Shruthi -- 4PM and CS80 filters have vastly different output volumes?

I feel like this must be totally obvious, and I’m missing something… but is it common for Shruthi filters to have vastly different volumes on the same patches? I realize that some patches play better with specific filters and such, but I am consistently getting much lower volume on the CS80 (same as Dual SVF) filter compared to the 4PM (they are installed in 2 separate Shruthis).

Using the basic “SPL Meter” app on my iPhone, I am measuring around 17dB difference in output between the two filters when loaded the same patch. It’s very noticeable on every patch.

Is this by design? If not, what could be wrong?


The patches are designed for a well-calibrated SMR filter board.

There’s no guarantee that they’ll be “meaningful” on other filter boards.

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Thanks for taking the time to reply – and to design these beautiful machines and gift them to the world, Émilie!

Is there any way that those of us who are “late to the party” (and can no longer buy the Discontinued devices from you) send you some small token of thanks via Paypal or ?