Hi, I'm going to swap out the stock electronics in Yamaha TRBX-505 with an Aguilar preamp. Aguilar manual says `use the pots suggested by pickups' manufacturer'. Actually I was going to keep those pots, but it seems like the stock volume and blend pots are wired directly to the stock preamp board (i.e. without cables -- they just sit on the board), so it may be easier to swap it all. TRBX-505 electronics have a A250K pot for blending (probably that's not a real blend pot, as pickups seem blended at the preamp, not at this pot) and something marked `3J2' as a volume pot (googled and still have no idea what it is). The pickups are two alnico humbuckers. From what I've read it seems like I want a 500k blending pot and a 250/500 one for volume. But I'm really not sure. Any suggestions? Thanks.