Quote:
Originally Posted by guitaniac
I've had mixed results with the two preamps which Dieter mentions. The Baggs PADI (10 Mohm input impedance) gave me way too much bass when EQed flat. The Fishman Platinum (10 Mohm input impedance) was more balanced.
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That should tell you a lot, Gary. The problem with this impedance question is that a lot of people compare apples and oranges and make a conclusion about pears from it :-) In this case, you have two preamps with the same impedance with different results, which should be a clue that it's not the impedance that's affecting the results. If you try a preamp with variable impedance (like the Grace Felix), you can do an apples-to-apples comparison and hear the effect of impedance without the unknowns of all the other circuitry that's involved. (Hint: K&Ks sound indistinguishable to me with 1M or 10M or even 20M)
The impedance behavior is actually fairly simple, tho there are some complexities if you really dig in - the "match" acts like a passive tone control. Feeding a passive source into an input with lower impedance tends to reduce the bass (it may also have more complex behavior, especially when you have things like a guitar cable that has a capacitance involved into the equation). Above a certain impedance, you won't get bass loss (but you won't get boost) A passive circuit cannot "boost" anything, so there is never the big bass boost that people talk about, just due to the impedance. There could be a cut to other frequencies, or a relative lack of cutting the bass, and then you turn up everything, which *sounds* like a bass boost (which is what I think all the K&K stuff is about - the pickup is naturally bassy, so using a lower impedance can tame some of the bass by cutting it - but you have to get below about 500K to really hear it).
The area where things get more complex is that with high impedances, you run the risk of other interactions. Plug a passive pickup into a high impedance input with either a crappy cable or a very long one, and all the capacitance and other aspects of the cable come into play. That's why, for the best sound, especially over long distances, you want to use a low impedance cable and input (like running a DI to the PA)
Back to the original question, Larry gave a good answer, IMHO. I've played K&Ks and other pickups thru a lot of preamps. I've not come across one that has some special pro/con with respect to the K&K specifically. Preamps are of varying quality, have different features, and may have a different tone. Depending on your taste, you may like the tone of one vs another. Most preamps these days aim for "flat" and with the state of electronics these days, there's little reason for even the lowest end preamp to not achieve that to some degree. I don't know of any preamps that deliberately add a bass boost to the "flat" sound. There are some preamps that set out to "color" the sound, (the Session DI, and AER Colourizer come to mind), but these generally promote the fact that they aren't flat as a feature.
The highly regarded red-eye is a very nice, clean, quiet and flat preamp, that raises the gain with almost no other features, and if that's what you need, it's great. (Personally, I tend to use very little EQ, so the Red-eye, with its simple treble control is more than sufficient). Other preamps give you more features that you may like. Many are central "hubs" that route your signal to both a PA and a stage amp, while providing an effects loop, mute switch, boosts, and so on. Some have great EQ, if you need that. The SPS-1 with 3 fully parametric bands per channel is hard to beat there. I like dual-channel preamps that can power and blend in a mic, because that's a feature I like to use.
One preamp that I like for SBTs in general is the Grace Felix - my favorite feature is the high pass filter, which you can turn up just enough to get rid of the annoying "thump" that comes from all SBT-type pickups, even active ones (it doesn't come from the impedance, it seems, to me, at least, to come from being in direct contact with the body of the guitar). The high pass filter can really clean up the sound, and tho Felix also has very nice EQ, the high pass filter is often the only one I actually need.
So my advice on "what preamp?" is to think about what features you need - what your setup is like, or how you like it to be. You can get anything from a preamp that clips on your belt or plugs into the end-pin jack of your guitar to ones that require a full rack, and anywhere in between. Then there are features: do you need EQ? a 2nd channel? a mute switch? a tuner output? etc. Between those kinds of choices, your budget, and checking a few out to see if you like the sound, your choices should be narrowed down to very few - and virtually any of them will be fine with the K&K.