Amp buzz / rattle / hiss on certain notes

[switters]

I have a Fender Hot Rod Deluxe combo that rattles every time I play an E note and a few other notes nearby. The E's are the worst. 7th fret A string or its octave on the G or D string as well. The rattle sounds like a hiss - like something loose and quickly vibrating every time I hit those particular notes - regardless of which guitar I'm using. The tubes seem to be seated firmly and it doesn't sound like a speaker issue. Any ideas? Help much appreciated. I'd love to DIY this one and avoid yet another costly visit to the amp doctor. Thanks in advance.

[da Geezer]

I'd lean towards a rattling tube (internal tube structure loose & is sympathetic to certain notes/frequencies)

Do you have extra tubes you can sub in?
If so, try swapping them out one at a time to see if the problem is solved.
If you don't have other tubes, remove/separate the chassis from the cab & see if there is any improvement., or gently tap on each tube to see if there is any noise generated.

Geezer

[Paragon]

When you get the rattle, place your fingertip or eraser on the tip of the tubes. I had a preamp tube that would rattle the same as you described. Placed finger on tube and it went away. Can also be a screw or nut rattling. Make sure everything is snug.

[rp]

I just had a post on this, same problem I think: https://tubeamparchive.com/viewtopic.php?t=13225

If it's not s simple tube swap then you must be totally methodical and you must eliminate all the mechanical possibilities first ie cab and chassis, then you can start on the tubes and components. And just to complicate things chassis noises can induce noise into the electronics I found out. I went at it half hearted and scatter-shot for a few months but only made progress once I sat down and approached it methodically. Took up most of the day.

I finally got 97% of it. I home built a very tight champ and I think proximity of the 6v6 to the speaker accounts for that last little bit. Your production amp shouldn't have that problem.

If you are lucky it is just one one thing, if you are unlucky it sure will keep you busy. I might have built my last combo.

[Firestorm]

Not sure about the Hot Rod Deluxe specifically, but on the Blues Jr. the position of the ribbon cables that connect to the preamp tube PCB can induce both hum and parasitic oscillations. When the amp is assembled, these ribbons wind up being positioned in a sort of random loop. Chopsticking them down, closer to the tube, may help. You have to be careful not to bend the cables too much or too many times or you can fatigue the internal wires enough to break them.

[Normster]

I believe the noise you're hearing is a low/fuzzy sound as the note fades? FWIW, I completely gutted and rebuilt my Blues Deluxe as an AB763 and it still has that noise. I think it may be the Legend speaker but I haven't tried another speaker yet. I'll keep you posted if I make progress. (I have another build underway so it may be awhile.)