[sdiy] SID output protection?

[Gordonjcp]

On Mon, Jul 28, 2025 at 06:36:26PM +0300, Antti Pitkämäki via Synth-diy wrote:
> 
> As it is, there is a already a single transistor buffer (2SC1815) at the
> output of the SID in a stock C64/C128. However, apparently the transistor
> doesn't do a very good job at protecting the SID.
> 

I wouldn't expect it to

> I've found several suggestions for SID output protection: an optocoupler, a
> ground loop isolator, diodes that short overvoltage or an additional op-amp
> buffer.

I can't see how an optocoupler would work because they're not especially linear. An opamp buffer with protection diodes ("backwards" ones between the output and supply rails) would be the gold standard here.

-- 
Gordonjcp