Guild pickup operation tutorial

I used to think that the two pickups in my Starfire and NS X175B were separate circuits, but were in series if I have the switch in the middle position, so that each volume and each tone control had nothing to do with the other, but I believe I have been wrong. Seems to me that one effects the other and it is NOT always a linear change.

So, could someone give me the Reader's Digest version of how to operate your Guild pickups ?

Don't think I've ever come across a guitar where, say, the bridge pickup's volume & tone pots affect the neck p'up's sound when only the neck p'up is switched on. Now when you've got both pickups going each p'up's vol & tone will affect the overall sonic blend, but normally this works in parallel rather than series. (Danelectros and some Teiscos are among the exceptions…a triple pickup model with all p'ups on puts out some serious oomph! And the controls become quite interactive too.)

With my Bluesbird I often have both pickups going, with the neck volume rolled off to the point where it adds just a touch of warmth to the overall sound. With some guitars there's a kind of notch in the dual-pickup blend where, when rolling back the neck vol, the sound will jump forward in clarity. On my Heritage "LP Custom" this notch is so pronounced it sounds like flicking a switch on & off.

Overall: just twiddle the knobs 'til you hear something you like.

-Dave-

With both pickups on all controls are active in parallel in most guitars. They kind of have to be because the two pickups signals are combined into a single mono output which connects them together. If you had a Guild wired in Stereo, then each pickup would be sent to a different speaker which was an option I've seen mostly on '70s Guilds.

I don't have a 4-knob schematic ready, but you are right that the two pickup controls are in parallel and everything affects everything else. This is actually a fairly complicated thing from a "how it really works" standpoint due to the nature of electronics and how they interact.

There is no simple answer here - dial it in until you like the way it sounds.

It always helps to understand what to expect and why it does what it does, otherwise, I feel like it's just random knob twisting and hoping.

JohnW63 said:

It always helps to understand what to expect and why it does what it does, otherwise, I feel like it's just random knob twisting and hoping.

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"Random knob twisting and hoping" pretty well describes my teens.

Just finished this for my S300. White = neck, red = bridge. As you can see they both feed (yellow) into the pickup selector switch where they are combined and send (blue) to the output jack.

GAD said:

"Random knob twisting and hoping" pretty well describes my teens.

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You weren't alone....lol.

Cool schematic diagram, GAD.

Let's walk through it.

Looking at the neck pickup section alone, the signal comes from the pickup, and goes to the volume and tone pots in parallel, but there is a .047 micro farad capacitor in between them. I assume that is to filter what frequencies get to the second potentiometer. Is this what makes it a tone control rather than just contributing to the volume ? I need some help on how that pairing works, I guess. The signal comes from the volume pot to the selector switch and out to the jack.

The bridge pickup system could be exactly the same, but with a smaller cap in the knob combination. But, what is the switch in this section ? Obviously , it's part of the guitar you are reviewing, and not a standard two pickup system, like my Starfire.

When the two pickup systems are both in play, in the switches middle spot, I could see they would each be seen as in parallel with each other ( Bridge and neck pickups in mean ). With that in mind, would the effects of the tone pots and volume pots do things to the overall sound because the signal goes through both before it hits the jack. Just like resisters in parallel ?

JohnW63 said:

Cool schematic diagram, GAD.

Let's walk through it.

Looking at the neck pickup section alone, the signal comes from the pickup, and goes to the volume and tone pots in parallel, but there is a .047 micro farad capacitor in between them. I assume that is to filter what frequencies get to the second potentiometer. Is this what makes it a tone control rather than just contributing to the volume ? I need some help on how that pairing works, I guess. The signal comes from the volume pot to the selector switch and out to the jack.

The bridge pickup system could be exactly the same, but with a smaller cap in the knob combination. But, what is the switch in this section ? Obviously , it's part of the guitar you are reviewing, and not a standard two pickup system, like my Starfire.

When the two pickup systems are both in play, in the switches middle spot, I could see they would each be seen as in parallel with each other ( Bridge and neck pickups in mean ). With that in mind, would the effects of the tone pots and volume pots do things to the overall sound because the signal goes through both before it hits the jack. Just like resisters in parallel ?

