Listened to an hour on Triode mode this morning without the heartbeat-like tapping sound appearing. Knock on wood, but it seems like the issue was tied to the amp being set at 4 ohms. Overall, the amp sounds fantastic. How much of an upgrade it is over the CMII is harder for me to say though (maybe that'll change over the next couple weeks). It's definitely quieter. Would be interesting to A/B the two amps to see if my memory is playing tricks on me.