Now that I see your schematic, I suspect that you might want to experiment with different caps for C7, C8, and C9.
Since Jantzen are metalized poly, you might find a considerable improvement by going to MIT film & foil caps: RTX series (styrene/tin) for values 3uF and below, or MIT PPFXS (polypropylene/tin) for values 3 < 12 uF. I use these for high end DIY, and I suspect that your M1's are worth it too.
Since Jantzen are metalized poly, you might find a considerable improvement by going to MIT film & foil caps: RTX series (styrene/tin) for values 3uF and below, or MIT PPFXS (polypropylene/tin) for values 3 < 12 uF. I use these for high end DIY, and I suspect that your M1's are worth it too.