Is some protection possible for the SID chip?

How much effort do you want to take?
Photoelectric couplers will certainly do the trick.
Or are you looking for something cheaper
and less complex?

A user of this forum published a project for this some time ago: SID-Schutzschaltung - it needs to be powered from one (internal) or two 9V (external) batteries to keep the output fully isolated from the C64.

Or maybe you could buy a cheap ADC box that provides optical SPDIF on its output and mount it inside the C64?

Maybe that is a Approach for You -> Click

Zitat von mUItAnt

Unseen the cheap ADC box sounds interesting, if it is not too much trouble do you have a link or some further information about that?

Something like this (assuming it is really an ADC and not a DAC, the description seems to be mixed up). Since the optical output is completely isolated, you can hot-plug that all day long without any risks for your SID, as long as you don't disconnect the connection from the SID to the box.

As it's not clear how exactly the little box is operating,
you're only 100% safe using the optical output.
It's the only way to ensure you can touch the output
cable without risk for electro-static discharge, as it is
not an actual cable but an optical fiber.
This means that your amplifier will need to have a digital
optical input. It would need to have a digital input
even in case you'd only need the electric SPDIF.
Though, the reverse kind of box might exist which converts
the optical Toslink back to a standard line signal with
RCA outputs. That could be plugged into your vintage
amp.

Then get another little external box that converts the optical signal back to an analogue which you can feed into any old amp. The optical transmission is only needed for making electrical isolation 100% sure.
@Unseen linked to a nice schematic that will do the same which you could integrate into the C64. But you'd have to build the circuitry yourself.

Zitat von i u s

As it's not clear how exactly the little box is operating,
you're only 100% safe using the optical output.
It's the only way to ensure you can touch the output
cable without risk for electro-static discharge, as it is
not an actual cable but an optical fiber.

Still got my C64 from 1983 - so nearly 40 years of connecting/disconnecting my breading using dozens of different amps. Never got problems - so is this protection stuff really necessary?

It seems very theoretical to me, too, but if this would make his sleep better, why not try to help him. The only chip I remember that I actually destroyed was an AMD Athlon from the generation that had no heat spreader, and I broke it mechanically when I installed the heatsink. This chip has been my keychain pendant for the last 15 years....

Any conversion from analogue to digital and back can induce unwanted changes to the signal. But I doubt that you will hear them, unless you can also hear the grass grow.

There is a multitude of possible causes of damage that could happen to the SID. A malfunction or wrong pinout of the video plug, especially in combination with malfunctions of the connected equipment might lead to whatever effects. ESD is mostly caused by electro-static charge of someone who touches any lead that is directly connected to the SID. So, the paddle inputs could be damaged while the chip is still playing fine. Another possible enemy might be a failure of the power supply, applying over voltage from inside. And, of course, heat might also speed up the chip's decay, but there is no proof for or against that. It's just that we know that with higher power dissipation per chip area, heat becomes an obvious chip killer, while we don't know for sure about the SID. So, we're certainly not doing anything wrong if we cool it. Well, like with your birthday cake, it's in best shape if it's not being consumed.

if price does not matter, put a stagebug sb-5 or sb-6 inbetween.