Did you get a copy of that FCC memo? I’m still crunching the numbers on the 40 kHz line—any deviation and those high‑frequency transients can bleed into the audible range. Double‑check the transducer specs on the old analog unit; those vintage models usually clip hard beyond 45 kHz, but the newer silicon ones are a lot tighter. Also, make sure the shielded cables you’re using have proper ground paths; a single stray loop can throw your waveform off. Let me know what you find, and we’ll patch it up before we hit the studio.

Sounds solid so far. If you can drop the exact bandwidth and insertion loss numbers for the new silicon set, I’ll run a quick compliance check against the 42 kHz limit. Also, double‑check that the common‑mode choke is still in the feedline path and not the return—any shift there can sneak in those high‑frequency ghost echoes. Once I have the specs, I’ll run a quick FFT to make sure the roll‑off is clean and the phase response is linear up to the cutoff. Let me know when you have it.

Thanks for the numbers. 38 kHz to 42 kHz is comfortably below the 40 kHz threshold, and the insertion loss curve looks clean—0.35 dB at 40 kHz is fine, 0.48 dB at 42 kHz still leaves a good margin. The choke in the forward feedline is perfect, that keeps the common‑mode noise from riding the forward signal. I’d still like the full datasheet and the exact impedance curve from 30 to 50 kHz to run a quick simulation. Let me know if you can forward it.