12-way, variable cutoff, resonant peak, passive low-pass tone control (prototype).

I call it the 'Wolftone', it's a bit catchier than that unholy mouthful in the title...

Inspired by Helmuth Lemme's investigation of various pickup and capacitor interactions, this is an excellent DIY project for guitar hackers who aren't willing to spend a lot of cash for a pro version. I was able to put a couple together while I'm on tour, with parts readily available from Jaycar and DSE here in Australia.

Nothing annoys me more than when somebody takes common knowledge, and passes it off as mojo. I'll grant that some people out there make a very slick product, but if you have the ability to solder it into your guitar, you can make the damn thing yourself! Do yourself a favour and read this article here: http://www.buildyourguitar.com/resources/lemme/index.htm

This type of tone control relies on the interaction between your pickup's inductance and the capacitance of the tone circuit. Most people are aware that they get a boost in the lower frequencies when they dial a passive guitar tone all the way down - once the resistance is dropped, the frequency response has a steep cutoff with a resonant peak just below it. It's a fairly musical sounding low-pass filter at it's most basic; if you pick the right capacitor you can get sounds similiar to a cocked-wah effect, for example, or even a presence boost.

In a standard tone control however, there's typically only 2 or 3 positions on the dial that get used: fully on, fully off, or just a tad rolled off. Turn the tone down too much, and you lose midrange as well as treble, which results in a weaker output. The frequency resonse is a shallow slope until you hit no resistance. By switching through multiple capacitors running straight to ground, you get to take advantage of the steep cutoff to preserve as much of your signal as possible.

You may have heard of the Varitone as used by Gibson and other manufacturers - that uses the same principle, but grounds through an inductor to maintain top end, thereby creating a mid-scoop effect. The advantage to this version is that you don't have to obtain an expesnive and quite rare electronic component! I have borrowed the 10M resistor network from the Varitones however, as they keep pops to a minimum. My earlier 6-way proto sounds like popcorn through a PA system...

The rotary switch used is a modified 2 pole, 6 position switch available at most electronics retailers. In this case, one terminal has been removed, as is the stop-tab (to allow full rotation) and the two centre lugs are made common. If the resistors are wired in first, with some care, then there's plenty of room for all the components. Don't do what I did on this one and start with the caps; it's too fiddly.

The 10M pulldown resistors need to be attached from each lug to the centre terminal, then it's a simple matter of soldering each cap to the appropiate lug and tieing their ends together so they can be wired to ground (again, there's a much tidier way to do this than I achieved here, so please pardon the gaffa tape used for insulation purposes).

Smaller 6 way switches are even easier to do - the main purpose of this 12-way version was to allow me to determine which values I find most pleasing. I can then install those on a 6-way to save time & thinking effort mid-set (always important once the drinks start making things fuzzy!)

The astute will notice I haven't used a bypass position; first and foremost, I'm a bass player - there's just not a lot of content over 2.9 kHz generated by my basses, particularly as I use flatwound strings. Indeed, on the 6-way proto, I can't hear any difference between the bypass and 2.5 kHz settings. I misplaced my 670 pF capacitors when doing this one (they eventually turned up under my Toneport!) otherwise I would have used them instead of the 470 pF caps.

Finally, if you've got the capability, import the audio into a wave editor & look at the waveform plotted vs dB. All but the last setting (0.1uF capacitor, cutoff around 200 Hz) on the dial have very consistent outputs. I noted some signal attenuation in the clip - in practice, through a pumping PA system, that 200 Hz cutoff sounds enormous and would be fantastic for Dub or Reggae.

cheers,

Wolfy // Rude Mechtronics

Category:

Music

Tags:

• passive tone
• varitone
• stellartone
• low pass filter
• rude mechtronics
• Helmuth Lemme

[xxmanx1]

Hey!! If you can make one of these for guitar in a small box that can mount on my strap please email me!!

[rud3m3chanical]

@xxmanx1 - wouldn't be a bad idea; you could make it kind of like the old Orange Squeezer that plugged straight into the jack.

[DavidRavenMoon]

Keep in mind that the cutoff frequencies listed will change depending on the impedance of the pickup, and the value of the volume and tone control pots. Hotter pickups will have lower cut off frequencies. I've been using .022 caps in many of my basses for years. It rolls off the top end, but leaves he mids. There's nothing wrong with getting high end from a bass, and it allows you to be heard better in the mix. Even the old Motown recordings had more highs on the bass than people think!

[rud3m3chanical]

@DavidRavenMoon: Helmuth Lemme's original article is linked above.

The key thing with this tone control is that you are achieving the steepest possible attenuation (for a passive device, anyway) at a frequency of your choice.

As for basses and high end - I remove or fully attenuate the tweeters in my cabs, so most of them roll off around 2.5kHz at best. Still plenty of brightness from roundwound strings and active basses.

[belmontmaster]

can you provide the wiring diagram? and the value of the caps and the resistors ? i have the switch, and a bunch of resistors and capacitors, but i need to know how is wired and the value of the caps and so...

[rud3m3chanical]

@belmontmaster

10M resistors. Capacitor values are displayed in the viedo itself. Do a Google Image search for 'varitone' and you'll turn up heaps of schematics :)

[Drblooter99]

Great pal -- thanks to this, I replaced my bass's factory 0.0223uF cap with a mylar 0.1uF cap, and THEN I added a .047 uF cap in parallel, for a total of .147uF. Now I got a very tight compressed sound. I hate treble, and so I should -- it's for guitarists!

[ivandruping]

Mate... I use your vid for test the condensors of my preamp...

[PhuckHue2]

@rud3m3chanical I made a 12 pos varitone in a box and it sounds great. I hooked the inductor to a DPDT switch to turn it on/off. thanks