Hi All! I was told that there was some talk about the Bass Purity preamp so I thought I'd pop my head in and give you all some details. I'll try to reply to responses, but I don't get to visit TalkBass all that often (much to my dismay). I try to keep myself shackled to my workbench whenever possible. Here's a little history of the Bass Purity for those who really have too much time on their hands. The rest of you can skip right over this... The development of the Bass Purity has taken place over the last year or so (with many years of electronic design and amp work behind it). The very first prototype is still in existence, although rather mauled by modification on top of modification. It was pretty cool, though. It was as close to a straight-wire preamp as I could get. The bass signal went through two stages of tube gain and then out to the power amp. Nothing too exciting there, but for kicks I had two sets of tubes: one 12AX7 and one 6SL7, with a toggle switch to select one, the other, or cascade both for an interesting effect. Lots of folks tried it out and really liked the sound, but said "Where's the eq?", so I added an Alembic/Kern/Fender tweed style eq section. I was not happy with that at all. I changed it to more of an audio style eq, but wasn't happy with that either. I eventually developed my own eq design, which is a 4 band eq (bass, low mid, high mid, treble) along with a unique mid emphasis control. There are also deep and bright switches which do a very good job of helping to shape the overall tone without ever mucking it up. My primary design goal was to keep the bass signal Pure, yet offer tonal flexibility. The eq system took a long time to develop and is certainly the most complex part of the design. Speaking of complexity, I spent far more time eliminating components from the signal path than I did designing them in. The first "real" unit was a 2 space box finished in Shoreline Gold with white chicken head knobs. Why? Partly because I had the paint and the knobs laying here. Don't ask me for pictures of that one! After that was built I had some custom toroidal power transformers made so I could get this all down to one rack space. I also incorporated an effects loop, a DI level control, transformer coupling for the output signals, and an EQ Bypass switch. The latter was something I had in mind from the very beginning and is an indispensable feature. I strived to make the preamp as open and natural sounding as possible; capture some of that tube magic (warmth, depth, and a certain three dimensional quality that I have never found in solid state designs); and maintain quick response and clarity without any harshness. I think I can probably walk a tight rope now, though I've never tried. I use very high grade components in every part of the signal path wherever it makes a difference. I build high end tube audio gear now and then and much of the Bass Purity design was influenced by that. I don't use any printed circuit boards (not that there's anything wrong with them if they are designed properly). Components are mounted on a 1/8" epoxy/fiberglass board and are soldered to turrets (not eyelets). Everything is point-to-point wired. Tubes are 12AX7 and 12AU7. The final result will show here if I can figure out how to post a picture. Hey, I'm a TalkBass newbie, what can I say! Some of the features of the final design I've already mentioned. I've included an impedance selector switch for the input. I find that most basses sound great using the high impedance setting (equivalent to the "passive" input on some amps), although there is a slight difference in tone with some active basses if you use the low impedance (aka "active input"). The setting to use is the one that sounds best, really. I'm also offering a version of the Bass Purity with a 6SL7 preamp tube as a custom order. It's pretty cool- a slightly softer, more rounded sound. If someone wants a full blown custom preamp I can build a 2 rack space unit that has *both* sets of preamp tubes and can be switched back and forth between the two, along with lots of other neat tricks. I'm afraid it would not be cheap, though. I was interested to read that the Alessandro preamp uses 6SL7s. I've seen that he's fond of them for his guitar amps. I tried 6SL7s, 6SN7s, and a host of others, but I liked the 6SL7 the best of all the non-12AX7 variants that I tested. The Bass Purity will be up on the Read Custom website as soon as I can get around to it. Full production starts in a couple of months, and right now I'm building each one by hand. Now, to clear up any possible misconceptions: -I did not reverse engineer from alien space craft, and I am not related to Corso. As far as you know. -I didn't invent the EQ bypass, by any means! Lots of amps have it, and many high end audio preamps have it. -Plugging a bass directly into a power amp with no preamp works, but generally not all that well. The voltage swing at the output of your bass is not enough to drive the power amp to its full potential, and the low input impedance of your power amp will probably suck some of the high end out of your bass (especially if it's a passive bass). You might get away with it using an active bass depending upon the impedance match/mismatch. -A few folks tried out some of the later prototypes; the real thing is a big step up. I hope this didn't bore anyone to tears, and I hope this isn't the longest post to ever appear in this forum! Sorry for yammering on like this. Cheers, Jack Read- Read Custom Instruments, Inc. Custom Guitars & Basses Custom Tube Amps & Tube Preamps Pay us a virtual visit: http://www.readcustom.com (978) 779-0075 Also offering Stewart Audio power amps and more. Read Custom is featured in the new book, American Basses, by Jim Roberts (Backbeat Books, http://www.backbeatbooks.com).