Treble cap cuts, global vs individual, fixed vs adjustable

[ssstonelover]

I had someone ask for my advice yesterday. He needs to cut the highs from a Strat type guitar, and as he has 500K on all pots (import guitar), he wanted to know if all pots should be changed to 250K and if not, in which order they should be changed to not go 'too far' in cropping highs and/or increasing his work and cost.

1) POT fix: I remember Kinman pickup talked about this once (though with the idea of ADDING highs, so of course his advice (if good) would be done in REVERSE. Overall does this chart make sense? What advice would our brainiac mentors weigh in with?
Kinman said something like this, if my memory is accurate:


2) GLOBAL fix: I have heard about adding a cap on the output jack to 'trim off' excessive high. This would be a 'global cut' which has its strong and weak points of course. I'm assuming it is something TINY such as 0.0012uF to something up to about the 0.0018uF or so..... this discussion can include all manner of 'global high fixed value trim' on any guitar, though the SSS type is the immediate issue on the table. JohnH and his graph ability would be perfect for this, but all info and discussion is perfect as this is really a knowledge question, more than just a desire for a 'quick fix' to help the guy.

3) INDIVIDUAL fix: In the vein of the second way to handle the situation but without prejudicing any of 3 pickups (or any other number of pickups installed) I saw this video which attempts to tune the cut per pickup Try This Before Buying New Pickups | Cheap & Easy Mod It seems straightforward enough

For discussion of 2 + 3 (above) maybe we can start with this drawing I modified, so we can zero in on 'individual' and 'global' 'ice pick' fixes, should that be a desirable thing.
Relocating caps onto pots or pickups for Global or Individual frequency cuts is yet another option, and open for discussion and theorical improvement of layouts. Yes, everything is on the table and open for discussion.

[mikecg]

Hello ssstonelover,

One way to approach this requirement would be to insert a selection of small capacitors in parallel with the guitar lead. The user could then select each pickup in turn, and run through the capacitor selection until he zeroes in on the tone he is looking for. He can then make a note of his selected capacitor value and arrange for a fixed component to be wired into the guitar as indicated in your wiring diagram. If the user has some soldering skills this should not be difficult to put together. If the user is not able to assemble a switch with suitable capacitors, he could try using this pre-assembled module :

www.alegree.co.uk/products/artec-qtp-passive-quad-tone-selector

To avoid messing with the guitars internals, it would need to be wired to a 1/4" jack and socket, and inserted between the guitar jack socket and the users guitar lead.
As it is designed to be wired in place of a standard treble cut capacitor, it may be wise to wire in a 'dummy' (i.e. external) treble cut pot, and to make sure that the guitar's normal treble cut is set to minimum cut, during the tone switch testing operation. 

[gckelloch]

Adding low value caps on a typical Alnico SC doesn't just cut the highs, but also produces a mild boost of ~3dB, depending on the R load. It's important to know the pickup inductance to know where the boost freq will be centered. ~2kHz is generally good with it down a few dB by 3kHz. Icepick is a result of a strong 3-3.5kHz peak and/or strong transients directly from the string and/or speaker.

What about the idea of using one of these transformers to create a ~3khz dip with one 500k pot along with a standard 500k tone pot to adjust the peak level?
www.aliexpress.us/item/2255800936817835.html?

You could wire individual ~1n5F caps from each pickup pos lug to the transformer and then to a pot going to ground. You can ground the open outer lug to keep the peaks from being too strong when it's down low and the tone knob is up all the way. Wire the other pot as a master tone knob to adjust the peak levels and to lower the mid-dip freq center when it's turned down below ~4. Wire one or both options on a p/p pot to be disengaged, depending on what the customer prefers. That way you could leave them set a certain way and quickly switch to just one or neither tonal option. I have that on one guitar and it's really useful. I just wired a 220k R to ground from the side of the P/P pot without the attached tone and mid-dip knobs. You could make the other pot a P/P as well if you want to add a cap for a different tone knob peak or a lower mid-dip value, but you really wouldn't need it with this setup.

[newey]

For a more technical explanation, as well as for some graphic representations of the effect of various capacitor values, ChrisK had a couple of posts that bear on these issues. What @gckolloch noted as a "mid boost" was what ChrisK was demonstrating here.


Pickup coil response tuning

The passsive high-cut tone control

For "brightest", I have in the past used a 1M pot with a 500K. This gives a combined resistance of 333KΩ. It is very bright (some would say "ice pick") with the tone at full rotation, and I usually play this guitar with the tone rolled down a bit, but it is still pretty bright (It has a single GFS "lipstick tube"-style HB at the bridge, so would have been bright to begin with.)

[mikecg]

Just a quick update on my previous suggestion regarding the Artec QTP passive switched tone module. I don't have the circuit diagram for this module, but I can see from the published data that it consists of a five way rotary switch, giving five tone selections, bypass (open circuit), extra high cut, high cut, mid cut, and warm tone (extra mid cut?). It would appear to consist of 4 sets of simple RC low pass filters, and a single pole five way rotary switch. It has two connection lugs, and is designed to be installed in a guitar and connected to the hot lug of the guitar volume pot and guitar ground. If it is wired externally, in parallel with the guitar lead, as I have previously suggested, it will not require a dummy tone pot to be added and so my previous comment regarding that addition, should be ignored. However, it is important to point out that, if the module is used externally, its effect on tone will be determined to some extent by the guitars volume pot setting, and so the volume pot setting should be set to maximum, during tone testing, to avoid this interaction.

