@Mitsurugi-w
I also noticed some people on AO talking about crackling in the sound. After switching to the J17 I noticed something similar, but it was really faint and after playing for a bit it went away. Might be worth investigating if all of the people getting the crackling are using the J17, and all the people who can't get the CN5 jumper to work are on revision 3 boards.
Also, a big thank you to you and Dark for this awesome project!
I know at least one was a Rev 6 pcb. I still do not see a correlation between all of them but my hypothesis is that it is more to do with the setups used. Here is a list of some potential culprits:
1. Insufficient/missing ground.
2. Insufficient/too much 5v. Some mentioned no sound problems when using original roms. This kit will draw a bit more power so it may be worth measuring 5v at some point on the main kit pcb to make sure it is not starving.
3. Volume too high? Some cabinets have volume control and the A-boards have volume control. Is it possible the pcb volume is turned up too high? Maybe if the cab/supergun volume pot was turned up higher but the pcb volume was turned down lower it would dissipate the static.
A few have mentioned trying it on different setups and still getting the same results so I'm not real sure. I'm pretty sure it's not the kit itself but anything is possible. Kits from the same batch are working flawlessly so it would be a long shot. I would recommend trying a different B-board but many bought a single B-board for use with this kit. I could try some different things but I need to have my hands on one of the crackling kits myself. I have not personally come across any problems yet.
Maybe someone can troubleshoot the three ideas up there and let me know.
1. Find a place that has ground on the main kit pcb and run a separate ground wire to see if feeding it better ground helps the sound.
2. Check the 5v and try raising and lowering it a bit around 5.08 - 5.12v
3. Experiment with adjusting volume.