I want to know the eq of my pickups?

[cenizasblancas]

Hi, i want to know how to mesure the eq of my pickups because i want to add a graphic eq to my guitar.

Thanks

Juan

[David King]

Hi Juan,

I'm not sure i understand the exact meaning of your question but if you want to measure frequency response of the coils you'll need some sort of signal generator (freeware for PC and mac OS) and a way to excite the coils (using a small voice coil from a speaker might be good enough). You then need a way to measure amplitude of the generated ac signal coming from the pickup coil. (Again shareware or an iOS app.) It's going to give you a rough idea of where the response dips and peaks but I'd think you would have better luck building a low impedance (flat response) pickup of the types discussed here frequently. That will save you from adding the noisy graphic EQ to your signal chain.

[cenizasblancas]

yeah, that's what I want, sorry for the confusing question. my idea is to build a pickup which can be as versatile as possible, in this case a blade pickup for my strat. I was thinking maybe to ad a ultra low noise op amp for shaping some frecuency.
Can you give me some help on how to build this device for testing the pickups? the voice coil, for example.

Juan

[David Schwab]

If you want the most versatile, and you are using EQ, wind a medium impedance pickup. Something like 1 or 2k. This will place the resonant peak higher than normal, and give you a wide flat response without a characteristic sound of its own. It will be more like an acoustic guitar tone. The output will be lower, but since you are using EQ you can use a gain stage after the pickup.

This is what Alembic does, and they use a variable low pass filter with adjustable Q. This allows you to get tones similar to high impedance pickup, by introducing a resonant peak and high end roll off. That might be better than a graphic EQ if you want to simulate common guitar tones.

[Mike Sulzer]

. This allows you to get tones similar to high impedance pickup, by introducing a resonant peak and high end roll off.

If that is what you want to do, you can do it passively by switching in different values of capacitors across the pickups. Then you just need pre-amplification , either in the guitar or off-guitar in front of the rest of the chain.

[cenizasblancas]

here i have found this page about the same thing:

https://sites.google.com/site/distor.../pickup-shaper

I have another alembic circuit but you post in another thread but it has only a gain control, Could you post the circuit you are referring to if it´s better than this one?

Juan

[David King]

Hi Juan,
Read this article: BuildYourGuitar.com :: The Secrets of Electric Guitar Pickups

[cenizasblancas]

Thanks David!!!

Juan

[David Schwab]

If that is what you want to do, you can do it passively by switching in different values of capacitors across the pickups. Then you just need pre-amplification , either in the guitar or off-guitar in front of the rest of the chain.

Right, so if you are using a preamp, why not use a LP filter as part of that circuit? It's more variable.

The LP Recording guitar had a decade switch to switch caps across the pickups.

[David King]

David, LP as in Les Paul or Low Pass or both?

[cenizasblancas]

here is some information about this guitar, (with commentary by David Schwab)

Main - Woody's Gibson Les Paul Recording guitar page Kalamazoo, Michigan MI

Does anyone have this guitar schematic?

Juan

[Mike Sulzer]

Right, so if you are using a preamp, why not use a LP filter as part of that circuit? It's more variable.

The LP Recording guitar had a decade switch to switch caps across the pickups.

Well, there are various reasons why different people might want to approach this problem differently. As for "more variable", the active filter provides a continuous range of resonances, yes, but for me, six pretty much covers the useful range of sounds, and you can do that with a switch. With medium impedance pickups, you can get any resonance you need.

Switched capacitors allow a fully passive guitar. Not everyone feels comfortable putting active electronics in an electric guitar. I have done quite a bit of it, but now I kind of like a passive instrument where possible. That is just a matter of preference for me, but some people just do not like to do active electronics.

If you want to have separate control over the resonances of two or three pickups so you can switch easily between very different sounds, the active electronics gets more complicated since you need multiple filters. Nothing you cannot do, but in this case it really seems to me that "guitar here, and active electronics there, at the end of a cable" is more satisfying and flexible.

Also, if you want to have a really quiet system (no significant hiss at all from the active electronics), you cannot do this with a combination preamp-filter with one op amp. There are no really quiet op amps. The ones with low noise voltage have significant noise current. Getting all of this done right and into the guitar with a long life battery is still a really big challenge. On the other hand, a super quiet preamp outside the guitar is relatively easy. (I am referring to the use of medium impedance pickups.)

[cenizasblancas]

Well, there are various reasons why different people might want to approach this problem differently. As for "more variable", the active filter provides a continuous range of resonances, yes, but for me, six pretty much covers the useful range of sounds, and you can do that with a switch. With medium impedance pickups, you can get any resonance you need.

Switched capacitors allow a fully passive guitar. Not everyone feels comfortable putting active electronics in an electric guitar. I have done quite a bit of it, but now I kind of like a passive instrument where possible. That is just a matter of preference for me, but some people just do not like to do active electronics.

If you want to have separate control over the resonances of two or three pickups so you can switch easily between very different sounds, the active electronics gets more complicated since you need multiple filters. Nothing you cannot do, but in this case it really seems to me that "guitar here, and active electronics there, at the end of a cable" is more satisfying and flexible.

Also, if you want to have a really quiet system (no significant hiss at all from the active electronics), you cannot do this with a combination preamp-filter with one op amp. There are no really quiet op amps. The ones with low noise voltage have significant noise current. Getting all of this done right and into the guitar with a long life battery is still a really big challenge. On the other hand, a super quiet preamp outside the guitar is relatively easy. (I am referring to the use of medium impedance pickups.)

Thanks for the explanation, my interest in using pre amp filter is because I wanted more control and versatility in my pickups, but i don`t want the hiss,
there are some other ways to equalize passively pickups like putting a capacior and choke in series, is this could be useful?
I´m also interested in using low/medium impedance pickups.

Juan

[Kindly Killer]

I tinkered with this unscientifically. I made a driver coil to excite the pickup. I can't remember the gauge or turns, but I remember it was a small number of turns (in the hundreds) of larger wire. I may have bought the magnet wire at radio shack and just used the whole spool - can't remember...

I wound it on a plastic strat type bobbin and hard wired it to a 1/4" jack so it's easy to hook up to my audio interface.

I used TrueRTA for the sweep, and measured the pickups a la carte - not in the guitar. I have a pretty low-end pro grade/high end hobby grade sound card and it has plenty of gain going in and out to do tests without an additional amplifier.

To me now that I've gotten better at building winders and pickups - thanks to this forum - I find it more useful to just vary one thing at a time and listen for the change. The most useful analytic tool I have is a guitar that is routed out the side to allow hot-swapping pickups, plus i can mount any type. That way I have a reliable baseline. I also like to make a quick recording where I build up layers with one pickup. One thing I've found over decades of playing is that the keeper instruments sound okay by themselves, but they really sit well in ensemble. The more you stack something with wonky frequency contours, the more you notice it.

I think a response curve might be useful if you could design a pickup reliably with math - so you could check your work against expectations - but for me all it really did was put a label on what I could already hear.

HTH

Michael