Resonant frequency causing rattle with 5w Supro

Gdecernay

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Hi all, I just got a 5w Supro Delta King, and I love it overall. I’ve read some of the previous posts on the subject of rattle and microphonic tubes. I don’t think this is a bad tube. First off, they’re enclosed, and while I could get to them by taking things apart, I’m hesitant to do that on an amp I could still return. Also, based on past experience of having a microphonic tube (on a Blackstar), that doesn’t strike me as the issue. The rattle only happens when I play an A. It is most pronounced on an A3 on the guitar, so fifth string 12th fret, fourth string 7th fret, etc. It does happen on the A2 but not as pronounced. Literally doesn’t happen on any other note. I’ve checked on four guitars to eliminate anything like fret buzz, etc, and have played on another tube amp…a 10w Blackstar. No issues otherwise—guitars don’t have fret buzz and the other amp doesnt rattle at all. Is this something that could pass as the speaker breaks in, or is this worth returning the amp over?

I’ve checked all the screws on the casing and everything seems tight. Again, don’t want to go taking everything apart this early into having it if I could just exchange it or return it. Was just curious if anyone has experienced this passing or not. It’s loud enough to be distracting and problematic when playing. If it’s something that passes, I’d be inclined to keep the amp.

Thanks
 

schmee

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Can you plug into another speaker cab to test? Voice coil buzz can do that.
Are there any ceramic tube sockets in the amp? They have been known to buzz in the metal holding ring. Crimp the ring tight a bit, or squeeze a little silicone seal into the ring.
 

Gdecernay

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The amp has a line out that I could plug into another amp to check, but I don’t have another cab I could dedicate to this amp, and would like to use it as the little combo it is. I’m not sure of how its sockets are set up. I’m hesitant to take it apart to check having had it for less than 24 hours. I did find a pic of the internals, but don’t know enough about amp specs to know if it tells us anything.
 

Gdecernay

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97A396F5-D599-440F-8986-AA13FDAD7037.jpeg
 

PhredE

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I had a similar problem occur in a cabinet I built several years ago. Ironically, I was getting a similar vibration on open A (110hz).

I also cinched down all screws (or, so I thought..). It turns out, I o overlooked the mounting screws for the speaker itself. Once I gave them a little more torque the buzz went away.

Bottom line is: check everything and try to be as systematic as possible.

Some of the experts may chime in about tube rattle/ microphonics. In the past, I had good luck doing the touching of the eraser end of a pencil against each tube (while powered up--so be careful of course if you do the same).

Good luck.
 

Gdecernay

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I had a similar problem occur in a cabinet I built several years ago. Ironically, I was getting a similar vibration on open A (110hz).

I also cinched down all screws (or, so I thought..). It turns out, I o overlooked the mounting screws for the speaker itself. Once I gave them a little more torque the buzz went away.

Bottom line is: check everything and try to be as systematic as possible.

Some of the experts may chime in about tube rattle/ microphonics. In the past, I had good luck doing the touching of the eraser end of a pencil against each tube (while powered up--so be careful of course if you do the same).

Good luck.
Awesome, I’ll double check to see if I can get to the speaker mounting screws and give them a turn.
 

PhredE

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Also, it isn't that common, but sometimes objects in the same room can produce a noticable sympathetic vibration. Try to isolate the buzz back to the component as much as possible (speaker, amp, or something else..).
 

Gdecernay

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All right, took the back panel off and tightened all the screws I could see. Several of the speaker-mounting screws handled quite a few more turns in them to tighten. I didn’t see anything that could be crimped to hold the tubes any tighter, and the eraser technique didn’t suggest any problems with the tubes. The buzz was still there at the same intensity on the A’s when put all back together. Thinking I might go exchange it as it’s quite distracting and loud enough to stand out even when drive is used.
 

Gdecernay

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Ok very interesting. I took the amp to another room and the issue is gone. I’ve never had a resonant frequency come up in that way. Going to put the amp in a different part of the original room to see if that helps.


Put the amp in a different spot in the original room, and the rattle is gone. That’s definitely something I’ve never encountered, personally. Makes sense though and is good to know. Thanks for the heads up on that, as I wouldn’t have though of that as an issue.
 
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