Changes

Standard 3.5mm 2-pin switched mono microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled); selectable +20dB boost.

Standard 3.5mm 2-pin switched mono microphone jack; selectable 2V DC bias; selectable sensor-input mode (DC or AC coupled); selectable +20dB boost.

On the XO-1, mono data is measured, the left channel, the tip (usually the red wire). The XO-1.5 and the XO-1.75 can read both the left and right channel.

On the XO-1, mono data is measured, the left channel, the tip (usually the red wire). The XO-1.5, XO-1.75, XO-3 and XO-4 can read both the left and right channel. (Currently on the XO-1.75, XO-3 and XO-4 stereo input is disabled).

The XO-1 is protected at the input by a 5V zener diode. The allowable input is -0.5V to 5V. Inputs outside this range will cause excessive current and damage. Even a single 1.5V battery can cause damage if connected reverse polarity.

The XO-1 is protected at the input by a 5V zener diode. The allowable input is -0.5V to 5V. Inputs outside this range will cause excessive current and damage. Even a single 1.5V battery can cause damage if connected reverse polarity.

The XO-1.5 and XO-1.75 are protected by a resistor,(1/16W 470 ohm SMD0402) and a pair of diodes to ground and to +3.3V which should protect -6V to +9V continuously, and up to higher voltages for shorter periods of time.

The XO-1.5 and XO-1.75 (XO-3 and XO-4 presumably too) are protected by a resistor,(1/16W 470 ohm SMD0402) and a pair of diodes to ground and to +3.3V which should protect -6V to +9V continuously, and up to higher voltages for shorter periods of time.  

 

The XO-3 protection is expected to be the same.

For the XO-1, the addition of a 150k ohm series resistor would (I expect, no guarantee) give a reduced sensitivity in voltage mode (0-4V) but allow inputs to +- 100V without damage. Input impedance in resistance, volume and pitch modes is much lower but a 1k ohm series resistor should still allow inputs to +-12V.  

For the XO-1, the addition of a 150k ohm series resistor would (I expect, no guarantee) give a reduced sensitivity in voltage mode (0-4V) but allow inputs to +- 100V without damage. Input impedance in resistance, volume and pitch modes is much lower but a 1k ohm series resistor should still allow inputs to +-12V.  

<i> 680 ohm series resistor on a 3.5mm audio plug</i>

<i> 680 ohm series resistor on a 3.5mm audio plug</i>

Test leads with a zener diode and series resistor would expand the safe range for the XO1.5 and XO1.75.

Test leads with a zener diode and series resistor would expand the safe range for the XO1.5, XO1.75, XO-3 and XO-4.

Damage can also be caused by applying voltages between the grounds of any of the external sockets.

Damage can also be caused by applying voltages between the grounds of any of the external sockets.