Low end farting out on palm mute chugs 36watter

bigdakota · Post by **bigdakota** » Tue 11/11/08 9:16 am

I have a 36 watt TMB head with a 4x12 cab and I've had some ongoing issues, I didn't build it. Overall has great tone but now I notice when I have my distortion pedal (trex mudhoney) on and chugging (palm muting) on lower notes (low e and f) the amp farts out a bit. Doesn't happen when chugging higher notes. I tried on other amps and it does not do this. Any ideas?

Has new JJ tubes.

I've been playing a while but not great diagnosing tube amp issues.

Thanks,

J

bigdakota · Post by **bigdakota** » Tue 11/11/08 9:22 am

Sorry, just realized from doing some searching it's prob blocking distortion. Is there any way other than modding the guts to temporarily fix this? I have a show on Saturday and would rather not fart out on stage..lol.

PaulBlandford · Post by **PaulBlandford** » Tue 11/11/08 12:03 pm

With a distortion/OD pedal engaged I don't think you'd hear blocking distortion. You'd notice blocking distortion when playing loud pushing the amp by it's self. What drivers are in the 4 x 12? It sounds to me more likely that the speakers are running out of excursion. Have you tried it through a different cab? Can you make it happen at low volumes?

-Paul

bigdakota · Post by **bigdakota** » Tue 11/11/08 1:06 pm

Well usually I have the amps volume on about the 10 o'clock range. Without distortion pedal it has a nice light crunch to it. With distortion on (gain to 12 o'clock) it has a nice fatness great open chord sound but as soon as I chug on E or F it farts out.

The cab is a Marsh, not sure what speakers, it's the rehearsal spaces. I'll try their other cabinet tonight.

Any use of matching the ohms differently? It's 16ohm out to 16ohm cab.

BooBird · Post by **BooBird** » Tue 11/11/08 1:48 pm

+ 1 on what Paul Said, EL84's are not Known for a havin a big bottom sound, more like Sparkly, more good upper end, I would for sure try a few diff cab's before tearing into the amp ! and make sure you got a Fresh battery in the pedal !

Dead battery's can make some pedal's sound funny,
Boo

bigdakota · Post by **bigdakota** » Tue 11/11/08 2:04 pm

Cool, I'm trying the mesa cab they have there tonight. My pedals are run though a power supply pedal board.

JohnnyCrash · Post by **JohnnyCrash** » Tue 11/11/08 2:25 pm

I know the OD pedal's Gain is up, but is the Volume or Level set really high too?

As mentioned EL84's aren't known for giant bottom end, but I just can't see a 4x12" running out of excursion. Not saying it isn't the case, but looking at all angles won't hurt.

You mentioned you've had ongoing issues with the amp... what other issues?

bigdakota · Post by **bigdakota** » Tue 11/11/08 2:32 pm

When I first bought it. it had some grounding issues that I took to a tech and they had fixed it. It died on me once after putting new tubes in it, tubes that came with it were doing the frying pan bacon crackle.

Happened the second time I fired it up after the tech fixed it.

Volume on the pedal is at 12 o'clock, to match level of the amps clean sound. It doesn't happen until the amp is pushed hard.

Any chance a fan on the back to cool things down may help a little?

bigdakota · Post by **bigdakota** » Wed 11/12/08 9:17 am

Ok last night was a good rehearsal. No FARTING! lol. But really, I had picked up a 12AY7 to reduce some gain and put it in the position directly next to the EL84's as I was told. I tried moving it to the furthest from the power tubes and voila! No farting out..pretty weird. I did have the bass turned down to 1, since its very bass heavy to begin with.

Thanks for your help guys!

ajkimba · Post by **ajkimba** » Wed 11/12/08 12:09 pm

bigdakota wrote:Ok last night was a good rehearsal. No FARTING! lol. But really, I had picked up a 12AY7 to reduce some gain and put it in the position directly next to the EL84's as I was told. I tried moving it to the furthest from the power tubes and voila! No farting out..pretty weird. I did have the bass turned down to 1, since its very bass heavy to begin with.

Thanks for your help guys!

I've been following this post, glad you getting some results. A 12AY7 has a gain facter of 44, low compaired to a 12AX7, 100. Maybe trying a 12AT7 in the first position, gain of 60 might sound better and no farting. If the the 12AT7 sounds OK and you like the tone, yo ucan get closer with a 5751, gain of 70. Just some suggestions for more versatility.

I commonly use a 5751 in the first stage of an overly gainfull amp to tame her a bit. That 12AY7 without a pedal will definitly put a damper on the gain and probably too tame...?

bigdakota · Post by **bigdakota** » Wed 11/12/08 3:13 pm

Thats good advice thanks! I'm going to pick up a couple tubes you mentioned and see what effect it has. At least the amp performed with no problems, so I'm headed in the right direction.

Thanks!

bigdakota · Post by **bigdakota** » Sun 11/16/08 10:54 am

Well, during sound-check before the show last night, the amp crapped out. Sounded great for 5 minutes, then went into this weird oscillating noise that wouldn't stop until I shut it down.

So new amp for me.

Post by **zaphod_phil** » Sun 11/16/08 12:05 pm

Looks like you probably found the real problem there. Sounds like a bad solder joint, bad filter cap or a flakey tube. I reckon the farty sound was likely just an early symptom of something on its way out....

phsyconoodler · Post by **phsyconoodler** » Sun 11/16/08 4:57 pm

Here's a quote from the Trex site about the MUDhoney pedal.

Quote: The Mudhoney is a Distortion/Fuzz pedal with a very wide tonal range. It features a typical 3-knob gain/volume/tone layout plus a boost switch. I played this for a few minutes with the boost off and it is quite impressive; very thick tone with warmth that could quickly find its way to being your main dirt for jazz, blues, etc. Then I pushed the boost and cranked up the gain! The speakers in my little Princeton cried for mercy.

It sounds to me like you have the volume on the amp too high when hitting it with this pedal,and it simply overdrives the preamp too much.If you just put the 12AX7 back in and set it to about 1/2 or even less,it would eliminate any farty bass problems.

bigdakota · Post by **bigdakota** » Mon 11/17/08 9:06 am

Well, I wish I could..but the amp is dead. There are way more higher gain pedals than the TREX. I find the TRex to be slightly more drive than a TS9 Tube Screamer to be honest.

Post by **zaphod_phil** » Mon 11/17/08 1:40 pm

Generally, a dead amp is a lot easier to fault-find and fix than a farty one.

bigdakota · Post by **bigdakota** » Wed 11/19/08 2:10 pm

Thats good to hear, but I think it's gonna be buried lol. Time for a new reliable amp.

kedsinger · Post by **kedsinger** » Wed 11/19/08 10:18 pm

Let me know where you bury her so I can go dig'er up!

blaren · Post by **blaren** » Fri 11/28/08 12:38 pm

WOW! Who built it? Was it a Ceriatone kit or a Dweeber?...

Shrapnel · Post by **Shrapnel** » Fri 11/28/08 2:01 pm

I wouldn't mind a few more dead amps being buried on my doorstep

Hmmm, now how can I get the general public to do that for me

Imagine all the fodder for projects for those that are otherwise complete losses.

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Low end farting out on palm mute chugs 36watter

Low end farting out on palm mute chugs 36watter