I got a lot of recurring questions about guitar wiring back when I worked as a guitar tech.  I decided it’s finally time to post some answers with helpful, informative pictures!  Without further introduction, here is part four.

Guitar Controls 4: Treble Preservation Circuits

Guitars seem to lose some clarity as the volume is turned down.  What is the best way to preserve that clarity without getting too bright as you turn down the volume?  Is there any downside to adding a treble bleed mod to your guitar?  Let’s find out.

And before we get started, I’m so sorry.  10 graphs this time?  Too many, yes, but I’m not getting rid of any.

Let’s look at five different setups:

Standard wiring (pickups and tone controls wired to input lug of volume pot when viewed from behind)

“50′s Gibson” wiring (pickups wired to input lug of volume pot, tone control wired to output/middle lug)

Ibanez treble bleed (330pF capacitor wired between input and output lugs of volume control)

Seymour Duncan treble bleed (0.0022uF capacitor and 100k resistor wired in parallel between input and output lugs of volume control)

Kinman treble bleed (0.001uF capacitor and 130k resistor wired in series between input and output lugs of volume control)

In each of the images, each line on the graphs represent one notch on a volume control from 2-10; 1 would be completely silent and wouldn’t show up on the graph.  A sonically perfect volume control would create the same frequency response across its entire range, only quieter.  Therefore, if the traces on a graph all exhibit the same shape, the volume control configuration in question will sound similar through its entire range.

The first two images show the Standard and Gibson wiring schemes, neither of which requires any additional parts.

On the standard volume control (image 1), the resonant peak basically flattens out between 7-9 and then appears again as the control is turned down below 6.

The Gibson wiring (image 2) smooths out the overall taper of the volume control between 5-10 on the dial (as can be seen in the more evenly spaced traces on the graphs), without changing the output level at 2 on the dial.  The resonant peak gets smaller between 7-9, much like the standard control, then gets slightly bigger than the max volume peak below 6 on the dial.

The second row of three images show the Ibanez, Seymour Duncan, and Kinman treble bleed responses, all of which require one or two extra parts.

The Ibanez method (left image, second row) preserves the resonant peak a little better than the Gibson method, and it maintains the same dynamic range as the standard volume control again.  However, its resonant peak ends up about 2.5x larger than the max volume peak as the volume control is turned down below 7.  Thus, this treble bleed ends up being significantly brighter and thinner sounding at low volume settings than at maximum volume.

The Seymour Duncan method (middle image, second row) manages to keep roughly the same intensity of resonant peak through its rotation, though the resonant frequency drops by about an octave.  Also, it has a huge effect on the taper of the volume control.  The Seymour Duncan volume control stays loud longer, but has a sudden huge drop-off between 1 and 2 on the dial.  It’s so much louder that 2 on the Seymour Duncan dial is about as loud as a 5.5 on a standard dial.

The Kinman method (right image, second row) keeps the resonant peak at about the same frequency, but the resonant peak grows about twice as large as it is at max volume, and a significant amount of mids are enhanced at the same time.  This results in a treble bleed circuit that is fatter sounding than the Ibanez, but brighter than the Seymour Duncan.  Its dynamic range is still in the same ballpark as the standard control, unlike the much louder Seymour Duncan control.

But wait - what about side effects?  It turns out that treble bleed circuits can have unintended consequences, such as making your tone control borderline useless at any volume setting below 10…  Read on.

The third row of two images shows the Standard and Gibson wiring schemes again, but this time with the tone control turned down half way.

The standard volume control (left image, third row) shows what we would expect of a guitar with its tone control turned down a bit and the volume being gradually lowered: smooth response (mostly evenly spaced lines) with no resonant peak and treble frequencies rolled off.

The Gibson method (right image, third row) is pretty much the exact opposite of what we want: the resonant peak, which we tried to knock off with the tone control, distinctly reappears as soon as the volume control drops below 10.  Its response is almost the same with the tone rolled down as it is with the tone all the way up, but with the overall output lowered by -5dB.  The tone control is much less effective at volume settings below 10 with the Gibson wiring method.

