I have a California Audio Labs tube DAC that uses two 12AX7 tubes. today I noticed the one of them sounds very muddy and muted in the mids and highs.

So i swapped it with the right one... and sure enough it follows the tubes. Could a filament have come lose or broken and that's why it's sounding the way it does? I did have the music cranked when i noticed it.. but I have acually been hearing this muddy highs for about a month now.. so I know it didn't just happen today.

Has anywone else had this experience with a tube going out on them?

When i hav had tubes fail, the sound is jut gone. I have yet to hear one fail in the manner yours has. Of course, thats not saying it isnt possible for it to occur that way. Since the sound follows the tube, I suspect your diagnosis is accurate. I would order a pair of replacement tubes and get back to listening to music.

Regards
Mister Pig

Wowee! i replaced the bad tube with a new one. of the same kind. Groove Tube gold series.. Bam! my music sound good and balanced again.

cool, thats good to hear.

Soon I will be expirementing with other tubes... these Groove tubes are just tad to harsh in the top end.. I want a tube that will keep the detail in the highs, but smooth things out a little bit.

I really want to try some Amprex Bugle Boys. but I don't have an arm or leg I can spare for the cost of them.