Preamp tubes ran their life?


I believe I do know the answer, but I would like to hear inputs from the community.

Approximately 1.5 years ago I replaced the stock tubes in my preamp with some vintage Mullard UK ECC83’s.  I spend a fair amount of time listening to music.  I’d say, on average, anywhere between 10-15 hours a week.  For the first year I had them in, I was running my Home Theater with my 2-channel, via HT passthru; which would swing that 10-15 hours/week way up.   I liked the tubes and how they’ve sounded, pretty smooth throughout the band.  Today, I started noticing weird “slurring/distortion” in certain frequencies, especially with vocals and cymbal crashes.  I believe what I’m hearing is the tubes have ran their lifecycle.  Note: I do have room treatment and room/speaker correction and what I’m hearing just started happening this morning.

I won’t hold anyone to their words if it doesn’t end up being the tubes, but that’s my initial hunch.  Would your educated guess be the same?
toddcowles
The NOS tubes in my phono stage have been sounding great for nine years now, so if it is your Mullards that seems short lived or a defect. Are the Mullards supposed to be NOS? Is it coming from both channels? Both tubes, both channels, same time, does not sound right. If one channel then switch the tubes and see if your distortion has moved.
Kenny
Todd, as Kenny pointed out a little judicious tube swapping can lead you to a bad tube if the distortion is channel-specific.  You don't mention what "way up" might mean but 15 hrs/week for 1.5 years puts you in the 1,200 hour range.  Unless you have a preamp that is know to run tubes exceptionally hard (Audible Illusions comes to mind), preamp tubes can usually be counted on for 5,000-10,000 hours of life.  Dick
@kennythekey @djohnson54 thank you for the input.  I should have qualified a little more...

”Way up”, they probably ran for about 4-6/day for the first year, due to the preamp being inband of the home theater signal.  I’ll swap the L/R channels, but it sounded more as if it was coming from the L channel; which could be due to the pan/mix.  I bypassed my preamp all together and am running it direct from my DEQX unit and it’s DAC.  I use a McIntosh C2500, I don’t know if those run super hot or not, per your comment @djohnson54 .  Running it through the DEQX, the harshness is removed.  Faulty tube, very well could be.  I probably have about 2.5k - 3.5k hours on them.

@kennythekey They are NOS.  I bought them from Kevin at Upscale Audio.  They’re the Mullard CV4004 12AX7 NOS.


@noromance , I’ll check them out.  Do you have any input on their musical characteristics?