Removed the resistors and used my little oscilloscope to check output voltages on the likes of the Headphone output, mostly of the minus quantity, oddly even when reversing the connections! After a cup of tea and some thought ahhhhh the Master I/O and checked that, positive to 2.5 Volts, again even with the connections reversed.
Put the mono 3.5mm plug in and there we go, I was able to tune 2 oscillators to B easily, normally blue but goes green when smack on the note.
This looks nice. And yes - the AE Modular never puts out negative voltages. It's all between 0 - 5V.
The METER module has a nifty tuning mode where you attach a 3.5mm stereo cable from the Meter to the MIDI input on the MASTER module and then connect CV to pitch on an oscillator and connect the output of that oscillator to the Meter module. In tuning mode, the Meter module will then send Midi notes and show you how far the oscillator is from it.