So I’ve finally had a chance to test this, and it does seem the unloader mechanism is working. At least when I follow American Locomotive’s directions above, I do hear the “pssshhh” of air coming out of the pressure switch.
I’ve since repeated the test - of either letting the compressor start and trip the breaker or covering the intake temporarily and having it run - a number of times, with the tank starting at varying pressures. It continues to exhibit the same behaviour. Filter off or Solberg filter without my finger results in tripping the breaker, original Mastercraft filter or my finger momentarily on the Solberg intake allows it to run without tripping.
My experience with the brand has me favoring the notion that the restrictor on the original filter was a deliberate add-on fix to deal with inadequate reliability of being able to operate on an everyday outlet.
I'm sure you could add a "restrictor" to the solberg filter if you wanted but reducing the orifice might undermine the goal which is to minimize noise. In my experience, the solberg filters are just that, filters. They're not silencers. Solberg sells silencers, but those are a completely different things that look like mufflers and are intended to be used in conjunction with the filters.
Here's a link to what I'm talking about. And I say all this as someone with a Solberg "filter" on my compressor.
Other than something like that, the best way to reduce noise at the intake is to add some bends to the intake line, and/or run a hose to a location that won't annoy you as much. For example, if your compressor is in your shop, run a hose up and outside.
If course the best way to reduce noise is to stuff your compressor in a custom sound proof shed outside. That is what I ultimately ended up doing after trying nearly everything else.