The fourth row of three images shows the Ibanez, Seymour Duncan, and Kinman methods again, but with the tone control turned down half way.

The Ibanez method (left image, fourth row) responds properly to the tone control until the volume gets down to about 6 on the dial.  Below 6 it develops a resonant hump, but it’s much wider and less pronounced than the frequency response was with the tone set to 10 (take another look at the original response of the Ibanez control to remember how huge the treble spike got).  In other words, it has more treble than the ideal standard volume control, but the tone control is still knocking about -9dB off the resonant peak and eliminating a noticeable amount of treble as it should.

The Seymour Duncan method (middle image, fourth row) responds properly to the tone control and barely develops much of a treble hump at all, but the dynamic range of the volume control is still skewed very much toward the “loud” side of things.

The Kinman method (right image, fourth row) rolls off its treble resonant peak but keeps its hefty upper-mid hump.  Much like the Ibanez method, its response is far from the standard volume control, but the tone control is still rolling off treble and smoothing out the tone as it should.

Conclusion

What recommendations can we take away from all of this?

The standard volume control loses some treble between 6-10 on the dial, but regains it at lower settings.  The tone control works properly all over the dial.  However, some people find this arrangement too dark (especially when playing with a dirty amp where a little extra treble keeps things crisp as the guitar’s volume is turned down) and would rather have their treble frequencies boosted at low volumes for a brighter, smaller sound.

The Gibson method boosts those treble frequencies a bit at low volumes, but it makes the tone control pretty useless at any volume setting below 10.  Personally, I do not recommend it because it doesn’t actually improve treble response by more than about +2dB, and I can’t stand losing the use of my tone control.

The Ibanez method creates a huge resonant peak as the volume is turned down.  This can be pretty harsh with bright pickups (such as single coils) and is best suited to very dark pickups.  Some players may find it too shrill.  On the other hand, the tone control still works and the dynamic response of the volume control isn’t compromised.

The Seymour Duncan method provides fairly even frequency response with or without the tone control engaged, but it compromises the dynamic range of the volume control.  On the other hand, this would be great for players who mostly play clean or low gain amps and need finer control over the “medium/loud” end of the control than the “soft/whisper quiet” end of the control (which is usually only useful to clean up a super distorted signal).  For example, it is well suited to archtop guitars for jazz.

The Kinman method not only boosts treble frequencies, but also gradually blends in significant amount of extra mid-range.  The tone control still works  This keeps the pickup brighter than the standard control without being as shrill as the Ibanez method.  This is a good choice for players who use a lot of distortion and need the extra clarity in the upper mids without a shrill resonant peak as they roll down their volume control.

In summary, each method has its pros and cons.  Changing the values of the capacitors and resistors used for the Ibanez, Seymour Duncan, and Kinman methods will change their frequency responses slightly, but their basic behavior will stay the same unless you make a radical departure from the standard values.

Note: this test simulated a 7k underwound PAF-style humbucker, 500k audio taper volume and tone pots, and a 0.022uF tone capacitor running into the input stage of a blackface Fender amplifier through a moderately priced cable.  Frequency response will obviously vary with different pickups, controls, cables, and amplifiers.

I got a lot of recurring questions about guitar wiring back when I worked as a guitar tech.  I decided it’s finally time to post some answers with helpful, informative pictures!  Without further introduction, here is part three.

Guitar Controls 3: Potentiometer Size

What effect do the size of your volume and tone controls have on the sound of your pickups?  Are large potentiometers (pots) brighter?

Let’s look at four different setups:

Cyan: 1M volume and tone controls (sometimes recommended to brighten up dark pickups)

Blue: 500k volume and tone controls (common in humbucker-equipped guitars)

Green: 500k volume with 250k tone (rarely seen)

Red: 250k volume and tone controls (common in single-coil equipped guitars)

The first image shows these four control setups with volume at 100%, 75%, and 50%.  With our volume control set to 100%, we see that the larger the controls, the larger the spike at the resonant frequency.  That resonant peak accounts for much of the treble character of the pickup.  Note, however, that the treble content beyond the resonant peak is eventually the same for all the controls: super-high treble is mostly unaffected by the pot size.

