These are the passive hum-cancelling Jazz Bass pickups, using two of the "long" versions. These replaced the MECs in my Warwick Thumb BO 5 String. Right now, the Bartolinis are running through the stock MEC pre, most often with the pre bypassed. I still think the MEC pre is darkening the sound somewhat, so I'll post again later when I replace the pre with either an Aguilar pre or just some good quality passive pots. For the tests, before and after, the path was the Warwick strung with DR Long Necks and a fresh Duracell 9v (MEC pre bypassed anyway save for a quick test- see the last "Con" section below) into a George L cable into a SansAmp Bass DI into a Canare/Switchcraft XLR cable into an ART Tube MP into another C/S XLR cable into a QSC PLX 1602 into a Canare/Neutrik speaker cable into an Avatar SB112. I'm still awaiting my SansAmp RBI and a friend is borrowing my Great River pre, so the Bass DI and Tube MP had to do for now. At no point were any controls on any device changed during my comparisons. Ok, first thoughts... About the same output, but seemingly less magnetic strength. I can get the pickups closer to the strings without getting weird overtones and tuning problems on the higher notes. There's also much less finger noise with the Bartolinis- the MEC pickups had a low frequency THUD behind each note. That's absent with the Bartolinis, but there is a more defined attack- not "attack" as in high frequency transient sound, but a real "plucked" sound. A much improved sense of depth and air. This can be nebulous to describe in type, but they sound much more real. Very present and articulate, much more pleasing to listen to. Each pickup sounds bettter individually and they sound better together. The neck pickup has more lower and upper mids than the MEC neck pickup, which had gobs of lows and a semi-scooped midrange. The Bartolini isn't midrangey, but it's full. The Bartolini bridge pickup lacks both the nasal midrange of the MEC and also the brittle highs. It still has the mids, but they are much more musical, less compressed, and the highs are still "rounded" for lack of a better word. They are present without being piercing. It's not a bright sounding pickup, sans EQ, but neither is it dark. I think it will respond excellently to EQ changes and be very usable. General note: the bass doesn't sound active anymore, but it has a loud output and is very very quiet (see below). Best of both worlds, perhaps? Pretty darn close, at least. I'll know more when I change out the wiring. PHENOMENAL increase in harmonic response. Not only in terms of the sound of a fretted note, but I can now get harmonics on every fret except the 1st, 11th, 13th, and 23rd. The MECs were a real struggle to get 4th fret harmonics on, let alone all the others, and the MEC favored the 12th fret harmonics over even the 5th and 7th. This bass is now a harmonic machine. Only con: a very very very slight increase in noise when the blend is set in the middle and the treble is boosted on the EQ. This may be something that will "go away" when I rewire the bass. Either way, it's very slight and wouldn't be noticed in a live performance or even solo'd in a recording.