Shock mounting tubes

[petemoore]

At least one diagram showed metal on metal, the spring only served to pin them together...zero shock absorbtion unless there are no hard surfaces touching.
Then there are the tube wires, by the time it's spongy enough to protect the tubes, the wires are going to have increased wiggling.
Heat tends to harden things, solidly mounted is probably better than anything loose and 'clanging' against a stop point.
The best way is to have sprung and unsprung weight, the chassis helps to increase the sprung weight, giving the tubes a 'caddilac' like ride.
I liked the mushy stuff idea linked to Mcmaster Carr...
But instead I tend to build heads and simply make extra-cushy feet from rubbery stuff that came off of old bicycle rims.
Very easily made from tube [or even some tire], I like the ride and traction it offers. Set down hard to wood surface, makes no noise, I estimate almost 100% vibration dampening.

[tedmich]

metal tube retainers are reported to make tube microphonics much worse, see some of the Kittyhawk amp/preamp discussions at HC. Tubes falling out is a relatively long wavelength phenomenon (albeit abetted by high freq vibration) so dampening higher freq. vibration requires some elastomers IMO. Some high end tube amps have two elastomer covered rails which clamp the tubes in, thus avoiding most undue thermal insulation and dampening both high freq. and the dreaded low frequency waggle/fall out.

[BackwardsBoB]

Morgan Jones recommends that you simply use some elastic from your knickers to suspend a chassis section. Best part of the book.

[Enzo]

That would be the same elastic that no longer stretches and is largely disconnected from the rest of the pants?

[Ptron]

Sorry to drag up an old thread. So I thought I might try this subchassis idea on a resurected project after finding a brass bar at the hardware store that I thought would be pretty nifty for something like this. Here's a picture (obviously without the holes drilled and grommets inserted)

Someone could convince me that it's more trouble than it's worth if they felt like it but the main reason I bring this back up is what Mr. Frondelli brought up in his original post: heat. Will those grommets just cook right away, or will I be able to get away with replacing them every few years? Steve, you said you've used reverb mounts before with good results but I don't know if they were that close to the tubes.

[R.G.]

Reducing vibration to a sensitive part consists of much more than simply spring mounting it. Springs can carry vibrations nicely - that's what is used in reverb tanks, after all. What you need is compliance - the ability to move back and forth in response to a force - and damping, the characteristic that eats up vibrations, not conserves them to bounce around. Compliance is car springs. Damping is car *shock absorbers*.

If you spring mount a subchassis, consider adding some damping materials to it to eat some of the vibration energy. O-rings are modestly OK, as they're mostly neoprene or butyl rubber, both of which are partly dissipative. Something like floating the subchassis on a couple of pads of neoprene foam cut from old mouse pads would damp vibrations better than springs.

[Chuck H]

What you need is compliance - the ability to move back and forth in response to a force - and damping, the characteristic that eats up vibrations, not conserves them to bounce around. Compliance is car springs. Damping is car *shock absorbers*.

Right. Best would be to mount the sockets individually on soft, heat resistant silicone AND use the same soft material under the nuts on the chassis side too. Isolation... Compliance and damping.

[trobbins]

You certainly have to start with an appropriate self-resonant frequency to gain any tangible benefit in isolation. You can diy check the resonant frequency yourself to chose the right mounting 'spring'. The brass bar provides the mass to help you get a suitably low resonant frequency. This link may help:
Microphonics