Hi Luka,
Till 1987 I was a free-lance electronic-engineer and did many repairs in musical instruments. (Amps, organs, keyboard etc.)
In those days, organs and keyboards were equiped with conventional circuits and e.g. soundprocessing was done by non-processor-controlled electronics.

Today almost EVERY function can be processed by micro-processors and/or custom-made chips.
In the SD1 the entire operating system is controlled by CPU's and with the software ALL needed operation changes can be arranged.... no doubt !

I'm not 100% sure about the DSP's in the SD1. It is possible Ketron used dedicated circuits (chips) for the Digital Soundprocessing, switched on/off and controlled by the software. If this IS the case, I'm afraid the 'chorus noise-problem' cannot be solved with only software......

The microphone-input contains a 'hi-sensitive' electronic (op-amp) circuit to amplify from 1-5 mV signal to a much higher level of 300 mV. The hiss in my opinion is too loud for an hi-end instrument. (OK for stage but NOT suitable for studio-work)
Software changes won't help in this case either. (My micro-input is set to INACTIVE)

Perhaps DAN01, George or Henry are able to supply more details because they probably own schematic diagrams and technicians ?

At the end of August, the Ketron engineers return from their holidays and within a few weeks we will see what they can- or cannot do for us ........ even with the 'dislikes' the SD1 is great !

kind regards,
Roel