Just replaced all the electrolytics in my '66 BFPR and although it sounds great, there's what sounds like a 60 cycle hum that is louder than I remember hearing with the original caps. It's not overbearing and I don't notice it when I'm playing, but I feel like it could be quieter at idle. The hum is present even with nothing plugged in and the volume at zero. The only thing that effects the hum is the tremolo intensity which has me thinking it has something to do with the bias filter cap. The original cap was a 50uf 50v and I replaced it with the same values- positive to ground. Any ideas?