Simulated Coil Tap?

[gckelloch]

Jan 6, 2023 15:10:08 GMT -5 asdaven said:

Jan 6, 2023 14:38:25 GMT -5 JohnH said:

yes exactly right!

One side of your switch connects the tone control to the volume pot, for normal use. When you pull the switch, it disconnects it.

You have the 330k and 0.56nF cap in parallel, all I'm series with the hot lead of the pickup. The second side of the switch bypasses the R and C to get the full P90 when pushed in, but disconnects when pulled out.

I'll sketch a diagram.

Thats an idea.


It would be nice to have a tone control on the single coil mode to tweak the sound though so its not a wide open bright sound.

I wonder how going up to a 680K resistor would affect things?

And I guess putting the resistor in series with capacitor would just have the same affect as the volume pot?

First, I deleted the part in my last post about 50's wiring affecting the peak. It doesn't make sense that the peak would change with the Volume pot up. I used GuitarFreak v6 to determine that, but I don't think I configured things right. The peak should be 5dB down with the 50s wire as well.

I'd assume a 680k R would just reduce output below the peak a bit more than 330k. At some point the R value will be high enough so the majority of signal passes through the cap, and increasing the value more shouldn't matter.

You'd need a much lower R value in series with the cap to not decrease output too much, and I think it would lower the peak freq. I'd stick with the RC in parallel.

You can actually wire the P/P to use the tone knob with the pickup on one setting, and the R//C in series with the pickup on the other setting, but with the P/P pot acting as the R. That would allow increasing the output (up from -6dB?) while decreasing the peak level as you turn the knob down. Again, adding the pot in parallel with the pickup would reduce the peak so much that the pickup would sound virtually like it would without the R//C in series. It might make more sense to leave the tone pot off the standard P90 setting, and just wire a 500k R (or 1M trim pot?) over it. Not much point in turning the tone down for that setting if you get the peak sound you like. Then you can leave the knob where you like it for the R//C setting.

I'd try that, but you'd really want the very low C cable so the peaks for two switch settings are different enough to be worth it, and so the R//C peak is above the most harsh 3-3.5kHz range. You could source and order 5 or so ~120pF caps. BYOC has 100pF ceramic caps for $1 ea. Overpriced, but they are close enough to 120pF. Get some 47pF or 51pF to fine-tune things if you want. Use just one 100pF for the R//C switch setting, and wire one in parallel with the pickup on the other setting to lower and sharpen the peak freq a bit. Then try wrapping on one or more caps over that one until you find the peak freq and emphasis you like best, and solder them on. I find ~2.2kHz has a certain "smooth edge" I like. Above that gets more gritty and below is smoother. No right or wrong choice.

[JohnH]

With 50's wiring and GuitarFreak, in 50's position, the tone pot is after the volume, and so also after the bass cut. In Modern position, I put the tone before the bass cut. Sp although usually, at full volume 50's and Modern wiring are the same, if bass cut is also engaged, then they differ. I chose to arrange it that way so that PTB wiring can be modelled as intended.

gckelloch - Im happy that GF6 is working for you. If you see an arrangement that looks interesting, you could take a screen shot, either full screen, or just select-copy a chart and paste into a graphics program. TBH, I wrote most of GF on excel from a few versions back, mostly 2007 and 2010. Now, all my computers are running the latest Excel 365. it still works ok but the sliders are not sliding smoothly like they used to. Have to click on each end of the slider to shift them. hmmmm...

[asdaven]

Im wondering about being able to use the tone control with this "new" tone. If I wire it to bypass then I have no tone control. Dont know if a 680K resistor or a smaller value capacitor would do anything to adjust for the tone control being in the circuit? Its also relative too because the tone control is the circuit normally.

[JohnH]

Not really. Going to a 680k resistor instead of 330k will cut more bass, wheras having te tone pot in circuit, even at max, will cut away at the high treble that you are trying to create to make this 'tapped' or 'SC' sound

If any of these ideas are of interest, then you should try them as a test. Then you can make sure that the added sound is good after picking which values you like best

[asdaven]

But on the graph, isnt the single coil sound curve im trying to emulate also going through a tone control as well?


