Triaxis/2:90 into 2x12's - tone problem

[prsrose]

I'm hoping someone can help me shed some light on a problem that has been plaguing me for some time...
I'm beginning to lose hope in this rig, even though I know what it is capable of but for some reason can't get to cooperate. I bought each seperately and used, and it has never really worked up to par since day one for any host or reasons. First it was bad tubes in power amp, then it was incorrect effects loop hookup (only running one channel vs stereo)

I have had an ongoing saga of problems with my rig, each time I fix/replace what I think the problem is something different seems to be the culprit.
So far I've replaced all the power amp tubes, all the preamp tubes, and had the power supply checked for proper voltage load etc.

Currently I’m convinced its not the amp but the speakers… But I'm not sure.

Here's my deal, hopefully you can follow:

I run stereo with 2x12 left channel and a 2x12 right channel. Each 2x12 pair has 2 8ohm load celestion speakers originally from a Randall 4x12. If I'm not mistaken they are run in series.

One pair (pair A) sounds better than the other (pair B), but they are all the same speaker/ohm load/wiring. I never noticed a problem when they were all rigged up in the 4x12, so what am I missing? Did one pair get ruined (pair B) from the transfer from the 4x12 to the 2x12? How could that be? Overall my tone seems more vintage/sabbath buzzy sounding than the bright/punchy mesa/triaxis tone I've come to be familiar with.

I’ve replaced the power amp tubes, the preamp tubes, tried switching the channel output cables to make sure it wasn’t one channel working over the other… The speakers that sound better are consistently in the same 2x12 cabinet (pair A) regardless of what channel A or B they are run on.

I dont want to sytematically replace every freaking component that is suspect until I get a consistent result. Its too freaking expensive. What if I buy a new 2x12 or 4x12 and it still doesn’t sound right? My new tubes are at fault?? They already cost me a fortune to replace in the first place.

Anyone have any ideas?
I'd love to get this figured out so I can finally play the dang thing.

 

[TOOLGUY]

Do you have a bud that can lend you another cab (ANY CAB) for a few hours? I would try thet before you buy anything else.
I am pretty sure G.Center (if you are in the states) will give you your $$ back if you return anything under 30 days. You could go "buy" another cab and just return it the next day saying you don't like it.. :wink:
I am sure you have but... also look at the cables. I had a bad speaker cable before (was marked as a speaker but was an cheap instrument cable inside ) that would thin out my sound under high volume/power.

 

[Screamindv]

Make sure the speakers are wired in phase/ Positive to positive, negative to negative. Make sure left speaker is in phase with right speaker. Out of phase speakers will sound thin and lose their bottom end.

 

[Jmcthe3rd]

Who installed the speakers in the (2) 2X12's? If the speakers were ALL 8 ohms the 2X12 cabinets could be wired for either 16 ohms or 4 ohms. (I believe series is 4 ohms and parallel is 16 ohms but, I'm not 100% sure it might be backwards. I AM sure (2) 8 ohm speakers can only be wired to 16 or 4) I would find this out to make sure you are running the correct load to the speakers. I think getting a test speaker cabinet is a good idea also. This will allow you to make sure that it's a cabinet problem versus a Triaxis/2:90 problem. One more thing regarding one speaker sounding good and the other bad. I would open up the back of the cabinets and make sure they are wired EXACTLY the same. Good luck.

 

[mrcomputer]

Make sure the speakers are wired in phase/ Positive to positive, negative to negative. Make sure left speaker is in phase with right speaker. Out of phase speakers will sound thin and lose their bottom end.

+1. This is the most likely cause. Make sure you use top quality speaker cable as well.

FYI...

Impedance for speakers wired in series is the sum of the impedances (8ohms + 8ohms = 16 ohms), speakers wired in parallel calculate as follows: 1/s1 + 1/s2 + 1/sn ... = 1/stotal (1/8 + 1/8 = 1/4, 4 ohms. 4 speakers @ 16 ohms each: 1/16 + 1/16 + 1/16 + 1/16 = 4/16 or 1/4, 4 ohms. A mismatched pair: 1/8 + 1/16 = 3/16 or 1/5.333, 5.33 ohms impedance).

jbw

 

[prsrose]

You guys are AWESOME! I will report back with any progress.
THANKS!

