Bass contour with push-pull knobs?

[Jet-Jaguar]

Reverend Guitars have this thing they call a "bass contour knob" which allows you to roll off the lower frequencies the same way you would roll off the higher frequencies with a tone knob.  Guitar Electronics sells a knob that does it as well. 

But I'm wondering If you could just do the same thing with a regular push-pull knob. I've searched the internet and haven't found anything ... perhaps I was using the wrong search terms?  It just seems like something you could do.

 

[line6man]

It is probably a simple passive HFP, similar to the G&L bass cut pots.

What you do is place a capacitor in series with the signal path, which passes high frequencies, but blocks low frequencies. Then you put a pot parallel to the capacitor to vary the impedance across it. As you start to decrease the impedance across the capacitor, low frequencies are passed to the output. The cool thing is, when you set the pot "flat," there is absolutely no effect on the circuit. The control is bypassed, so you don't need any switches.

 

[drewfx]

But I'm wondering If you could just do the same thing with a regular push-pull knob. I've searched the internet and haven't found anything ... perhaps I was using the wrong search terms?  It just seems like something you could do.

If you google the terms "rickenbacker cap bypass" you will find a lot of people use a push/pull to bypass the bridge PU bass cut cap in classic Rics.

 

[line6man]

But I'm wondering If you could just do the same thing with a regular push-pull knob. I've searched the internet and haven't found anything ... perhaps I was using the wrong search terms?  It just seems like something you could do.

If you google the terms "rickenbacker cap bypass" you will find a lot of people use a push/pull to bypass the bridge PU bass cut cap in classic Rics.

You can do that, too. All you need to do is place a capacitor in series with the signal path, and place a SPST switch across the capacitor, to bypass it.

 

[Jet-Jaguar]

Would a Fender TBX do the same thing?

 

[drewfx]

Would a Fender TBX do the same thing?

TBX is a bit different. Turned one way it's a "normal" tone control; turned the other way is described as a bass cut, but it's a different circuit and doesn't sound the same as a simple series bass cut cap. Personally, I'm not particularly a fan of the TBX, which came on one of my Stats (I rarely, if ever, turn it to the "bass cut" side), but YMMV.

But it depends on exactly what you're trying to achieve and what sound you're starting with. I believe that passive tone circuits have to be particularly well matched to the guitar to work well. For instance Ric bass cut caps on the bridge PU accentuate the natural jangle of the instrument. And the bass cut controls on G&L basses work well because G&L's MFD PU's are capable of putting out ridiculous amounts of bass to begin with. But with other instruments the same circuits might be useless.

 

[Jet-Jaguar]

But it depends on exactly what you're trying to achieve and what sound you're starting with.

I started the thread just to learn about bass cuts in general, but I'm (very) slowly putting together a tele-ish guitar. I've bought an alder Jazzmaster (telemaster) body, as well as a Seymour Duncan '59 neck, and a tapped Quarter-pound tele bridge.  The plan is to get a Pau Ferro neck. I imagine it will be pretty bright as is, but I'm thinking I could go for a bass cut if I needed to go brighter. I started thinking about it when I saw a video with a Reverend Buckshot.