Sounds about right. But in all honesty @thecarpathian, I don’t believe Ted has ever disclosed this information, at least not through my readings anyway.
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Q: Are fuses directional?
A: Yes, fuses are directional. Electricity should flow from the left to the right when you view the fuse (from "S" to the "R"). If you do not know the direction of flow, you should listen to the fuse inserted in both directions. One direction will sound more detailed. This is the correct way.
I’ve studied the direction of electricity flow prior to inserting any of these fuses in the gear. Therefore, "set and done" so to speak. For those of you with any ModWright Instrument Amps specifically the KWA150 Signature Edition, one needs to be delicate and extra careful during the process of fuse removal and installation.