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
@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?
A few years ago I thought I had a tube issue in my pre-amp.  Turns out the volume control pot was dirty, and the sound cleared right up after I sprayed some Caig De-Oxit into it.
The control pots from the old days (I.e., Dynaco, Eico, etc.) were known to get dusty and make noise. Yup, you had to spray them. I would not think your Mac would have that problem, but I'm not familiar with it. If you move the volume control back and forth do you hear a static like cracking?
Kenny
I have a Mac C2500 preamp and the tubes should last 10,000 hours per the manufacturer.  However, I have found that the NOS Mullards can get noisy in a year or two time.