Amplifiers without the UL mark or CE mark

If I bought such a product from a store (or online), could I get any problem related to safety?
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...to say nothing of the potential problem with whatever
insurance company underwrites your fire insurance when they
find out you had an uncertified electrical appliance in the
house after a fire.

Dr. Gregory Greenman

This will not answer your question. UL, CE, and CSA are all a sign that a particular level of safety has been done. However, UL is very expensive for a small manufacturer. Building a unit that would meet UL specifications is not difficult, but having it tested and then having to pay regular "maintenance" fees is quite costly. Our PARC does not have UL listing, though it is built so that if it were tested I'm quite sure it would pass. It was just not cost justified to have it UL listed. It does have the CE mark, because as a small manufacturer you can self certify that you meet the requirements.

Because a product is not UL listed does not mean that it is not safe or would not comply to the same or even higher standards as a UL listed product. However, you have no assurance from an independent agency that it does meet at least some minimal set of requirements.

I will tell you a funny story about a large company that had a complex electrical device (it had nothing to do with audio). They were getting it UL listed. They had been told that the UL listing inpsectors need to find something wrong so that they can show their value in the process. So the company floated a ground purposely knowing full well it would be found, they would rectify the problem, and get the product listed. The inspector went through the process and found about a dozen things they he felt needed to be changed. Guess what wasn't found?

The CE has been a pain in many manufacturers' asses with their "no lead" solder and their plastic covered binding posts. In part their concern is safety and in part the environment. Remember, your parents and grandparents survived without the advice of UL or CE. You may be paying a sonic price for the "safety" that both give you.

UL is not governmental and get paid to apply its standards. CE is governmental and has governmental authority if companies want to do business in the EU.