My TS 6F8Gs have a very loud noise floor compared to my Sylvania 6SN7GTs. Maybe I haven't given them sufficient time to burn in, but they seem to introduce a very loud hum that is not present with the 6SN7s. I'm using them in my WA22, so you may get different (better?) results with your Glennamp. I do like the sound of the tubes, though. They seem to give very clear mids without giving up anything in the lower end compared to the 6SN7s. Just something to consider.