[BELGIUM] Legality of custom audio electronics (mostly guitar amps and effects) with/without CE marking

Hello, r/legaladvice. I've been wondering and researching this issue for a while but I can't seem to find any definite information for my specific case.

I am an electronics hobbyist and have been building stuff for myself and close friends for several years now, but I want to start selling devices as well. The things I build are mostly tube guitar amps (internal voltages up to 600VDC) and effects pedals (internal voltages normally up to 24VDC, but some plans for higher voltage tube based pedals are there). The amps are built on turretboards and the pedals are built on PCBs.

Now the problem I have is that getting an accredited lab to check over the equipment I build, would cost many times more than the actual amps. Since every amp is a custom build for each customer, I don't think I can get legitimate CE markings to go on them.

Would it be possible/legal to sell these amps as prototypes even if they share components/circuit topologies? What if something goes wrong? Worst case scenario: someone buys an amp, plugs it into an un-grounded electrical socket and gets an electrical shock. Am I liable in this case or would there need to be proof that my build was the actual cause of the issue?