A novice welds 1875 to practice

I have limited basic DIY skills. I only learned a little bit of electronic knowledge in school. I only know what resistors and capacitors are . I know nothing about circuits and implementation! I have been lurking in the forum for half a year and have learned a lot.

Finally, I couldn't help but make the kit , and luckily it worked in the end! Then of course I couldn't help myself! I decided to try it myself, and bought a few 1875s (cheap, suitable for cannon fodder), but it turned out to be a stupid mistake. One of the positive and negative power supplies was wrong , and one 1875 was scrapped...

Production requirements are: small size, short signal path, and single point grounding.

Used a P3 heat sink

Basically, it can be put into practice. Except for the power supply and input ground, no additional wires are added. The grounding point took the most time to design. The noise is OK! The listening experience is basically the same as what everyone said. I only have a 30VA square transformer, and the dynamics and low frequency are gone. There is very little noise, and the high and medium analysis is also good. In terms of investment, it is definitely worth it!

But there is still a problem: when turning the machine on and off, there is a loud "puff" sound. The 3875 on the forum uses the same power supply and there is no such problem. I wonder why?