 

[prsrose]

I checked the wiring to see if the speakers were out of phase... didn't help. I tried someone elses cabinet and thought it resolved the issue, but the more I play with it I realize its still faulty!

 

[prsrose]

I'm back :evil:

I'm noticing with the new cabinet that the same problem exists. One channel has the balls and power of the amp, and the other channel is more tinny and has no bottom/balls to it.

I have a new 2x12, when I run stereo into one channel the other channel sucks, but not dramatically enough that it sounds blown or underpowered-- just... not ballsy.

This has GOT to be in the triaxis or 2:90.
What variables do I have to check now? I have new tubes in both pre and power (JJ's, matched octet on power)

Could a resistor, tube grid, or anything of that sort be blown and or needing change? What am I looking at here, this isn't making sense?

PLEASE HELP!

 

[ando]

It should be easy to see which component is at fault. Try plugging a different preamp into your 2:90 - or even just a modeling pedal like a POD or Boss GT.

You can test whether it's the Triaxis by plugging it into a PA or simply by reversing the inputs to your 2:90 (the problem should switch sides. Finding the faulty component should be the easy bit. Then you have to find the reason or be prepared to pay for an expert to find it.

 

[mr_fender]

Try swapping the cabinets on the channels. If both cabinets sound the same one each channel, you know the problem is not the cabinets. Next open up the 2:90 and swap the 12AX7 tubes around and see if the problem changes channels. Then swap the output tubes between the two channels. When swapping something makes the problem change to the other channel, you've found the culprit.

 

[scottkahn]

I would confirm that you really have four IDENTICAL speakers. Some companies have made cabinets where they use two different speakers to create a blended tone. Maybe you actually have two cabs with different speakers in each (they might look close, like at a glance all are Celestion 8 ohm).

Obvious hookup issues... with a Triaxis/2:Ninety, you have TWO output cables (Left and Right) from the Triaxis going into the TWO inputs on the 2:Ninety.

The two cabinets should be connected to the appropriate speaker jacks on each side... you don't accidentally have two speaker cables plugged into multiple jacks on Chan. A or Chan. B I hope!

You should have volume and presence set the same for both channels on the front of the amp. On the back, the input switch should be at LINE, not Instrument.

Scott

 

[prsrose]

Hey guys-- New 'symptom'...
If I pull the level a or b knobs of the 290 outwards (towards me) the volume jumps up a notch. I have not fiddled long enough to be sure, but I am also noticing a slight tonal change when I do this. Is it possible the volume pots would mess with the tone if they were faulty?

Also, the amp buzzes wayyy too much. I've tried the ground switch on the triaxis with minimal/very little change. Other amps plugged into the same power strip and/or outlet don't give me this much buzz. This was also evident before the fresh re-tube.

 

[scottkahn]

did you retube with genuine mesa/boogie tubes? if not you may just need rebiasing, which is unnecessary with Boogie tubes.

 

[TOOLGUY]

Hey guys-- New 'symptom'...
If I pull the level a or b knobs of the 290 outwards (towards me) the volume jumps up a notch. I have not fiddled long enough to be sure, but I am also noticing a slight tonal change when I do this. Is it possible the volume pots would mess with the tone if they were faulty?

Try removing the pots and rebending the little tabs on the side that hold them together. They get bumped/banged and will spread apart over time.This will cause all sorts of problems.
I had one that was about to fall apart (wish it was the cause of my 2:90 "issue" but it was not.. )

Be careful when you pop that hood!! 450+ stored volts in those caps.
Two things you can do. Unplug the amp and let it sit with the speakers plugged in for an hour with the standby switch off (like you were playing).
I have checked my 2:90 and can confirm on MY AMP this will bring the caps down to 0 volts (but there is NO WAY I can tell you this will work on your 2:90 so check it with a meter to be sure).

