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  1. #1

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    Hi guys, I am hoping someone might be able to set me in the right direction in terms of finding out how to fix this. I got a Monoprice 15 watt tube amp - been extremely happy with it and was going to do a video review. When starting to record I noticed this odd sound that only happened on some notes. Trying to figure out what it was I also found that if I tip the amp forward, speaker facing the ground, that it goes away. I've tried holding things that might be vibrating and looking for loose parts but am not finding anything.

    If possible I'd like to not return the amp and fix this if it is something simple. I haven't had a tube amp for probably close to 20 years so I don't know if this is a sound someone will recognize that might be unique to a tube amp. The only work I've done is changing two of the preamp tubes to 5751 tubes.

    Is this a speaker issue? Something tube related?

    I also ended up having the sound mysteriously disappear after messing with the amp for an hour a couple of nights ago. It just came back though so I came here. Thanks so much for any help.

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  3. #2

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    IME the most common cause of this sort of buzzing is something else in the room vibrating sympathetically. I get it a lot, because I have lots of things that can vibrate lying or hanging around. Other guitars hanging on the wall seem to be the biggest culprits, but all sorts of things can vibrate. But without being there, I couldn't possibly point to anything as being the certain vibrator.

  4. #3

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    When you tip it and the buzz goes away that tells me it mechanical so something is loose. It could be in the amp or something in the room.

    Some years ago I recorded a trombone quartet in a church. One of the trombones had a slight buzz not enough to be concerned so I forgot about. A few months later there was a concert with a small brass band. The French horn had the same buzz and happened to be in the exact same spot the trombone was in.

    It was something in the room but sounded like it was coming from the horn. I never did find out what it was.

    Make sure all bolts, and screws are tight. Grill cloth is not acting like a drum head. Check inside the chassis for loose wires.

    If none of that works send it back.

  5. #4

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    Thanks for the advice so far. It is definitely coming from the amp - I moved it around to see if it was something close to the amp and the buzz happens anywhere I put the amp. It’s hard to say but the buzz sounds like it is coming from the speaker when I put my ear close to the amp and move my head around to try to hear where it is loudest. I wasn’t sure if it was something tube related - do tubes buzz or rattle or something is wrong with them?


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  6. #5

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    Speakers can be the source of some really weird sounds. One amp I struggled with made a very odd, digital sounding "ring modulator" sound when certain notes decayed. Turned out to be something mechanically loose under the dust cap of the speaker and required a recone. I've also had odd sounds when bits of "debris" get trapped between the grill and the baffle or speaker cone. Don't discount the room vibration either. I swore a particular rattle was coming from the amp itself, but when I ran a looper into the amp, it turned out to be one screw on an air intake vent on the ceiling. Had something similar happen with a slat from a window blind. Tubes can jiggle in their sockets, loose solder can jiggle in the chassis, debris can jiggle in the chassis, loose nuts/washers/bolts can rattle in the chassis/cab. If you have a looper, identify the offending notes and let them repeat over and over again until you track it down. (You'll go nuts doing this, by the way.)

  7. #6

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    Timely subject.

    My new-to-me Polytone Baby Taurus has a buzz on the note G above middle C- strongest on the B string at the 8th fret, also present at the 12th on the G string, but oddly very minimal on the E string at the 3rd fret. This happens with each guitar I've tried and has been present in two different houses, so I am sure it comes from the amp.

    I tightened up all the screws I could find (lots of them on the bottom of the amp- feet, screws holding down the PT and other things), thinking that something just came loose during shipping, which not only didn't fix it but seemed to adversely alter the sound of the amp! Sort of like excessively heavy strings choking a guitar's top. Backing off a half turn on the screws resolved that. Other than this, the sound of this amp is just amazing with my archtop. Somewhere in there something is vibrating and I just haven't tracked it down yet. The looper idea is a good one.

    rio, my first thought is that the speaker wire is contacting the speaker frame and that tilting the amp changes the angle it's hanging at and gets it out of the way. Tubes can rattle and make noises- you can find YouTube demonstrations of this- once they're hot, tap the tubes gently with a wooden pencil (with the amp volume on) and you can often hear a bad tube send noise to the speaker.

