Possible use of very simple filters and such for basic effects?

[diemilchmann]

I thought the other day about perhaps just running a guitar through a basic hi-pass or low-pass rc filter. Will something like this work? Or for that matter, any kind of basic filter or circuit, hoping to diverge away from the usual transistor/IC/Op-amp effects.

[Mark Hammer]

It will "work".  The question is whether what comes with it appeals to you or interferes with what else you need your guitar signal to do.

First off, a simple RC lowpass or highpass will cut out part of your signal, such that switching it in and out will result in changes to volume level. That may be exactly what you want (e.g., if the filter is set to produce a desired rhythm one), or it may not.

Second, the passive filter may create undesired loading effects and impedance problems.

Again, neither of these are intrinsically "problems".  They are merely consequences that may or may not be in alignment with what you're striving for.

[petemoore]

  I watched it go this way:
  TC Goes in and TC"s, but the volume drop intolerable...
  Puts a buffer before the TC, which changed [percieved to be for the better] the way the TC controls functioned, the heavy loading TC circuit fragment had plenty of current and worked more predictably, the volume was restored' somewhat.
  A 'booster' AkA 'gain recovery' [stage with active component] was then placed after the TC and set to a gain amount that fascilitated output settings well above unity.
  I put in a circuit I've seen labled as 'tone control' on a FF. It only presented near 0 through small impedance to only the HFrequencies, just noticable enough that the HF's were sufficiently tamed, plenty of output and nothing else needed.

[Taylor]

Your guitar already has an RC filter in it, no? It's the knob labeled "tone".

I admire the interest in stepping outside of the usual, and this was how I got into DIY effects as well. My experience has been that I'm not all that clever, or smart, or knowledgeable (3 different things which people often conflate) compared to the big electrical engineers of the last century (or even the prominent denizens of this forum!), so if I'm working with the same tech that they had more time with and that they understood better than I do (i.e., the basic building blocks of electronics), I will never come up with anything that they didn't. In fact, every time I've thought that I've come up with some slick little abuse of a part, it turns out it's explained in detail in an app note from the 70s.

That's not to discourage you from trying to do interesting stuff with electronics. My personal direction has been towards digital hardware. I find that I'm able to do more interesting and weird things than I ever pulled off in analog tech, and it was even easier to learn for me, believe it or not. This isn't for everyone, and it might not be the way you want to go, but I guess what I mean to say is that if you're trying to break away from the usual, you can either be really smart, clever, and knowledgeable, or you can start with tools that haven't been explored as much.

We may within our lifetime have access to a new building block of electronics, the memristor. So that might be the next frontier of stompbox design.

[diemilchmann]

What about vacuum tubes instead of transistors? I have no knowledge of tubes, but my understanding (based from Wikipedia ) is that they work similarly. Could one be run off of 9V?

[Taylor]

There's plenty of fertile ground in doing weird stuff with tubes, however it does require a fair amount more knowledge than fooling around with transistors. If you want to play around with tubes at low voltage to do some interesting things, I'd recommend submini tubes. Check out this thread:

http://www.diystompboxes.com/smfforum/index.php?topic=71381.0

[humptydumpty]

I saw an interesting filter in a book I got from the library, I'll try to find it and post it.

[Processaurus]

Your guitar already has an RC filter in it, no? It's the knob labeled "tone".

Yes, the simplest filter effects are often built into guitars, Jaguars have what people sometimes call a "choke" switch, it cuts out the bass by running the guitar signal through a .003uF cap.  I like it.

There's also the varitone, a six position rotary switch that does all kinds of stuff:
http://alexplorer.net/guitar/mods/varitone.html

[diemilchmann]

Could i use a wien filter to oscillate the filtering?