Resonance of case affected audio

[Jimbo]

Those one-piece top and sides looks pretty slick, Mark! Don't think I've got the kit in my garage to do that though!

James, nearly 20 years ago I experimented with weights and also Dynamat (soft bitumen sheets with aluminum backing and adhesive). The weights worked to good effect and the Dynamat seemed pretty similar in the results, though far better for aesthetics and practicality. However, 20 years on, and the bitumen has hardened up mostly. So I imagine it is doing far less for my hifi than it once did... and that is with a solid state preamp which can't be putting out a whole lot of heat.

I did find that the greatest result was on my CD transport, and the least result was on my power amp. The SS preamp did benefit, though I'm sure that anything with valves would notice the change far more. Whether with dampening sheets or weights on tops, I found it important not to over dampen. Too much Dynamat or too much weight and the energy started to get sucked out. Too little and you got no appreciable result. And with the weight, it seemed better to use material that doesn't ring in and of itself, so no steel or glass, but sand or lead shot both worked well.

(... this keyboard seems to be slowly going south. I can't seem to type a single sentence without letters getting dropped and having to go back and correct!)

The chap who tried weights was using lead but as you say aesthetics may be compromised

[brucew268]

The amount of vibration my cases were picking up was unbelievable, they felt like a massive tuning fork. So what does that imply for the rest of the components and obviously the valves in the case?

I did a bit of research into valve amp Isolation some time back and found various forms from removing the casework to placing massive weighted metal objects on top of the casing to reduce vibration, bit strange However not sure if any of these stopped the valves themselves vibrating?

The only total solution as far as i can think would be to have the amps in another room, but this would be a bit impractical. Not sure if vibration platforms /racks would stop this either as the casework as you have found can ring like a bell!

Difficult one this.

I did take the case off and listened and there was a definite improvement especially in overall clarity but this may be peculiar to valve amps in that there can be some electrical magnetic interaction between the valves and the casework, so I believe? Does anyone ( Anthony TD) know if this can be the case?

If I recall theories on sources of vibration include:
Vibration from sound waves of speakers
Vibration transmitted through the floor from walking, trucks going by, etc.
Vibration transmitted through the suspended wood floors, just due to the resonant nature of such.
Vibration from mechanical movement of transports/turntables, which could affect the transport itself or anything else on the same equipment stand.
Vibration from electrical currents and fields operating within a specific piece of kit, exacerbated by physical and magnetic interaction with casework.
Vibration produced by the filaments of valves themselves.

It seems that solid state could be affected by any of the above, though in some cases imperceptibly, and valves being microphonic would likely to be more highly affected by all of the above.

[brucew268]

I only made them because I thought it would be cool to be able to see the internal LED's and circuit board.

In making my mains distribution hydra, I thought it would be cool to see inside the box, and also thought it an extra measure of safety to be able to see in the odd event that a live wire came loose before opening the lid. Some have noted that distribution boxes tend to sound better if not made with ferrous metal or even aluminum. The downside would be that they may be more susceptible to EM and RF fields. I have noticed significant results by addressing this just as strenuously as physical vibration. But then I have my telly and Sky box close by (at the top of the equipment stand).

[StanleyB]

One of the problems that has affected metal cases in the last twenty odd years is that they are being made thinner in order to save on shipping weight and material. The lighter cases vibrate a lot more, which affects CD and DVD players a lot more for some reason. Next comes the level of coating. A lot of metal cases tend to have just a coat of paint over them these days, and maybe a primer underneath. But it is again a cost cutting measure. I noticed this problem when I was in the repair business, but it is not the kind of thing you go shouting about. The exist door and loss of a job is never far away if you start saying things like that. Who wants to employ a nut case after all?
But I myself decided to try to find a solution when I started to look for a case maker for my first products. I settled on a far thicker metal sheet, which is 2mm instead of the almost universal 1.2mm. The 2mm is far more rigid. It is also made of a denser steel, instead of the softer steel alloy now coming out of China. I also electro plate the case before priming and praying it. But it is not the kind of stuff one mentions in the product description.