Rewiring for Resonant Peak Shift & Mid Scoop

And here's what it will look like to test the neck, with the bridge component values selected:

HH Resonant Peak Testing Neck.png
 
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I've been waylaid, but I'm finally sitting down to start wiring to test various values to lower the resonant peak of the bridge with my optimized method. The pickup selector moves in large leaps of nanofarads, the rotary moves in finer increments of picofarads in parallel to the pickup selector, which will add the two values to create the overall capacitance loading the pickup, and the B500K pot tames the Q. The 250K trimpot simulates the load of the 250K volume pot I'll use. I'm not using a tone pot, so I'm created the load of a 500K volume pot with a 500K tone pot.

I measured the DPDT Dual Gang 250K pots I have, and found an actual value of 243K for the one I'll use for the bridge. I measured a 500K trimpot to be 511K, so I tested various 470K fixed resistors until I found one that would get the overall resitance close to 243K. I finally found one that, when wired across lugs 1 and 3 of the trimpot, yielded a value of the two resistors in paralle to be 245K, so I was within 2K, which is fine.

Here's an updated diagram:

HH Resonant Peak Testing Bridge.png
 
Man, it has been brutal just waiting until I could continue with my project, just life getting in the way. Tonight I finally sat down to start testing component values in the guitar. Let me tell you, this is the way to do it! The first thing I realized was, the way I had the Q Taming Pot wired was backwards from how I wanted it to function. I wanted it to act a little like a volume pot, so that, when it was at 0 on the knob, the guitar was silent. It turns out to achieve that with this wiring I had to have the hot wire connected to lug 1, not lug 3, so I did that. What I found was that I was getting great tones with 2.2nF||470pF||~250K for brighter tones and 4.7nF||470pF||~250K for warmer tones. I'm guessing the pot is somewhere around 250K because it's somewhere in the middle. I didn't actually put on a knob for the pot, so I'm just guessing. When I know for sure I have good tones I want to use, I'll measure the pot's resistance at that setting. It was funny to me that the rotary and Q taming pot sounded best in the same spot, when I was making a big jump between 2.2 and 4.7nF on the course selection at the pickup selector. These are huge shifts of the resonant peak to get a natural and good sounding tone. Going between 2.2 and 4.7nF sounded like two different guitars with a bridge humbucker, but both guitars sounded great!

What I did tonight was just to start going through the Axe-FX III factory presets, the updated ones design for firmware 27.03. This to me is a great way to set the load on these pickups: these presets really sound wonderful when others play through them, so I'm using them as a starting benchmark to get my guitar also to sound wonderful playing through them. Next I'll continue playing through many more of these presets, but I'll also create four block presets with just an amp block and a single static factory IR, matching the Speaker Impedance Curve, to make sure my resonaont peak shifts sound just as good between those dry presets, which are my preference, and the factory presets. I think this is best overall method to get the guitar's tones where I want them. Tonight was very encouraging, so I'm excited for the next time I can sit down to try more!

Here's an updated diagram with the corrected Q taming pot:

HH Resonant Peak Testing Bridge.png
 
A couple things I forgot to mention:

  1. I did not measure the actual values of the caps I installed, so I'm just acting like they're actually what's intended, but when I land on the components I like, I'll use those actual capacitors, because they likely are not actually the values stamped on them.
  2. I meant to list the overall values that worked for my guitar. Although they were 2.2nF||470pF||~250K for brighter tones and 4.7nF||470pF||~250K for warmer tones, when you put two caps in parallel, the capacitance adds together, so if you go by the stamped values, it was really 2.67nF||~250K for brighter tones and 5.17nF||~250K for warmer tones! Again I just find it interesting that what hit my ears just right was for the warmer tone to take just about double the capacitance of the brighter tone.
 
Resonant peak manipulation is also a great w;ay to "tune" the tone of your pickups to match your favorite pick. I have a massive collection of various picks, and I whip it out every once in while. I decided to give it a try tonight, and I'm finding that different picks very much like different resonant peaks with my pickups, and it's awesome to be able to switch resonant peaks on the fly like this to test. Although I've been a Dunlop Orange Standard .60mm guy for many years now, I know it's not the most efficient pick for my picking technique, so I'm comparing to the Jazz III in many thickness, the various Flow shapes and thicknesses, several Claytons, Ultex, even V-Picks, and I'm finding that it is probably no problem for me now to priority first how the pick feels, then tune the pickups to match that pick to get the best tone out of it!
 
I tried so many picks, but I came to the same conclusion that I've come to over the past decade or so, that the Dunlop Tortex Standard just gives me a greater range of tones using just different angles. The Jazz III made shredding easiest, but no matter what I just couldn't get the same range of technique out of them!
 
