Just bought this TV yesterday. The volume seems to go up and down on its own. Like when people are talking and music starts playing, the volume will go up and will go back to a lower volume after a while

It sounds like you're using a set of stereo speakers to play a surround sound output. I would try going in the TV menu and turning off surround sound

Tubes run hot in order to function. They degrade over time unlike transistors which usually work or don't work.
You should keep some spares around especially if you are out doing gigs.
Guessing at which tube is bad will be expensive.
With the renewed use of tubes in amps, there may be some tube testing available at a music store. Call around and see. Pull all you tubes and go test them.

The volume buttons on the side of the phone are sticking. My up volume button seemed fine, but someone told me to keep pushing it and the button will release. Sure enough, the volume controls started to work. I played with both the up and down buttons some more and the button below started working. A few more minutes monkeying around with the volume buttons and now all the buttons work.

i do have lg kp500 cellphone how to start the speakers

If you don't have the manual it is here:http://www.behringer.de/EN/downloads/pdf/DJX700_P0165_M_EN.pdf Have a look at page 4 under Monitor, mode switch and mix control. You might be having problems with them.

It seems like the problems starts after using an audio streaming app (Slacker)It also seems to correct after a reset(battery out and back in).

try to increse the volume centre channel level so that u could hear better vocals. or do one thing if u r connected with optical cable only. just connect single RCA cable from dvd players centre channel output to the TV input (Left/mono) so that u can only hear the center channel volume thru TV and all other from speakers even the LG is working..

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Turn down the mic volume down on your chat settings.

Not Mac compatible largely.

ALL Mp3 players have a disclaimer telling you not to play it at max volume. Get adjustable headphones to resolve problem