  8. #7

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    Did you check to see what if a tube is microphonic? I have a Gibson BR-9 that was doing a very similar thing on certain notes when turned up past about halfway. When I tapped the 6SJ7, it rang like a bell, cured with a tube swap.

  9. #8

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    I have news!

    When I hold a pen lightly against the first power tube the noise goes away. I set my Freeze pedal to continuously play E since that makes the sound happen the most prominently and just touching the tube makes it go away. If I take the pen away it will stay ok for a few seconds and then come back, and I can make the sound come back by very lightly tapping the tube as well.

    Does this mean I need a replacement tube? It wasn’t exhibiting being microphonic from what I read (which was described as being almost feedback-like in sound), and since the tube otherwise is working just fine is there some fix where I could put something on the tube or otherwise have contact with it while I’m playing? I don’t want to shell out money for tubes (I would need two new power tubes, having read they need to be matched?) if I don’t have to considering I got this as a cheap amp and have already put more into it with the new preamp tubes.

    Also do you think the tube developed the problem since I got it about a week and half ago? Or did it come that way and I just didn’t notice it? I did find out about it at first due to recording solo guitar and I’m not sure I would have noticed it playing full volume with a group.

    Thanks again for the help - I would have never thought of testing like this to actually find the problem.


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  10. #9

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    Replace power tubes with a matched set and re-bias the amp or on the cheap buy a EURO tube dampener as a bandaid fix.

  11. #10

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    Before doing anything that costs money just try reseating the tube.

  12. #11

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    I assume you mean the output tube. There is usually only one power tube. The power tube is the rectifier tube.

    Just replace the one. Low cost low power tube amps do not need to be replaced with a matched pair or do they need to be biased.

    Matching and biasing in the audio range is a myth perpetrated by wannabe techs to get you to part with your money.

    Unless there is a bias control biasing would require changing resistors.
    Last edited by BBGuitar; 03-09-2019 at 02:23 PM.

  13. #12

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    Make sure that the speaker is tight. There are typically 4 small bolts. Frequently, some are reluctant to use the appropriate amount of torque to snug the 'gasket". That's the most frequent cause.

  14. #13

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    The two EL84s need to be matched. Those types of power tubes are known to rattle. I'd get some JJ ones, those were best for me back when I was using a Fender Blues Junior. I recommend getting some of the silicone O-rings for tubes you find on eBay or the pricier ones on Eurotubes. Stick two on each tube plus the retainer and that should help. The V1 preamp tube (the one closest to the input jack) is very important. I find the JJs are the least noise prone, the Tung-Sols are brighter sounding but a little more prone to noise. JJs are your safest bet for tubes.

  15. #14

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    Take the speaker off, it's possible there's a bit of wood or other debris between the cone and grill cloth and it will only "dance about" at certain freqs.

  16. #15

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    +1 on the damper rings, given it stops when you hold the tube down.

  17. #16

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    Swap tubes in V1 and V2. Your V1 might be a tad microphonic. Whatever V1 does is amplified and passed down the line to be processed and amplified subsequently, so switching your slightly noisy tube in V1 to V2 will probably solve the problem. Could even be a loose fit in the socket. I'm assuming you have the same tube in V1 and V2.

  18. #17

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    I think tubes can be microphonic out of the box or after a few weeks—especially cheap ones. But you are much more likely to notice a microphonic tube if it’s in the first stage of the preamp since the microphonic are amplified by subsequent stages. If a power tube is noticeably microphonic there might be something seriously wrong with it. A short in a power tube can damage other components, so it might be best to replace it with another and see if that fixes it. [edit]

    Any tube amp owner should keep a spare set of tubes on hand, so it’s not really a waste.
    Last edited by KirkP; 03-10-2019 at 02:50 PM.

  19. #18

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    I think I have it resolved now thanks to the advice here (which I really would not have thought of both with finding the issue and resolving it). I tried reseating the tube and it didn’t do anything. However, after seeing the mentions of the silicone tube cover thing tho help with tube rattling, I cut up a silicone oven mitt, put some on the tube and the problem seems to be fixed. I am going to record a bit tonight to check since my ears might be missing something. Thanks again guys.