[ssstonelover]

Oct 13, 2024 17:20:00 GMT -5 mikecg said:

Hello ssstonelover,

One way to approach this requirement would be to insert a selection of small capacitors in parallel with the guitar lead. The user could then select each pickup in turn, and run through the capacitor selection until he zeroes in on the tone he is looking for. He can then make a note of his selected capacitor value and arrange for a fixed component to be wired into the guitar as indicated in your wiring diagram. If the user has some soldering skills this should not be difficult to put together. If the user is not able to assemble a switch with suitable capacitors, he could try using this pre-assembled module :

www.alegree.co.uk/products/artec-qtp-passive-quad-tone-selector

To avoid messing with the guitars internals, it would need to be wired to a 1/4" jack and socket, and inserted between the guitar jack socket and the users guitar lead.
As it is designed to be wired in place of a standard treble cut capacitor, it may be wise to wire in a 'dummy' (i.e. external) treble cut pot, and to make sure that the guitar's normal treble cut is set to minimum cut, during the tone switch testing operation. 

I don't think he's going to go for something like a 5 or 6 way rotary with various caps externally built for testing and then select a fixed value cap based on results for installation. That was actually one of my first suggestions to him. I have implemented such a solution (through with the selector itself permanently installed) on one of my personal guitars and found it highly effective(refer to the 2nd and 3rd images). Here is a link, though on this particular one a lot of other stuff is going on as well Rotary cap selection that you can ignore. I show the rotary connected to a tone pot, but it could be a stand-alone, and just affecting the very highest frequencies, with the other tone pot doing the 'normal' tone cut'.

For sure Artec has some valid sound sculpting solutions. I have used their MT3, EXP, and BCU (all battery operated) on a few builds.
The passive QTP looks like a simple solution to this guy's issue, but substituting for one tone control while leaving the other onboard to cut into mids if needed. It ould be pretty fool-proof and the Artec instructions are easy enough to follow.

[ssstonelover]

Oct 14, 2024 0:48:35 GMT -5 gckelloch said:

Adding low value caps on a typical Alnico SC doesn't just cut the highs, but also produces a mild boost of ~3dB, depending on the R load. It's important to know the pickup inductance to know where the boost freq will be centered. ~2kHz is generally good with it down a few dB by 3kHz. Icepick is a result of a strong 3-3.5kHz peak and/or strong transients directly from the string and/or speaker.

What about the idea of using one of these transformers to create a ~3khz dip with one 500k pot along with a standard 500k tone pot to adjust the peak level?
www.aliexpress.us/item/2255800936817835.html?

You could wire individual ~1n5F caps from each pickup pos lug to the transformer and then to a pot going to ground. You can ground the open outer lug to keep the peaks from being too strong when it's down low and the tone knob is up all the way. Wire the other pot as a master tone knob to adjust the peak levels and to lower the mid-dip freq center when it's turned down below ~4. Wire one or both options on a p/p pot to be disengaged, depending on what the customer prefers. That way you could leave them set a certain way and quickly switch to just one or neither tonal option. I have that on one guitar and it's really useful. I just wired a 220k R to ground from the side of the P/P pot without the attached tone and mid-dip knobs. You could make the other pot a P/P as well if you want to add a cap for a different tone knob peak or a lower mid-dip value, but you really wouldn't need it with this setup.

I'm afraid he is looking for a fast and easy. There are 8 leads on that transformer and unless we drew him a detailed diagram (which is beyond me as I don't know the overall layout well enough) it's going to fall on deaf ears entirely, and might even then. As far as the theory, it's attractive enough, and I like what you are describing (low value caps drop highs and boost output too at a lower frequency) as very close to ideal.

I might like to try it personally on a build, could you do a "rough sketch" including which of the 8 transformer connections are used (or of the setup on your personal guitar) and I will redraw and add to it for your double-check? It think it would be something good to have in the arsenal of choices.

[ssstonelover]

Oct 14, 2024 7:43:40 GMT -5 newey said:

For a more technical explanation, as well as for some graphic representations of the effect of various capacitor values, ChrisK had a couple of posts that bear on these issues. What @gckolloch noted as a "mid boost" was what ChrisK was demonstrating here.
Pickup coil response tuning
The passsive high-cut tone control
For "brightest", I have in the past used a 1M pot with a 500K. This gives a combined resistance of 333KΩ. It is very bright (some would say "ice pick") with the tone at full rotation, and I usually play this guitar with the tone rolled down a bit, but it is still pretty bright (It has a single GFS "lipstick tube"-style HB at the bridge, so would have been bright to begin with.)

I love it! ChrisK really knew his stuff that @gckolloch is kind of echoing in his post too. Thanks for bookmarking a great resource.

The fast-and-dirty of adding a resistor to the existing pots to lower them is also a great idea, and certainly way low cost, plus he hardly has to disturb his exiting wiring.

