The "New" Mesa preamp tubes

[3124+]

This is very interesting. The maximum heater to cathode voltage of the JJ 12AX7 is 180VDC, but the cathode follower and FX send stages in a Dual Rectifier present cathode voltages well over 200VDC.

This is actually quite common. To get around this voltage rating, most manufacturers "float" the filament windings. That means neither end of the winding is directly connected to ground, so the voltage potential between cathode and heater ends up being much less than 180 volts.

In the 3ch Dual Rectifier, the center tap of the filament winding is grounded.

 

[R_ADKINS80]

I talked with Rich at mesa just last night. I am having a problem with my Triple Rec losing a ton of volume when in spongy mode and he told me that he "wants to send me 3 of the new Slovakian made tubes" to try in different slots of my amp before having the amp checked by a tech. Apparanty I am the very first to experience any kind of volume loss that is soley related to switching from bold to spongy reguardless of what pre/power/rec tubes are in my amp, what channel my amp is on, what mode the channel is on or even if I am running tube or diode rectification. Once I switch to spongy i have to jack the volume 1/4 turn higher to compensate for the volume loss. We'll see in a week, I guess.

 

[MusicManJP6]

I think it's funny that they are covering the fact that the new tubes are JJs by calling them something else! Slovakian?!! :lol: C'mon!!

 

[CoG]

I think it's funny that they are covering the fact that the new tubes are JJs by calling them something else! Slovakian?!! :lol: C'mon!!

That's not actually weird, that's probably in the terms of their contract with JJ. They never named the manufacturers of the Russian or Chinese tubes either. They don't want you to think/realize you can just go buy the same tubes minus a hammer mark for half the price..

 

[dmt]

There is a video that is fun to watch on the mesa website . It shows them striking the tubes.
I stopped using JJ's ax7s as the failure rate is about 50% if not worse , as far as PRE-AMP tubes .
Mesa strikes them 2xs so they are probably throwing over half away . So buying those from mesa
may well be worth it .

Link.

 

[bigshooter]

Hey guys

I had a couple preamp tubes that needed replacing,so I picked up a couple of the new SPAX7-A High Grade tubes and noticed that the filaments did not glow. So,I returned them and picked up a couple more...same result-no glow!? Are there issues with these new tubes?

On a side note: I've been replacing preamp tubes because of a static crackling noise I get from my Single Rec head any time I hit it with any sort of gain (pedals).

I'm at my wits end here. Comments? Suggestions?

Thanks

 

[CoG]

Hey guys

I had a couple preamp tubes that needed replacing,so I picked up a couple of the new SPAX7-A High Grade tubes and noticed that the filaments did not glow. So,I returned them and picked up a couple more...same result-no glow!? Are there issues with these new tubes?

On a side note: I've been replacing preamp tubes because of a static crackling noise I get from my Single Rec head any time I hit it with any sort of gain (pedals).

I'm at my wits end here. Comments? Suggestions?

Thanks

did you actually, um, try them and see if they made any noise? different tubes have different amounts of glow, some are only visible if it's totally dark.

 

[bigshooter]

Obviously I tried the tubes out. I'm still getting a baffling crackling sound and I figured if the new tubes are not glowing (at all) this has got to be the issue. I've replaced "bad" tubes before and the issue goes away...at least for awhile.

Surely someone has experienced this situation before?

 

[CoG]

Sorry man, you never know, sometimes guys are really paranoid. If every tube you get has the same problem it's more likely your filament heaters or something else in your preamp circuit rather than the tubes. I'd try posting a specific question in "Modern Amps" with a topic like "Crackling sound in preamp, filaments don't light up?'

 

[bigshooter]

Hey,thanks man! It never occurred to me that the circuitry may be an issue. I think I'll take the head in after the holidays and get her checked out.

Cheers!