Weights on a preamp

In some cases it can work depending on the gear involved, the type of stand used, or other factors. I used to place a VPI brick on top of my Spendor 1/2e speakers and they helped stabilize the speaker/stand interface. However, I find that I don't need to use any weight on my Audio Kinesis Stormbringer speakers.

I also used the bricks on my amp to some good effect, but it was a marginal difference compared with the speakers. Only way to know for sure is to try it out. Of course your selection of weight materials will also have an effect. Lead sacks seem to work well. Fine sand placed in plastic zip lock backs also are a good starting point and cheap to use for a test. Good luck and let us know what you find out.

Try sand bags, or as Elizabeth mentioned rubber. You can go to McMaster-Carr and order a sheet of 40 durometer rubber. Make a nice sized square or rectangle, then place it on the component. On top of the rubber you can place some additional weight like a piece or metal, stone, or wood. Take a look at the HRS isolation devices as they use similar techniques and charge quite a bit for their products. I used their damping plates for a while and liked them a lot, but they are DIYable.

I would attribute the sound you were hearing to be the result of metal to metal contact. Having an interface between the metal might help (you might get the same result with just a piece of granite on top of the component).

Consider that to earthquake proof buildings the foundations are built on rollers. Symposium roller blocks, aurios, or FIM isolators perform a similar function for audio gear.