[ssstonelover]

Oct 14, 2024 7:58:56 GMT -5 mikecg said:

Just a quick update on my previous suggestion regarding the Artec QTP passive switched tone module. I don't have the circuit diagram for this module, but I can see from the published data that it consists of a five way rotary switch, giving five tone selections, bypass (open circuit), extra high cut, high cut, mid cut, and warm tone (extra mid cut?). It would appear to consist of 4 sets of simple RC low pass filters, and a single pole five way rotary switch. It has two connection lugs, and is designed to be installed in a guitar and connected to the hot lug of the guitar volume pot and guitar ground. If it is wired externally, in parallel with the guitar lead, as I have previously suggested, it will not require a dummy tone pot to be added and so my previous comment regarding that addition, should be ignored. However, it is important to point out that, if the module is used externally, its effect on tone will be determined to some extent by the guitars volume pot setting, and so the volume pot setting should be set to maximum, during tone testing, to avoid this interaction.

I think I will present this to the guy as an on-board option simply replacing one of the exiting tone pots. I have never had an issue with Artec stuff, though I have always used their battery versions for added 'oomph'. I'm seeing it almost as a poor man's Varitone in that it does more than just cut highs, i.e. it can do more than that.

[perfboardpatcher]

Hi ssstonelover,

I myself am more of a single humbucker kind a guy. Most of my guitars have a hot humbucker in the bridge. For a clean humbucking sound I use the coils in parallel with an added cap (stratotarts' mod). I've been brooding for a while over the following; is it possible to sonically bend the Bridge + Middle pickup combination om my strat in such way that it sounds more as a clean humbucker? My strat has a superswitch and the other 4 positions are kept unmodified.

[ssstonelover]

perfboardpatcher With a superswitch a lot of things are possible quite frankly.
--You seem to be asking to put middle and bridge in series (clean humbucker) and that is within a superswitch's capability, yes indeed. .
--Of course you could be saying you just want to put B + M in parallel but roll off some treble.... that too is possible with maybe a cap in that, if needed, and only in that position. Just know that the dB of M+B is weaker (just like a HB in parallel mode).
Probably best for you to start a new thread on that and you will get some responses. The key is to say what you want for the other 4 positions (stock Strat) plus we'd need to know more about your total setup (Stock Strat with position 4 with some kind of clean humbucker sound of MxB)

[gckelloch]

Oct 14, 2024 11:56:26 GMT -5 ssstonelover said:

Oct 14, 2024 0:48:35 GMT -5 gckelloch said:

Adding low value caps on a typical Alnico SC doesn't just cut the highs, but also produces a mild boost of ~3dB, depending on the R load. It's important to know the pickup inductance to know where the boost freq will be centered. ~2kHz is generally good with it down a few dB by 3kHz. Icepick is a result of a strong 3-3.5kHz peak and/or strong transients directly from the string and/or speaker.

What about the idea of using one of these transformers to create a ~3khz dip with one 500k pot along with a standard 500k tone pot to adjust the peak level?
www.aliexpress.us/item/2255800936817835.html?

You could wire individual ~1n5F caps from each pickup pos lug to the transformer and then to a pot going to ground. You can ground the open outer lug to keep the peaks from being too strong when it's down low and the tone knob is up all the way. Wire the other pot as a master tone knob to adjust the peak levels and to lower the mid-dip freq center when it's turned down below ~4. Wire one or both options on a p/p pot to be disengaged, depending on what the customer prefers. That way you could leave them set a certain way and quickly switch to just one or neither tonal option. I have that on one guitar and it's really useful. I just wired a 220k R to ground from the side of the P/P pot without the attached tone and mid-dip knobs. You could make the other pot a P/P as well if you want to add a cap for a different tone knob peak or a lower mid-dip value, but you really wouldn't need it with this setup.

I'm afraid he is looking for a fast and easy. There are 8 leads on that transformer and unless we drew him a detailed diagram (which is beyond me as I don't know the overall layout well enough) it's going to fall on deaf ears entirely, and might even then. As far as the theory, it's attractive enough, and I like what you are describing (low value caps drop highs and boost output too at a lower frequency) as very close to ideal.

I might like to try it personally on a build, could you do a "rough sketch" including which of the 8 transformer connections are used (or of the setup on your personal guitar) and I will redraw and add to it for your double-check? It think it would be something good to have in the arsenal of choices.

I can draw up something once I know the options you'd prefer.

What about having one p/p or dpdt switch to bypass any tone options with just a 250k R wired to ground, and another switch to disable just the mid-dip and standard tone knob? You'd have the unencumbered pickup sounds when all tone knob options are disabled. When the tone options are enabled, the other P/P or switch would switch from an adjustable 1.5~2kHz peak using one knob to an adjustable mid-dip with the 1.5~2kHz (or a lower freq) peak b4 the dip, while the other tone knob can be used to adjust the peak levels.