Click to expand...

The extra switch is a phase switch, and you're right; that's not there in your Starfire. Your Starfire is likely the same in every other regard, though. Here is a Guild drawing of a Starfire's wiring:



There are some things that are not obvious when you look at a drawing like these. When I talk about the signal, it's easy to imagine that it's something that traverses in a straight line, and it sort of does, but audio is an AC signal, not a DC signal, and there is a lot going on in AC signals that can be hard to understand.

In an AC signal, a capacitor acts like a filter for certain frequencies. The tone potentiometer is a variable resistor and when you turn the tone pot the filtering frequencies change because of the complex relationship between the pickup, the capacitor, and the resistors (pots). If you look at the tone pot you can see that it's only connected to the volume pot and ground. Think of it like this: when you turn the knob more frequencies get shunted to ground.

In reality, the entire thing is one big complicated LCR circuit* and those have things like resonant peaks and frequency response curves. When you alter the values for any of the components in an LCR circuit, the resonant peak and frequency response changes, and that's what's happening when you twiddle the knobs. This is a fairly complicated topic that I'll cover in detail when I publish the article, but your thoughts about how it works are correct in principle.


* LCR means Inductance Capacitance Resistance. L means inductance because in electronics the letter I was already taken for current.

I'll dig out my electronics books out of the attic and review the LRC section. That way, I'll be the smart, sits up front, kid, when you publish the article ! I knew the cap and pot made a variable filter, somehow, but can't recall how.

JohnW63 said:

I'll dig out my electronics books out of the attic and review the LRC section. That way, I'll be the smart, sits up front, kid, when you publish the article ! I knew the cap and pot made a variable filter, somehow, but can't recall how.

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I'm no EE, so don't take any exams based on what I tell you. eaceful:

A lot of what I learned was force fed to me through studying for ham radio exams. LCR circuits (RLC on Wikipedia) are in the Extra exam and they hurt my head when I first started reading the books. It's a great thing to understand but it doesn't have much practical application outside of electronics - except that a guitar pickup is *itself* an LCR circuit, and that's where things get crazy. Time for a sine-wave smiley: :ambivalence:

Note that the S300 uses something called "decoupled wiring" while a Bluesbird does not. A Bluesbird behaves like a Les Paul where if you're in the middle position and roll one of the volumes down to zero the guitar goes silent. An S300 does not do this! On an S300 you can roll one of the volumes to zero at which point the middle position is the exact same as the remaining pickup. The 1997 S100 is coupled as well.

IMO the key thing to get re. capacitors is that they like to pass DC current and block AC. When it comes to audio signals this means they function naturally as high-pass filters, because to them higher frequencies look more like DC. Yet a guitar's typical "tone" circuit cuts high end as you turn down the knob (or turn it up if you're playing a Teisco). This works because the circuit's capacitor is used to divert higher frequencies to ground, thus rolling off treble. If you wire the same cap in line with the audio signal it'll cut bass instead.

-Dave-

Neal said:

"Random knob twisting and hoping" pretty well describes my teens."

Go to your room, GAD...

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What, you want him to take up where he left off?

GAD,

I was considering getting an EE, in college, but ended up with the computer sci degree. I hope this thread re-fires up some long forgotten brain cells.

JohnW63 said:

GAD,

I was considering getting an EE, in college, but ended up with the computer sci degree. I hope this thread re-fires up some long forgotten brain cells.

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If you'd like to learn more about electronics one way to do so would be to go for a ham radio license. A large part of the exam is electronics and they start from the basics and work up to some pretty advanced stuff by the time you get to Extra. I actually enjoyed the process a great deal and there's some good material out there that helps to explain it all. Plus, having an exam to pass makes it goal oriented which worked well for me.

If you did computer science then you understand logic and though there's more math with electronics (it's all physics, after all) once you learn to read schematics it's like reading a program. Sort of.

I had both A/C, DC, and Digital electronics before moving to Comp Sci stuff, way back when. Still got the books in the attic. I guess I should go up and dust them off...or see what Google throws at me. Probably some cool animation and videos by now. No internet when I was in school. Well, some static pages and lots of Usenet groups, by the time I got out.