Does anyone know how to make High/Low Pass Filters?

[shred101]

Does anyone know how to make high/low pass filters and can anyone advise me on what components would be most suitable for building them?
From what I can gather, they should be fairly simple with just a capacitor, potentiometer, resister and jack ins + outs. Kinda like on guitar tone controls maybe? Logically I deduct that youd have to stack 2 together to get the steep roll off that digital filters achieve but that still doesnt really complicate matters.
Im no expert when it comes to this stuff but it seems that they would be really cheap and easy to build.

The reason im thinking about this is that I use shedloads of DSP power on my digital desk just high/low passing stuff on input when it comes to recording multiple input sources at once and being able to farm out this simple task to a dedicated unit would save me tons of DSP power that I could be using for dynamics processing and normal corrective eq.

 

[John_C]

well in the simplest case, 2 variable capacitors, one double throw and one single throw switch would do it. However there's probably more commonly used configurations

sorry, and two pots

don't have a clue how to adjust the slope though.

 

[shred101]

Wouldnt you need a resister (or two) in that circuit as well though? Ive read that slope is defined by the resister value, capacitors set a frequency and the potentiometer is a control for the capacitor and thus the frequency cut off point. Feel free to correct me on any of this because im a noob when it comes to circuitry.

 

[JeffTD]

Sorry, but I heavily doubt you're using astronomical amounts of DSP power on hpf/lpf's.

 

[shred101]

Well, you'd be surprised. It quickly becomes a pain in the ass when Im recording guitars because Ive already got drums using compression, expanders, etc. which gobble dsp on my desk and also, the limitations of the Korg desk that im mixing on atm means that you cant similtaneously high/low pass and use effects on input and if you've already used the high/low shelf bands of the eq for corrective eq or whatever then it quickly becomes a ballache.

 

[John_C]

Wouldnt you need a resister (or two) in that circuit as well though? Ive read that slope is defined by the resister value, capacitors set a frequency and the potentiometer is a control for the capacitor and thus the frequency cut off point. Feel free to correct me on any of this because im a noob when it comes to circuitry.

well that would all depends on how they're wired up.........

 

[shred101]

Oh right ok... Its cool that im not the only human left alive who knows what a skeksi is lol.

 

[ruckus328]

Oh right ok... Its cool that im not the only human left alive who knows what a skeksi is lol.

DUDE! NOBODY at my job had any idea what that movie was. I couldn't believe it. I remember seeing that shit in the theaters as a kid. Sequel is in the works. Comes out in 2012.

 

[shred101]

No way... Sequal? Are they running out of films to fuck up with shit follow ups or something?

 

[B36arin]

I think that this was meant for you, haha

 

[shred101]

Yeah Im aware of it lol

 

[TheWinterSnow]

To the basics, a 3rd order filter only requires 2 components, one resistor and one cap. pretty easy actaully.


here are some links with schematics of a basic filter:

http://en.wikipedia.org/wiki/Low-pass_filter
http://en.wikipedia.org/wiki/High-pass_filter

A .5mH inductor and a 1K pot will give you an effective low pass selectable from 20Hz - 20KHz and a 470uF cap with a 1K pot will give you an effective high pass selectable from 200Hz to 20KHz.

 

[-Loco-]

if you want filters with a fixed cut-off point you can calculate roughly that point which you need.but depending on the quality of the capacitor, you can get up to a 10% margin either side on it's value. You only need a resistor and a capacitor for a basic filter circuit. Capacitor doesn't set the frequency, its a combination of the resistor and the capacitor which gives you the cut-off so it's about working in a balanced way to get the right slope and cut-off from the values, you pick.

 

[B36arin]

To the basics, a 3rd order filter only requires 2 components, one resistor and one cap. pretty easy actaully.

Are you sure about this? I seem to remember that third order filters require 3 resistors and 3 caps.

 

[ruckus328]

No way... Sequal? Are they running out of films to fuck up with shit follow ups or something?

Yup, I was wrong though, it's next year it comes out, not 2012:

http://www.imdb.com/title/tt0460907/

I actually have some faith this won't blow. They've recruited damn near everybody that had anything to do with the original. Same character designer as the original. They're doing CGI and live action. Most of the characters will probably be live action.

They're also doing a Fraggle Rock movie lol.

 

[TheWinterSnow]

Are you sure about this? I seem to remember that third order filters require 3 resistors and 3 caps.

that would be a 12th order. A basic RC and RL setup is the first filter.

 

[gabriel g.]

that would be a 12th order. A basic RC and RL setup is the first filter.

+1

RC and RL is 6dB, isnt it?

 

[JBroll]

Read the Wikipedia page, problem solved, end of discussion. If you know enough to proceed, you'll be set; if not, you'll find out what you need to learn.

Jeff