Sorry, I was mistaken about how the standard tone knob would work in conjunction with the mid-dip knob. When dialed down below~4, it would actually lower the freq of the peaks both above AND below the mid-dip (depending on the cap value on it), but you can use that knob as a standard tone knob when the mid-dip knob is up. FI: If you used a 22nF cap on it, you should get a very mild 400~800Hz and 1~1.5kHz peak with both knobs down, depending on how many ~2.5H pickups are in parallel.

The other option would be to use a ~1n5F cap on the tone knob. Then the peaks would be more like 1~2kHz and 2~4kHz when both knobs are down, but you won't have the very dark tone option a 10~22nF cap would offer. With that option, you could instead use a 22nF cap on the mid-dip knob if you want the mid-dip to be in the ~1kHz range of a typical Wilde Q-filter. In that case, the peaks with both knobs down would be like 400~800Hz and 2~4kHz.

Please let me know which option you'd prefer if you do want to use this wiring scheme.

[ssstonelover]

Oct 14, 2024 15:25:25 GMT -5 gckelloch said:

Oct 14, 2024 11:56:26 GMT -5 ssstonelover said:

Please let me know which option you'd prefer if you do want to use this wiring scheme.

I've been thinking about this and decided that with 2 tone pots the interaction could be hard to control, and while I'm a big fan of DPDT switches, needing two of them to shuttle between and control all the high/mids options for a small gain in overall shaping (from what I can sense you saying) might be a frustrating exercise. The interaction between pots, "it would actually lower the freq of the peaks both above AND below the mid-dip (depending on the cap value on it", is not something that sounds so great, unless I'm missing something, and seems to be the main reason for the pair of DPDT switches (to avoid nastiness) just to correct an issue which might not be there but for some original bad choices creating the 'ice pick' shrill sound in the first place (that could be solved more simply).

Let's skip this for now. no need to put any work into this. It's kind of funny to hear myself saying this. I know the KISS principle and disobey it many times and have lots of choices in my wire harnesses, some which I rarely use, "just because" I can.

Thanks for offering!

[gckelloch]

Oct 14, 2024 23:46:38 GMT -5 ssstonelover said:

Oct 14, 2024 15:25:25 GMT -5 gckelloch said:

I've been thinking about this and decided that with 2 tone pots the interaction could be hard to control, and while I'm a big fan of DPDT switches, needing two of them to shuttle between and control all the high/mids options for a small gain in overall shaping (from what I can sense you saying) might be a frustrating exercise. The interaction between pots, "it would actually lower the freq of the peaks both above AND below the mid-dip (depending on the cap value on it)", is not something that sounds so great, unless I'm missing something, and seems to be the main reason for the pair of DPDT switches (to avoid nastiness) just to correct an issue which might not be there but for some original bad choices creating the 'ice pick' shrill sound in the first place (that could be solved more simply).

Let's skip this for now. no need to put any work into this. It's kind of funny to hear myself saying this. I know the KISS principle and disobey it many times and have lots of choices in my wire harnesses, some which I rarely use, "just because" I can.

Thanks for offering!

Sure, but I could just as easily have one of the switches switch between the mid-dip and tone knobs so there would be no interaction. You could use whatever cap values you want from each pickup switch lug to the tone knob. The other switch could disengage both knobs or switch the cap values on either or both knobs. You could instead assign each knob to specific pickup positions and still be able to switch cap values on either or both knobs or don't bother with any switches and just wire the mid-dip knob on the bridge pickup. Let me know if you are interested in any of those options.

Cheaper still is this Ferrite core 600/600 Ohm transformer:

www.aliexpress.us/item/3256805854006562.html?

I see no reason not to use that one. Ferrite is non-conductive and shouldn't create any eddy -currents. Each side apparently measures 3.6H. I assume one coil on either side would then be ~2H. That's what I'd use for the mid-dip. The diagram under the specifications tab shows the coil configuration. You'd just wire a cap in series with one coil and a pot to ground. You can also wire a 5~10k R over the cap if you want some bass reduction and don't want such an extreme mid-cut when it's turned way down. That network is then wired in parallel with the pickup/s.

[ssstonelover]

Oct 15, 2024 0:29:07 GMT -5 gckelloch said:

Sure, but I could just as easily have one of the switches switch between the mid-dip and tone knobs so there would be no interaction. You could use whatever cap values you want from each pickup switch lug to the tone knob. The other switch could disengage both knobs or switch the cap values on either or both knobs. You could instead assign each knob to specific pickup positions and still be able to switch cap values on either or both knobs or don't bother with any switches and just wire the mid-dip knob on the bridge pickup. Let me know if you are interested in any of those options.

Cheaper still is this Ferrite core 600/600 Ohm transformer:

www.aliexpress.us/item/3256805854006562.html?

I see no reason not to use that one. Ferrite is non-conductive and shouldn't create any eddy -currents. Each side apparently measures 3.6H. I assume one coil on either side would then be ~2H. That's what I'd use for the mid-dip. The diagram under the specifications tab shows the coil configuration. You'd just wire a cap in series with one coil and a pot to ground. You can also wire a 5~10k R over the cap if you want some bass reduction and don't want such an extreme mid-cut when it's turned way down. That network is then wired in parallel with the pickup/s.

