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amp problems
http://leftybassist.com/viewtopic.php?f=6&t=2395		 Page 1 of 1
Author:  bugsy [ February 16th, 2011, 5:18 pm ]
Post subject:  amp problems
SVT3pro.
I have been getting a loud farting noise when i hit a low note.
This sound is louder than it should be and is like a speaker farting rumble.
one instance is when i slap open E
Now it doesnt happen all the time
only started last couple of months and i think it gets worse or more constance the longer its turned on.


I have tried out 2 cabs and it does the same thing.

Im thinking about changing the tubes as they are probably over 10 years old and the amp has done its fair share of travelling.
Always been in a road case.

Is replacing tubes the best point to start?
Author:  AzWhoFan [ February 16th, 2011, 6:01 pm ]
Post subject:  Re: amp problems
it could very well be. In general power tubes will wear out much faster than preamp tubes. Preamp tubes can last 10,000 or more hours.

Are the tubes glowing more than usual? That could be a symptom of bad tubes, or other worn out components further downstream.

Are you getting any funny squealing noises, or nasty harmonic overtones?

Not familiar with the innards of this particular model tho. Does it need biasing if the power tubes are replaced?
Author:  bugsy [ February 16th, 2011, 8:42 pm ]
Post subject:  Re: amp problems
i have just opened it up.
one of the 12xa7 looks like it has jumped up and out of its little grey seat.
I can see the tube pins
Author:  AzWhoFan [ February 18th, 2011, 8:17 am ]
Post subject:  Re: amp problems
you probably have loose pin sockets. Usually caused by folks wiggling the tubes in and out of the sockets, instead of pulling straight up on them.
With the amp unplugged, push that puppy back in it's socket. Then, gently put a fingertip on top of each and every tube and see if they wobble in their sockets.
It's unlikely to be the primary casue of your sonic issues, but every lil bit helps.

DISCLAIMER: Tube amps store potentially lethal voltages, even when unplugged for many days. if you don't feel comfortable about working on the guts of an amp, take it to a professional to get serviced.
Author:  bugsy [ February 18th, 2011, 3:11 pm ]
Post subject:  Re: amp problems
AzWhoFan wrote:
it could very well be. In general power tubes will wear out much faster than preamp tubes. Preamp tubes can last 10,000 or more hours.

Are the tubes glowing more than usual? That could be a symptom of bad tubes, or other worn out components further downstream.

Are you getting any funny squealing noises, or nasty harmonic overtones?

Not familiar with the innards of this particular model tho. Does it need biasing if the power tubes are replaced?

Im not getting nay funny squealing noises just a loud farting sound when i hit a low E but not all of the time
It has probably come loose from travel ,
Author:  bugsy [ February 26th, 2011, 8:40 pm ]
Post subject:  Re: amp problems
has not fixed my problem.
took the top off last night and checked to see the glow on the tubes
the back 2 12AX7s seem to glow stronger than the front 2., i dont know if that is a problem?
there is not amp tech where i live but i am thinking of taking it to a guy who fixes electronics maybe he can see something :|
Author:  tac [ February 20th, 2012, 10:19 am ]
Post subject:  Re: amp problems
Hi, try moving the amp away from the cabinet, across the room if possible and rest it on a cushion or foam. Does it still do it? if not, then the vibrations from the cab are effecting something in the amp, possibly the valves. If it does still do it, it may be they speaker.
Author:  pjmuck [ February 20th, 2012, 10:43 am ]
Post subject:  Re: amp problems
Hmm. The problem you're describing sounds typical of a torn or cracked speaker which can't handle lower frequencies. Or, it could be the the foam surround of the speaker is worn or not keeping the edges of the metal of the speaker off the wood of the cabinet enough so it's vibrating.
I had this problem with a Marshall cabinet recently. Farting and buzzing when I played the lowest guitar notes. Opened up the cabinet, checked the speakers for tears - nothing. I discovered that the foam surround wasn't cushioning the speaker off the cabinet enough, however, so I replaced it. Problem solved! So check your speakers too.
Author:  Stingray5 [ February 20th, 2012, 2:09 pm ]
Post subject:  Re: amp problems
bugsy wrote:

I have tried out 2 cabs and it does the same thing.




Just make sure you also eliminate all other culprits - cables, battery, bass etc. so you know 100% it's the amp. good luck!
Author:  velalv [ June 19th, 2012, 6:21 am ]
Post subject:  Re: amp problems
As always, thanks for the thoughtful replies and not flaming me for resurrecting a zombie. Here is an OP I started at talk bass to explain my situation fully. Further thoughts always welcomed. But you all gave me a lot to think about so far.

So, the amp at my church is about to die. Specifically, the graphic eq no longer works, and the speaker is crackling with no rhyme or reason. I have had enough. The amp is not mine. It is a old Peavey TNT 115, with 150 Watts worth of sound. I usually set the master volume at noon, and the gain at 10 o'clock. I play with a clean signal, no effects. Our sanctuary holds 75-100 people. My personal amp is a 20 watt practice amp.

I am looking for a bit of advice about whether to get a new amp or a DI.

I play primarily at church, and every so often will hit an open mic night or a classic rock gig where I use someone else's amp. Our church is set up with a Mackie PA system that has three 8 inch wedges as monitors and two 15 inch mains. I was the only person not going through the sound system. We have no subwoofer. Our church space is used by a lot of other churches and outside groups, so my worship leader does not thik it is worth getting something too nice, or having something I can lug every week. I rather not.

Ok, I primarily play a American Jazz Deluxe bass strung with high beams or DR dragon skins. Occasionally, I will also play a p-bass with TI flats. I know that I won't get kick you in the chest lows since I don't have a sub.

I don't have a lot of money for a good amp right this second, so I thought spending $200 for a good DI could remedy teh issue. I could be talked out of this. What do you guys think?

1) Should I get an amp, or a good DI?

2) If you think I should get an amp, what type should I start looking at under $300, if they exist?

3) What are good DI's that would work in this situation?

4) Any other thoughts?
Author:  danomite64 [ July 4th, 2012, 6:53 am ]
Post subject:  Re: amp problems
If the church wants you (or anyone in general) to play bass there, and it has a bass amp there to use, then they should be willing to have the amp repaired, as that will likely cost less than replacing it would. If not, then I'd suggest finding something like a used GK400RB or a used Ampeg Portabass 250, which is what I use at my church (great little amp!). If you could add an input jack to the back of the TNT (or if it already has one), you could use the speaker and not lug your own. I'm not really into DI's, and certainly wouldn't want to hear my bass coming out of an 8" monitor wedge, all mixed in with the rest of the band.
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