periodic, considerable volume loss when on spongy mode

I am experiencing an odd volume loss every once in a while when in spongy mode on my 08 triple recto. pre/power/rec combinations don't matter. I can completely swap tubes and it goes away and then it'll slowly have a considerable volume decrease to the point of my home-jamming volume setting being at around 8:00 on the master and to achieve the same volume i'll have to crank it up to around 9:30-10:00 and even then the tone is way off. It lacks some low end and some gain. Any ideas?

I have the same problem with my amp. I played very long in spongy mode, when i'm playing at home, to conserve my tubes. And i experienced a volume and punch loss, like you did, but they told me, that the 6l6 tube need to be changed, although the problem is the same, when i'm running the silicon diodes. so i think it must be a preamp problem, but i want to have a confirmation of somebody who knows that exactly, i am only speculating.

I solved my problem over the weekend. I made a goof the first time I went through tube swapping. I accidentally put the same V5 tube in that I pulled out. My V5 was on it's way out. It would work fine in bold but didn't have enough oomph in spongy. Put a new tube in V5 and all is well.

Make sure you are running either mesa chinese or the new JJ relabeled mesa ax7s in your cathode follower positions of your preamp - V3 and V4.

There's a Mesa memo floating around the forums that elaborates on this issue... HTH

Someone posted this info in another thread.

"Mesa Memo

SOUND “DROP-OUTS” / INTERMITTENT SIGNAL

One Possible Cause



Most (but not all) Mesa/Boogie amplifiers have one or two “cathode follower” tube
stages in their preamps. Tube selection is CRITICAL in these stages.



Specifically, in a 12AX7 tube used as a “cathode follower”, the voltage difference
between that present at the cathode, as compared with the heater voltage, can be
withstood or tolerated by certain types of tubes, whereas other tubes will fail. The
failure of a “cathode follower“ tube will cause sound dropouts or signal loss.



For the past few years, Mesa has been using two types of 12AX7 tubes: ones
originating in Russia (Sovtek EH), and ones originating in China. The Russian (Sovtek)
tube is NOT reliable as a cathode follower. Of the tubes we are using today (March
2008), ONLY THE CHINESE 12AX7 IS RELIABLE AS A CATHODE FOLLOWER.



In conclusion, if you are troubleshooting for signal dropout in a Mesa/Boogie amp,
suspect a cathode follower tube, and try replacing it with a Mesa 12AX7 that is marked
as “CHINESE” (silk-screened on the tube itself).



Below is a partial list of Mesa amps and cathode follower tube locations:

GUITAR AMPS BASS AMPS

Lone Star & LS Special: V3
M-Pulse: V2
Stiletto: V3 & V4
Venture: V2
Road King I: V3 & V4
Big Block 750: V4
Road King II: V3 & V5
Titan: V4
Roadster: V3 & V5
M2000: V2
Dual & Triple (2ch or 3ch): V3 & V4
Bass 400+: V2
Tremoverb: V3 & V4

ANOTHER POSSIBLE SCENARIO may occur in the “SPONGY” (or on some models,
“TWEED”) power setting: the reduced filament voltage may cause very low output from
a RUSSIAN preamp tube. Again, the recommended fix is to replace the “sagging” tube
with the CHINESE type of Mesa 12AX7 - which are more immune to this type of failure."

Hope it helps.

-dave