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Old 05-14-2013, 06:51 PM   #1
BusGoesCh00Ch00
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active pickup questions

Do pickup makers/winders only make actives with a preamp that drives the pickup really hard making them very hot?Are there actives with a weaker preamp that give you the advantages of actives but still have the headroom of an average p.a.f?another question is why don't they make actives with 4 wire(would a ground still be necessary)so you can split them and do other custom wiring options?Thanks
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Old 05-15-2013, 08:50 AM   #2
MrFlibble
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Quote:
Originally Posted by BusGoesCh00Ch00
Do pickup makers/winders only make actives with a preamp that drives the pickup really hard making them very hot?
Nope! In fact most active pickups have no more output than a typical higher-output passive pickup. A good example I like to use is the Seymour Duncan Hot Rails for Tele, which actually has more output than an EMG 81. Another example would be the EMG 60AX and Gibson Burstbucker #3; I've measured them in my guitars and the EMG only has around 15% more output.

Quote:
Are there actives with a weaker preamp that give you the advantages of actives but still have the headroom of an average p.a.f?
Both! You can get active pickups with a weaker preamp and actives with more headroom, or both in one. You can give older-style active pickups more headroom by powering them with 18v instead of 9v. Seymour Duncan Blackouts have a bit more headroom to them and more output than most other active pickups; Shadow Electronics' actives pickups have a little more headroom and a little less output than most other active pickups of a similar type. EMG's 'X' pickups have more output on paper but in reality they hit the amp a little bit weaker; they have vastly increased headroom over any other active pickup currently in production.

Another thing to note about both of these questions is that it only really applies to the active humbuckers you comonly see. Lots of companies make active single coil pickups that fit all sorts of sizes, such as Strat, Tele and P-90, and you can get those single coil pickups inside a humbucker mount, too. These active single coils are much lower in output and much higher in headroom than their humbucker counterparts (just as most passive single coils have much less output than most passive humbuckers).

Don't make the mistake of thinking that all active pickups are high-output humbuckers for metal. There are actually more varieties of active single coil than there are active humbucker. Don't forget, the active design was first invented for jazz and country musicians.

Quote:
another question is why don't they make actives with 4 wire(would a ground still be necessary)so you can split them and do other custom wiring options?Thanks
Because splitting them would stop them from working at all. To undestand this, you need to know how active pickups are made and why they are made that way. If you don't want to learn more, the short answer is simply that they wouldn't work but EMG do make some active humbuckers with dual modes so you can get a singlecoil sound out of them, and they make a phase switch for out-of-phase tones, too.

Long answer to follow
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Old 05-15-2013, 08:51 AM   #3
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A pickup is basically one or more coils of wire and one or more magnets.
The stronger the magent is the more power you get, but it also becomes a little less sensitive, more compressed-sounding and if the magnetic field is really powerful on the strings then it can even pull the strings out of tune or shorten sustain.
With one coil you get a very wide frequency response—that means the deepest bass and the highest treble—but you also get 50/60-cycle hum and more background noise. When one coil is by itself it doesn't really emphasise any particular frequency range more than any other, so the sound is quite flat and even. The weaker or 'cooler' a coil is, the more treble and bass frequencies you get and the more even the sound is but the sound also becomes so quiet that you may not be able to hear everything properly anyay. The stronger or 'hotter' the coil gets the less extreme bass and treble you get but everything is louder so it can seem like you're getting more.
With two coils you can cancel noise but you also lose some of the most extreme low and high frequencies. Additionally, when using two coils wired in series—normal humbucker wiring—the sound of both coils gets added together, making everything much thicker-sounding and more powerful.

Active pickups were invented because people liked the low noise of humbuckers but wanted the wider and more even response of having one coil. Humbuckers were considered too powerful and muffled by a lot of people, but as venues got bigger and volume went up, noise and feedback became a real problem with single coil pickups.

Active pickups get around this by always having two coils inside but making both coils very, very weak. They are also not evenly matched; one coil is more powerful than the other.
By having weak, uneven coils, you are able to cancel some noise but not all of it; you get some of the 'lost' high and low frequencies back but not all of them. This is why the early 'PAF' humbuckers were quite popular, as they were made very randomly and often had mismatched coils.
Active pickups simply take this a step further. The coils are wound so weakly that even when put together they are only a fraction as powerful as a passive single coil pickup. They still cancel some noise but their frequency response is even more sensitive, wider and more even than a single coil.
To get rid of the rest of the noise they are simply shielded and sealed off by themselves. This is why you can't open an active pickup up and why, when you look underneath one, you see a thick layer of epoxy.

