tonefiend's "experimental" tone control

[theswiftbrownfox]

hey guitarnuts!

Lurker here,don't often post but wanted to get your opinion on something.
I had been thinking lately about how one could wire a tone control with a variable cutoff frequency.
a little googling brought me here: tonefiend.com/diy/new-tone-control-concept/
it's an interesting idea, and in another one of this guys post he shows off a build with 3 lipstick style pickups
and this kind of tone control and it does sound pretty good!
Couldn't find much else information on this type of tone control. does sound appealing though, i want to give it 
a try when i can get the chance. just wondering if anyone here has any experience with this kind of thing or something
similiar. 

[JohnH]

Hi and welcome back

Id say that gadget would do what it says, but I dont think that I would like it because there would never be a fully bright max tone setting. Always at least the small cap is there, in parallel with a normal tone circuit. I might like it bette with a fully 'off' switch though, maybe a push pull switch on tbe same pot to completely disconnect it.

[theswiftbrownfox]

ya i would think a push pull to take the caps completely out would be a must. i'm really intrigued by this. i got into analog subtractive synthesis awhile ago, and now that i am actually thinking of the tone knob as a low pass filter it seems weird that you can't adjust the cut off frequency. Could you use another pot before this one as normal "mix" control? maybe a no load for that pot, instead of a push pull to take the caps out of the circuit? since i've heard of this its been stuck in my mind(don't have a guitar i can try it on currently). i've been thinking it would be interesting to have the variable mix and cutoff frequency for high cut and low cut. 5 pots total with master volume. do you see any reason this wouldn't work?

[theswiftbrownfox]

So I've been thinking about this variable cutoff frequency tone control again as i may have a guitar to try it in. I'd really like to figure out a way to have the cutoff frequency variable while retaining the "amount" control like a typical tone control. I've drawn up  what i think the wiring would look like for a three knob version (volume, hi cut amount and hi cut cutoff frequency) and a five knob version based on a PTB tone control (Volume, Hi cut amount, Hi cut Frequency, Low cut amount, Lo cut frequency). I'm not sure about the capacitor or potentiometer values, or what having that many pots in the circuit would entail. I was thinking the "amount" knobs could be no load? not even sure it would be very usable. so if anyone can tell me if my diagram makes any sense, or can see any other problem with this, it would be much appreciated

seems like i'm having trouble directly posting the pictures, but they're both right here
imgur.com/a/9V6jj

[JohnH]

A much better way to vary the frequencies with one knob, with the 'amount' on another, would be a rotary switch to switch capacitors (up to 12 if you want), with a pot to vary the amount.

The two-cap-with-pot system for varying frequency will probably not sound so good in the in between settings. Id suggest trying a test build first.

[theswiftbrownfox]

hmmm, i see what you're saying about the rotary switch and many capacitors but i don't know why it would sound any better than the two capacitor method. as long as you had the right two capacitors and the right value and taper for the pot. i'd prefer to make this work with the two capacitor method as its for a jazz master with already modified wiring and the cutoff frequency knobs could go where the rhythm circuit thumb wheel vol and tone are, i don't think i could make rotary switches work in there... but yes i guess a test run is in order. did you take a look at the diagram i drew in the link? does that make seem to make sense? I'm pretty sure about the high but but not so sure i've got the variable low cut right.

[newey]

seems like i'm having trouble directly posting the pictures

Direct posting of images isn't supported by the forum software. You have to host the image elsewhere.

Here's how: Image Posting

I'm not sure on your low cut control either, we'll need to get more eyes on that. I think JohnH's point is that, with a rotary to select your caps, you only have two potentiometers (V and T) loading the circuit instead of three, as you're doing. With 2 pots in series (for just the HPF side; double everything for the 5-pot version), things could tend to get muddy.

[sumgai]

foxy,

newey has observed your potential problem correctly - putting that many pots into the circuit will reduce your tone to a pig-sty's worth of mud.... and that's just from the pots going to ground, effectively adding impedance in parallel with the pickup.  When we count the capacitance factor involved, things really get out of hand.

Your HPF additions are noteworthy, but I think that again, you've introduced more resistance directly into the signal path (instead of shunting it to ground), and this will greatly reduce your overall volume output, I should think.   And that's before you turn the Volume pot down any amount at all.  Reducing the overall volume just adds more resistance into the signal path, and combined with the HPF two controls, I'm fairly sure that you're not gonna like having to constantly fiddle with everything in an attempt to achieve that Mojo^® Tone.

Overall, a switch with various capacitors is a better choice insofar as reducing load is concerned, but then again, unless you have an ironclad recording contract, and earned it for having this exact tonal control capability, then no one is gonna realize the effort you've put into devising a modified tone circuit like this. What I'm saying here can be boiled down to one phrase: The KISS Principle.

For further cogitation on these, and other kinds of tone modifying circuits, you should take a gander at our sub-forum, Tone Control Discussions.

HTH

sumgai

[JohnH]

I thought Id show you how those tones pots might act. These are frequency response plots using the treble cut only. They assume a PAF pickup and all 500k log pots. The issue with the design is whether or not you find the in between settings useful, since they are not the same as an in between cap value due to the extra resistances:



The dark blue is full treble, and the other positions show what happens if you turn the treble to minimum and sweep the capacitor pot. The tendency appears to be a range of not so interesting muted sounds in the mid settings of the cap pot

Alternatively, if you have a switch with various cap values, you get a sweep like this:



..which shows a better sweep of capacitor-induced peaks as you turn the switch knob.

But I think your diagram works ok, if this is what you want to do.

Im not so concerned about the max settings. You should still get the same tones at max treble / no bass cut as any normal wiring, and you can use a no-load pot for the treblw cut if you want a bit more.

For the bass cut, to get the max effect, use as high a value pot as possible. 1M is probably a good choice. Log is best, wired so no bass cut is at 0. (even better, a reverse log pot, no bass cut at 10)

[reTrEaD]

I think John's assessment is correct. Your two-capacitor, two-pot approach does have some merit. But the "frequency" control won't do the same thing as changing the value of the capacitor. It might do enough to satisfy your needs. And the loading effect won't be any worse than an conventional treble-cut arrangement.

May 9, 2016 22:22:12 GMT -5 theswiftbrownfox said:

i'd prefer to make this work with the two capacitor method as its for a jazz master with already modified wiring and the cutoff frequency knobs could go where the rhythm circuit thumb wheel vol and tone are, i don't think i could make rotary switches work in there.

Yes, I would think adapting a rotary switch to a thumbwheel arrangement would be a monumental task.

Could you use your thumbwheel pot as a conventional treble-cut control and place a rotary switch to select the capacitor in the physical location where the normal tone control currently resides?

[hattydamp]

I view tone controls as essential. I also on the other hand try to limit their use. You mentioned if steve mastered every recording, and while true it may be much better sounding and neutral, that would still leave all the abnormalities of room and hearing responce on your part, plus many recordings are simply mixed or recorded differently and even with a consistent mastering engineer, most recordings would still vary in sound quality and also in relative tone. Some stuff simply sounds better with a tad more or less treble or bass, and no equipment or room treatment will change the fact that most recordings dont have the same relative tonality.