I recently serviced my AB165, clean, inspect, tighten tube sockets and all new electrolytics. I was surprised to find the first stage had 250uf caps instead of the Fender spec 70uf. I figured the last tech who serviced the amp (I believe it was Tony Bruno back when he was a local repair guy) just put in whatever was lying around, so I put in the modern equivalent 80uf. Testing the amp it didn't sound right, the bass was not as tight, the amp wasn't as punchy and I definitely could hear some ghost notes around D on the scale. On the advice of Wally and Commodore 64 on this forum I went just installed a pair of 220uf caps instead -- in series so 110uf instead of 40uf. BOOM! She's back! Clear, punchy, loud and dripping with syrupy goodness! I guess Tony was doing the boutique thing back then too, making the amp better with some heavy filtering. Thanks Tony, Wally and Commodore 64. I learn more every day. One of my favorite amps, wish it was lighter and smaller -- nowadays you walk into a club with a head and cab, you get the stinkeye.