    Edit: problem is back again. This has taken a large amount of my practice time and I’m about done with it. I guess I’ll sleep on it but as much as I love the sound of it and have missed tubes, this is exactly why I’ve used solid state for so long. I want to play, not play around inside a piece of gear and being unsure if something is going to work on the job. At least this has all happened at home. If I took this out to record tomorrow and had this problem come back then I’d be both upset and embarrassed. Sorry, just a bit frustrated.


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    Last edited by rio; 03-09-2019 at 11:29 PM.

  20. #19

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    sounds like you have tried everything except replace the Tube. which can cause it .

  21. #20

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    Quote Originally Posted by JaxJaxon
    sounds like you have tried everything except replace the Tube. which can cause it .
    I wouldn’t mind buying a pair of tubes for it if it weren’t for biasing it since I have absolutely no recollection how to do that anymore. It’s been since high school that I used to know how and all I remember is that I could hurt myself inside the amp.

    I’ve been reading all night about tube amps (against my better judgement, missing another night of practice) and I saw one thing that ill try tomorrow. Someone said that to fix this issue he essentially padded the tube at the end so that it wasn’t firmly fit against the plug. He used electrical tape to do this and this inhibited vibration and fixed the issue. A couple other people chimed in as well to confirm it worked for them so it’s worth a shot. One thing to try toothat they mentioned is to swap the two tubes to see if the problem was the socket or the tube. In that case the same socket rattled after the swap. We’ll see... this has the tone I’ve wanted for a long time with that edge of breakup old school sound and it compliments my guitar and the way I play. I really want it to work out.


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  22. #21

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    BTW, many techs say you don't need matched power tubes in a guitar amp. Of course you should adjust the bias though. I don't care for the difference within 10 ma personally. Some folks even state they prefer the tone of unmatched sets. I'm not sure about that. I understand, technically you lose the more harmonic frequencies (?) the more you match the output balance. Correct me if I'm wrong.

    Also, I've always wondered why those who religiously trust "matched power tubes myth" don't care for a matched PI tube or perfectly matched turns of OT windings.
    Last edited by takauya; 03-10-2019 at 03:11 AM.

  23. #22

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    Quote Originally Posted by rio
    I wouldn’t mind buying a pair of tubes for it if it weren’t for biasing it since I have absolutely no recollection how to do that anymore. It’s been since high school that I used to know how and all I remember is that I could hurt myself inside the amp.

    I’ve been reading all night about tube amps (against my better judgement, missing another night of practice) and I saw one thing that ill try tomorrow. Someone said that to fix this issue he essentially padded the tube at the end so that it wasn’t firmly fit against the plug. He used electrical tape to do this and this inhibited vibration and fixed the issue. A couple other people chimed in as well to confirm it worked for them so it’s worth a shot. One thing to try toothat they mentioned is to swap the two tubes to see if the problem was the socket or the tube. In that case the same socket rattled after the swap. We’ll see... this has the tone I’ve wanted for a long time with that edge of breakup old school sound and it compliments my guitar and the way I play. I really want it to work out.


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    You don't have to match tubes or rebias the amp. Yes, doing so is part of optimizing the set-up, but nothing bad will happen if you don't, and something good (cure the noise) might. That amp might even be self-biasing.

    John

  24. #23

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    Quote Originally Posted by John A.
    You don't have to match tubes or rebias the amp. Yes, doing so is part of optimizing the set-up, but nothing bad will happen if you don't, and something good (cure the noise) might. That amp might even be self-biasing.

    John
    From what I’ve found it is fixed bias, and inside the chassis there is a bias adjust knob so not self biasing unfortunately (the preamp tubes are, though). That would be great, though, if nothing bad would happen. I read (so much reading the past few days) that it could potentially damage the amp if you don’t rebias with new tubes. Others said that if using a matched set (with this amp, which is a Laney Cub clone) that you don’t have to bias but it would definitely be beneficial. I actually would like to learn to bias an amp. I did it once in high school but completely forgot how and given that a mistake could hurt me I’d like to take my time but at the same time want to get this fixed ASAP so I can get back to playing and recording with it.

