Ungrounding an Amp--Any Danger?

Nsgarch: I own vdH The First Ultimate and The First Metal Screen coaxial IC's. Metal-free TFU uses a carbon fiber screen/return, which far from being especially immune to EMI/RFI, is actually not recommended for use in situations where hum is likely to be picked up, including connections to tube amps -- a drawback in an otherwise outstandingly high fidelity design that I can personally attest to. TFMS was introduced to help in just those applications, by virtue of (as the name implies) an additional metal-mesh screen layer. vdH also makes several other models employing coaxial construction for analog use, both all-metal and metal/carbon hybrids (The Bay, The Name, D-300, The Source, The Well, D-310, The Combination, and MC Silver are all coaxial designs intended for audioband signals). WireWorld is another company that makes coaxial analog IC's, using a variation where the inner and outer conductors are both tubular. (It might be worth adding that, although coaxial cables by definition have their screens connected at both ends, WireWorld still claims these models are audibly directional due to grain orientation.)

By all means, contact the factory or authorized dealer/tech about the problem. Until then, just put up with the a little hum. No doubt this can be repaired or corrected. Just my 2 cents.

Apart from what's already been said, I have found that not grounding my amplifier yields better dynamic range.

I have to agree with Bob above. Manufacturers connect one side of a single ended interconnect to ground (except in a truly balanced system-a discussion for another day.) In a 2 wire cable with a shield, one wire and the shield will be connected (the shield being at one end for this discussion but it could just as well be connected at both ends) to ground in the unit. The other wire is considered hot. Since the audio signal is AC (alternating current) it has to be referenced to ground. If you lift the chasis ground (and this is what you're doing), it will leave any overload (short, etc.) to travel through the interconnect. You have to look at it as house wiring. On 115v, one line is hot, one is neutral(the neutral carries current but has no potential-hence the name neutral) and the other is ground (shield.)This is exactly like an interconnect. One wire is hot and the other is neutral, BUT, the white (neutral) also goes back to the grounding buss!(This is why a two wire cable w/a shield is no different than one with a wire and a shield and both work. The added wire gives a better balanced path for current.) One side of the interconnect has to be neutral at some point or it want flow current. (Current is what pushes voltage BTW-can't have one without the other) That doesn't mean the signal doesn't transverse both wires, it does, but one is always going to be referenced to ground(neutral) somewhere.
I would always leave the source of largest current draw grounded (the amp.) If something happened to the transformer(like a short) it's maximum amperage will have to be pulled through the interconnect of another component that is tied to ground since you no longer would have a separate chasis ground to carry it.
I use a Theta Dreadnaught with a 2.2 KVA transformer (2200 watts.) Theta specifically says do not float the ground. I can see why.
Is floating grounds safe, yea, for the most part and long as you don't have a power supply failure. Smaller components will draw much less current if a problem occurs.
I have never understood why people make audio out to be something so special in electrical principles. It's not. It conforms to basic electrical fundamentals like anything else. Go to a book store and read up on the subject. Interconnects are nothing but wire to transfer a small AC signal from one point to another. It works EXACTLY like household wiring which is AC but at a much lower voltage for audio. (Household AC is usually around 115v-120v @60hz. If you could find a driver to handles the current it would make for a loud 60hz note!!!!!)
Another point is when current is unbalanced in your electrical box, it balances itself by sending a differential current down the neutral to create a balance. It's always good to ground most things! Better it travel the ground than through you if a disaster strikes and you touch the appliance. BTW, just for general information, even though ground and neutral end up at the same buss, they are NOT the same. The 3rd wire ground is for your protection. Neutral is to complete the circuit.