Reverb Tank Shielding

[ChewyNasalPrize]

Just when I was worried I wouldn't have some new problem to fix... :dbtu:

I recently put a new set of WGS speakers in my Lab Series L5 and the magnets are so strong, they are distorting my reverb!

If I have the reverb up anywhere over 2, I get a harsh, clinky, metallic echo/delay effect then it goes to normal reverb sound. I assume this is the spring vibrating temporarily against the tank because the magnet has pulled it out of center and so close that it is vibrating against it at higher settings. I pulled the tank out while still connected and it works fine. I put it back in and shifted it over and away from the speaker magnets as much as I could and it is better but still there over 2.

Is there a material that can be used to easily, cheaply and effectively shield the tank from the speaker's magnetic field? Or is there something else I could do short of building a separate reverb tank unit?

Thanks.

[Roly]

Just when I was worried I wouldn't have some new problem to fix...

Haw haw haw -  :lmao:

There's Ohm's Law, but rather more general and basic is Murphy's Law, which in the general case states "Anything that can go wrong, will go wrong".  Now Murphy's Law is very funny, with literally thousands of special cases, but we laugh at our own risk because every single one of those cases is also true.

Murphy's Law is sometimes called "the fourth law of thermodynamics" to stress its timeless nature, and has been with us since a cave man nipped outside in the middle of the night to take a quick leak and came face to face with a saber tooth tiger.

Murphy himself is a victim of his own Law in that nobody is really sure who he was, but we can be sure that he spent at least some of his time hopping up and down after whacking his thumb with a stone axe, having just touched something with a lot more voltage than he thought, or being told by his girlfriend that she was pregnant.

Really, given that the entire universe is grinding down to uniform luke warm sludge, it's a bloody wonder that things like aircraft, cars, guitar amps, or even hammers, exist at all.  I once remarked to an engineer friend that I was a pessimist, to which he responded "Anyone who starts out with a bag full of components and expects to end up with a guitar amp has to be an optimist."


Which brings me to another point;

easily, cheaply and effectively

Engineers have a saying that goes something like "You can have it cheap, you can have it quick, or you can have it good, but you can't have it all three".

The ideal stuff is called Mu-metal, and you can forget about that right away.  The best thing I can think of that won't cost more than the whole amp is a thick (3-5mm) sheet of mild steel (the common stuff, not stainless) fixed between the speaker magnets and the reverb tank.  You may find some sort of suitable cake tins at the supermarket to experiment with as magnet covers, but whatever it is you need to first check that a magnet will stick to it - if not it won't help.

I actually doubt that it's the springs getting dragged into the case because that would be happening whatever the settings, but it is possible the line drive and pickup magnets at each end are being pulled out of line.  (see http://www.ozvalveamps.org/reverblines.htm for details)

If that can't be made to work, and you really want to stick with the new speakers, then an alternative to reboxing the reverb line would be to rebox the speakers, make the combo a head.

[Enzo]

ANything is possible, but I don't buy your theory.   The steel shell of the reverb is shielding enough for anything, plus the aluminum spring subassembly is not attracted to magnets.  And I don;t think the springs are being mucked with either.   But maybe.

[ChewyNasalPrize]

Not a theory, just a speculation...

Whatever is the specific cause of the noise from the reverb, it is directly related to the proximity of the tank to the speakers.