    Edit: just spent an hour actually playing and seems like a bandaid fix...turns out both tubes were rattling, which might explain why putting silicone one one didn’t fix it. On another forum someone said to just expect rattling from these tubes, and it doesn’t matter which amp it is so long as it is using EL84 tubes which doesn’t make me happy. But with silicone on both tubes it seems ok for now. I’ve also read that these are biased cold so I will do some research to refresh me on how to safely set the bias, where I need to be testing the bias on this model in the chassis and probably do a tube swap anyway. Maybe if it is already cold then swapping the tubes and not setting the bias wouldn’t hurt the amp? I don’t know, I’ve read so much on this stuff the last few days that, although I’m learning, I am having a hard time with what’s what.


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    Last edited by rio; 03-10-2019 at 01:27 PM.

  25. #24

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    If you swap output tubes without checking the bias, I don’t think there is a risk of damaging the amp. If the bias is too cold (low plate current) there will be some crossover distortion between the two sides of the push pull circuit, which can be unpleasant. If the bias is too hot (high plate current) it will probably sound fine, but may begin to overdrive at a bit lower volume levels than before (less headroom) and the lifetime of the tubes will be reduced.

    I think the situation is similar for bias balancing. If the bias levels are reasonably close to nominal I don’t think it’s a big deal if they aren’t identical. But if one is way to cold or way to hot you may have the tone or tube life issues I mentioned earlier.

    I’ve actually tried playing through a Twin Reverb while adjusting the bias. The change in tone is subtle over a fairly wide range, but it definitely does change. The tone seemed to slightly warm up when biased on the hot side. But with 4 6L6GCs I can’t afford short tube life, so I brought the bias back to a hair hotter than the nominal value.
    Last edited by KirkP; 03-10-2019 at 03:32 PM.

  26. #25

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    Quote Originally Posted by rio
    I wouldn’t mind buying a pair of tubes for it if it weren’t for biasing it since I have absolutely no recollection how to do that anymore. It’s been since high school that I used to know how and all I remember is that I could hurt myself inside the amp.

    I’ve been reading all night about tube amps (against my better judgement, missing another night of practice) and I saw one thing that ill try tomorrow. Someone said that to fix this issue he essentially padded the tube at the end so that it wasn’t firmly fit against the plug. He used electrical tape to do this and this inhibited vibration and fixed the issue. A couple other people chimed in as well to confirm it worked for them so it’s worth a shot. One thing to try toothat they mentioned is to swap the two tubes to see if the problem was the socket or the tube. In that case the same socket rattled after the swap. We’ll see... this has the tone I’ve wanted for a long time with that edge of breakup old school sound and it compliments my guitar and the way I play. I really want it to work out.


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    I replaced my power tubes without rebasing. I mean, it’s a $200 amp. I ordered a couple of nicer power tubes and just put them in. They were matched, but other than the swap I did nothing else.


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  27. #26

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    I have a Cube 30 that buzzes at low G, and it was quite prevalent and it was worse depending on the guitar, for instance a Telecaster would bring it about, the Holdsworth Fatboy would as well, but the Jazz box made that amp unplayable when I hit that low G.

    So what I ascertained was the metallic Grill screen was actually vibrating towards the middle of the screen right over the speaker.

    Prior to attacking the screen, the first thing I did was tighten every screw on the amp, the corner protectors, the amp set screws, any screw on that amp was tightened, and then I pulled the grill screen off.

    I wove a strip (pencil thickness) of felt down the middle both horizontally and vertically through the holes in the grill, which as I said was a metallic grill. I did look around for another type of grill material but was unsuccessful I was thinking wicker might not buzz as much but after doing a bit of a search I found out that that's not necessarily the case.

    After I wove the two strips of felt horizontally and vertically into a cross I then have some rather thick felt discs that are used for piano action repair and I positioned and glued 4 to 5 evenly spaced around the perimeter if the speaker, which the edges of the metallic Grill cloth would rest upon, and then I took four more of those disks and put them under the screws when I screwed the grill screen back on.

    Problem eliminated? Almost but in my case it was the grill screen that was causing the sympathetic resonance that was totally unusable.

    When I record I usually go direct so that wasn't really an issue but it could influence in the ambient microphone in the studio.

    When I searched I used the term Grill Buzz, transient vibration and resonance vibration in guitar amps.

    It actually is a fairly prevalent issue as many hits came up describing exactly what people are experiencing and their fixes. And all the fixes included, but was not limited to making sure all screws are tight. And some people even use Loctite on their screws, but if you go that route I would recommend you use the lightest Loctite product rather than the heavy duty stuff.

