First: Switch equipment: Isolate the Problem: preamp?/amp?/speakers?
Don't jump around changing tubes before you know if it is the speakers themselves or your amp or your preamp.
go from there
You might have tinnitus!
What is tinnitus?
Tinnitus (pronounced tih-NITE-us or TIN-uh-tus) is the perception of sound that does not have an external source, so other people cannot hear it.
Tinnitus is commonly described as a ringing sound, but some people hear other types of sounds, such as roaring or buzzing. Tinnitus is common, with surveys estimating that 10 to 25% of adults have it. Children can also have tinnitus. For children and adults, tinnitus may improve or even go away over time, but in some cases, it worsens with time. When tinnitus lasts for three months or longer, it is considered chronic.
The causes of tinnitus are unclear, but most people who have it have some degree of hearing loss. Tinnitus is only rarely associated with a serious medical problem and is usually not severe enough to interfere with daily life. However, some people find that it affects their mood and their ability to sleep or concentrate. In severe cases, tinnitus can lead to anxiety or depression.
Currently, there is no cure for tinnitus, but there are ways to reduce symptoms. Common approaches include the use of sound therapy devices (including hearing aids), behavioral therapies, and medications.
What are the symptoms of tinnitus?
The symptoms of tinnitus can vary significantly from person to person. You may hear phantom sounds in one ear, in both ears, and in your head. The phantom sound may ring, buzz, roar, whistle, hum, click, hiss, or squeal. The sound may be soft or loud and may be low or high pitched. It may come and go or be present all the time. Sometimes, moving your head, neck, or eyes, or touching certain parts of your body may produce tinnitus symptoms or temporarily change the quality of the perceived sound. This is called somatosensory (pronounced so-ma-toe-SENSE-uh-ree) tinnitus.
Most cases of tinnitus are subjective, meaning that only you can hear the sounds. In rare cases, the sound pulsates rhythmically, often in time to your heartbeat. In these cases, a doctor may be able to hear the sounds with a stethoscope and, if so, it is considered to be objective tinnitus. Often, objective tinnitus has an identifiable cause and is treatable.
The first step is diagnostic—isolate the source of the problem before proceeding with random “solutions.” I would start with figuring out if it is from both or one channel. Preferably, use a mono recording where you hear a problem and, if you have a balance control, swing the balance from one side to the other and listen for a difference. If you don’t have a balance control, try sitting much closer, and in the direct path of one speaker, then the other, to listen for differences. The best approach would be to do switching at one end of the system until you find the culprit. I suggest starting at the CD player. When switching interconnects, it is best to have the system turned off or the volume all the way down. Pull one channel and listen to just one channel. Then do the same to listen to the other channel. If the problem is in one channel, now switch the single channel left to right to see if the problem moves to a different channel; if it does, it is the CD player or its interconnect that is the source of the problem. If it doesn’t it is something downstream. If the problem is in both channels, it will be hard to definitely isolate the problem without trying other gear to see if the problem goes away. If you have determined it is not the CD player, do the switching routine to determine if the problem is the amp or the speakers. For this step, avoid playing with one speaker disconnected from the amp (tube amps don’t like this). Hopefully you will hear any difference with both speakers playing, If switching left and right speakers does cause the problem to switch channels, it is the speakers at fault.
As Elliot recommended try an isolate the problem. Most likely its either the speakers or the tubes since you’ve replicated the problem with multiple sources. You’ll need either an alternative amplifier or alternative set of speakers and see if you can replicate the problem after replacing one of them. Also is this coming from both speakers or just one side?
When it comes to tubes its more about hours played then age, power tubes can last around 2500 hrs and preamp tubes about double that, but like any piece of electronic gear, they can fail at any time, if you have single tube or single driver fail the problem would more likely be in one side. If it’s gradual decay over time its would be on both sides. So first see if its the amp or the speakers, then go from there.
I listen at lunch and again in the evening with my adult beverage. I have post-concussion phonophobia, which I suspected at first. But my wife also noticed it so I can rule that out. I don't have any sources for spare gear around here to swap in and out. What I may try is plugging the CD player into other output taps from the amp, and fooling around with some different cables. By my estimate I have over 5000 hours on these tubes, so they need to get replaced in any event. I don't recall the brand but the were made in England and sounded wonderful for a long time. Hopefully Upscale has my purchase history if I can't run down the receipt.