With the volume control set to 75% and 50%, the result isn’t quite the same.  At 75%, the 1M pot drops below all the others (in terms of output) and all four arrangements more or less lose their treble peak, which results in the pickup sounding darker.  With the control set lower yet at 50%, a smaller treble peak has developed at a higher resonant frequency, but it’s still not as large as it was with the controls set to 100%.

Conclusion

The larger the pot size, the higher the resonant peak at maximum volume (and the brighter the guitar sounds).  Pickups with a low resonant frequency (like high output, high DCR humbuckers) might sound better with a 1M control.  pickups with a high resonant frequency (like Strat style pickups) are often paired with the smaller 250k controls to tame their treble frequencies a bit.  None of the controls do a good job maintaining a consistent resonant peak as the volume is turned down.

Side Note

Why did I include the 500k volume / 250k tone combination?  Well, the smaller the tone control, the finer the control you have over the low end of the control.  The second image shows a 500k volume / 500k audio taper tone control, while the third image shows a 500k volume / 250k audio taper tone control. Each line on these charts represents 1 notch on a tone control marked from 1-10. The smaller tone control lowers the resonant peak by about -1dB compared to the matched 500k controls, but the “tone control minimized” setting has the same frequency response.  Meanwhile, the 250k pot devotes more of its sweep to the dark end of the control, evening out the behavior of the control a bit more.

Conversely, a 1M tone pot will give very poor control over the low-frequency end of the control compared to a 250k tone pot.  It helps brighten up the guitar, but the control becomes more difficult to dial in at the bottom end of its rotation.

Side Note Conclusion

If you can get away with a smidgen of treble loss, a 250k tone pot will give you much finer control than a larger pot.  If you can’t handle the treble loss, you could try a switched pot that takes the control out of the circuit when it is turned all the way up to 10, giving you the best of both worlds: no treble loss from the tone control when it’s maxed out, and finer control over treble content when it’s engaged.

Note: this test simulated a 7k underwound PAF-style humbucker, variously sized audio taper pots, and a 0.022uF tone capacitor running into the input stage of a blackface Fender amplifier through a moderately priced cable.  Frequency response will obviously vary with different pickups, controls, cables, and amplifiers.

I got a lot of recurring questions about guitar wiring back when I worked as a guitar tech.  I decided it’s finally time to post some answers with helpful, informative pictures!  Without further introduction, here is part two.

Guitar Controls 2: Tone Capacitor Size

What effect does capacitor (cap) size have on a tone control?  Is there a difference when the control is all the way up at 10?  Let’s look at the frequency response of five different cap sizes:

0.100uF (some vintage Fenders use this)

0.047uF (many modern Fenders use this)

0.022uF (most modern humbucking guitars use this)

0.010uF (I use this in my guitars)

0.005uF (I’ve never actually seen this used, but it’s interesting to see!)

The first image shows the tone control set to 10.  As you can see, the different sizes of cap all show such similar frequency responses that they basically sit on top of each other on the graph.  In other words, capacitor size makes no measurable difference when the tone control is all the way up.

The second image shows the tone control set to 6.  Comparing the largest cap (green line on the graph) to the smallest (magenta line), the smallest cap has about +2dB higher output at 1KHz, making it sound slightly clearer.  The three most common cap sizes in production guitars (green, blue, and red lines on the graph) are almost identical.  The treble rolloff is basically identical above 3KHz for all five sizes of cap.

The third image shows the tone control set to 3.  At this point we start to see a noticeable difference between the different caps.  The tiny 0.005uF cap begins developing a resonant peak at 900Hz, the 0.010uF cap has a couple decibels more treble than the more common cap sizes, and the largest 0.100uF cap is loading down the pickup’s signal through its entire frequency response.  Again, the treble rolloff is basically identical above 3KHz for all five sizes of cap. 

The fourth image shows the tone control set to 1.  With the tone control set to its minimum, all the caps (except the 0.100uF) develop a resonant peak somewhere in the midrange of the guitar.  Smaller caps develop larger resonant peaks at higher frequencies.  This peak gives the guitar its “honky” sound, like a wah pedal somewhere in the middle of its sweep.  The higher frequency and larger resonant peak of the smaller caps is what makes them sound brighter with the tone control rolled all the way down.