    Also, it is not limited to metallic grills or even just to Wicker grills. It also occurs on cloth grills because the frame material that the cloth Grill is stapled to will vibrate and that needs to be padded.
    I have a fender Rumble 500 bass amp that I also had to put some padding in place in order to counter a vibration that I was having on that amp.

    Drummers even have issues with lugs because the lug housing has a spring in it that will vibrate, so what they do is they stuff that with cotton as in a cotton ball, and that stops the Springs from vibrating inside of the lug nut housing. So if there's a vibration and there's an airwave you might have a problem.

    Best of luck!

  28. #27

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    I have a Fender Custom Champ amp. I'm sure you guys know better than I do the amp I'm talking about but just for clarity, its the recent 5w hand-wired model, tweed covering, from Fender, not a boutique or anything. It's about two years old and lightly played, like maybe 20 hours max? (doubt it is the tubes)

    Ok well it is making a vibratey - buzzy sound. Now, I know what 60 cycle hum is, this not that. Mostly because it doesn't do it when the guitar is just sitting there, even if I turn the volume up high. I also do not think it is fret buzz, (unless I have multiple frets that all at once went caddy whampus) because it makes this noise on multiple spots on the fret board, on different strings. To be very specific, it only makes this noise when I play a E, F, or F# believe it or not, No matter where I play these frequencies on the fretboard, or what octave (except way down on the low E or way high on top E string).

    This sound does not sound electronic, to my inexperienced dullards ear it seems like something vibrating at a certain frequency and rubbing against something else. Like a loose screw or cable connection or something? The buzz does not SEEM to increase as I increase amp volume, but it does not happen at very low (3 or less) volume. I put the amp in the center and walked around it playing the offending note, it is definitely the amp, not the doorknob or drawer handles or something.

    Any ideas on how to start troubleshooting this? I have a couple of amps and guitars so I can try a few different instruments or the same amp with a different guitar (the guitar I noticed it with is a Heritage 575).

    Before you tell me to un-solder the pressure sprockets from the flux capacitor diodes, or re-align the magnetic constrictors on the cochrane core, keep in mind I'm a novice lol. I can turn a screw or two if needs be but not a lot more. I have no problems taking it in, but I'd rather save the money (plus I can't take it anywhere right now due to the COVID).

  29. #28

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    It could be something loose on the amp, and just tightening every screw you can find might fix it. It's also very possible that it's the guitar that's buzzing. Archtops have lots of bits and pieces that can get loose and rattle. It's often the pickup vibrating, and that can sometimes be fixed by raising or lowering the pickup. Sometimes it takes wedging something between the pickup and the mounting ring. Or it could be almost anything. There are at least a couple of threads on the forum about troubleshooting archtop buzzes. It can take persistence and careful investigation sometimes. I've found more than once that what I thought was an amp buzz was actually something else in the room, even though I was pretty sure it wasn't.

  30. #29

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    verify that a different guitar does it.

    tighten ever screw you can see without getting electrocuted. If there's a reverb tank, make sure the connections are tight.

    Make sure the tubes, if it has tubes, are seated well. Just press them in.

    Then, take something that doesn't conduct electricity, like a pencil or a drumstick, reproduce the problem and press the stick against every part of the amp.

    If it's a vibration, you ought to be able to affect if, and then you'll know where it is.

    Press the speaker, the tank, the knobs, the jacks, the back panel, the chassis, the rubber feet, whatever, all while the buzz is there.

    When you figure out what is vibrating, invent some way to make it stop. A shim, tighten something etc.

  31. #30

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    If you have a tone pot on the guitar, try turning it to 10 and see if your buzz is still there. I have had bad tone pots create a strange buzz on certain notes when the pot is engaged.

  32. #31

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    I experienced something similar years ago. The cabinet had a loose brace, so it took some dismantling to find the cause.

