New(used) Mesa Boogie Mark IV owner and pentode problems

[rosewoodblues]

At least I hope it is some setting somewhere. If I set the amp to use pentode I get an unusable warble (clipping) noise on the lead channel. I can't seem to find any info on this and hopefully it is just a problem I can fix changing tubes or something of the like. the tubes are the original mesa 6L6's

as a side can anyone recommend some tubes(maker) for a vai kind of sound. not looking for fender sounds.

thanks in advance and if i missed it in a search please point me toward the answer in the forums....

thanks,
ken;

 

[zeppman]

If you just bought the amp, and it was used, I would say replace all the tubes in it first. The majority of problems with tube amps comes from the tubes. The clipping noise could be cause by a power tube creating too much gain, and slamming into the voltage rails of the tube. If that doesn't fix it, call mesa, they are very nice people over there and will know more. There is a new mesa tech floating around the forum too, maybe he can help.

As far as the tone you are going for, the only tube "maker" I could think of are the JJs because they are just a bit darker from what I have heard. But the majority of your "vai" sound will come from your settings, guitar, pups, effects, not as much the tubes. Just get good quality tubes, my guess would be that you would probably want the el34/6l6 mix for his leads, all 6l6s may sound too clean for you. Not and expert on Vai though, so I could be wrong.

 

[rosewoodblues]

thanks for the thoughts on mixing the tubes. I did just order 4 matched 'Winged "C" (SED) 6L6GC SV-6L6GC' tubes as they seem to be well liked. I will try them out and if it still a bit darker I will slap in a couple of EL's

thanks again. I think that it is the tubes myself. It worked fine in the triode setting and man I am in love with tubes again

I have been over in modeling land (not sure if Line6 is a bad word here or not) for variety and ease of recording (so I thought)...

i promise to never leave home again

ken;

 

[rosewoodblues]

well I tried two sets of tubes and here are the results;

1) Ruby tubes 6L6 (2) - EL34 (2 - outer sockets of course) -- the warble disappeared and I actually like the sound of the tubes (dirty)
1) SED winged C 6L6's (4) -- the warble is still present with these.

I even tried a combination;

RUBY 6L6's on inside and SED 6L6's on outside. The only one that seemed to work was if I had 6L6's in the inner sockets and EL34's in the outer. 4 6L6's would consistantly produce a warble in the output, rendering it unusable in pentode mode.

any other suggestions? i am going to break it down and give her a good thorough cleaning however, I am not sure this will do the trick...

thanks in advance,
ken;

 

[scottywompas]

Have you downloaded the manual from Mesa's website. There is some good information about the various settings. I seem to remember some notes about High lead channel gain and the pentode switch.

Scott

 

[Monsta-Tone]

Hi Ken,

Without being there to look at the amp, here is where I will start:

1. Where do you have the Bass set on the Lead channel? I could not turn my Bass on the Lead channel above 4 without getting similar results. This is due to the placement of the EQ in the signal path. It is directly after the 1st gain stage. This is why I switched to the DC series amps, but the Mark IV is a sweetie.

2. Have you changed the Preamp tubes yet? It could be that one of them is making the sound and it falls out of the frequency response of certain Power tubes, or is causing the Power tubes to distort in an unpleasant way.

3. I would replace all Preamp tubes 1 at a time and try the amp. I would use a known good tube from another amp if you have one. Then, after you isolate the problem (assuming this isolates the problem) you will know exactly how to fix it if it happens again.

4. Then, I would call Bob at Eurotubes and order the High-Gain re-tube kit. This did wonders for the tone of my Mark IV. I used it with 6V6's for a while, but didn't like the fact that I would destroy my tubes if I accidently bumped some of the settings on the back. The tone was phenomenal though, not Vai like at all, but extremely Bluesy.



In the end, before I sold my Mark IV, I was using 6L6's in the inner sockets and JJ E34L's in the outer sockets. The E34L's are by far my favorite for their tone and durabillity, more Hi-Fi than standard EL34's.

Hope this helps, if not, PM me and maybe we can look at some other things.

Mesa is very helpful also. They can't believe it when I tell them what kind of following the older amps have. They are very busy, so sometimes it takes a few hours to return a call. Mike B seems to know the most about the Mark IV's.


Andy

 

[rosewoodblues]

Monsta-Tone ....

thanks a ton! I will go through this and see what I can find. I have changed the power tubes (gone to 6L6's and EL34's) however I haven't cahnged any of the others yet....

more to follow!

ken;