OK, that sounds more interesting, and as this is something new to me (and probably a bunch of others here too) it merits a good drawing / wiring diagram so we can see how it all fits together. In fact It might be fun (and useful) to go from clear highs to soupy mid dips (by which I think you mean heavier mid tones) on a single guitar with flip of a switch (or two).
For modeling purposes the base you could use to overlay these mods could be a Strat layout, as that is pretty archetypical for mods.
I buy from Aliexpress already at least several times a year, so that aspect is totally fine as well.

Out of curiosity, and in your opinion, how would this compare the the Fender Greasebucket mod which is supposed to give some nice mids yet limits/avoids 'bass' mud and I assume brings down the highs and/or resonant frequency?
Different approach to the same issue (limiting ice pick yet avoiding mud) or something else entirely? That's another one I have not tried (or researched much) and as I understand it, it forms an RLC circuit (a resonant circuit comprising a resistor, an inductor, and a capacitor) so has at least some elements in common with your mid dip? (maybe without the coolness of switches however?)

[mikecg]

Hello gckelloch,

Regarding your recent link: www.aliexpress.us/item/1005006040321314.html?

You say that this is a ferrite core transformer, but I see no reference to ferrite in the description?

I would be very surprised if it was ferrite, as the permeability of even the highest permeability ferrite grades, is very much less than, Permalloy (80% Ni, 20% Fe).
Typically, the higher permeability ferrite grades (Mn-Zn) are semi-conductive, and have mu values in the 1000's, whereas transformer steel (97% Fe, 3% Si) is in the 10,000's, and Permalloy is in the 100,000's.

I would guess that your linked item describes a Permalloy cored transformer. 

[perfboardpatcher]

Oct 14, 2024 14:33:08 GMT -5 ssstonelover said:

perfboardpatcher With a superswitch a lot of things are possible quite frankly.
--You seem to be asking to put middle and bridge in series (clean humbucker) and that is within a superswitch's capability, yes indeed. .
--Of course you could be saying you just want to put B + M in parallel but roll off some treble.... that too is possible with maybe a cap in that, if needed, and only in that position. Just know that the dB of M+B is weaker (just like a HB in parallel mode).
Probably best for you to start a new thread on that and you will get some responses. The key is to say what you want for the other 4 positions (stock Strat) plus we'd need to know more about your total setup (Stock Strat with position 4 with some kind of clean humbucker sound of MxB)

The single coils of my strat copy are not that hot but bridge and middle in series sounds a bit too dark for my taste. I've experimented with a lot of pickup combinations but my plan for now is to have the stock setup apart from bridge and middle in parallel. Yeah, better start a new topic. Thanks anyway!

[gckelloch]

Oct 16, 2024 7:25:46 GMT -5 mikecg said:

Hello gckelloch,

Regarding your recent link: www.aliexpress.us/item/1005006040321314.html?

You say that this is a ferrite core transformer, but I see no reference to ferrite in the description?

I would be very surprised if it was ferrite, as the permeability of even the highest permeability ferrite grades, is very much less than, Permalloy (80% Ni, 20% Fe).
Typically, the higher permeability ferrite grades (Mn-Zn) are semi-conductive, and have mu values in the 1000's, whereas transformer steel (97% Fe, 3% Si) is in the 10,000's, and Permalloy is in the 100,000's.

I would guess that your linked item describes a Permalloy cored transformer. 

EE25 references Ferrite in a search. Of course, simply labeling it EE25 does not mean it is actually Ferrite but EE25 ferrite cores like that are very cheap. The spec does claim 3.6H +/- 20% on each side. I wouldn't know if that is accurate, or what the core really is. I'm no expert in this stuff, but I think I've read that mu only affects coil inductance to a point. Even 100x the Mu of EE25 Ferrite might not increase inductance all that much. Maybe it's worth spending more for the Z11 or Permalloy deals?

[gckelloch]

Oct 16, 2024 1:34:21 GMT -5 ssstonelover said:

Oct 15, 2024 0:29:07 GMT -5 gckelloch said:

Sure, but I could just as easily have one of the switches switch between the mid-dip and tone knobs so there would be no interaction. You could use whatever cap values you want from each pickup switch lug to the tone knob. The other switch could disengage both knobs or switch the cap values on either or both knobs. You could instead assign each knob to specific pickup positions and still be able to switch cap values on either or both knobs or don't bother with any switches and just wire the mid-dip knob on the bridge pickup. Let me know if you are interested in any of those options.

Cheaper still is this Ferrite core 600/600 Ohm transformer:

www.aliexpress.us/item/3256805854006562.html?

I see no reason not to use that one. Ferrite is non-conductive and shouldn't create any eddy -currents. Each side apparently measures 3.6H. I assume one coil on either side would then be ~2H. That's what I'd use for the mid-dip. The diagram under the specifications tab shows the coil configuration. You'd just wire a cap in series with one coil and a pot to ground. You can also wire a 5~10k R over the cap if you want some bass reduction and don't want such an extreme mid-cut when it's turned way down. That network is then wired in parallel with the pickup/s.