  33. #32

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    The possibilities are almost numberless. I had one guitar on which I eventually traced the buzzing to the tone pot. It was a push-pull for coil splitting, and it was worn enough so that the shaft vibrated and buzzed. I've seen internal wiring vibrate against the back or even the top. Pickguards can buzz. Loose hardware on the headstock. Pickups. Bridge hardware. The fact that it only happens at certain frequencies points to mechanical vibration, and that can be almost anything. And once again, more than once I was convinced that the buzzing was from the amp, but was actually something else in the room being vibrated. Take the amp to another room and see if the buzz persists. I know it's hard to believe, and it was for me the first time I encountered it, but it's possible.

  34. #33

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    If a little piece of something gets between the grill cloth and the speaker it can dance around and make all sorts of bizarre noises.

  35. #34

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    Also, my heating/cooling vents in ceiling used to rattle in such a way that sounded like it was coming from the amp. I used a looper pedal to loop the offending notes then walked around the room touching literally every surface—sections of the amp, stacks of paper, books—until I discovered it was the screws in the vent above the amp.

  36. #35

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    Okay thanks everyone I will try the ideas you put forth and let you know if I can determine anything at all, its annoying but not the end of the world. Thanks again everyone, I will let you all know,

    I hope you all are well.

  37. #36

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    Perhaps the best help I can be is to list the number of things that have caused buzz for me thru the years in different amps:

    1) Speaker not sufficiently tightened. (But don't over tighten !)

    2) Speaker wire hitting against the speaker.

    3) Amp chassis not sufficiently tightened and rattling against the cabinet. This took several tries to fix. Finally ended up using strips of rubber weather stripping around the chassis to cushion it. Also discovered that one of the screws had an issue while I was at it. (It was an old second hand amp.)

    4) Back panel on the cab rattling. Tightening the screws didn't help. Ended up using the weather stripping trick again.

    5) Pictures rattling on the wall.

    6) My personal favourite: An obnoxious buzzing when I played certain notes. Tubes? Nope. Speaker rattling? Nope. Finally smartened up and plugged into another amp. Buzzing still there! The answer: rattling truss rod in the guitar. Sheesh !

  38. #37

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    The last Fender amp I bought was a Showman (SS) with an EV15L in 1983. Unpacked it, plugged in, turned it on, hit the open 6th string and heard buzz like it was full of bees. Found problems with chassis mounting, front grill, speaker mount, speaker wires and probably other things. Used a bunch of rubber weather stripping, rubber washers and RTV to get it to stop making extraneous noises. It was then my main amp until 1991.

    Danny W.

  39. #38

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    Hold the amp up in the air by the handle power off unpluged.

    Tap the cabinet lightly with a rubber mallet.

    Tap it in all directions till you hear the buzz.

    Remove or tighten what you can one piece at a time. Tubes, speaker, etc.

    Keep at it till the buzz goes away. It's the last thing you did.

    Fix that and your done.

  40. #39

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    Keep in mind that screws that are TOO TIGHT may also be the cause of buzzing. I had one amp that buzzed at certain frequencies. Lossening the chassis bolts just a touch cured it. Strange, I know.

  41. #40
    Capacitors can develop vibrations. This is usually the high-voltage ones.
    Unless you know what you are doing, I don't recommend poking around in the innards around the ~450V caps - it'l kill you (really).
    If you are ok with that (and drain the caps), you might check that they are fastened down - often with hot-glue.
    Just a thought.
    Hans

  42. #41

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    Quote Originally Posted by rio
    Hi guys, I am hoping someone might be able to set me in the right direction in terms of finding out how to fix this. I got a Monoprice 15 watt tube amp - been extremely happy with it and was going to do a video review. When starting to record I noticed this odd sound that only happened on some notes. Trying to figure out what it was I also found that if I tip the amp forward, speaker facing the ground, that it goes away. I've tried holding things that might be vibrating and looking for loose parts but am not finding anything.

    If possible I'd like to not return the amp and fix this if it is something simple. I haven't had a tube amp for probably close to 20 years so I don't know if this is a sound someone will recognize that might be unique to a tube amp. The only work I've done is changing two of the preamp tubes to 5751 tubes.

    Is this a speaker issue? Something tube related?

    I also ended up having the sound mysteriously disappear after messing with the amp for an hour a couple of nights ago. It just came back though so I came here. Thanks so much for any help.
    Speakers can decay or otherwise get torn and create noises, as well as the voice coil leads.

    Filaments in tubes can also actually rattle.

    Probably a process of elimination if you haven't solved it yet.