Passive electronics: Mid cut

[pandathe3]

So we all know that we can only cut frequencies with a passive electronic system. Our tone knob rolls off treble.

What capacitor would i use too roll off mid frequencies? Or maybe build a switch that will cut certain mids? Maybe making my own 'Slap switch'.


Cheers

[slyjoe]

Probably would need an inductor as well. Generally not a real good idea. See more here:

3-band onboard passive EQ idea

Or do a search on passive mid cut.

[megadan]

It can be done but it's tricky.

Read up the Wikipedia articles on RC, LC, RLC networks;
http://en.wikipedia.org/wiki/Band-pass_filter

[SGD Lutherie]

You need a capacitor and an inductor. This is commonly known as a Varitone control. They usualy have 5 different value caps and a bypass position on a rotary switch, but Gibson included a single knob midrange cut control on the Ripper bass.

If you want to try it, the easiest thing is to go to Radio Shack and pick up the audio output transformer they sell (Model: EI-19, Catalog #: 273-1380). You want to use the 1K Primary as an inductor. Then try using that with a .1 cap. The inductor would go between the cap and ground, wired like a standard tone control.

Smaller cap values will raise the notch frequency, and larger values will lower it.

You can also use a transformer model TL021-R that you can find at Mouser Electronics. Torres sells a Varitone kit that uses that same part.

Here's the Ripper schematic.

[pickles]

The villex system has this, I didn't really like the way it sounded. The mid control took some highs along with it so it wasn't useful for getting any kind of sharp mid scooped sound.

[SGD Lutherie]

The Villex version is actually part of the pickup.

I used to use the inductor types and it works real well with bright bass tones. I didn't have an issue with high end loss.

It's a cheap thing to try out though.

Passive controls like this are never the same tone as an active system though.

[3506string]

http://www.guitar-mod.com/rg_passive.html

[mjolnir]

Originally Posted by pandathe3

So we all know that we can only cut frequencies with a passive electronic system. Our tone knob rolls off treble.

What capacitor would i use too roll off mid frequencies? Or maybe build a switch that will cut certain mids? Maybe making my own 'Slap switch'.


Cheers

There's a user on here that goes by has-sound, his name is Stan Hinesley. He used to sell something exactly like what you're looking for, though I'm not sure if he still does. Hit him up with a PM, maybe he can give you a pointer or two on how he did it.

[SGD Lutherie]

Originally Posted by mjolnir

There's a user on here that goes by has-sound, his name is Stan Hinesley. He used to sell something exactly like what you're looking for, though I'm not sure if he still does. Hit him up with a PM, maybe he can give you a pointer or two on how he did it.

http://www.stanhinesleypickups.com/passive_controls.htm

First item on the list.

[mjolnir]

Originally Posted by SGD Lutherie

http://www.stanhinesleypickups.com/passive_controls.htm

First item on the list.

Yeah, that one. I bought one for my Warwick back when I still had a Warwick and enjoyed it immensely. I don't have the bass anymore though so I can't take a look at it for the OP, and I don't think Stan would appreciate me trying to reverse engineer his work anyway.

[SGD Lutherie]

Originally Posted by mjolnir

Yeah, that one. I bought one for my Warwick back when I still had a Warwick and enjoyed it immensely. I don't have the bass anymore though so I can't take a look at it for the OP, and I don't think Stan would appreciate me trying to reverse engineer his work anyway.

Yeah, Stan's a good guy.

I already explained how to make one.

[Suhr]

Originally Posted by pandathe3

So we all know that we can only cut frequencies with a passive electronic system. Our tone knob rolls off treble.

What capacitor would i use too roll off mid frequencies? Or maybe build a switch that will cut certain mids? Maybe making my own 'Slap switch'.


Cheers

We make the inductors you can use for this. They can be used as a bass control or midrange when used with a cap. It is hard to find the correct pleasing values unless you make them yourself.

[SGD Lutherie]

Originally Posted by pandathe3

So we all know that we can only cut frequencies with a passive electronic system. Our tone knob rolls off treble.

I just want to point out that you can, and do, get slight boosts with passive tone controls. The passive treble cut does boost the low end slightly when you have it all the way off. Villex has some passive boost systems as well. It's not a lot of boost though, but it works by making a resonant peak in the frequency response.

The problem with making a regular passive tone stack, like from an amp, is that there is insertion loss, so you loose signal through the entire circuit. These types of circuits have an active stage to boost the level back up.

[Stealth]

Originally Posted by SGD Lutherie

I just want to point out that you can, and do, get slight boosts with passive tone controls. The passive treble cut does boost the low end slightly when you have it all the way off. Villex has some passive boost systems as well. It's not a lot of boost though, but it works by making a resonant peak in the frequency response.

Going by basic filter logic, I assume this is due to the filter being first-order. (first-order Bessel, right?) Could better tone control be gained (no pun intented) by creating, say, a second-order or third-order filter?

[fullrangebass]

Originally Posted by SGD Lutherie

Villex has some passive boost systems as well. .

Villex offers up to 12dB passive boost through his PRTB line of products (Passive Rotary Tone Booster)

[SGD Lutherie]

12dB? Wow!

I heard some clips of one of the systems, and it didn't sound that large.

[fullrangebass]

When the first version came out it was 3, 5 and 7 db

I asked for more (I am a sucker for more power) and I am very demanding and Mr Villex came with the new version that provides 6, 9 and 12dB!!!

I call them PRTB I and PRTB II respectively (I think that Mr Villex will follow the same nomenclature)

[slyjoe]

How does he get 12db of boost with a passive circuit?

He should by a ticket to Stockholm.

[fullrangebass]

I have no idea but it is true

[slyjoe]

If you have no idea, how do you know it's true?

Sorry, I am just a little confused.