Assessment of Results

0.100uF, 0.047uF, and 0.022uF caps sound pretty similar all the way from 3-10 on the dial, and only show a significant difference between 1-3:

With the tone control rolled all the way down, the 0.100uF tone cap is attenuating frequencies well down into the playable range of the guitar - it’s not just rolling off overtones!  The open high E string is already at -3dB, and it’s down -27dB by the time you get to the 24th fret.  This is way too much treble attenuation to be useful.  The 0.047uF tone cap isn’t much better: it’s still down -20dB at the top notes of the guitar.

At the other end of the spectrum, the smallest 0.005uF tone cap shows no attenuation at the top notes of the guitar - in fact, its resonant peak is focused right in the top octave of the instrument.  The peak is even taller than it is with the tone control all the way up at 10 (though at a lower frequency), giving those notes a noticeable boost.  This could be useful if you enjoy a “cocked wah” lead tone.

Sitting right in the middle, the 0.022uF tone cap has a resonant peak at about 500Hz.  The 0.010uF tone cap’s peak is at about 750Hz, which is similar to the frequencies that usually get the most push by a certain green overdrive pedal.

Keep in mind: all these frequencies depend as much on the DC resistance and the inductance of the pickups being used.  A higher output humbucker will move all of these frequencies lower and a single coil pickup would move them all higher.

Conclusion

The largest tone caps are too dark to be useful when they’re turned down to zero.  The smallest 0.005uF tone cap would provide a nice, smoothed-out, mid-rich tone with high output humbuckers, the 0.010uF provides the similar response for low output humbuckers, and moving up one more size (0.022uF) will provide a similar response with Strat and Tele style single coil pickups.  Larger capacitors will tend to provide a dead, lifeless response with the tone control rolled all the way down.

Note: this test simulated a 7k underwound PAF-style humbucker with 500k audio taper pots running into the input stage of a blackface Fender amplifier through a moderately priced cable.  Frequency response will obviously vary with different pickups, controls, cables, and amplifiers.

I got a lot of recurring questions about guitar wiring back when I worked as a guitar tech.  I decided it’s finally time to post some answers with helpful, informative pictures!  Without further introduction, here is part one.

Guitar Controls 1: Tone Control Taper

Which is better to use for a tone control?  A linear or audio (logarithmic) taper potentiometer (pot)?  Let’s look at the frequency response of the two controls:

The left image shows the response of a linear taper pot.  Each line refers to a notch on a knob numbered 1-10.  Between 10 and 3 on the dial it reduces the intensity of the pickup’s resonant peak (2.5kHz in this case) without rolling off much extra treble above that frequency.  Almost 80% of the control’s rotation is devoted to this subtle change.  Between 3 and 2 it suddenly eliminates the resonant peak entirely and rolls off an extra ~3dB above the peak.  The final chunk of the tone control’s rotation from 2 to 1 rolls off a whopping -24dB of treble and introduces a new resonant peak in the mids turned all the way down to 1.  This is a pretty drastic shift for the final ~20% of the control’s rotation: a mild resonant treble peak down to almost completely eliminated treble content with a resonant peak in the mids.

The right image shows the response of an audio taper pot.  Again, each line refers to a notch on a knob numbered from 1-10.  Between 10 and 6 on the dial it reduces the treble resonant peak to nothing.  Between 6 and 3 on the dial it gradually introduces up to -12dB treble rolloff.  Between 3 and 1 on the dial it completes its total treble rolloff and introduces the mid-range resonant peak.

Conclusion

The audio pot is better if you want a more even response spread over the entire range of your control’s motion: a half turn of the knob flattens out your treble resonant peak by -6dB, another quarter turn rolls off about -12dB treble, and the final quarter turn gives you fine control over the final -12dB and the introduction of the mid-range resonant peak.

