Rogue ST-100 hum

I am borrowing a rogue st-100 from a friend with the intention of maybe buying it. When I installed it in my system there was a humming, that seemed to be coming from amp itself NOT a ground loop. I checked that the st-100 and my preamp (rogue RP-1), were both plugged into the same circuit. I then turned everything off and just turned on the st-100 same humming noise. I did notice the speakers were silent for about 30 seconds then there’s the same noise coming from them as well as the amp. I originally was using a Schiit Audio Aegir and I swapped that with a Bottlehead SEX v2 my friend had that was not being used. He said after putting the Aegir in his system he noticed a big improvement in the bass of his system, compared to the st-100.  He was using the st-100 with a rogue rh-5 and Klipsch Forte 3 speakers. When listening to the ST-100, I noticed the same bass issue in my system. Rogue RP-1 Zu Audio DW6 speakers, with a SVS SB3000, I am using the RP-1 in the HT bypass mode (with an Emotiva XMC-1, which was turned off at the time), I notice I get no change in bass output unless I make adjustments in the HT mode on the sub app. Is this humming normal in this kind of tube amp and is it usually this weak in the low end. I didn’t seem to notice this problem with the Bottlehead. Or my original Schiit Aegir. I did like the sound of the Bottlehead and was thinking of buying the latest version. But after reading reviews of the ST-100 I was thinking of buying this from my friend. Three more pieces of info. I am using the 8 ohm speaker outputs in the triode and checked the output tubes were biased to 40 milliamps. Any thoughts on what’s going on?