Single knob tone control question.

[Ice-9]

I have recently been messing with FETs for overdive circuits but have never been happy with the BMP type tone control. It does give the required top end but when its in the bass position it just losses all high end making the bass response very muddy. I know i'm asking a lot from a  single pot control and I have played with different values and also used Duncans tone stack calculator to improve the response.

I have tried a Baxandall 2 pot control which is a lot closer to giving the control I like, ie treble up gives a nice bite without affecting the bass too much and that is also true of the other way round. I was just wondering if anyone has had any better results using a one pot setup and if so what type of schematics have you tried.

Thanks

[~arph]

This:

http://www.muzique.com/lab/swtc.htm

Treble boost/cut without affecting bass.

Not better than the James stack, which uses two pots .( http://www.ampbooks.com/home/amp-technology/james-tonestack-analysis/)  though. That gives you the option to dial in scooped or boosted mids too..

[Mark Hammer]

In past, I've raised the idea that there are essentially two categories of tone control.  One is what you might call a "re-voicing" control, as exemplified by the BMP format.  The other is a compensation type of control, as exemplified by the original SWTC and things like the Rat filter control.

The one is directed at changing the sound in a fairly substantial way, and the other is directed at trimming something that you might have just a little too much of, given the amp settings.

I'm not saying you have to pick one or the other, but given that they are both passive, there needs to be some sort of additional gain stage added to the mix to make use of both categories in the same pedal.

The "contour" control found on some amps, and the tone control I borrowed from Alessandro Charissis for the Chaos distortion ( http://hammer.ampage.org/files/Chaos.gif ) are nice examples of single-knob re-voicing controls that don't give you an excess of anything when changing the tone, without excessive passive loss.

[Ice-9]

Thanks guys,

I have tried the James stack as I mention, it does get me to what i wanted but obviously the drawback on this pedal I really only want one pot to control the tone. I like the look of the tone control in Marks Chaos circuit, to me it looks like an adaptation of the BMP stack but the configuration looks like it may offer more flexibility to tinker with the values.
I'm off to Scotland for the weekend to get pished so won't be able to have a tinker till Monday.

BTW the circuit i'm working on is a low gain SSRP FET based distortion for a blues sound. The first stage runs quite clean giving a boost to level that drives the second stage FET's into breakup. Nothing flash but I think it's getting there soundwise.

[edvard]

Try the "tilt" control towards the bottom of the page here:
http://gilmore2.chem.northwestern.edu/projects/equal_prj.htm

Or try out this circuit that I worked out sometime around the late 90's/early 2000's, before I discovered the Internet:

This is straight out of my personal notebook, re-drawn in ExpressPCB.
The component values will most likely need some tweaking, but as I remember it sounded pretty good tacked on the end of a Bosstone.
I also remember something about the 22k resistor serving double duty as a tapering resistor as well as another node in the filter network, so if you experiment with a different pot, keep that resistor at ~20% of the pot value.
Or not...

Mr. Orman must have picked this up telepathically at some point, because the "combined" version of his Stupidly Wonderful Tone Control 2 was designed with VERY SIMILAR thinking involved   :
http://www.muzique.com/lab/swtc.htm
The only difference is I knew nothing of Mark Hammer or anybody else at the time.
All I had back then was a hand-traced Op Amp Big Muff, a PopTronics article on filters, and a friend who let me repair some pedals for the music shop he worked at.  

Learned a lot back then...

[CynicalMan]

This is a good mod for the BMP to make it act like a shelf filter on either side, thus avoiding losing all bass/treble.



If you want a more subtle control use a 50k pot and change C1 to 10n.

[Ice-9]

This is a good mod for the BMP to make it act like a shelf filter on either side, thus avoiding losing all bass/treble.



If you want a more subtle control use a 50k pot and change C1 to 10n.

I like the look of the graph,it really seems to do the bass/treble the way I'm looking for. To put this into real terms with the schematic of the BMP and this variant , to me it looks like a std BMP with the addition of a parallel cap (C1). I will give it a try also as it looks promising

[Ice-9]

Try the "tilt" control towards the bottom of the page here:
http://gilmore2.chem.northwestern.edu/projects/equal_prj.htm

Or try out this circuit that I worked out sometime around the late 90's/early 2000's, before I discovered the Internet:

This is straight out of my personal notebook, re-drawn in ExpressPCB.
The component values will most likely need some tweaking, but as I remember it sounded pretty good tacked on the end of a Bosstone.
I also remember something about the 22k resistor serving double duty as a tapering resistor as well as another node in the filter network, so if you experiment with a different pot, keep that resistor at ~20% of the pot value.
Or not...

Mr. Orman must have picked this up telepathically at some point, because the "combined" version of his Stupidly Wonderful Tone Control 2 was designed with VERY SIMILAR thinking involved   :
http://www.muzique.com/lab/swtc.htm
The only difference is I knew nothing of Mark Hammer or anybody else at the time.
All I had back then was a hand-traced Op Amp Big Muff, a PopTronics article on filters, and a friend who let me repair some pedals for the music shop he worked at.  

Learned a lot back then...

Thanks Edvard this also looks good, i shall get this one breadboarded up and tinker to suit.

[~arph]

Wow I see some nice one knob controls I haven't come across before! always inspiring this place

[Ice-9]

Indeed, every man needs some knob control

[ayayay!]

Also check out the Boss BD-2 tone control.  Very similar to the SWTC and you can fiddle with the input cap on it quite easily for more/less bass. 

