Triple Rectifier issue- random tone changes?

[Rocknrolldoc]

After years of thinking, talking, researching and saving I have finally invested in a Boogie. I got a great deal on a used 3 channel triple rec and I love it...Most of the time. I have had it for a few months and there are nights where it sounds absolutely killer and then other nights where I have trouble dialing the sound in the way I want and I just can't figure out why.

I'm not sure what year it is (purchased used) but I think it is mid-2000's (Raw/vintage/modern options on ch. 2 & 3 and no low power option). I use a 2-12 Genz Benz cabinet and I stand about 5 feet from it so I don't think it is an issue of teh room acoustics changing the sound, I'm not that far away from it. I use the spongy tube power setting and I have a Line 6 Pod XT that I use through the effects loop just for volume, chorus, reverb, delay, etc. (I don't use the amp or cabinet modelling) and I use the front loop return as a master volume so that is usually around the 10-12 o'clock position.

So far there seems to be no rhyme or reason to the changing tones, some days it sounds great and others it just doesn't sing no matter what I do with the eq settings. I don't have a hum issue at all, even at high gain settings and all of the channels always work. I didn't replace teh tubes when I got the amp and the three of the 6L6 tubes have similar burn marks on the inside but they all seem to work.

I'm not very knowledgeable when it comes to tubes but I know that when they get old and go microphonic you will usually hear hum and or squealing, right? Could this be an indicator that I need to change the tubes, will the tone change randomly if they are getting old? I have tried bypassing the effects loop also and that does not seem to solve the problem so I don't think that is the issue. I have a power conditioner that gives me a voltage readout and I have always between 112-124 v, the amp is not THAT sensitive to different power, is it? Any suggestions would be appreciated, thanks.


Guitars- Carvin DC127, Carvin Bolt
AMp- Mesa Boogie Triple Rectifier
Cabinet- Genz Benz 2x12
Effects- Line XT Pod 6

 

[rectofried]

put a chinese tube in v3 and v4 and try it.. i just went through something similar.. do a search on here about cathode follower

 

[domct203]

Here is the info on the cathode follower positions from this post: http://forum.grailtone.com/viewtopic.php?f=4&t=25102

Hey Blakkspider, I hope that you got your amp back up and running. Here's the info from the 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.

Dom

 

[hcd631]

I'll tell you what, I've always liked my 3 channel triple rec. But recently I ordered a complete set of JJ tubes KT77's from Eurotubes.com and WoW! I freakin love this amp now. You run the KT77's in the EL34 mode. It added some mid range and overall clarity, tightened up the sound overall. It sounds so much better now I can't stop playing it. I did this 3 weeks ago and haven't touched my JCM 800 since.