OK, that sounds more interesting, and as this is something new to me (and probably a bunch of others here too) it merits a good drawing / wiring diagram so we can see how it all fits together. In fact It might be fun (and useful) to go from clear highs to soupy mid dips (by which I think you mean heavier mid tones) on a single guitar with flip of a switch (or two).
For modeling purposes the base you could use to overlay these mods could be a Strat layout, as that is pretty archetypical for mods.
I buy from Aliexpress already at least several times a year, so that aspect is totally fine as well.

Out of curiosity, and in your opinion, how would this compare the the Fender Greasebucket mod which is supposed to give some nice mids yet limits/avoids 'bass' mud and I assume brings down the highs and/or resonant frequency?
Different approach to the same issue (limiting ice pick yet avoiding mud) or something else entirely? That's another one I have not tried (or researched much) and as I understand it, it forms an RLC circuit (a resonant circuit comprising a resistor, an inductor, and a capacitor) so has at least some elements in common with your mid dip? (maybe without the coolness of switches however?)

AFAIK, the Greasebucket is much like a standard tone control. This is a midrange cut (mid-dip) control. Soupy/syrupy is a good description of when it's down to ~5, depending on a few factors. The H value determines how deep the mid-dip can go, and the C in series determines at what freq it starts to dip. An R over the C lets some signal by the C for some bass reduction when the pot is down low. Lower R values reduce bass more. I think it also moderates the peaks when the pot is way down. Bill Lawrence recommends 5-10k for the neck and as much as 25k for the bridge. Maybe try 15~20k as a universal value, or skip the R and just don't turn the knob down too much. I don't turn my Q-filter knob down below ~4 anyway, and I don't have an R over the cap. The other option would be to use a 5-10k R in series with the entire network so the pot can only go down to the value of that R. That can be added later if you really want.

I thought of another switching option you might want. One switch could select between the tone and mid-dip knobs. The other switch could select the C values for each knob. That might make the most sense if you don't need a switch to deactivate all tone mod options. Two switches can be pretty quickly set with some practice. I think I can use the second common lug on a 5-way switch so you'd only need 4 total caps rather than 6: a ~1n5F off each position lug, and just one 22nF coming off the common lug-- all going to their respective outer lugs of the C select switch. The center lug of that switch then goes to the center lug of the knob select switch. One outer lug of that switch then goes to the tone knob, and the other lug goes to the mid-cut knob. That should do it.

I can draw up any of the previously mentioned options if you let me know which one you prefer. Can you recommend a simple free app for that as well?


P.S. I went to take some SPL response graphs of my Q-Filter (w/5nF cap) last night by running white noise through an earbud pressed against a 2.4H pickup, and the inductor has become detached or shorted. Gotta remove the strings and open it up to see what's up. Will post graphs somewhere when it's fixed. I may change the cap to 3nF, or try different values for each pickup if it's possible with the wiring. Not adding any more switches though. Four (including the pickup selector) is already one too many. Have had luck with the push pot switches on that guitar, though, Still working after 15 years (of light use). I'd avoid push pots anyway-- unreliable in general.

[mikecg]

Oct 16, 2024 16:45:17 GMT -5 gckelloch said:

Oct 16, 2024 7:25:46 GMT -5 mikecg said:

Hello gckelloch,

Regarding your recent link: www.aliexpress.us/item/1005006040321314.html?

You say that this is a ferrite core transformer, but I see no reference to ferrite in the description?

I would be very surprised if it was ferrite, as the permeability of even the highest permeability ferrite grades, is very much less than, Permalloy (80% Ni, 20% Fe).
Typically, the higher permeability ferrite grades (Mn-Zn) are semi-conductive, and have mu values in the 1000's, whereas transformer steel (97% Fe, 3% Si) is in the 10,000's, and Permalloy is in the 100,000's.

I would guess that your linked item describes a Permalloy cored transformer. 

EE25 references Ferrite in a search. Of course, simply labeling it EE25 does not mean it is actually Ferrite but EE25 ferrite cores like that are very cheap. The spec does claim 3.6H +/- 20% on each side. I wouldn't know if that is accurate, or what the core really is. I'm no expert in this stuff, but I think I've read that mu only affects coil inductance to a point. Even 100x the Mu of EE25 Ferrite might not increase inductance all that much. Maybe it's worth spending more for the Z11 or Permalloy deals?

The basic formula for the inductance of a coil wound on a closed core (i.e. no air gap) with a relative permeability u_r, where u_r = u/u₀  is: L =u₀.u_r.N².A/l 
Where L is the inductance in Henrys (H), u₀ is the so called permeability of free space = 4.pi.10^-7 (H/m), u is the permeability of the core, N is the number of turns, A is the cross-sectional area of the core (m²), and l is the length of the magnetic circuit (m). 

This formula dictates that the inductance of the coil will be directly proportional to the magnitude of the permeability of the core material, and to the square of the number of turns.

A close inspection of the description of this EE25 inductor reveals that the 'material' is identified as 'metal', and the photo seems to show an E-I core, and not the standard EE25 E-E core pair.

My guess is that, in this particular case, the manufacturers have utilized a standard EE25 bobbin, but replaced the standard EE25 ferrite core with an E-I Permalloy core.

EE25 ferrite cored transformers are typically designed for pulsed operation or for switched power supplies, where core losses at high frequency must be minimized.
  

