Hello!
I have a Zynthian v2, and I would like to upgrade it to get audio input (so this would be called a v2+?) with as little expenses and effort as is reasonable.
I see that I need the HifiBerry ADC+DAC Pro, and there is obviously some plugs missing. I can handle drilling the extra holes in my alu case.
My question is if I can buy the audio connectors meant for Zynthian v3 which includes input. Will it fit in my v2 with the new HifiBerry?
Do I need anything else?
You only need an extra “Stereo Jack” connector. I will send you one for free. Also the harness. No problem! 
Ahh! Remember that you have to solder the 40 pin extra connector to the HifiBerry DAC+ADC PRO.
If you don’t want to do it, the soundcards we sell in the zynthian shop are customized and already have the extra connector soldered on.
Regards,
Ohhh
I really appreciate that offer 
. Love the spirit here.
I’ll buy the card from the Zynthian shop I think.
I’ll send you my address by pm.
Question: can I then plug my guitar and bass directly to the Zynthian to use it as an effect? (No issue if I need to run it via my portable mixer, but wondering)
The answer to whether I could plug my guitar right in and use it as an effect turned out to be yes! 
I also added a 6.5 stereo jack output so I can plug my headphones right in when practicing
Did you get the upgrade already?
Yes! Works perfectly.