Some reverb tank isolation ideas?

[dragonbat13]

I've built an Hoffman Princeton reverb and it works great but the reverb tank is very microphonic.

I only have it in a bag right now. Doesn't even have a cover over the springs when the unit is removed from the bag (the bottom).

What are some good ways to isolate it?

[martin manning]

What type of bag? Tuki makes a well padded bag that works great.

[ChopSauce]

Couldn't just cardboard help?

I saw carboard simply taped to a reverb tank - inside the bag - on some amp(s)

[TUBEDUDE]

A well made bag and the cardboard usually suffice. If more isolation is needed sorbothane pads under the tank inside the bag will help isolate them.

[norburybrook]

which reverb tank is it? I had trouble with the tank in my Princeton build and eventually realised the tank was faulty and about 6 months later that batch of tanks was officially acknowledged as bad. This was the MOD tank.

Just a thought.

Symptoms were it would start to self oscillate randomly and feedback , most strange!!


M

[R.G.]

Hmmmm. Speculating on this,

Vibrations get in by the box vibrating the tank through the mounting of the tank, or by air vibrations from the speaker.

Most tanks I've seen in commercial amps use rubber grommet isolators on the screw mounting holes, or stuff the whole tank into a bag, like you have. I have always thought that a better bag than the vinyl leatherette stuff that I've seen could be helpful.

If you're mounting it to the box, you could get felt in 1/4" or so thickness, and staple the felt to the box then velcro the tank to the felt, or something similar. That ought to help with structure-borne vibrations. There are some self-stick vibration damping sheets used in the thumpa-thumpa car stereo biz that might help with airborne noise as well. They're a metal layer on a high-damping vinyl layer designed to eat up vibrations. I think "DynaMat" or something similar is a brand name.

One radical and possibly heretical suggestion is to not use a tank. Bel-Tone sells a semiconductor module that emulates a reverb tank well enough for many critical ears. I did a design to adapt it to the same RCA jacks and audio levels that a reverb tank would use. It's hard to vibrate a silicon die enough to make it microphonic.