[ashcatlt]

We’re way down the street here, but back to the OP, I’d like to point out that in your table 3 and 4 will be the same when both pots are up all the way. I’d expect the smaller V pot to lose less treble as you turn it down because there’s less series R introduced, but I’m not willing to bet anything big on that.

Either way, turning down the existing T pot accomplishes the same thing as reducing its value, so if they turn it down til it’s sounds good, then measure it’s resistance, you can do the math to figure out the parallel value and then decide whether replacing a pot or adding a parallel resistor makes the most sense.

Also you left out option #4: Get a longer cable. It’s the same as adding a parallel cap, but doesn’t require modifying the guitar at all.

[gckelloch]

Oct 16, 2024 20:03:26 GMT -5 mikecg said:

Oct 16, 2024 16:45:17 GMT -5 gckelloch said:

EE25 references Ferrite in a search. Of course, simply labeling it EE25 does not mean it is actually Ferrite but EE25 ferrite cores like that are very cheap. The spec does claim 3.6H +/- 20% on each side. I wouldn't know if that is accurate, or what the core really is. I'm no expert in this stuff, but I think I've read that mu only affects coil inductance to a point. Even 100x the Mu of EE25 Ferrite might not increase inductance all that much. Maybe it's worth spending more for the Z11 or Permalloy deals?

The basic formula for the inductance of a coil wound on a closed core (i.e. no air gap) with a relative permeability u_r, where u_r = u/u₀  is: L =u₀.u_r.N².A/l 
Where L is the inductance in Henrys (H), u₀ is the so called permeability of free space = 4.pi.10^-7 (H/m), u is the permeability of the core, N is the number of turns, A is the cross-sectional area of the core (m²), and l is the length of the magnetic circuit (m). 

This formula dictates that the inductance of the coil will be directly proportional to the magnitude of the permeability of the core material, and to the square of the number of turns.

A close inspection of the description of this EE25 inductor reveals that the 'material' is identified as 'metal', and the photo seems to show an E-I core, and not the standard EE25 E-E core pair.

My guess is that, in this particular case, the manufacturers have utilized a standard EE25 bobbin, but replaced the standard EE25 ferrite core with an E-I Permalloy core.

EE25 ferrite cored transformers are typically designed for pulsed operation or for switched power supplies, where core losses at high frequency must be minimized.
  

That math is a bit "beyond my pay grade", and we don't know all the coil specs, but I'm inclined to favor the Z11 core pair in my first link due to all the straightforward info in the description:
www.aliexpress.us/item/2255800936817835.html?#nav-description

In fact, I just ordered a pair that should arrive between 10/24 - 10/31. I'll try wiring up a mid-dip filter with one and post the SPL graphs when I get them.

[mikecg]

Hello gckelloch,

Don't be put off by the math - I just wanted to point out that the mu of the core material has a fundamental impact on transformer design.

And I hope your Z11 pair meet with your requirements.

For those readers interested in the details of 'Magnetics' design, I stumbled across this excellent reference:

vias.org/eltransformers/index.html

Finally, I would encourage those with an inquiring mind to browse the vias.org web site.

[ssstonelover]

Oct 16, 2024 20:10:40 GMT -5 ashcatlt said:

We’re way down the street here, but back to the OP, I’d like to point out that in your table 3 and 4 will be the same when both pots are up all the way. I’d expect the smaller V pot to lose less treble as you turn it down because there’s less series R introduced, but I’m not willing to bet anything big on that.

Either way, turning down the existing T pot accomplishes the same thing as reducing its value, so if they turn it down til it’s sounds good, then measure it’s resistance, you can do the math to figure out the parallel value and then decide whether replacing a pot or adding a parallel resistor makes the most sense.

Also you left out option #4: Get a longer cable. It’s the same as adding a parallel cap, but doesn’t require modifying the guitar at all.

Thanks for all that.

Hendrix was famous for using a long curly cable, and whether intentionally, or by happy accident, would have gotten that extra capacitance you mention.

[ssstonelover]

Oct 16, 2024 18:02:31 GMT -5 gckelloch said:

AFAIK, the Greasebucket is much like a standard tone control. This is a midrange cut (mid-dip) control. Soupy/syrupy is a good description of when it's down to ~5, depending on a few factors. The H value determines how deep the mid-dip can go, and the C in series determines at what freq it starts to dip. An R over the C lets some signal by the C for some bass reduction when the pot is down low. Lower R values reduce bass more. I think it also moderates the peaks when the pot is way down. Bill Lawrence recommends 5-10k for the neck and as much as 25k for the bridge. Maybe try 15~20k as a universal value, or skip the R and just don't turn the knob down too much. I don't turn my Q-filter knob down below ~4 anyway, and I don't have an R over the cap. The other option would be to use a 5-10k R in series with the entire network so the pot can only go down to the value of that R. That can be added later if you really want.

