Hi guys, I bought a first or second generation Rumble 25 used and . . .
There was no V2 Rumble 25, it was "upgraded" to a 30. So, yours is a V1 Rumble 25 that is from 8 to 15 years old. Any hissing noise or static could be from old, corroded connections on the outside or inside, which may require an amp tech to find and fix, if possible.
Hopefully, any other V1 Rumble owners here can tell you how theirs is doing and what they may have done to clean up the sound.
. . . The headphones feel like they will explode and make me deaf, loud popping, when I plug my headphones into the 1/4" to 3.5 headphone adapter as well as the aux cord into my phone also. . . .
Please, DO NOT wear your headphones while plugging them in to a powered up amp! I hope I misunderstood and you're not doing that! And plug the AUX cord into your phone first, then the amp; just like like plugging your instrument cable into your bass first, then the amp. Better yet, turn the amp off while plugging in any connections. Hearing is too valuable to risk so easily.
. . . . The only way to control the aux signal or "cd input" is from my phones volume so I assume the signal is always maxed out. Is this how these amps are supposed to operate?
Yes, that's how the AUX input works, even in the latest V3 Rumbles. You control the volume from whatever device you're plugging into the amp. This helps keep the amp cost down.
. . . . I'm also suspecting the house wiring as well, as I had an issues with noise before on an Irig Pro I/O when plugged in with a power adapter. . . .
Auck! House wiring is really difficult to diagnose over the internet. Get a very knowledgeable person to troubleshoot that in person. Enough said.
Good luck!