Eagle said:
It never occurred to me either but a friend of mine tested a whole bunch of caps , materials and voltage and we listened back to the clips . The big voltage version in all materials was more balanced as you turned it down.
Click to expand...
Then the capacitance of the higher-voltage capacitors is different enough to make an audible difference.
 
Rex said:
Then the capacitance of the higher-voltage capacitors is different enough to make an audible difference.
Click to expand...
TBH I don’t know but I always choose them in blind tests as having a more useful effect. Is you roll them down. That is tested with the same pot.
 
State of Epicicity said:
I tried so many picks, but I came to the same conclusion that I've come to over the past decade or so, that the Dunlop Tortex Standard just gives me a greater range of tones using just different angles. The Jazz III made shredding easiest, but no matter what I just couldn't get the same range of technique out of them!
Click to expand...
Used Jazz III picks for a while 30-35 years ago.

Prefered the tone/feel of the black ones, but the ability to be found and used again after being dropped was far superior on the red ones.... 🤔
 
Also, the guitar is so incredibly quiet now. I turned off the noise gate of the input block in the Axe-FX III, and there was nothing there until I massive gain, and even then it was minimal. I think the shielding around the pickups really worked well; I'm glad I tried it.

I'm debating now whether I want to stick to my preset idea or not, to have a dark and bright setting for each pickup position. I'm still doing extensive testing for my bridge, settled at least on the bright Les Paul tone, and wondering if I really want the dark setting too. I have some regular dual gang pots in case I go that route.
 
I have decided not to go with different presets for the same pickup tones. It really does seem to be the case that I gravitate toward one ideal tone for each pickup style; the idea I had of a warm and bright version of each just doesn't work for me in reality. I realized that the warm settings I was getting just sounded like the tone knob rolled off a bit. The big lesson for me here is that, as long as the pick attack sounds good, I get everything I want from the combination of picking technique, volume knob with very careful treble bleed selection, and whatever gear I play through.

That said, I've streamlined my diagram. I've also corrected the mid scoop, which needs to run in parallel to the hot, not in series. I reread posts on Guitar Nuts 2, where passive mid scoops have been discussed in depth, everything from the Bill Lawrence / Wilde Pickups Q-Filter, to the Torres mid scoop, to the Rothstein. I see that there are also many passive midscoops available from KellingSound on eBay. In fact, that looks like a great store for all sorts of interesting guitar circuits prewired. Special huge and massive thanks to GCKelloch on Guitar Nuts 2 for all of the info he has posted on passive mid scoops, breaking down how each component works in those scenarios.

I've streamlined to five tones only:

Position 1: Les Paul Bridge
Position 2: Strat Bridge
Position 3: Quack of some kind
Position 4: Strat Neck
Position 5: Les Paul Neck

So, the long and short is: the Les Paul tones are attained by shifting the resonant peak down, using a cap and resistor in parallel to the pickup. The Strat tones are attained by passive mid scoop, which also shift up the resonant peak.

I've settled finally on the resonant peak downshift on my bridge humbucker, so I've added that to the diagram: 2.2nF||680pF||423K

HH 5-Way Dual Gang VV Resonant Peak.png
 
Now that I have the component values for the resonant peak of the bridge selected, it's time to test for the neck, since that will not require a huge amount of rewiring from my bridge test. I'll show my bridge testing setup again, then my neck setup:

HH Resonant Peak Testing Bridge.png


HH Resonant Peak Testing Neck.png
 
I've now wired in the components for the bridge HB tone, using a trimpot in lieu of a regular pot so I can just tuck it into the cavity, as I drew in the diagram in my last post. I've also wired the bridge so that I have four course resonant peak downshifting caps from which to choose, 1nF, 2.2nF, 3.3nF, and 4.7nF, using the 5-way blade switch. The cool thing here is, the 1st position of the switch selects the bridge pickup! This way I can make sure that what I choose for the neck sounds balanced with the bridge. The rotary is on at all times too, with the 1st position providing no extra cap, but in the other five positions, these are fine increases in the overall peak downshifting capacitance by about 150pF, in addition to the course selection, on the neck only. Then of course there's the Q taming pot, wired as before.

To load the neck properly from the get go, I measure the gang of the dual gang I'll use for the neck HB tone, and it was 233K, so I grabbed all of my 500K trimpots and 470K fixed resistors and measured actual values until I found a combination that in parallel equals 234K, close enough to replicate the actual pot I'll be using.

Last night I also took all my regular 250K / 250K dual gang pots and put liquid electrical tape on them to make it so they'll hopefully be immune to dust. I used a toothpick to seal the pots in a way where I could get into the tight spaces. I used my solder fume extractor while working with this stuff, because the fumes from the liquid electrical tape are strong.

I've tested for continuity, so everything should function as I hoped when I put it together. Fingers crossed haha!