What about a capacitor down near .25nf or .2nf?

Thanks

[JohnH]

Yes, but a real SC that we are trying to get near to comes from a light, bright, low inductance single-coil. We are trying t fake that by carving the tone out of that of a big, thick, high-inductance P90. So to get anywhere close it will need as many helpful measures as possible, which includes reducing load with no tone pot.

Im sorry I cant run any more curves for a while now, Im back at work tomorrow then overseas after next week. Happy to keep chatting if it helps. Seriously, if you want to do this , you should get a few parts and try it for real. Only that will allow you to decide what you like.

[asdaven]

Thanks for the help-

I got resistors on the way to try. Im just trying to achieve what a coil split or parallel wiring does to a humbucker. Yes its not a true single coil but just trying to emulate that. Thats what im trying to do here. A P90 is a single coil but with a humbucker output.

Ideally, id like to retain the tone control even in this mode. I dont know if that can be adjusted out by tweaking the resistor or cap values or not with the 500K pot on 10 as a reference point? Or which direction should I tweak your intial recommendation if im keeping a normal tone pot. Im trying to round out the sound without being too bright. I do see why I need a resistor because the cap alone just takes the bottom end out much like with the volume turned down with 50s wiring. The cap alone only accounts for one side of the spectrum. Its the same sound with just the bottom end taken out.

I do see this on the graph but I might need to try it in real life. Ive tried no load pots in my guitars and the difference between no load and a normal pot at 10 has always been negligible to my ears especially so with a 500K tone pot. Ive always gone back to a standard pot. Im also using a .022uf cap on that tone pot. But that doesnt play as much as a role on 10. In my experience, the volume pot plays a much bigger role in affecting the tone and placing a load on the circuit than the tone pot on 10.

That could be a consideration, bypassing the volume pot vs the tone pot with this. And maybe the tone pot could be used in a way to adjust volume. I was noticing with the cap only bass cut...the tone acted more like a volume and completely silenced the guitar on 1.

[gckelloch]

Jan 8, 2023 11:57:34 GMT -5 asdaven said:

Thanks for the help-

I got resistors on the way to try. Im just trying to achieve what a coil split or parallel wiring does to a humbucker. Yes its not a true single coil but just trying to emulate that. Thats what im trying to do here. A P90 is a single coil but with a humbucker output.

Ideally, id like to retain the tone control even in this mode. I dont know if that can be adjusted out by tweaking the resistor or cap values or not with the 500K pot on 10 as a reference point? Or which direction should I tweak your intial recommendation if im keeping a normal tone pot. Im trying to round out the sound without being too bright. I do see why I need a resistor because the cap alone just takes the bottom end out much like with the volume turned down with 50s wiring. The cap alone only accounts for one side of the spectrum. Its the same sound with just the bottom end taken out.

I do see this on the graph but I might need to try it in real life. Ive tried no load pots in my guitars and the difference between no load and a normal pot at 10 has always been negligible to my ears especially so with a 500K tone pot. Ive always gone back to a standard pot. Im also using a .022uf cap on that tone pot. But that doesnt play as much as a role on 10. In my experience, the volume pot plays a much bigger role in affecting the tone and placing a load on the circuit than the tone pot on 10.

That could be a consideration, bypassing the volume pot vs the tone pot with this. And maybe the tone pot could be used in a way to adjust volume. I was noticing with the cap only bass cut...the tone acted more like a volume and completely silenced the guitar on 1.

Say asdaven, I can't tell if you want me to participate or not. You have yet to address me or comment directly on anything I've offered, but I think I have a good solution for you.

First, I think we all know you want to emulate a lower inductance SC with a P90 at this point. Pickup output has little to do with being a SC or HB. Output has mainly to do with inductance, permeance, and magnetic power within a given design. FI, Filtertron neck HB pickups are lower inductance than typical Fender Strat SCs, but they have an efficient magnetic circuit and high permeance Steel screws...and a Steel plate on the bottom of an AlNiCo V pole Fender SC will increase the output and reduce the Q (resonance peak).

