vibration in head

[dbw]

When I hit certain notes (D, F) something in my head vibrates.  I suppose it must be the tubes... it's a little like the noise when you shake a busted light bulb.  I don't think any of the tubes are bad, it sounds like it always did and all the tubes heat up...  Could a tube be loose or something?  I'm afraid of fiddling with it   Should I just check if all the tubes are in all the way?

 

[tfarny]

You should really see a doctor about that - sounds serious! Don't open up your head by yourself, whatever you do.  :icon_jokercolor:

 

[dbw]

Apparently I need to clarify... my AMP head.  A Carvin V3.    :doh:

 

[RLW]

Turn it one, turn the volume real low, tap the tubes (gently) with a pencil or something equally non-conductive. Replace the tube(s) that make a noise.

 

[dbw]

RLW, none of them made a noise.  I should clarify that the sound is not coming from the cab, it sounds like a mechanical rattle in the head itself.

 

[blue313]

It could always be something else loose in there, but as previously stated poking around inside an amp with a metal rod (screwdriver) can be extremely hazardous.  Does the rattle stop if you move the head off the cabinet (or put a pad or something between the head and the cabinet to dampen vibration transfer) or is it more about frequency and volume than physical contact?

I've also heard of people using various items and devices to dampen rattling tubes, but I haven't tried em personally.

 

[neilium]

I'm almost sure it's the output tubes. Get a stethescope and probe around.

I have yet to hear a tube dampener that can quiet a rattling tube.

 

[bpmorton777]

you should also try moving the amp/cab to another room just to make sure its not the location that is buzzing.

Brian

 

[dbw]

I tried various things... seems like it's a preamp tube vibrating.  I could mostly stop it with a pencil's eraser on the middle preamp tube.  I pulled that tube and reseated it and the buzz is still there but a lot quieter.  I guess I'll reseat all the tubes and see if that fixes it.

 

[-CB-]

do the tubes have shields on them?

 

[dbw]

No... it's 5 12AX7s and 4 EL34s, no covers on any of them.  This noise just developed recently and I haven't done anything to the head, though I did move the amp across the room... maybe I knocked a tube loose or something?

 

[DiMitriR33]

Turn it one, turn the volume real low, tap the tubes (gently) with a pencil or something equally non-conductive. Replace the tube(s) that make a noise.

aaaak not a pencil. graphite is a good conductor.  don't ask how i know, it was a painful experience. shocking if you will.

 

[-CB-]

covers..... add em, even just the wire kind.... full metallic covers do drain off some highs.... but... the wire ones, not nearly so bad.

(yes, the tube forms a capacitor between its charged interior, the glass "dielectric" of the envelope, and the shield (which is grounded)

 

[dbw]

I'm not worried too much about draining highs... this amp has a lot of high end... you've got to keep the presence knob under 3.  But I have no idea where to get shields or how to install them... there's not a lot of space around the tube where it enters the chassis, will they even fit?

 

[-CB-]

take off the back cover and snap a pic or two or three of the tube area, pls

 

[dbw]

:help:

 

[-CB-]

Those things come in 2in, 1-3/4 and 1-1/2 inch lengths

I"m thinking what you'll do is pop rivet ( or nut/bolt size 4-40 ) the bases to the chassis, then slip the covers over.  I'm also thinking that the 1-1/2 ones will be the ones to use.- but go ahead and measure whats sticking up above the chassis opening.

 

[spauldingrules]

There is a really easy solution to this particular problem - PLAY LOUDER!

 

[dbw]

Good point spaulding.  FYI there are 7 other apartments in this building, and I'm giving your number to all of my neighbors and telling them who told me to crank it up! 

CB, is this just general advice?  Why am I putting shields on my tubes?  Is this to improve sound, or stop the buzz, or to get rid of interference?    :icon_scratch:  Not that I don't blindly follow your advice, because I do, but I like to know the logic behind it.

Also, should I put shields on the power tubes or the preamp tubes or both?  There's plenty of clearance above both.

And won't they get really hot with those shields?

 

[-CB-]

if they're buzzing.... to stop the buzz  - no other reason