Which tubes do I change??


My preamp uses both 12AT7's and 12AX7's tubes. I've installed Gold Lions, 
and after a couple hundred hours of play, I feel that the bass is a bit boomy. 
Which of the aforementioned tubes would you recommend changing
markj941
What preamp do you have? And your source - analog or digital? 
Jolida fusion pre. Digital source.
X tube has highest gain among 12A'7s so more vulnerable to hear differences in any tube preamp.

It depends on the function of the tubes. The input or voltage gain tube is going to affect the sound more. I’d guess that is the 12AX7. The 12AT7 is probably a cathode follower (or something like that, someone correct me if I’m wrong).

I am assuming that you have the other tubes that you replaced with the Gold Lions. Put both pairs of your old tubes in and listen for a while to get a good handle on the sound. Then, first change the 12AX7 to the Gold Lion, see if that causes the bass problem, then do the same with the 12AT7. It may turn out that the Gold Lions in one position and the old tubes in the other, or some other combination, works best.

There are a number of threads on the Jolida Fusion here. Do a search and you’ll find lots of info.
I'd change them all and be done with it.  That is the approach I take with my cj amp, preamp, and phono stage.  The whole magillah all at once.  Saves a lot of worry.  It's only money.
Few 100 hours is not many for preamp tubes. They may be just broken in and you are hearing them as they should be. Perhaps there is something else amiss in your set-up.
Why do you just assume that changing tubes will ameliorate your problem?  For example, first of all, what evidence suggests that the problem lies in your phono stage?  Bass boominess could be the result of a mismatch between cartridge compliance and tonearm effective mass, if the combo of those two results in a resonant frequency that lies too close to the audio spectrum (commonly taken to be 20Hz to 20kHz).  Or the problem could certainly be in your speakers.

If this is an MM phono stage, then it is likely that the 12AX7 provides all or nearly all the gain in the system, whereas the 12AT7 may either be a cathode follower, which adds no gain, or a second gain stage with lesser mu. If you change the 12AX7, the phono will likely sound "different" if not necessarily better.
@lewm he said "Jolida fusion pre. Digital source."
So no records, cartridges etc

@markj941
the tubes does effect the sound, i would recommend you to try NOS old tubes from the 60s or 70s. Telefunken military ECC801s are not bass heavy, but christal clear and holographic. Sylvania Gold 6bq5 with gold pins are great and not expensive, really worth to try them! Vintage Matsushita 12at7 pinched tails are rare, made on Japanese factory build by Mullard, this is also great tubes.

12AT7 and 12AX7 are all relatively cheap, so you can easily replace all of them to the NOS tubes. Have you ever compared NOS tubes from the 60/70s era to the modern tubes ? Those Gold Lions made in Russia.

The Russian tubes are not bad, but in my experience the NOS tubes are better if you know the exact brand or model to look for.
Dear @markj41: All. Put on sale your Jolida and buy a SS preamp. Tubes are not for audio home system MUSIC reproduction no matter what. Period. Sop to degrade your digital recordings.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.
I'm also listening to vinyl. Probably 35% vinyl 65% digital.
Dear @markj41: All. Put on sale your Jolida and buy a SS preamp. Tubes are not for audio home system MUSIC reproduction no matter what. Period. Sop to degrade your digital recordings.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

There is only one thing wrong with your advice Raul, it does not take into account the element of taste.  Some people prefer a Bordeaux, some a Riesling, whatever.  It is all good.

Regards,
Bill