[edvard]

It's been a while since I actually implemented my own tone control, just tried it out on a 4049-based circuit.
WOW!!
You can really hear stuff happening throughout the whole sweep, I wonder what's actually going on?

BRB, gonna run this through LTSpice...

[Ice-9]

I'm pretty much done on the tone control now, just a little tweaking to do now. I have breadboarded all the options you have all given me and what seems to work best is a slight variation on the BMP but i am torn between the one CynicalMan pointed me to and the circuit Edvard passed on to me as well. I think I will have a final decision by the weekend when i can get the chance turn turn the volume up on my amp and in turn would like to share the final full schematic and layout if anyone is interested in a LOW gain amp driver type of effect.  Thanks for all the input everyone.

[thetragichero]

This:

http://www.muzique.com/lab/swtc.htm

Treble boost/cut without affecting bass.

+1
so simple, sounds good!

[resansom]

Here's a vero board diagram for CynicalMan's shelf filter, which I call a "single knob tone control." I've used this circuit in about a half-dozen otherwise tone control-less pedals and it has never failed to impress me with both its simplicity and its usefulness.  I highly recommend you try it if you are looking for a low-parts, single knob, bass and treble cut/boost capability.

...If you want a more subtle control use a 50k pot and change C1 to 10n.

If you want to experiment, I recommend using a socket for the 4.7nF capacitor and trying values from 1nF to 10nF, along with a B50K tone pot.

[ElectricDruid]

In past, I've raised the idea that there are essentially two categories of tone control.  One is what you might call a "re-voicing" control, as exemplified by the BMP format.  The other is a compensation type of control, as exemplified by the original SWTC and things like the Rat filter control.

The one is directed at changing the sound in a fairly substantial way, and the other is directed at trimming something that you might have just a little too much of, given the amp settings.

I've been thinking about similar things recently, and like you I came to the conclusion that there are basically two types of tone control for guitar pedal use. However, the two types I came up with are slightly different to yours, so please indulge me for a moment;

My "type 1" is the mid-boost/mid-scoop control. Many pedals have one or the other of these responses, and the tuning of what exactly is "mid" is crucial. "Type 2" is a tilt control, offering more bass/ less treble or less bass/more treble. Again, where these cross over is a key factor in how it sounds.
Seems to me that most of the time, when you want to change something, you want one of those four things. Of course, that's still a lot of variables - both of those controls could have a "frequency" control at which they take effect, and an "amount" control that controls the amount of cut/boost or tilt either way. So either you choose some numbers for a given situation, or you offer several knobs.
The modified BMP stack that CynicalMan posted turns it into a clear tilt control, whereas the original has much more mid scoop character, at least in the centre.

It's a fascinating area for experiments, because any circuit that can "do it all" is going to have a lot of knobs and be pretty complicated. So then there's a clear need for something that can do "all the useful stuff" or even just "some of the useful stuff" with only one or two knobs.

T.

[Mark Hammer]

I really like the single-knob/3-way-toggle arrangement I implemented in the "Aefea Drive" ( https://www.diystompboxes.com/smfforum/index.php?topic=107216.0 ).  I was pleasantly surprised by how broad a range of tones could be obtained.  The 20k "shift" control moves the point of the midscoop around, but can also act as a variable lowpass filter in the middle switch position, or as a variable mids and upper bass, when the switch engages the 36k resistor.  It doesn't provide the mids-boost of the circuit that Tom is fond of (and is often labelled as"Contour" on many amps), but offers a lot of variety.  I used something similar to the contour control on the "Chaos" distortion, years back.  The distortion was nothing special but the tone control was nice.

Having said that, I'll stand by the distinction between "revoicing" and "tone-shaping".  The contour-type control strikes me as one for revoicing a guitar and giving it a different character.  I say this because full scoop and full boost will generally sound like two different guitars.

[ElectricDruid]

Totally agree about a distinction between "revoicing" and "tone-shaping". It's really just a question of how you see it and how you choose to divide up the possible responses. You were perhaps focusing more on the end-user's purpose, whereas my interpretation was focusing more solely on the frequency response without regard to purpose.

So yeah...same, but different. Like people.

Sorry, I think I might have hijacked this thread a bit. Apologies.

T.

[pinkjimiphoton]

i know some will say nope, but try faking a variable cap where ya would put a snubber cap in the b/c feedback loop of a transistor. the bigger the cap, the more treble reduction with little loss of gain.
so like, try a 250k-ish pot <my fav> and stick a 2.2n-4.7n cap on pin 3 , a 22p - 100p cap on pin 1, tie the ends of the caps together and take  that end to b and the wiper of the pot to c.
as ya sweep the pot, you reduce treble frequencies. if it sweeps backwards <my hippy brain is tired> just reverse the connections at b and c.
its been my fav tone control now for a while, if all ya need to do is shave off noise and high end. the bigger the cap is when ya turn it down the deeper into the mids it will cut. i like 47p and 2.2n for guitar use.
to me, it doesn't seem as lossy as most other tone controls i've tried. ymmv and probably should.

[sixthfloor]

There's also the blackstar ISF tone control which uses a single knob. See this link for more in-depth info :

http://revolutiondeux.blogspot.com/2012/05/blackstar-isf-control-whats-going-on.html

EDIT : my excuses, that would be two knobs actually. One for mid frequency (ISF) and the other for the mids themselves. If one desires, additional pots can be added for bass and treble too.