Wierd humming noise

[Bulls Hit]

My Fender Frontman 25W amp makes a funny boomy, buzzy noise on certain notes, esp when palm muting, kinda like a resonance, speaker flapping sort of noise.
I've just replaced the speaker and it's made no difference. There doesn't seem to be anything loose in the cabinet. Any ideas??

 

[ez_willis]

Change the cords and use a different guitar to make sure it's the amp and not something else.

 

[Bulls Hit]

Yeah did that, had it in the shop with their guitars, leads etc.

It seems to do it mainly on a G. If I let it ring, this loud row frequency hum/buzz overtone takes over. You can see the grill mesh vibrating, and it's pushing a lot of air. Would it be something in the amp circuitry?

Maybe I'm just going to have to leave G out of my tunes from now on

Edit: Could the reverb springs have anything to do with the noise? Dialling the reverb in or out doesn't make any difference though

 

[ez_willis]

Yeah did that, had it in the shop with their guitars, leads etc.

It seems to do it mainly on a G. If I let it ring, this loud row frequency hum/buzz overtone takes over. You can see the grill mesh vibrating, and it's pushing a lot of air. Would it be something in the amp circuitry?

You said that you replaced the speaker, did Fender cover it?

Have you tried different amps of the same model? It could be a flaw in the build. I could only find one other reference to this problem with a search so it doesn't seem to be a problem with the design.

It may have been built on a Friday or the first morning back after a long weekend.

 

[Anfontan]

That Frontman is solid state right? Is it old enough that the electrolytic capacitors in the power supply might be drying out and causing the current needed to be distorted? I had a Lab Series amp that had similar problems and the power supply caps were the problem.

 

[ez_willis]

The amp has "2 selectable channels (Normal and Drive)" is it doing it on both channels?

 

[Bulls Hit]

Yeah it's a solid state. Reasonably new, probably 4 or 5 years old.

ez yeah it does it on both channels, but its worse/more obvious on the clean channel. I disconnected the reverb as well but that made no difference.

I'm starting to think it's something like Anfontan says, some dodgy component on the board. Wierd how it just does it on a G though

 

[Dani Pace]

I have a Fender Princeton Chorus which had a similar problem. On the lower notes, especialy the low G, I was getting a really weird sound, for lack of a better term we (my friends and I) called it a "speaker fart." That is exactly what it sounded like. It was frustrating to say the least. I tried different speakers, different settings, cords, guitars etc... Finally I noticed a little rough spot in the bass control so I decided to change the pot, not normaly a problem but the chasis design of solid state Fender amps is a little tricky to work with. I not only had to pull the amp but had to remove all the jack/control nuts just to get inside so I could get to it. Once there I discovered the pot to be 3 prong, soldered to the board with a soldered on shield around it. The pots on Fender amps are small and require exactly the same part to replace (there isn't room for a larger size to fit.) Anyway my half hour repair turned into a two day nightnare of part hunting, finally i found one, managed to install it, somehow managed to not loose any screws or nuts and got the thing back together. It was a lot of hassel but it did get rid of the speaker farts. Unless you have the patience of a saint, let a qualified repairman figure it out for you.

 

[Bulls Hit]

I think you might be on to something there Dani.

My normal volume pot is scratchy, although it does happen on the overdrive channel as well.

If you get a chance, I wonder if you might have a listen to the sample and tell me if it sounds anything like your amp farts
http://www.recordingproject.com/bbs/viewtopic.php?t=21335

 

[ggunn]

I think you might be on to something there Dani.

My normal volume pot is scratchy, although it does happen on the overdrive channel as well.

If you get a chance, I wonder if you might have a listen to the sample and tell me if it sounds anything like your amp farts
http://www.recordingproject.com/bbs/viewtopic.php?t=21335

It sounds (reads, I mean; I can't listen to sound files here) to me that you've got some sort of resonance problem either in the cabinet or electronics. If you disconnect the internal speaker and play it through an external cab, is it still there?

 

[Dani Pace]

I can hear some sort of "flutter" but it isnt quite the same, my "amp farts" were pretty extreme. From the small sample you gave your's almost sounds like a cracked speaker, have you checked for this? You might try cleaning your pots, a little dust or corrosion can cause flutters. A good shot of Deoxit 5 might clear things up for you, it's worth a try before tearing into the amp.