Dennis Had Inspire Amps

[Ruleof72]

Originally Posted by FloridaBoy

What does your entire system consist of? I have 3 Inspire amps and none of them have that issue with 99db speakers.

Here's my system, though it doesn't appear that and of the other components add or subtract from the hum:

Technics SL-1210GR turntable
Lounge LCR MKIII phono preamp
Raspberri Pi streamer going to Schiit Modi Multibit via SPDIF
Oppo disc player going to Schiit Modi via Optical
Modi and Lounge going to NAD 326Bee Integrated (used as preamp for now)
Inspire Fire Bottle
12 gauge no-name speaker wire
Tekton Enzo XL towers

I've been trying different combinations and it seems to come down to the amount of time after the amp is powered up. Initially the hum becomes apparent about 10 seconds after the amp is turned on and diminishes to "slightly audible" (have to put my ear to the speaker) after about 20-30 minutes (when the amp is toasty warm). At that point it's a non-issue but during the first 20-30 minutes I can hear it from my listening position.

After floating the ground and reversing the polarity I don't think that either of those has a measurable impact. Other possibilities I came up with after some searching are:
1. Microphonics of tubes/transformer?
2. DC offset issues?
Don't know if either of them is applicable to me or not.

I love the sound of the amp it's just the slight hum in the initial half-hour or so that triggers my OCD-ness and makes me wonder what is going on.

Like I said, I'm a tube noob so any insight, suggestions would be helpful.