possible mK5 problem?

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K-Roll

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guys,

I know this will be quite difficult for you to consider but I've been running into this rather unclear problem. My point is that I've been swapping pickups like mad just to find a match, but somehow I came to a conclusion that something may be off the hook with my amp.

The thing is that I've got a sevenstring guitar where I've changed several pickups - BKP painkiller, then holydiver, nailbomb and now emerald 7 and god nows what else but i'm somehow getting lost.. I keep telling myself that it's not because of the amp..
My main concern is that even with my pre-EQ bass on 0 and the first two sliders on the GEQ fairly low (like on the middle line and sometimes lower) I get too much round bass and an unhealthy spiky/flubby sound. If i raise bass even by a tiny bit higher i get flub, shitloads of it... it doesn't sound nowhere as good as I've heard other players/vids and stuff with more bass heavy/mid heavy and less trebly settings

the reason why i think someting is not all right is that even with the crunch channel set to max trebles/gain mids on 10o'cl, and bass on 0 i still get too much rounded bass and a weaker sound which is just working against m while i play.. if i set ch2 to lower treble/gain setting i lose so much juice that it becomes unplayable and is like a weird flubby radio.. it sounds as if it was choked or i dunno.. the same applies for mk1 channel2 with similar settings and presence on 2o'clock it sounds unhealthy until i set the channle master to something like 2o'clock.. from what i know it should be chunkier and almost as heavy as ch3 but..its as if it got choked and was covered with a blanket and in general with all channels it sounds as if it sounded ok only on one certain setting.. all the other make it nasty/scratchy/wiry/flubby

for instance, my sound is totally weird if I put channel 3 trebles to a lesser position than 1 o'clock being on mark 4, it plays like crap and i am no soft picker..its got wiry tones, same applies to gain if i put less than 1-2o'c i get some flubby sound that is no where near tight/searing/full.. i run all my bass knobs on all channels on 0 and yet, with bright pickups like the emerald is I still fight some weird low end frequencies that sound like a subbass flub which are somehow working against my rhytm work..
the reason why i mention this is that usually my guitar sounds uppermidrange-y/trebly and tight with most amps..
for instance this guy has a serious problem with his ch2 http://www.youtube.com/watch?v=KhS-P_8052Q but yet his ch3 on 0:44 sounds so great when he switches over, that i'd be happy if i get it out of my amp..
the weird thing i noticed it that somehow i like the loop activated sound better than the hard bypass mode which should be the other way around..
what i noticed is that when i popped in a fresh set of winged =C=s it got mushier and bassier, like, i could not get any articulation out of it and it got worse..so i putthe old mesa 6L6 back
i know that the only way is to try a different guitar/cab/head to identify where the catch is but have any of you came accross such problem that you would be fighting low frequencies on mark 1 normal (even with 0 bass,EQdisengaged), crunch and ch3mk4? ch1 as well does not sound chimey, its usually either piercing/bright or flubby/wiry oh and by too much bass i don't mean a nice full tone, but something that is overbearing and i can't just accept the fact that an amp like this would sound ok on only one setting out of more..this is not like finding sweet spots between a great sound and a good one, but trying to make it sound at least ok and bearable..
the problem is that I've had it for 9months, i bought it brand new, it's a 3600serial runm i know how to tweak it, at the beginning it sounded great but it somehow degraded?! and i dunno if this is something i could use as an argument when dealing with the shop/warranty/tech check..
i dunno it's either tubes/internal problem/guitar/cab or me getting crazy
 
just an update, I've tried to troublehsoot the amp/guitar/cab possibilities and it's definitely the head. I've used my guitar, a friends 1527 and a LP greco and it definitely acted strangely with all 3.

the thing is that with hard bypass engaged, i can hardly get all the volume i used to with my channel masters set to 9-10, I know have to run ch2 and 3 on almost 11-12 to get the loudness i am used to.
next thing is i tried working with the mk1 mode and here's the result - with bass completely down, mids on 9-10, trebles maxed, presence noonish and the GEQ in an ascending shape with the first slider completely down.. i still get an unbearable amount of bass frequencies.. if i switch to my neck pickup i sound like a bass guitar :)
what i realized is that on ch2 and ch3 I get feedback sqeuals even with my ns2 engaged in situations/settings that used to be normal for me.. (e.g trebles/gain at 2oclock and GEQ trebles both between middle and upper line)
on ch2 and ch3 i can definitely tell that no matter what i do if i set the pre EQ to bass 0 and keep the sliders neutral, bass frequencies are still jumping out and I can't really describe the tone as tight, but rather grainy,rounded, choked and somehow undernourished/weak
one more thing to mention is that i get a shitload of amp hiss/noise, i mean, it's really too obvious..
if i take a look at the back, all 6L6s are glowing clear, the 5u4G is completely dark (but as i know some tubes do not really shine too much, only a little)
Don't get me wrong i dont need loads of gain but in order to get a decent sound i have to compensate with extreme settings


my questions are
- would a failing 5U4G have such impact on sound?
- does this sound more like a preamp problem (maybe PI?)
- what other internal issues could have similar impact on the sound making it bassy/choked/undergained
 
Considering all the folks that viewed your post so far, suggest that a call to Mesa directly be made and see what their best recommendation would be....
 