Compare that to the linear control: the first half turn of the knob barely reduces your resonant peak by -2dB, the next quarter turn reduces it by another -3dB, then the final quarter turn reduces your treble by -25dB.  Not smooth.

In my opinion, the audio taper tone control slays the linear taper control.

Note: this test simulated a 7k underwound PAF-style humbucker with 500k pots and a 0.022uF tone capacitor running into the input stage of a blackface Fender amplifier through a moderately priced cable.  Frequency response will obviously vary with different pickups, controls, cables, and amplifiers.

Belle Gen. 5: Body coats

In the last step, I “filled” the pores with black grain filler.  I say “filled” because although every pore got some filler in it, they are not filled perfectly flush to the wood surface.  Some filler always gets pulled out of the pores as I’m wiping the excess off, so it is not yet perfectly flat.  Therefore the clear coat will have to fill in what remains of the open pores and then be sanded back to leave a perfectly flat finish.

It’s basically the same process no matter what kind of film-building finish you’re using (whether it’s shellac, lacquer, varnish, or water-based): apply lots of coats of finish until the film is thick enough that you can sand everything flat (i.e., sand down to the level of the low spots, such as the pores) without cutting through the film and hitting the wood at any point.  Different finishes will have different limitations on how to apply the multiple coats in order to get them to bond properly, but the overall concept is the same no matter what the finish.

I like to use shellac because it’s non-toxic (aside from the alcohol in which it is dissolved), I can apply it in my kitchen, it dries and cures quickly, and there’s no limit on re-coat time because each application of shellac bonds completely with the layer below it to form a single solid film.  It is extremely forgiving to work with.  Its resistance to scratching, liquids, and solvents is not as high as a good varnish or water based finish, but it is a big step up from the other easy-to-use kitchen-safe finishes (i.e. oils).  (Bob Flexner’s book is a great resource for this kind of information.)

After applying a few applications of shellac to the bodies, the finish is starting to build (bottom photos).  The bodies are getting glossy and the clear coat has enhanced the blackness of the grain filler (which tends to dry a bit grey).  It will take at least a week of brushing on shellac once or twice a day to build up a thick enough coat to confidently sand the finish flat without having to worry about “burning through” and hitting the wood below, which would wreck the dye job.

Belle Gen. 5: Filling the grain

Swamp ash has large, open pores.  It takes a lot of shellac to fill them up and leave the wood smooth and level.  It’s quicker if you fill those pores in with some sort of grain filler.

Traditional French Polish pummice methods won’t work.  If applied before dye, the dye won’t penetrate the wood properly.  If applied after the dye, it burnishes most of the dye off the surface as it abrades the wood and fills the pores.  Therefore I will use TIMBERMATE (center photo).  This is the same grain filler as we used at [unnamed boutique bass guitar manufacturer] when I worked there.

Before applying the grain filler, the entire guitar needs to be sealed with shellac.  (Freshly sealed wood with no filler can be seen in top left photo.)  Tinted grain filler has dye in it and it will tint bare wood, but it won’t penetrate shellac.  The layer of shellac has to be thin enough that it doesn’t fill the pores (and it leaves them with nice crisp edges to catch the grain filler as you smear it in), but thick enough that when you don’t burn through the shellac and nick your dye job as you clean the excess filler off.  You can see that the body is a bit shiny in many of the above photos due to the shellac sealer.

I chose black grain filler because I thought it would look pretty rad on #13.  I also figured it would provide some interesting contrast for #12 (above), and I just wasn’t sure what other color I could pick that wouldn’t clash with the red-to-yellow burst.

THE PROCESS

Mix some water in with your Timbermate until it has the consistency of warm peanut butter.  (Not shown.)

Smear some grain filler onto the sealed wood.  I use old cotton t-shirt material  wrapped around a couple cotton balls as a rubber.  Don’t be afraid to lay it on thick!  Really work it into those pores.  (Top center photo.)

Wipe off the excess with an old cotton t-shirt before it dries too hard.  (Top right photo.)  Some filler will remain in the open grain, making it darker.  It also means you won’t have such deep holes to fill with shellac later (although I find that it never fills quite perfectly flush to the surface).  There will still be a thin film of filler on the surface, leaving it looking a bit blotchy and hazy.  It will be cleaned off later.

