User manual

11
Audio Input Voltages
The two audio inputs – Filter FM (Tip of what used to be the Headphone jack) and Audio
In to Filter (Mix In jack) require line level signals. Microphone or guitar signals are not
high enough. -10 dBm line level signals will be OK, but you may want to drive
something harder so you will need a higher level. You can’t do any damage by driving
large audio signals into these inputs.
Gate, Slide and Accent Inputs
The three new inputs – Gate, Slide and Accent are all high impedance inputs expecting a
positive input voltage. Impedance is at least 10k ohms and no damage will result from
putting + or - 15 volt signals into these inputs. They are all “On or Off” inputs – where a
positive voltage above about 2 to 4 volts is seen as “On”. The typical thresholds are:
Gate In 3.5 V. (1.5 V for versions 2.1C and earlier.)
Accent In 2.3 V.
Slide In 2.3 and 4.0 volts for the two aspects of its operation. (This is for V2.1D
and later – see the more detailed information below in the Slide section).
A typical application is the Accent In voltage being driven by the velocity output of a
MIDI to CV converter, so that those notes with a velocity above some particular value get
played with Accent on. Similarly, the Slide In could be driven from another output
voltage from the MIDI to CV converter – such as a mod wheel output voltage.
Filter CV Input
This enables an external control voltage to affect the filter frequency, in addition the
internal processes which are driving the filter frequency, and in addition to the audio
frequency modulation input on the tip of what used to be the headphone socket. That
audio frequency input is capacitively (AC) coupled. It only passes rapid changes in
voltage, so it does not enable normal CV control of the filter frequency.
The Filter CV Input socket is directly (DC) coupled, so all components of the input
voltage will affect the filter frequency. An audio signal into this input can cause audio
FM of the filter, but the primary purpose of this input is to enable an external voltage,
such as that produced by a MIDI to CV converter from MIDI Mod Wheel messages, to
control the filter frequency.
Beginning with version 2.1C, the Filter CV input is approximately 1 volt per octave.
(Previous versions were linear and are described below.)
The “resting” voltage of this input is approximately 3.3 volts and its input impedance is
about 105k ohms. When no signal is applied to it, its voltage is 3.3 volts.
If a higher voltage than this is applied, the filter frequency will rise. For instance, if 4.3
volts is applied, this will raise the filter frequency approximately an octave above what it
would otherwise be, as a result of the internal factors which affect the filter frequency