Vibrating Woofer, old tubes?

I have a dual mono tubed phono section that even has an active tube line input for a cd player. Now, I have a little problem with it, and I am not sure what the cause is.

When I open the volume wide open it causes my speakers to vibrate and gives and it hums in strange way. The weird thing: It goes away after I let the unit heat up for a couple of hours, usually. After using it for a couple of hours I can open the volume pot wide open, I mean wide open and it is as quite as a Church.

Is the thing scrap metal or is it something easy to fix?

Can it just be the tubes needing to be replaced?

I am a little freaked out about, becuase I really do love the item and have no desire to purchase another tube phono section or even tube pre at all; though I would like to be able to use it without damaging my loudspeakers. I will be getting a new pair any day now and I am a little worried. Please help me out guys, thanks a million.
It would be helpful to know the manufacturer, model, etc. of the problem equipment. I probably can't answer your question even with that info, but there may be others here who can.
I hear you, I ommited the detail since I am almost 100% sure no one has ever heard of it, perhaps I should have included the manufacturer spec anyways. Here it is:

It is a:

Wait for it,

wait for it,

Soundtech Preamp one
If I'm not mistaken; that unit is 15 to 18 years old(at least). Probably time to have the dual mono power supply filter caps replaced.
This might be a stupid question, but suppose that everything is in working order, all else constant. Does doing so change the character of the sound?

Yes this is certainly an old unit, and that could be a solution. So who manufactures an excellent filter cap? I was thinking of doing it myself. Despite being a beginner I have done a lot of soldering and work with basic electronics, like RC cars when I was a kid. I understand that I might be a little out of my league with tube equipment though. Perhaps this might be better left to an expert.

So suggest an excellent parts manufacturer, and I will check the specs on the unit and get the best part possible put in there. Thanks for the heads up. \

Does this mean you have actually heard of this unit? Very unusual. At the local shops when they ask me what I am using I ordinarily receive blank stares upon my reply.
You have bad filter capacitors in the power supply. This condition is called 'motorboating' and can be affected by temperature and the length of time that the unit is one.

It is something that needs service! I would not operate this unit until this is fixed. If left unattended, you run a good risk of frying the power transformer! Trust me, that is a very unpleasant experience.
Where can I order some good quality filter caps, please post a link.
Thanks for the heads up, I really appreciate it. If you are right, and I think you are, then you have saved me a an immense amount of headache.
Some nice, high quality caps can be purchased here(other manufacturers can be found, bottom of page):( or here: ( I've found both suppliers to be very reliable and prompt. The salesmen at your local shops probably used to sell sneakers or change oil for a living, and know little about audio(outside of what they've read on a component's blurbsheet). That's been my experience with the majority of salepersons I've encountered over the decades.
LOL, very true Rodman.

BTW, what was it like playing for the Bulls?
No! didn't he play for the Detroit Pistons??!!

Gosh - now I've been taking to heart audio advice from that to think about this one. :-)
how much do you think I should be paying for the labour? I talked to a local tube expert today, he will give me an estimate a couple of days after I drop off the unit. I don't want to overpay, help me not get ripped off. Thanks again.
Dfelkai, most shops in the US will charge about $75-$80.00 per hour. That allows them to pay the technician and their overhead. Filter caps do not take a long time to change, and this is entirely off the top of my head, so unless there is something really unusual about this preamp I would guess that 2 hours is all that is needed.

Without even seeing the unit, that's the best I can come up with- diagnosing at a distance has its problems :)
What you may find is a "bench charge" or a diagnostic charge. Maybe $30-50 to be applied against repair if you go ahead. some shops will have a 1 or 2 hr minimum. Lots of variability in terms of minimum charges, etc. If $75 or $80 seems high, my plumber has a $100 minimum! 'Course his family is the biggest real estate holder in the most exclusive suburb in my region!!!
Bench tested absolutely flawless!! I am happy, it was the tubes, got a wack of news ones experimented with rolling and problem is 100% fixed. I am happy to say the least. Thanks for helping me out, guys.