GuitarBizarre

The reason for active circuits is that because the signal is boosted straight out of the pickup, output is higher in general, can drive an amp harder, is less susceptible to the 'skin' effect in wiring or cabling (Which is detrimental to sound)

Theres also significant advantages in sound. A passive, high output pickup is achieved using strong magnets and lots of wire. There are two 'flaws' (IE not flaws, but preferential differences) with this approach.

1 - If you use a high strength magnet, you create a large amount of magnet pull on the strings which leads to decreased sustain, among other effects. It also means that high frequencies from the strings high order harmonics are dulled, since those frequencies have very little energy to themselves and will be 'dulled' by the strong magnet pull. Net result? Less sustain, and a more 'dulled' tone with less high frequency action.

2 - If you use a lot of wire in the pickup to make up for that, you end up with a progressively more and more bassy pickup, as the longer the run of the wire, the less treble frequencies survive the trip through that amount of resistance. You also end up increasing your own costs and increasing weight. Net result: Limited range of voicing within the pickups, and higher cost.

An active pickup solves both these problems. Because the signal is boosted internally, its possible to wind a very weak, low output pickup, and simply boost it using an internal, shielded low noise preamp. A low output pickup costs less to manufacture, naturally has low magnet pull and low resistance, and hence can have a lot of high frequencies naturally. Its also possible to use active circuitry to reduce noise in the circuit as it hits the initial preamp, meaning even less noise throughout your signal chain, in conjunction with high output. Its for this reason that David Gilmour, everybodies favourite MASSIVE PEDALBOARD toting guitarist, uses EMGs. They're low noise to begin with, and the high, stable output means he can drive more effects pedals at once without adding too much hiss and buzz to the stupid crazy long circuit his board creates.

The DISADVANTAGES of an active approach are as follows (As a note Dave, actives don't so much have an 'active' sound any more than passive have a 'passive' sound, at least, not in terms of the technology itself. EMGs are just a little weird and honestly, not very well designed IMO. Don't take them as representative of the technology.)

1 - Limited headroom. Because you have a whole circuit being powered by one 9v battery, theres only so far you can go up or down in volume. This leads to natural compression within the pickup, a reduction in dynamics, and a generally less 'alive' and 'responsive' sound. If you guage how much output you can get out of a pickup, an active design will reach a point where hitting it harder results in no more volume. A passive design shouldn't do that.

This also explains the 2 9v batteries in that bass. They're probably not powering 2 circuits. They're probably wired in series so that the active circuit has a lot more headroom and isn't susceptible to this hard limit (Within reasonable limits. Its possible to overload any circuit, but an 18v active circuit, youll have to be hitting the strings hard enough to risk snapping most of them, to overload an 18v circuit.

In fact, 18V mods are very popular with EMG pickups to alleviate the hard compression. Many artists use them. Seymour duncan take the opposite approach. They actually design their blackout pickup range to work pretty much like a 'new and improved, 18v modded and slightly revoiced' EMG set, but using a circuit designed to work optimally at 9v. They claim an 18v mod improves the sound only negligibly at best with their design.

2 - Because the circuit needs power to operate, if you leave your guitar cable plugged in while you aren't playing, you will eventually drain the battery well before its time, as the act of plugging in the cable turns the circuit on.



Hope that clears things up guys. You can thank me in any way you wish, though do bear in mind monetary gain would be preferable to propositions of sex or marriage. :P

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