Problem with 5:25, extra noise/artifact after notes.

[LTE]

My dads brand new 5:25 has been treating him well so far, but recently he noticed there is some noise that comes after certain notes. It's not the cable, guitar, or anything like that, its definitely in the amp. When certain notes are played, an audible noise that sounds like distorted vibrations is repeated a few times. Its more audible when listening to the back of the amp. I think it's the reverb tank or tube, although even when the reverb is footswitched off it still happens.

Any ideas? If possible i could record it.

 

[soundchaser59]

Is this noise coming thru the speaker? Or you hear it but its not coming out of the speaker?

If it comes thru the speaker, then try disconnecting the reverb unit briefly and see if it goes away.

 

[LTE]

No i'm almost positive it's coming out of the speaker.

I think its something with the reverb because you can hear the note, the normal working reverb, and then a distorted warbling like a really fuzzy reverb or delay. And its consistent, meaning its the same sound every time, but once again, its only on certain notes on the g, b, and e strings, its not a guitar problem too, i tested it.


Oh, and how would i unplug the reverb?

 

[gezza]

Hey Guys,

I had the exact same problem. I think.

It was more noticeable on the burn channel, but I also noticed it on the clean.

It was a weird noise, sort of a low buzz/hum out of tune with the notes being played, appeared after the notes was fading out.
I tried different Guitars, speakers, Cables, played with a few tubes, but hey it was one week old.
I rang the guys I bought it from, let them hear it, they swapped it on the spot.

I returned the amp as it was 1 week old. They swap it for a new one.

Sorry, I never found out what it was, but the replacement one has never missed a beat since.

Gezza.

 

[wizard333]

Let me preface this by saying that I do tech work on amps.

What you are describing sounds like severe crossover distortion. This is caused when either 1) your power tubes are severely mis-matched; I've seen brand new supposedly "mached" Mesa tubes that were at extreme oposite ends of the scale; or 2) One tube is just not working at all. The most common cause of this is a bad screen grid resistor, I've seen it happen quite a few times.

A two or more tube amp can work and actually almost sound ok with 1 tube not functioning (but in the circuit), except you'll get a bad distortion/hum that fades in as the note decays. The broken screen grid prevents the tube from flowing current. It will still light up, have plate voltage, etc, but not flow signal.

If you have an extra set of power tubes, you can put them in and see if the problem goes away. If it doesn't, its probably a bad screen grid resistor. I do not recommend Mesa tubes by the way; the quality is generally pretty bad. If you want tubes to work in your non-adjustable bias Mesa, just make sure your specify "medium bias range" matched tubes when you order from Tube Depot, Tubes and More, whoever; or get a Groove Tube that falls in the 4-6 range. I recommend JJs since they are a very robust tube that will put up with a lot of abuse. That would be a Groove Tube with the "S" designation; ie. GT EL-84 S.

If all that is greek to you, and since its under warranty, call Mesa and find out how to get it to an authorized repair center, and give them the information above.

 

[fredm]

Just thought I would give you something to check. Had a similar problem myself. The following is from a previous post.



" if I play certain notes or chords (open G, D, C etc) I get a high pitched ringing which is mixed in with the played notes. "

Had a very similar issue myself. I traced my rogue noise down to the aluminium spring loaded retainers/heat shrouds for the 12AX7 valves. While someone plays the note that seems to produce the noise apply a gentle pressure using a thin piece of wood to each of the metal shrouds in turn.
On mine it was the middle one that was vibrating and could be heard through the speaker. A gentle pressure with a piece of wood made the noise dissappear.
I removed the shroud but could not see anything wrong with it, anyway I refitted the thing and the noise wasn't there anymore.

Unfortunately it has since come back. It's the same valve causing it and if I gently push against it the noise stops as before. It's not quite as bad as it was before so I just live with it now.

Actually I've just had a thought, a piece of folded cardboard wedged between the the offending valve and it's neighbour might just do the trick.

 

[StevenL]

Mine did that when I first got it. Made a low pitched distorted warbling sound that faded out with certain notes. Drove me crazy. I thought it was the speaker so I pulled it. The stock speaker had 2 holes punched in it so I replaced it. But..that wasn't the problem. Replaced POWER TUBES. That was it! Been fine ever since.

Good luck. It's probably something pretty simple.

 

[LTE]

Went out on black friday and got some groove tube el84s from guitar center. Works fine now!

 

[wb1dx]

I have the same issue. The amp was purchased used (e-bay), not sure how old it is or if it is still covered under the 5 year warranty. Serial number is E25-2731.

The noise is definately coming from the speaker, and is a "buzz" like a very low volume distortion that kinda peaks as the note is fading. This will happen on only certain notes. I did replace the power tubes with some Groove Tubes EL84-S with a 6 rating. This stopped the problem for a bit, maybe 2 months. Now the same noise is back, prompting me to think that something else is going on. I grabbed a full set of pre-amp tubes from my son's collection and swapped them out, noise is still there.

My son says I'm crazy, but it really sucks to hit a note that you want to sustain, and all I can focus on is that friggin noise that slowly develops, peaks, and fades away.

Sometime it sounds like those cicada bugs you here in the summer months bussing up in the trees.... Really annoying.

Someone mentioned a resistor that may be bad. Where can I get a schematic for the board? And I wonder if this is the problem (bad resistor) that it would reappear 2 months after replacing the tubes. Iw ould have expected that the noise would be there all the time, even with new tubes....

ANy help would be really helpful.
Thanks