2. amps-preamps
  3. 133505-86238

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
toddcowles OP
135 posts
 
@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.


toddcowles OP
135 posts
 
@noromance , I’ll check them out.  Do you have any input on their musical characteristics?
p59teitel
312 posts
 
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.
kennythekey
593 posts
 
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
stereo5's avatar
stereo5
6,373 posts
 
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.
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