Combo amp valve rattle

TTBZ

I've noticed a rattling coming from my amp (Marshall Mini Jubilee combo) which I'm almost certain is preamp valve rattle. It happened on my old one as well, V1 went microphonic. Before I replace it I wanted to know if there's any good way of preventing it happening again? Short of re-housing it into a head shell which I've been tempted to do for a while now!

I've seen the Eurotubes damper rings but do they actually work? https://www.eurotubes.com/store/pc/eurotubes tube damper rings.htm

If so, any UK based equivalent?

IIRC V1 has one of them metal covers on it (possibly where the rattle comes from?) - I guess that won't fit with these rings on so is there any downside to removing the cover?

ICBM

If you remove the cover the amp will probably pick up unwanted noise - that’s why the cover is fitted.

This is just a problem of putting valves in a box with a speaker.

p90fool

Those damper rings don't really do much to stop internal valve components rattling around in my experience. 

RiftAmps

A 10mm grommet 'threaded' onto the shield spring works wonders

ecc83

Could actually be the spring that is rattling! BTW I have not found the cans do much if anything to screen valves but I suppose it depends on the amp layout?

You will find some high temperature damping foam on the EL84 retainers of "our" 30&15W amps for just that very purpose.

Dave.

TTBZ

@RiftAmps what size is that rubber grommet and where would I source something like that?

RiftAmps

TTBZ said:

@RiftAmps what size is that rubber grommet and where would I source something like that?

https://www.ebay.co.uk/itm/RUBBER-GROMMET-OPEN-FOR-CABLE-HOLE-6MM-10MM-CHASSIS-HOLE-X-5PCS-HG-4-GROM/262643933892?hash=item3d26cc62c4:g:tpEAAOSw~fJanVLI:rk:2:pf:0

TTBZ

Perfect, thank you!

mrkb

How hot do the 12ax7s get? Is there any chance that it could melt the rubber grommet?

RiftAmps

mrkb said:

How hot do the 12ax7s get? Is there any chance that it could melt the rubber grommet?

160 Celcius is the hottest bulb temperature for a 12AX7 type, but you won't get anywhere near that in a gtr amp. Grommets usually rated for a minimum of 200C.

mrkb

RiftAmps said:

mrkb said:

How hot do the 12ax7s get? Is there any chance that it could melt the rubber grommet?

160 Celcius is the hottest bulb temperature for a 12AX7 type, but you won't get anywhere near that in a gtr amp. Grommets usually rated for a minimum of 200C.

Thanks!

mbe

If that fails replace the valve with a Tung-Sol Re-issue. 

TTBZ

Finally got round to fitting a rubber grommet as @RiftAmps suggested and it's made bugger all difference. Anything else I could try?

@mbe - are the tung sols less prone to this sort of thing then? I think the stock Marshall ones are rebadged JJs.

I don't get any rattle when the combo is plugged into a cab instead of the internal speaker btw. So I assume it's something to do with the internal speaker making the valve casing rattle still?

57Deluxe

U2 dedicated a whole album to this issue...

timmysoft

I had rattle from my old jubilee too, I cured it by putting a gasket around where the amp chassis meets the cabinet. I just picked up some self adhesive rubber profiles off of the internet.

mbe

TTBZ said:

Finally got round to fitting a rubber grommet as @RiftAmps suggested and it's made bugger all difference. Anything else I could try?

@mbe - are the tung sols less prone to this sort of thing then? I think the stock Marshall ones are rebadged JJs.

I don't get any rattle when the combo is plugged into a cab instead of the internal speaker btw. So I assume it's something to do with the internal speaker making the valve casing rattle still?

Tung sol Reissue solved my rattly preamp valve in 2 combos where those rubber things didn't work. One replaced JJ, the other a Ruby (Chinese). Better tone and gain factor was a bonus.