Help me! New tubes for Mesa Quad and placements questions

[Friedmett]

So I want to get my Mesa Quad preamp back in action. The preamp tubes in channel 2 were giving me lower volume than channel 1 after a while (pushed master to 7) and microphonic feedback so time to change them.

I took the lid of and found Groove tubes in all 8 positions. I took out the channel 2 tubes which were:

GT12AX7C and GT7025.

In total 2 of each of those. Now I can't remember the order 100% but the channel 1 tubes goes as follows:

V21: GT7025
V22: GT12AX7C
V23: GT12AX7C
V24: GT12AX7C

Now I think the Channel 2 order were:

V11: GT7025
V12: GT12AX7C
V13: GT7025
V14: GT12AX7C

As I recall the sounds were very good so how do I go about replacement of the channel 2? Are there better tubes available in that tone area aka higain? GT7025 hard to find or called something else?

Now I am based in Denmark on a 240 voltage so keep that in mind. Maybe the tube are called something else in US?

 

[boola]

7025, 12ax7 and ecc83 are all the same type of tube. I think the 7025s are low noise and so suitable for first stages.

The tube functions are detailed here: http://www.freeinfosociety.com/electronics/schemview.php?id=290

You shouldn't have a problem with lack of distortion with any type of ecc83, in my experience the Quad has got insane amounts of gain available on both channels. If you don't have enough distortion after changing the tubes, I would suspect another issue.

I can't really advise on current production tubes. I use Telefunken smooth plates in V11 and V21, the rest are Mullard short plates.

 

[Friedmett]

Thank you for the reply

I read about 7025 and what it means earlier today on another site.

The Quad gain is enough and sounds awesome but it is the first time I am about to change some of them as they sound not so fresh anymore.

But 7025 in V11 and V21 with 12ax7 in the rest seems to be the try out to do.

 

[Shane C]

Hey Friedmett,

Just in case its not a tube problem, I would inspect the capacitors for leaks when you have the lid off.


Good Luck!

Shane