Why does my stereo have a loud, humming sound?

It use to be just fine, but now, when I turn it on, it makes a loud noise. It sounds like a humming noise and won't go away whether I have it on radio or record player. The noise is there constantly and doesn't get quieter when the volume is turned down. 
Any ideas?

Check all the connections for speakers, turntable, etc. Then check all settings.

Hmmm, it doesn't get any quieter when the volume is turned all the way down?
Maybe the speaker wires are plugged into the wrong connections?

Going to try to show you what my stereo is....

This is not my stereo, but is exactly what I have. (mine doesn't have the problems this one does. lol ) It's an older stereo.. vintage?...
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Oh WOW Breezey.. That is such a cool record player. I have never seen one like that before. How old do you think it is?
I Love playing records and have quite a collection. Elvis Presley, Abba, Bee Gees, Barbara Streisand, Johnny Farnham, Eagles, Hits from the 70's, 80's, Countdown, etc etc etc.. and many of Mum's old records and even some of my grandfather's 75's. The very first record my Mum and Dad bought I still have.. "Turn Back The Hands Of Time" is the name of the record and is one of the songs on it... A collection of wonderful old songs, but that one is my favourite. It takes me back to being a little girl and marvelling at the magic of music echoing through our house... and Mum singing along with it. Recently i played it for her, as she no longer has a record player, not long before I boxed it up and she burst into tears and we sat and listened to the whole record together. She had forgotten how quick a record played through before you had to reload it.. not like today's cd's and multi stackers.

I don't know exactly how old it is... just that it's considered vintage. 
I love it and have tons of records... but now.. I can't use the radio or record player because of that loud humming noise.

To get back to your question after going off on a tangent because of how cool your stereo/record player is.....
I would agree with Tater's suggestions. Sounds like the speakers.. or it could be the needle needs a good clean. Does it make that sound for all records or just the one you were playing at the time? Could it be the record is really scratchy? When is the last time you dusted the speakers? It could be a build up of dust. Mine sounded really distorted and was making a loud noise till I cleaned them.

Your player reminds me of the old school desks they used to have in the schools in the early 1900's here in Aus. Not that I was around then... ha ha ha.. but I have seen them in Antique shops.

My stereo is supposed to look like an old school desk.
The loud humming noise is there no matter what...always the same.. can't hear the radio or record player music because of the loud humming.

It is just a beautiful piece of furniture Breezey. As for the noise..... Maybe it is getting "Old".. ha ha ha.

It sounds like pick up from the mains I expect. Check any earth connections, or see if it s better if you move it to a different place. If you cant get rid of the noise talk to a local repair specialist, things sometimes need a tweek or a new component.     Sadly many things age with time and dont work quite as well as they once did!