I finally had some free time to spend on this and, more important, have the needed components! So:
I have a Gunbird 2 PCB in a PS5 Psikyo pcb in which the high pitch noise is noticeable enough that in silent moments during gameplay noise is clearly audible while seated in front of the cab or even further back. This is a small footage I recorded where noise is clearly noticeable:
You can hear the high pitch noise even when the phone is not placed near to the cab speakers.
Then, first action to perform is make a full recap in order to see if I get some improvements. Another footage after recapping the pcb (recorded at the same volume level as before, I don't touch the volume pot):
Small to none progress... (Maybe a bit less hum noise from the PSU, but very subtle)
So, as previously discussed in this thread, we all now that PS5 psikyo pcbs have two variants regarding sound section. One using the Yamaha DAC: YAC516 and mainly seen in Striker 1945 III / 1999 pcbs, and one using another Yamaha DAC: YAC513. In this case, my Gunbird 2 pcb is the latter:
I also have a Strikers 1945 III pcb and in this case, it is the PS5 pcb first variant using YAC516 and it have a clear audio with no noise, so I decided to compare both pcbs and compile the differences in components apart of the DAC used in each one. Goal is make the sound section of Gunbird 2 work exactly the same as Strikers 1945 III and check if noise will go. Differences:
- Remove: R32, R34, C12, C19, C21, C22, U45 (YAC513)
- Populate: R21, R23, R28, R31, R33, C4, C5, C6, C7, C8, C9, C10, CP36, CP41, U39 (YAC516-M) where:
- C4, C5, C9: 10u, 16V
- C6, C10: 1u, 50V
- C7, C8, CP36, CP41: 0.1u smd
- R21: 10 Ohm smd
- R23, R28: 10K Ohm smd
- R31, R33: 0 Ohm smd (jumper)
- U39: YAC516-M
And now it looks exactly the same as Strikers 1945 III:
Well, take a look at the final footage after sound section replacement (also without moving the pot and same volume level), it speaks for itself

:
Now the difference is massive and only some little hum that is present in almost every jamma PCB is present so the high pitch is gone.
Definitely, the YAC513 variant is a low-cost (?) version providing a poor audio quality.
Sad thing is the PS3 pcb (for example used in Striker 1945 II) has no chance to do this, and the YAC513 option is the only one feasible due to the pcb desing.