As you wipe it on, you will notice the pores filling up and getting darker.  In the bottom left photo, the close half of the body is filled and the far half of the body is still unfilled.

Once the filler is completely dry (I wait 24 hours), clean the thin film of remaining excess filler off the surface with 400-600 grit abrasives.  I like foam-backed abrasives because they tend not to leave scratches like the corners of a folded piece of sandpaper will.  In the bottom center photo, you can see the body has been sanded clean with 600 grit, but the control cover has not been cleaned yet.  Notice how much dirtier it looks.  Take special care NOT TO BURN THROUGH YOUR SHELLAC because if you hit your wood you’ll leave a light spot in your dye job!

Finally, all the sanding is done!  The surface is clean, the pores are filled, and the wood is nice and smooth-ish and ready for lots of body coats of shellac!  (Bottom right photo.)  The grain filler doesn’t quite show up as black yet, but its color will darken up once coated with shellac.

Note: the maple is a closed-grain wood.  It does not require filling.  There are no pores large enough in the wood to catch any grain filler even if you tried, so it’s basically ignored through this entire process.

Belle Gen. 5: Five color coats

With #13, I was aiming for a rich golden brown color in order to take the best advantage of the roasted curly maple top.  With this guitar, on the other hand, I wanted to pay homage to the instrument that inspired these two guitars in the first place: the classic Les Paul.  The earliest LPs were all gold-tops, and then they switched to a cherry burst in 1958.  The factory hadn’t started exclusively searching for figured maple yet - they just used any old maple they could find in the appropriate dimensions - so many of the earliest cherry burst LPs exhibit fairly plain or irregular wood figure.  Thus, I decided this classic burst would be an appropriate match for the for the unusual quilt/birdseye maple top I used.

The front is a little more red in the middle than I would have liked, but the maple itself had a bit of a pink tint to it.  I probably would have had to bleach it if I wanted to make it a really bright yellow.  It was about this orange-y even before any red dye was added.

Two coats of Yellow-R, one coat of Red, one coat of Red/Black/Van Dyke, and a final coat of Yellow-R and Red/Black for final color blending.  The wood is still wet in this photo.  Note the matching cover plate!  (The other guitar has one too.)  The grain isn’t a perfect match, but at least the color is the same.

Belle Gen. 5: 4 color coats and some oil

After applying the first reddish undercoats of dye, I went back to the guitar with some sandpaper (specifically, a 400 grit foam-backed sanding pad).  My goal was to lighten up the center section (for more contrast with the burst), sand back any areas that got too dark, and sand back any end-grain that was sealed too well to absorb color (so it would absorb more dye in the next coat).

After that, I repeated the process with a brown dye mixture (Van Dyke brown mixed with a little red) and yet again with a deeper brown (almost the same mixture as before, but with an extra drop of red and one drop of black).  Once that was all dry, I gave it one final touch-up with the sandpaper again to clean up any needlessly dark blotches and improve the blend from dark edges to light center.

A common French Polish technique is to begin with a coat of drying oil before applying any shellac.  I think the oil adds some translucence to the top fibers of the wood, much like grease will make paper transparent (bottom photo).  Whether or not that’s what actually happens to the wood, adding a coat of drying oil before shellac adds visual depth to the wood and increases its chatoyance.  However, applying oil to an open-grained wood like Swamp Ash is problematic: the oil in the pores tends to cure slowly and often leaches out for weeks afterward, which is a pain.  Plus, I think it makes ash look kinda splotchy, and I don’t like that.

Therefore, I only oil the maple top of the guitar.  Any drying oil will do, but those that cure quickly are your best bets, such as polymerized oils.  I like to use Tried & True Varnish Oil, which is a blend of polymerized linseed oil and processed pine resin.  The important thing (in my mind) is that it contains no solvents or heavy metal driers, neither of which are healthy to work with (and neither of which I want underneath my later coats of shellac).

The next step will be to seal the instrument with a few thin coats of shellac, then fill the pores, and finally go to work on the top coats.