You haven't stated how you run the power section (90W/45W/10W Triode/Pentode etc).

Does the amp exhibit this behavior at full power (Pentode 90W)?

At 90W the tube rectifier is not used, it is only used in 10W & when selected in 45W.

It this was me I would at the least change V1 to a Tung-Sol reissue or a Chinese tube to see if anything changes.

Dom
 
I only run my amp on 90w settings..
I took the time today and swapped the PI for a brand new mesa 12AX7 and i noticed an improvement on ch2 crunch, it's really better now, but ch3 still seems a little choked and rounded and keeps squealing like a pig if i turn the treble and gain to 2 oclock and sliders slightly above the middle line.. so, I guess I'll need to buy more preamp tubes and take no prisoners..
hmm.. even if the rectifier tube is not engaged on the 90w setting, i think it's still in the signal chain or? i mean a failing one could have an impact on the sound or?
 
IME I've never had a rectifier tube slowly die off, they either work or don't.

Yes, the 5U4GB is in parallel with the diodes when they are selected. The Rectifier Tracking switches in/out the diodes. You can troubleshoot your theory by confirming you are switched to 90W and removing the 5U4GB (before powerup) to see if the amp's response changes but I doubt it will. I think this is in the preamp or EQ. I would still try changing V1.

Do you use Full or Variac power?

Dom
 
thanks for the response, I am using full power/90w only.. I've actually already swapped the V1 spot, too, maybe a weea or two ago as that was my first perception- a faulty v1.. i used the rubber head SPAX7 by mesa and it somehow did not help the ch3 squeals to get tamed down and did not have an impact on the flubby mk1/crunch or mk4 mode, i suspect it might be either some other V-spot or..i dunno.. I'll give a couple of more tries tube-wise and right after we're back from the gig, I guess I'll contact the shop.. the worst thing is that I have to really think about the whole procedure on how to address them with this problem cause an argument like 'my amp sounds differently than it should' might not be met openmindedly :lol:
 
here's an update in this old thread.. I went to Austria for a warranty checkup and after 3 weeks I got this reply from the shop:

--------------------------------------------------------
SHOP:

Hi
I think I understand what you mean, anyway I compared your top to a MkV Combo that we have in our store and differences did not really seem significant to me?
I had no problem to get that muffled tone from our combo too... (Your top was connected to a Mesa 1x12 Cabinet).
If it is easy for you I suggest you come by and have the opportunity to countercheck by yourself. The other possibility would be to send the amp to the distributor for checkup, which I wanted to avoid because of the shipping to Germany - and still I am not sure if it will show results.
Anyway, if you are absolutely sure about the issue the guitar dept. will do so.
Please keep us informed how to proceed.
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My reply to them from this morning:

Hi Georg


thanks for your reply. Hmm that is quite weird, I know these things are sometimes hard to tell cause the best way to troubleshoot the amp is when it's not working and won't start. This is more like a sound degradation that comes in hand with microphonics and lower gain when using normal stage volumes and settings.

I could definitely tell that when using louder volumes and usual gain settings I used to set before, I'd get a huge amount of feedback which forced me to use a noise reduction in all occasions.
I used to have a mark 4 before this one and I know about some settings that may have caused the sound to be muffled but I definitely know how to tweak the amp and avoid getting muffled sounds.

I'm not sure, but, could you as well try using a 4X12 and get it to open up a little, some problems tend to withstand with higher volumes, I remember that when we used a small 1X12 VHT cabinet at a friend's place at low volumes it seemed ok or at least there was no problem in the sound cause it was not apparent, but once I plugged it in into my big 4X12 traditional cab, all the 3 people in the room realized something was not quite ok on 2 out of 3 channels. I tried another 4X12 and similar results.

The thing is that when it was new I had no problem finding a good tone on mark 1 channel 2 mode or o use the crunch mode with less gain but now i have to set it higher and it sounds muffled..Same applies for ch3.
In the first place, I suspected a faulty preamp tube or perhaps multiple tubes degrading with time.

I might have two questions:

1. If we decided for a checkup with the distributor in Germany just to be 100% sure - Do they need to ship it further to mesa or do they have a certified tech? how much time extra would it approximately take for them to come back with a resolution?

2.If you have 12AX7 mesa tubes could you please try to completely retube the whole preamp section and test it old against new if you see any difference aiming mainly at higher volumes using a 4X12 cabinet if you have the option?

What I was planning to do was to buy brand 6 new mesa preamp tubes, but I did not want to sink something like +100e in case it would not help and the problem were somewhere else inside.

Thanks for all your time and patience with me.
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What would you guys do in such situation? Just blindly buy a batch of new 12AX7 and plug those in or rather send it to the distribution center (which may take even more time)
 
What would you guys do in such situation? Just blindly buy a batch of new 12AX7 and plug those in or rather send it to the distribution center (which may take even more time)[/quote]

From my experience calling Mesa, they will ask you if you replace your tubes first. If I was in your situation? I would do what you say by getting a new batch of 12AX7's and try that first. I know it's costly, but imagine if you hadn't tried that, send the amp for repair, posssibly all the way to Mesa, then find out it's only a few preamp tubes. Up to you if you have the time to part without your V. Although replacing all preamp tubes at once is costly.
 

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