The T pot on the series wired R//C (in the diagram at the link below) will increase output from roughly -6dB (compared to without the R//C) and round off the peak as you roll it down. That should help shape the SC sound as you want. Although, it will be rather bright at 0 because the 100pF cap will then be fully bypassed and the R load on the P90 will only be the 500k V pot. You could try a low-value R (like 10~20k? John H might know better) as the line going to the T pot from the upper-left switch lug so that won't happen, but you might not ever want it down that low anyway. Again, the intended results are calculated with a very low C cable, internal pickup C of ~100pF or less, and a 1M Ohm preamp input:

drive.google.com/file/d/11fDiWcXBiqMXtEzt5unw2rpJYNtg2ZOV/view?usp=share_link

You can wire the other switch setting either with or without the tone pot and use 50's or modern wiring if you like. Notice the two "or" options in the diagram. It's very unlikely the guitar will sound too bright with my recommendation. To begin with, the Steel screws in the core of a P90 will reduce the high end at the assumed ~4kHz peak by several dB. All mahogany glued-in neck guitars also aren't as bright as Maple neck bolt-ons. If anything, it may not be bright enough. Raising the P90 pole screws and lowering the coil to compensate will slightly increase brightness.

I'm not sure what bridge alloy the SG Jr came with, but you might even want to try an Aluminum bridge if the stock bridge is Zinc (pot metal):
www.ebay.com/itm/192708433616?chn=ps&mkevt=1&mkcid=28

Aluminum wrap-arounds have a chimey round brightness with a "guttural" midrange you might like a lot. Sounds more "lively" than pot metal, and is a cheap mod. Just make sure the measurements are correct b4 ordering.

That's really all I can offer on this. I'd love to hear a demo if do you use my wiring schema.

P.S. 01/10/23: You had asked about using ~5nF on the tone knob. That would give a standard 600-800Hz peak on an average ~7H P90. You'd want ~4nF for that on your ~9H P90. The peak would be very pronounced when the knob is at o. Grounding the outer lug on the T knob will reduce the peak a little, and shouldn't have any effect on the R//C setting.

[asdaven]

The guitar is actually plenty bright as it is. Its a Jr. Model so its bridge pickup only, no neck pickup. Don't know if I made that clear. I think too bright is actually the bigger concern. Im just simply trying to emulate a lower powered pickup wired to push pull to go from normal to "virtual" coil tap since this pickup cant be tapped since it dosent have the wiring nor was would like that. Nor can it be coil split because its not a Humbucker. Bridge pickups need a high powered pickup to not be too bright or thin.

So I need to be careful how much I cut because I suspect it ll turn into a thin icepicky sound. Also why I want to retain the 500K tone control even while virtual coil "tapped". But still need to retain enough lower frequencies to work with or the tone pot will essentially "shut off" the guitar.

Another idea could be to wire the tone control like a "greasebucket" tone control to make the tone control more usable and less muddy at the lowest settings and could probably get a more range of sounds out of the guitar.

[JohnH]

You are just going to have to try for yourself, only then will you know if what you have is what you want!

BTW, theres no magic in Greasebucket circuits (see in our tone controls section). The tone is virtually identical to a normal treble cut, except that at 0 where a normal tone will give a low honk sound, a GB wont do that and at 0 it sounds much like a normal tone at about 1.

[gckelloch]

Jan 12, 2023 15:29:46 GMT -5 asdaven said:

The guitar is actually plenty bright as it is. Its a Jr. Model so its bridge pickup only, no neck pickup. Don't know if I made that clear. I think too bright is actually the bigger concern. Im just simply trying to emulate a lower powered pickup wired to push pull to go from normal to "virtual" coil tap since this pickup cant be tapped since it dosent have the wiring nor was would like that. Nor can it be coil split because its not a Humbucker. Bridge pickups need a high powered pickup to not be too bright or thin.

So I need to be careful how much I cut because I suspect it ll turn into a thin icepicky sound. Also why I want to retain the 500K tone control even while virtual coil "tapped". But still need to retain enough lower frequencies to work with or the tone pot will essentially "shut off" the guitar.

