Vibration Control for Lightweight Tube Components

Thanks everybody for the input so far, but I have a theory...
both preamps have exhibited the same problem; both have an exposed tube design on top of the unit.
The preamp sits on a shelf enclosed in thick wood (pine) open in front and back. If the shelf is tapped on, it may create resonances surrounding the unit thru the sides and shelf above it. These resonances may be picked up by the exposed tubes which are in close proximity. (The shelf is 10" high with enough room for air to circulate).
That would explain why a 30 lb. Rogue preamp picked up noise from tapping on the shelf. Does this theory make sense to anybody?

@geoffkait
 Ok thanks, I understand the concept of "mass on spring" now. In addition to the Mapleshade Isoblock 1, following this concept, there are Bright Star IsoNodes for isolation...

http://www.audioadvisor.com/prodinfo.asp?number=BSISO&variation=L4
IYO, would these be a good size and provide the right amount of spring rate?

@almarg ,
Al, as a test I used a wad of bubble-wrap as a cushion under the IC's and was unsuccessful. 

Lowrider,

according to the blurb for the IsoNodes they are vibration control devices as opposed to real (mass on spring) isolation devices. They are not springs nor do they act like springs, in other words. They are apparently some sort of viscoelastic damper. No offense intended to IsoNodes.

"IsoNode Large Isolation Feet are 1.25" wide and .75" tall and are great for integrated amps, preamps, DVD players, CD players, and more. Use them by themselves or with other isolation accessories such as platforms. Adhesive backing is included for easy attachment and positioning on your components."

@geoffkait, I thought they might be "spongy" like the 1/2 tennis ball concept.

The ad goes on to state...
IsoNode feet are specially engineered from a unique polymer that rejects a wide range of vibration trying to enter from underneath the component. The highly compliant IsoNode acts as both a liquid and a solid for superior vibration control. Vibration and resonance that could interfere with the performance of sensitive electronic circuitry are converted instead to extremely minute amounts of heat and harmlessly released.

BTW, I googled "mass on spring" and I see that the spring has a non-negligible mass.

The preamp sits on a shelf enclosed in thick wood (pine) open in front and back. If the shelf is tapped on, it may create resonances surrounding the unit thru the sides and shelf above it. These resonances may be picked up by the exposed tubes which are in close proximity. (The shelf is 10" high with enough room for air to circulate).
That would explain why a 30 lb. Rogue preamp picked up noise from tapping on the shelf. Does this theory make sense to anybody?

I think what you are referring to is known as a "sympathetic vibration" effect.
I suppose the possibility can’t be completely ruled out, but it seems to me to be unlikely. In part because the tube types in the two preamps are different, and also in part because you’ve been using tube dampers. Also, I’ve had many different tube components on pine shelving over the years (what is referred to as 1 inch pine, which is actually about 3/4 inches thick), without a lot of space around the components, and without ever having that kind of problem. Although I don’t think the tubes in any of those components were quite as exposed as the ones in your two preamps. (I have used anti-vibration products under the feet of many of those components, btw. The particular products I’ve used are no longer made, however).

I have no particular knowledge of or thoughts about the IsoNode feet.

Best regards,
-- Al

Thanks for stating your experiences, Al. And as far as my thoughts on "sympathetic vibration" go, you're right about the different tube types and the use of tube dampers. The Rogue used 4 12AU7's which are low noise and rarely microphonic.

In both cases, with the Rogue and the Atma-Sphere, I've removed the stock feet. As mentioned earlier, the only solution to remove the noise with the Rogue was to isolate beneath the unit and mass load on top.

 I wonder if the new lightweight preamp should sit on some MDF with isolation footers between the pine and the MDF.