So now you've got a pickup that has no hum or noise but also has so little output that you can't actually hear it. This is where the battery-powered preamp comes in. The preamp takes the tiny, tiny signal the pickup makes and blows it up back to an audible level. Originally, they were only pushed back up to the same level as the standard humbuckers and single coils of the time, however as time went on and people wanted more power to drive their amps harder, it was discovered that you could take an active pickup and turn the preamp up a lot further without increasing the hum. The drawback is that those early preamps weren't designed to be pushed up that high, so the dynamics also got a little bit compressed (i.e. lost "headroom"). This is where we get our most standard active designs from.

In most active pickups there is also a much weaker magnet. Again, this gives you more sensitivity and sustain but also less power.

So, all those parts in an active pickup are carefully balanced to give the least noise with the most frequency sensitivity at whatever output you set the preamp to. What about coil-splitting?

Well, when you split a normal, passive humbucker, you're still left with a moderately powerful coil that is just a tiny bit weaker than most single coil pickups. You've also still got that big bar magnet at the bottom of the pickup which provides a lot of power.
When you split an active pickup, things aren't so simple. One of the coils is much weaker than the other, so if you split to the wrong coil you won't get any sound at all, even with the preamp turned way up. You also get a lot more noise than any passive single coil would give you; without its hum-cancelling partner, one coil in an active pickup becomes extra noisy as the preamp turns up everything it hears and compresses it. In fact splitting an active pickup results in more noise and hum than audible guitar signal. Those coils and that preamp aren't designed to be used in that way.

EMG (and a small number of other companies) get around this by making 'dual-mode' active pickups. These actually have three coils inside them and two preamp modes. At any one time you are using one preamp and two coils. When you use the side-by-side coils and the more powerful preamp, you get the humbucker sound. When you use the 'stacked' coils—one of which is even weaker than usual—and the clearer, lighter preamp, you get your single coil sound. It's similar to using series/parallel wiring with a passive humbucker instead of series/split, but since the 'single coil' coils in the dual-mode pickups are put one on top of the other, they sense a smaller portion of the string, giving you a much more single-coil-like sound.

A point worth noting about both active single coil pickups and the single coil mode of dual-mode active humbuckers is that the bottom coil often does not have any magnets in it, meaning it contributes absolutely nothing to the sound other than cancelling hum. So if anybody looks at active single coils or dual-mode pickups and doesn't believe they will produce a normal single coil sound, think again. There's only one coil in them that actually produces a sound, so go figure.

Phase and series/parallel switching can't be done with active pickups because the signal path from coil to coil and to the preamp is already locked in—quite literally, when you look at all the shieldind and epoxy sealer—and can not be modified. The series/parallel switch wouldn't really be any different from the normal sound, though, and phase switching can be done by a separate circuit outside of the pickup.

You should also note that though this is how the vast majority of active pickups are made, there are some designs that differ. Some of the earliest active pickups had normal-stength magnets and less shielding/sealing and some modern ones are now being made with four or five coils, selectable electro-magnets, etc. One that is really interesting is the Shadow Electornics SH EQ5, which is an active pickup where the preamp's controls are accessible on the top of the pickup, like the adjustable screw pole pieces found in most humbuckers. These allow you to control the frequency response of the pickup as well as the input and output gain, giving you whatever compression, headroom and signal level you want. It also does work with 4-conductor wiring, like a passive pickup. I'm surprised it's not more popular. Shadow also make the 'NanoMag', which is an active single coil that really is just one coil, and can be used as an acoustic-like pickup; Epiphone use them in their 'Ultra' series of guitars.

I think it's important to point out, too, that this is why all of those companies that claim they have made a passive that sounds like an active are totally, fundamentally wrong. No passive pickup can give you the wide response of an active design, not without vastly increasing the hum you get and vastly decreasing in output.


Oh, and one last thing: the actually difference in output between an average PAF-style humbucker and a typical active humbucker like an EMG 85 or SD Blackout is less than 1dB. It's about .6-.8dB, in most cases. That's less of a difference than you can actually hear and it makes very little difference to most amps. And since active pickups are so sensitive, it is very easy to simply lower them further from the strings and reduce the output greatly. Even as little as 1mm difference in height can reduce an active pickup's output by a third.
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Last edited by MrFlibble : 05-15-2013 at 08:57 AM.
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Old 05-15-2013, 09:45 AM   #4
BusGoesCh00Ch00
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Wow thanks a lot i really needed that info because i'm thinking of going to actives but all i think of them are there for metal/hard rock.I'll check out Shadow electronics too because their pickups look to seek my needs very well.
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