplers have been hand selected so that the channels will closely match
each other. The “stereo setup” routine (described in the VPM-1 Assembly Manual) uses software to
help match these optocoupler sets even closer. If you ordered your VPM-1 pre-built, this routine was
performed for you at the Lab.
The stereo function is controlled by the main board DIP switch (see “8. MAIN BOARD DIP SWITCH” on
page 10). Set Switches 1 and 5 to the “ON” position to enable stereo. The two TRS adapter cables
are used to “break out” the left and right channels. Plug them into the input and output jacks. The black
female jack on the adapter is the left channel (tip), and the red female jack is the right channel (ring).
While the stereo function is enabled, the VPM-1 can operate in two ways: panning configuration and
traditional stereo configuration. DIP switch 3 toggles between these two modes.
PANNING CONFIGURATION
When Switch 3 is in the “ON” position, the VPM-1 is in panning configuration. This means that
when the treadle is moved across its sweep, the pedal will pan between the left and right channels.
When the treadle is in the heel down position, only one channel will be audible; when the treadle
is in the toe down position, only the other channel will be audible. The reverse switch determines
which channel is active in each position; see “REVERSE TREADLE ACTION” on page 13. In the
middle of the taper’s sweep both channels will be audible (at half full volume when the linear taper
is used). We suggest using only the linear taper for the panning function; otherwise the sweep will
be lopsided, meaning one channel will fade in and out faster than the other.