EMT JSD High Output - Charlie Byrd Direct Cut

If Pass is correct that the INT-150 has the headroom to handle 8mv, it's difficult to imagine a nominal 1mv cartridge inducing overload. That said, preamps can suffer problems beyond simple overload that can distort loud peaks, and the passage you described is ideal for challenging such problems.

Of course it could as simple as VTF being a hair too low for those particular (torturous) passages. Before going crazy, trying bumping VTF up a hair.

It could also be that your tonearm in combination with the JSD resonates internally at certain frequencies. High amplitudes at such frequencies (or multiples thereof) can feed energies back into the cartridge generator... similar to the feedback loop when a microphone's gain is set too high. (Note: I am NOT talking about the generic arm/cartridge resonance test that people use mathematical formulae and test records to bring within the 8-12Hz range. That simplistic test has nothing to do with this problem.) Arm/cart acoustic behaviors can be tested by doing something as simple as sliding a sliver of paper between the cartridge body and headshell. This tends to change a cartridge/tonearm interaction significantly.

Many possible causes. Much experimentation in your future.

1. This distortion happens when the Audia's output is sent to the Pass. It occurs whether the connection is RCA or firewire/XLR.
2. The distortion does not occur when the Audia's output is sent to a headphone amp.
3. Therefore, this distortion is originating in the Pass (or the speakers, though that's unlikely IMO).

As I posted originally, lack of headroom is unlikely to be the problem. Atmasphere (who builds amplifiers and understands these matters better than I) has frequently posted that preamp circuits with slow slewing rates can exhibit distortions that sound much like mistracking. Slewing distortions are most audible on dynamic peaks with hard blown horns, strong vocals, etc., and they have little to do with a preamp's overall headroom or lack thereof. SS circuits, especially less expensive ones, are more prone to this.

Based on the information provided, this would be my guess. You could confirm by substituting another component for the INT-150 (perhaps higher end separates).