I hope U1 is not a 89S2051 type.
This design is around 89c2051, but this can be changed..
also I am working on one more version, using rotary switch, instead of micro controller.
Does it drop back to input 1 when the power is cycled, like Brit amplifiers?
Yes, on power recycle it drops to input 1.
And is the ground not switched along with the signal?
Its designed for unbalanced input, where ground is common.
if possible, keep a small footprint for
the PCB. Maybe by breaking them into two stacked
ones... makes it easier to fit into an old amp.
Sure this can be done, but will increase the over all cost of pcb, due to setup charges.
IMO in high-end equipment it is preferred to separate the grounds by using a second set of relays to switch the ground. This is very easy to implement with two relays in parallel for each set of inputs, one for signal and the other fro ground. This would help prevent ground loops and contamination of clean signal paths (such as from CDPs, phonostages and DACs) by dirty paths (such as PC, iPods etc.
yes, but this will increase the PCB size and components, thus increasing cost of project..
To prevent pop and click-free operation, it may be desirable to introduce make-before-break operation. If it is not embedded in the logic of the chip
This can be included in micro controller version,need to write codes for it.
Steps are as follows : IN1 -> Mute -> change to IN2 -> un-mute, by design other inputs which are not used are muted, (input tied to ground).
to make it remember previous input state. EEPROM with micro controller can be used to store the data, can read upon power on, I am new to embedded programming, it will be complicated for me to write the codes.