I thought of another switching option you might want. One switch could select between the tone and mid-dip knobs. The other switch could select the C values for each knob. That might make the most sense if you don't need a switch to deactivate all tone mod options. Two switches can be pretty quickly set with some practice. I think I can use the second common lug on a 5-way switch so you'd only need 4 total caps rather than 6: a ~1n5F off each position lug, and just one 22nF coming off the common lug-- all going to their respective outer lugs of the C select switch. The center lug of that switch then goes to the center lug of the knob select switch. One outer lug of that switch then goes to the tone knob, and the other lug goes to the mid-cut knob. That should do it.

I can draw up any of the previously mentioned options if you let me know which one you prefer. Can you recommend a simple free app for that as well?

Sorry for the delayed response. Yesterday I was busy on a host of other unrelated subjects, but that is life.

I personally use Adobe Illustrator for my drawings and it has a long learning curve and can be expensive, so I don't recommend it as I'm sure there are other far easier (and free) programs out there with lots of the right templates.

I have zero experience with other free apps, so others (hopefully experienced users) can chime in, but I do see
diy-layout-creator downloadable
Best Software for Generating Guitar Schematics a discussion link on Guitar Nuts 2
guitar-wiring-graphics has lots of graphic icons
Some mention Visio....
Phostenix used Microsoft Visio 2010 and also guitarstencilsproject too it seems, which is loaded with template/icon of parts and is quite elegant. If you follow the linked page, downloadable files, and follow up links you will find a lot there. Given the quality of the Phostenix work, it would be a good path to check out.

That for the info on Greasebucket and the key differences to your proposals.

Lots of choices and options but with no personal experience on Q factor or existing visuals/drawings to guide/inform me on the switch logic choices it's a bit hard to give a strong preference or direction to you, sorry.  I'm afraid it's a little like the chicken and the egg (and which came first). I can only say make it fairly universal so others are also attracted.

[frets]

I use the DIY Layout Creator that I have customized. But the direct version you can download comes with everything you’ll need and it is free. I would recommend at least playing with it. It really is easy to use.

[gckelloch]

Oct 18, 2024 15:42:33 GMT -5 frets said:

I use the DIY Layout Creator that I have customized. But the direct version you can download comes with everything you’ll need and it is free. I would recommend at least playing with it. It really is easy to use.

Thanks. I got it and I have the last wiring scheme I suggested almost done. It's really pretty simple.

[ssstonelover]

gckelloch That's great news, I look forward to seeing it.

[gckelloch]

Here's the diagram with one switch for cap values and one for the tone knobs. The switches can be SPDT (as pictured) or DPDT.

I thought about substituting just one cap for the low values. You could try it with just one 2~3nF, but using one cap for each pickup not only makes 2 & 4 have virtually the same peak as the single pos's, but you can use different values if you want more or less "bite" on a given pickup. I wouldn't go higher than ~3nF with typical 2~3H SC pickups, although I did write 1.5~5nF on them. 5nF would produce ~1kHz peak. You could temporarily wrap 2nF over 3nF to see if you like it on any pickup. Just one 22nF should be fine on all pos's for the lower peak option.

I added an R to ground on the mid-dip pot to limit the dip and peak. You could try it with just a wire first. You could also add a 10~20K R from the 5-way common lug to where the transformer attaches to the second switch, but it will reduce the mid-dip knob bass response the same for all positions. I don't see how different R's could effectively be used for each pickup position, but you could try just one 5-10k R from the neck pos lug to the transformer connection lug if you want some mid-dip knob bass reduction on just the neck. That might make the most sense.

Of course, ground all hardware. Not sure if the transformer core can be grounded. It might reduce potential noise if the pickup noise isn't louder.

[ssstonelover]

gckelloch

I like it. It's illuminating and clears up much ambiguity. Thank you very much for that work. Looks like that software worked out well for you.

Mid dip: which frequencies get cut and by how many dB? I know this kind of depending on the resistor, value of the transformer, whether the transformer pot is at 10, 7. 3, 0 or whatever, etc, but I just want to to get a initial feel so I could 'nudge' it one way or another. I'm thinking Strat pickups don't have many mids anyway, but the concept could be really useful with thicker sounding pickups (P-90s maybe) or it quite likely I'm just missing the point here, that mid-dip is actually thicker in the mids (dipping heavily into mid but cutting higher frequencies, not suppressing them). Maybe a quick and dirty graph would clear that up for me.

Transformer: do the P and S on the drawing have any meaning (parallel/series maybe?)? I see the connections are just to the outside terminals (on just one side)

Low value caps: I'm with you on the values. It backs up what I've found in my experiments. Also having individual ones makes sense (especially for the bridge which needs the extra help).
As far as the 2 and 4 position having the caps in parallel increases 'seen' cap value so even more highs are cut, so I'm not understanding what you said, "using one cap for each pickup not only makes 2 & 4 have virtually the same peak as the single pos's". I'm thinking the peak frequencies for 2+4 are going down, but maybe because the 2+4 are more 'thin' sounding it brings them back down? Anyway let me know how I should think about this.

SC pickups: I presume the 1-3nF range for the low value caps is for the normal and low wind Alnico 5 type", is that right?
I also have to work on a lot of Chinese ceramic SC with DC 5-6K, sometimes more. I suspect these same value apply but may be tempered as some say ceramics are less bright (I have done no testing) but sometimes find them annoying bright other times not so at all, but more mid strong.