IMG_1674.jpeg


IMG_1675.jpeg
 
Man, it took all of about five minutes to find the right resonant peak downshifting components to get the neck to balance with the bridge: 2.2nF||330pF||297.3K. I've now wired that in with its own trimpot, hidden in the cavity. Next I'll try some simple PEQ midscoops with no boosts in order to get a rough idea of what frequencies I want to target. With that info, I'll let ChatGPT know my inductance and resistance as well as the target frequencies to get a clue as to where to start, given the various transformers I have. I bought a box of electrolytic caps, because that was the only style I could find that was high value but physically small. In my AI chats just guessing values, the recommendations were for high value caps always, so I think I'll have what I need. This is already fun as hell, and getting this guitar to sound right on top of how it feels and acts is a true joy.

This has been the biggest learning experience for me about buying a guitar in the future, on top of everything else I've learned. I know now what definitely to avoid tone wise, that if there are just unacceptable frequencies being produced by a guitar, it might take something like this to get rid of them. Even in this case, I found I still have to pick carefully to avoid some of that terrible chirp creeping in to my tone. I found I could shift the resonant peak lower, but I started to lose character with the tone, not like a tone knob rolloff, just a kind of lack of personality.

So I've found the right balance here for my HB tones. The Strat tones are going to be where I haven't gone before, and what's interesting to me is that I'll be going for something where the single coil-esque tones sound good through Plexis and various Fender amp models. The volume riding is really important for that tone, so I'm going to have to consider how to do the testing. I know I'll dedicated two switch positions to what I have set so far, the Les Paul style bridge and neck tones with volume at 10, but if I want to dial in both a Q-taming pot as well as having a volume knob working, where I'll need to be able to dial in a treble bleed, while testing transformers acting as mid scoop inductors with various cap values, this is where I think having a rough idea of values to start with from AI will help! I'll draw a diagram for the next phase when I get a chance. I have a new guitar coming tomorrow on top of this, so that will take some time too!
 
First off: I find all this pretty interesting (even if I will never get into it that deep myself even remotely).

But let me ask you one thing: Aren't you running into noise issues with all those additional caps, resistors and cables?
From my personal experience, even some simple treble bleed circuits can cause more noise when you actually dial back your volume a bit. I observed this on quite some high quality guitars as well. And from my own experiments with c-switches (which I almost always slapped into at least some guitars until some years ago) I know it often happens with those as well. And those circuits were way less complexed than what you're doing here.
Or, the other way around: In case you don't run into noise issues, what would you say are the most relevant measures to avoid it?

Fwiw, I have an Epiphone LP that I could abuse for at least some kinda similar things (will be just one volume and tone pot, so there's plenty of space in the cavity), so knowing about possible noise-avoiding measures beforehand would be great.
 
Piing said:
How does that differs from using surgical EQ at the beginning of the Axe-FX chain?
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You can do it straight from your guitar. No need to save gazillions of patches just because you want your pickups to sound a little different. And it won't work anyway in case you have other pedals in front of whatever modeler.
Besides, for whatever reasons, usually EQs sound pretty different (even if they should be able to do the same things).
 
Sascha Franck said:
You can do it straight from your guitar. No need to save gazillions of patches just because you want your pickups to sound a little different. And it won't work anyway in case you have other pedals in front of whatever modeler.
Click to expand...

I think that it goes the other way: it is faster and less complicated to tweak EQ blocks than to rewire your guitar and conduct all the experimentation combining different components.

It would be interesting to know the opinion of @FractalAudio @Fractal M@ regarding the external EQ using components inside the guitar Vs EQ block. (assuming that you are not using an external Fuzz at the beginning of the chain).
 
Piing said:
How does that differs from using surgical EQ at the beginning of the Axe-FX chain?
Click to expand...

You really can't reproduce the load on a passive pickup with an active EQ; at least I haven't figured out how to make them sound the same. In this case, where I get an unlistenable pick attack I've tried to EQ that out, but I couldn't figure out a way without just getting rid of the high end altogether. I've tried every kind of Q and cut depth, but it just sounded awful.

What I'm doing here is a different thing altogether; I'm actually shifting the resonant peak of the pickup itself, getting it to act like a different pickup. It's the basic character of the pickup that changes. You can move the resonant peak up or down just by placing a cap in series or parallel, respectively. You lower the peak with a resistor. The effect is truly like a pickup swap, although with no change in coil wind; when I finally did it correctly, realizing parallel meant one leg of the cap goes to the hot lead and the other to ground, that was like a revelation to me.

An EQ can't change the resonant peak. You can try a version of this just by going though the different input impedances of the Axe-FX III input block plugging in to the front input. You'll hear how the different values load your pickup. I actually created a wishlist for the next hardware version to allow for a fine control of this feature to load the guitar not for recreating the input impedances of gear, but to change the character of the guitar itself.

It's what Hendrix did by using an extra long cable, which lowered the resonant peak of his pickups with a bunch of capacitance, I assume to get rid of bridge ice pick tones.
 
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