Also only touch inside the amp with ONE HAND. I was told to keep a my left hand in my back pocket when I mess inside an amp.
If you don't feel safe doing this take it to a pro. :wink:

 

[prsrose]

NEW PROBLEM!!!!
A consistent POP through the speakers, even with no volume. When looking at the back of the unit you see one of the power tubes 'popping' with bright blue flame inside.

Any guesses!?

*EDIT* Turned off, turned on-- it no longer does it. Just another weird symptom to the long list of weird things wrong with this amp.

 

[TOOLGUY]

I hear ya man. My 2:90 has been a pain in the arse as of late.
Not sure how old your amp is but build date on my 2:90 is 1993 so I guess I can't ***** too much.

Yours might be a bad plate resistor or a bad cap who knows.I have been all over my amp with a meter,replaced tubes ect and still have the A channel dropping out and getting tinny like yours.I have hit every help forum I could think of,called Mesa ect.A few folks told me to pull the board and do a re-flow of all the solder joints but thats a HUGE job.
Tossing in the towel and looking for a good tech in my area.
Sounds like it may be time to take it to someone for a look over.

What is driving me nuts now is trying to find a tube power amp in any of the local music stores (nobody in the Phila aera has anything in stock). You should see the funny looks I get when I walk in and ask if they have anything. Sure enough I get lead back to the live sound (pa.ss amps) section of the store...UGH Used 2:90s are selling for the same price as a new 50/50..With all of the cool new rack effects out now I thought tube power amps would be making a comeback.


BTW... Did you check those pots?

 

[ryjan]

Did you change the 3 12ax7's inside the 2:90? Night and day difference when I replaced the old ones in mine.

 

[prsrose]

Did you change the 3 12ax7's inside the 2:90? Night and day difference when I replaced the old ones in mine.

I did change them when I recently retubed. It's good advice though, I didn't even know they were there until it was time for a full retube and I was told they were there...

 

[prsrose]

I hear ya man. My 2:90 has been a pain in the arse as of late.
Not sure how old your amp is but build date on my 2:90 is 1993 so I guess I can't ***** too much.

Yours might be a bad plate resistor or a bad cap who knows.I have been all over my amp with a meter,replaced tubes ect and still have the A channel dropping out and getting tinny like yours.I have hit every help forum I could think of,called Mesa ect.A few folks told me to pull the board and do a re-flow of all the solder joints but thats a HUGE job.
Tossing in the towel and looking for a good tech in my area.
Sounds like it may be time to take it to someone for a look over.

What is driving me nuts now is trying to find a tube power amp in any of the local music stores (nobody in the Phila aera has anything in stock). You should see the funny looks I get when I walk in and ask if they have anything. Sure enough I get lead back to the live sound (pa.ss amps) section of the store...UGH Used 2:90s are selling for the same price as a new 50/50..With all of the cool new rack effects out now I thought tube power amps would be making a comeback.


BTW... Did you check those pots?

Mine is early model too-- I wonder if it's an age thing. I should have just bought a new one vs used. Lesson learned?
I'm tempted to trade mine in towards something new. Mine works, just not reliable enough for my taste. I'd really like a Mark IV (wonder how the Mark V compares) as that's the only setting I really use on the triaxis.

I havent checked the pots yet... IF I take it back to the shop (i have a tech around here that I like), I think I'll leave him to check it out.

 

[TOOLGUY]

wonder how the Mark V compares

Just played one Tuesday night.
It's awesome.

I was able to get my pre/2:90 sounds out of it and the new channel settings are great. If I felt I was a good enough player to deserve one I would have brought it home.I do worry about all that new stuff breaking down the road...
My pre is 20 years old and aside from a flakey loop (dont use it anyway) is still going strong.

Used here too (on the 2:90). Guess we both picked up someone else's problem.
I would hate to pass that along to yet another person but I might need to do the trade in thing too.