Another idea could be to wire the tone control like a "greasebucket" tone control to make the tone control more usable and less muddy at the lowest settings and could probably get a more range of sounds out of the guitar.

I thought you said the guitar sounded muddy? Ok, so don't change the bridge. Again, we understand what you are trying to achieve. You're not exactly dealing with a pack of monkeys here...maybe, closer to a chimp in my case . To be clear, tonal "brightness" has more to do with the level of the peak in the 2-5kHz range (mainly 3-3.5kHz) than how much the high end extends, i.e. a Hi-Z pickup with a strong 3.2kHz peak will sound brighter/harsher than a Lo-Z pickup that extends evenly up to 20kHz, but strong string harmonics above ~2kHz will create more harmonic clashes when more gain is applied due to slight string harmonic sharpness related to tension.

Timbral thinness also has to do with the balance of lower to upper note harmonics. Raising the coil and lowering the pole screws will help with that a bit (albeit, more so with a denser coil), as does keeping a peak in the 2-5kHz range down. Your P90 may even be as high as 10H depending on the coil tension. I assume thinness is not an issue with the two 500k pots.

I made a few additions to my wiring scheme. Notice the 3rd "or" option, and the 50~100pF value for the series cap. ~50pf would lower the peak level a bit more and may be needed to keep it enough above the 3-3.5kHz range to minimize harshness. Might as well try 50pF first.

drive.google.com/file/d/1fgVQBR5C8lKa987dLAXrkllQTl4VTMY3/view?usp=sharing

[ashcatlt]

Edit - Ah heck! This was in reply to unreg’s post 28-29. totally missed the second page of the thread!

guitarnuts2.proboards.com/thread/10178/simulated-coil-tap?page=1&scrollTo=107285


A slightly over simplified way to look at it is that a capacitor is like a resistor whose value is large for low frequencies and gets smaller at higher frequencies. A resistor in series with that makes that “resistance” look that much bigger for all frequencies. Neither (alone or together) really does anything except as a part of a voltage divider with some other component(s).

A V pot usually increases series resistance while decreasing parallel resistance. How and why that matters also depends on about everything else.

[asdaven]

So did something testing today. Tried several different combos and tried resistor only and cap only and RC with different values. And yes this is with a 500K normal tone pot.

Resistor only is out. I wanted to see what would happen with resistor only. Its what I suspected...the same as rolling off the volume pot.

Doing Cap only gets thin in the lower values. .0033uf was as low as I liked and was a little too much. Mightve been the best value for this route or maybe the .0047uf. Then the problem is if you go too high, you lose the effect of it being a different sound.

So that leaves the RC combos. I didint have a .56nf cap. But had 2 silver mica caps (.5nf and .68nf). I like the .68nf cap the best here. I like 330K resistor in parallel for all the combos. I also tried a 1nf cap and thats what in the guitar on my temp hookup right now. .5nf, the closest I had to .56nf was just too thin. I dont know if its me trying to compensate for not having a no load pot or my ears just like less cut more. With .68nf and 1nf combos, I can turn the tone pot all the way down and have a little sound still. When theres more cut, the tone pot can practicaly turn off the guitar. That tells me its cutting alot of frequencies. The .68nf might be the sweet spot for this guitar.

[asdaven]

I think im going to abandon this idea and go back to the drawing board. I was able to get good tones with some of these values but I think im just going to redirect to a more simple approach of either wiring it up 50s style or a special treble bleed. Because honestly I feel with the correct treble bleed values in place, these tones can be mimiced by turning down the volume knob and letting the treble bleed do its thinner and getting a more single coil tone that way.

I really do like the effect 50s wiring has and the milder treble bleed it gives. But I HATE how turning down the tone turns down the volume. If there is "mild" treble bleed that mimics 50s wiring, id be for it. I dont like the typical values, it makes the sound tinny and I hate it. Kinman ive had the best luck , never have had luck with parallel treble bleeds but ive only tried the typical values.