I just picked up a Cowtipper 45 Pro II almost new from a fellow member, with the extra "Tone" tube. This tube does not glow and any heat I've felt on the bottle seems to be reflected from V1. I 've played the amp with the tube removed, and did notice a slight difference in the tone, but not necessarily lesser in quality. I've also swapped the tube. I know this is a new model, but I'm wondering if anyone has had any experience with this. Also, I'll ask again. Is the bias pot only accessible by removing the chassis? Tag? anyone?