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 !