I am a sole trader doing what I want to do, I could go out cleaning windows if I wanted to. You are making unfounded allegations that are libelous, you should go very carefull.
No I am not. I did not imply you were in the tax evasion business. You declare your income like any other legitimate sole trader. Some (or all) of that declared second income comes from the manufacture of hi-fi components. That makes you a manufacturer of hi-fi products and thereby a person in the hi-fi trade. The fact that you are also an enthusiast is entirely unimportant, just as it would be to any declared income. You don't get to pay more or less tax because of your enthusiast status.
Yes, you could spend your spare time cleaning windows instead of building audio equipment, and if this were WindowWasherForum, I would suggest you change to 'trade' status. But it's not, it's a forum about audio, and you build audio components for other people. The fact you do this as an enthusiast... hurrah. It still makes you 'trade'.