I recently noticed that there is a SNES specific audio filter available called GPM-02 LPF. I gave it a try and it does what you would expect from an LPF and does a nice job giving the audio a more old-school "analogue" feel.
But I'm wondering if this filter was titled GPM-02 due to simulating the particular characteristic of a SNS-CPU-GPM-02 models, as distinct from others like SHVC-CPU-01, 1CHIPs, SHVC-101, etc., or whether that simply happened to be the source for making the filter but there are no major audio differences across SNES model revisions. There doesn't seem to be much info online on this topic that I could find.
For the past few years I've been using an SFC Jr, but I don't have access to it now so I can't do comparisons with real hardware. Personally, without access to a real console, I'd prefer to use this filter on the SNES core if it's meant to approximate the original audio of all SNES revisions, but not if it's particular only to the GPM-02 models. Will appreciate any info or insights on this question.