How to emulate a tone pot?

[silence2-38554]

I'm finding the Aftermaths in my Ibanez RGD to be a tad too bright.  Before swapping them out for a warmer pickup set, I also realized that this is the first & only guitar I've ever had without a tone knob.  While I never really use the tone knobs in my other guitars, I know that simply having them installed & set to 10 tames the treble a bit.  How would I go about wiring in a resistor to act as a permanently open tone pot?

[metale]

You could consider replacing the volume pot with a 300k or 280k one.

[megaup987]

Try tweaking the pole piece bolts first. Lower the row closer to the bridge and rise the ones closer to the neck. I found it helped me tame the treble of my Aftermath bridge a little bit and bring up a bit more low end.

[Skilpad]

Actually, this is quite easy; and I think it would do what you want.
Basically, you just have to replace the tone pot in wiring diagrams by a constant resistor. A 500k tone pot always set to 10/10 is just like a 500k resistor.
Practically: take a capacitor (0.022µF would be fine I think) and a resistor (500k). Solder together one side of both. Connect the other side of your capacitor to the ground, and the free side of your resistor to the non-grounded output. (So finally, your capacitor+resistor will link both connectors of your output jack. Actually, the sense as no effect.)

If you want to cut more highs, you can then change the resistor for a lower value.
If you want to keep more highs, you can take a bigger resistor (750k, 1M...). It will be like going above 10/10 on a standard 500k tone pot.

[silence2-38554]

Alright, well I wired in a 470k resistor and a .022µf cap in series between the pot's input lug & ground.  I think it helped a bit, but tremolo picking on the high E string with the bridge pickup is still pretty unbearable.  I came across this page:

http://www.guitarelectronics.com/category/wiring_resources_guitar_wiring_diagrams.wiring_faqs/

Which explains that having two 500k pots in the circuit is effectively the same as having one 250k pot.  In this case, I'm already hearing the guitar as if I swapped in a 250k volume pot rather than the 500.  I also read that the value of cap used affects the low pass frequency cutoff.  Perhaps I should try swapping in a .047 cap rather than the .022 to lower the cutoff frequency?  Or should I try a lower resistor value such as 350k first?

Also, I did try adjusting the pole pieces so that the neck side is higher.  Didn't really notice too much of a difference but may need to make the adjustment more extreme.

[Skilpad]

To sum up:
- Increasing C will mainly reduce the cut-off frequency (so at which frequency you start reducing the volume)
- Decreasing R will mainly reduce the volume kept for the highest frequency.

It seems you want to lower some given quite high frequencies, so a .022µF shall be ok (going to .047µF is more about getting a different tone).
So you shall reduce the resistor.

In fact, two resistors in parallel give a lower resistance. Actually, if R1 and R2 are the two initial resistance, you obtain a total resistance that is:  R = (R1*R2)/(R1+R2).  In particular, if R1=R2, it gives:  R = 0.5*R1 .

Note that:
- In order to find the right resistance in you case, you can replace the resistor by a tiny potentiometer (adujstable with a screwdriver). They are cheap, and you can still replace it with a resistor when you know the required value (if you want something proper). Experimenting and using your ear to find your optimum set-up is still the best!
- Just an idea: if you are just bothered by the high-pitched tremolo picking sound, you can even try to increase the cut-off freqency by using a smaller cap. Thus, you could keep more trebbles intact, and still reduce this unbearable picking noise. (Once again: your guitar, your sound. Stick to your ears, not to the "standard".)

[silence2-38554]

Great suggestion on the small potentiometer, skilpad!  I very well may do that!  The other question I had is if certain cap values give defined low pass frequencies.  For example, do all .022µF caps cut off at 12kHz & all .047 cut off at 8kHz or something?

[Skilpad]

Yes, and no.
Actually, in a first approximation, the cut-off frequency is related to the tone capacitance C, the tone resistor R, the cable capacitance (let us neglect it), and the input resistance RL of your amp/pedal/...
The cut-off freqency is then something like: 1/(2*pi*(R+RL)*C).   (Assuming I did not do an error when doing the math, but I think it is ok.)

Generally, RL is quite big. This is why R does not affect this much the cut-off frequency. Its role is mainly to define how much the highest frequencies are reduced.
Actually, reducing will lower the highest frequencies (more effect), but shall slightly increase (not decrease!) the cut-off frequency.

On the contrary, the cut-off frequency is inversly proportional to C: you double the capacitance, you divide the cut-off freqency by 2.
But still, the cut-off frequency will depend (quite a lot) on the input impedance RL of your first pedal or amp. RL will also affect a lot the level of the highest frequencies (the one you "set" with R).

[metale]

Please excuse my question, on a similar topic.

On a guitar with a P90 and a single coil, a master volume and master tone (both 550k), what would I have to wire with the single coil for it to behave a bit like it had around 250-280k pots?

[HTH AMPS]

Please excuse my question, on a similar topic.

On a guitar with a P90 and a single coil, a master volume and master tone (both 550k), what would I have to wire with the single coil for it to behave a bit like it had around 250-280k pots?

A fixed 470k resistor from the single coil 'hot' to ground would do the trick.

[Skilpad]

A fixed 470k resistor from the single coil 'hot' to ground would do the trick.

Won't it just slighty change the shunt resistance of the pickup? I doubt it will work, since you might change the resistance in series with the tone cap. (But I can be wrong...)

What shall work is using a toggle switch with at least 2 poles, that adds a 470k resistor in parallel with the tone pot when you want to have a lower resistance. (Note that when using both pickups, the tone circuit will be the same for both. Since pickups are connected in parallel, you cannot have a 500k tone resistor for the humbucker and a 250k tone resistor for the single coil.)

[Copperhead]

The Supermassive P-90 proved to be exceedingly bright and harsh in the bridge of my ash Cabronita. As you know, the Cabronita is not equipped with a tone circuit. I wired a full size 500k pot and .022 cap in the normal tone pot fashion, coming from the bridge side of the three-way switch. I rolled off the tone about 1/8 of turn on the pot. There was plenty of room to fit the new components inside the hot dog rout. Obviously I played with setting a little before I hid everything behind the cover. The slight treble bleed has worked wonders for smoothing out the pickup and getting rid of the obnoxious ice pick highs. If you try something like this consider that the tone circuit will be engaged in the middle position of the three-way switch as well. The neck pickup position will remain unmolested.

[darkbluemurder]

Please excuse my question, on a similar topic.

On a guitar with a P90 and a single coil, a master volume and master tone (both 550k), what would I have to wire with the single coil for it to behave a bit like it had around 250-280k pots?

A fixed 470k resistor from the single coil 'hot' to ground would do the trick.

It will do the trick as far as the loading on the pickup is concerned but when turned down the series resistance will still be bigger than with a 250k pot. So it does not exactly behave like a 250k pot but it is still a good option.

Cheers Stephan

[HTH AMPS]

Please excuse my question, on a similar topic.

On a guitar with a P90 and a single coil, a master volume and master tone (both 550k), what would I have to wire with the single coil for it to behave a bit like it had around 250-280k pots?

A fixed 470k resistor from the single coil 'hot' to ground would do the trick.

It will do the trick as far as the loading on the pickup is concerned but when turned down the series resistance will still be bigger than with a 250k pot. So it does not exactly behave like a 250k pot but it is still a good option.

Cheers Stephan

In practice I've found this to work to an acceptable level

[darkbluemurder]

Me, too.