How can i build a frequency analyzer?

noxon · Jun 8, 2005, 02:38 PM

Hi

I'm new to this forum and i don't know much about DSPs and audio-processing, but i thought i might give it a try to make and case-mod involving the audiosignal of my SB Audigy 2 SZ.

Here is, what i have in mind.
I recently bought the Lian-Li V-2000 case, which has thousands of little holes in the front. Each hole has a diameter of 3mm which is perfect for 3mm LEDs. So i thought i build a little LED-Matrix in the front of the case which i can use to visualize the frequencyband of the audiosignal of my soundcard.

I don't want to control the LEDs by software (e.g. by Winamp Plugin), because i want to be independent of the player-software. So i thought i use the output-signal of my soundcard and use this to extract the frequencies from it.

And there is my problem. I have absolutely no idea how i can do this. Do i need a DSP for that, in my eyes, easy task, or will it do some simpler IC which takes the input-signal and provides me with a couple of output-signals which represents the frequencies of the input-signal?

Are there such analog chips that can do this or will there be only digital chips which needs further processing to extract the frequencies?

I also don't know how to control a LED-matrix yet, but i think that's something i can figure out by myself.

It would be great if you could tell me, which components i need for this project or if this whole thing is just a stupid idea. I would very appreciate it if you could help me out.

Nappylady · Jun 8, 2005, 04:01 PM

Frequency analyzers out of LEDs are a lot of work and a lot of circuits.

Your most likely course of action will be to make a series of bandpass filters--one for each frequency band your LEDs will represent--and then to built a separate level meter for each band. (I do know of some ICs available that do the level metering for you.) See here:

http://sound.westhost.com/projects-6.htm

Projects #55 and #60 will be of interest to you. Please note that he mentions an analyzer he's planning, and that it will be posted "soon". It has said that exact thing for several years!

noxon · Jun 9, 2005, 10:03 AM

Quote:

Your most likely course of action will be to make a series of bandpass filters--one for each frequency band your LEDs will represent--and then to built a separate level meter for each band. (I do know of some ICs available that do the level metering for you.) See here:

That's a good idea.
Sounds easier than i thought it would be. Since the LM3915 does most of the work on it's own a VU-Meter seems pretty easy to build. That's the first step i'm gonna take. Once i realized the VU-Meter i still can consider building a frequncy analyzer consisting of multiple VU-Meters and bandfilters.
Although i can imagine how huge the circuit for a 15-band analyzer would be. Maybe it's really a little to much.

But i'll definately try to build a nice looking VU-Meter in my case. That shouldn't be much of a problem for me.

Thanks a lot for your help and i'll post you pictures of my case if i'm finished. (or no pictures, if i gave up

)

BTW: I also found a Video of how a VU-Meter-Mod would look like.

Duranix · Jun 9, 2005, 10:33 AM

just wondering..... why would you want flashing lights on your case for anyway??

oh, and whats the name of that song in the vid

noxon · Jun 9, 2005, 11:52 AM

Quote:

Originally Posted by Duranix

just wondering..... why would you want flashing lights on your case for anyway??

Thats a good question. I don't know. Why do so many people attach spoilers, alloy rims or other tuning parts to their cars?

It's just for fun. I don't even know if i will keep it installed permanently. It depends on how much i like it or not but i thought it's worth a try. Maybe it looks great, maybe it doesn't.
However. In both cases i had fun building a VU-Meter and that's the whole point of this.

Quote:

oh, and whats the name of that song in the vid

Don't know.

Daniel Drummond · Jun 9, 2005, 02:19 PM

Maybe some info here may help you achieve what you want: http://www.ucapps.de/ and www.midibox.org

TravelRec. · Jun 9, 2005, 03:04 PM

Quote:

Originally Posted by noxon

That's a good idea.
Sounds easier than i thought it would be. Since the LM3915 does most of the work on it's own a VU-Meter seems pretty easy to build.

Yes, it´s easy, but not very accurate in this case. It all depends on the input amplification and rectification stage, how accurate your peak-meter will be at last. For the Analyser I think, the hardest parts are the filter stages, that have to be very narrow and stable to get accurate analysing results. BTW, if no special accuracy is needed: have fun with the soldering

.

noxon · Jun 10, 2005, 07:40 AM

@Daniel Drummond:

Thx for the links. I'll look into it.

Quote:

Originally Posted by TravelRec.

BTW, if no special accuracy is needed: have fun with the soldering

.

I actually don't need an accurate measurement. I just want a few flashing lights in my case.

Jun 8, 2005, 02:38 PM	#1
noxon DriverHeaven Newbie Join Date: Jun 2005 Location: Germany, NRW Posts: 4 Rep Power: 0	How can i build a frequency analyzer? Hi I'm new to this forum and i don't know much about DSPs and audio-processing, but i thought i might give it a try to make and case-mod involving the audiosignal of my SB Audigy 2 SZ. Here is, what i have in mind. I recently bought the Lian-Li V-2000 case, which has thousands of little holes in the front. Each hole has a diameter of 3mm which is perfect for 3mm LEDs. So i thought i build a little LED-Matrix in the front of the case which i can use to visualize the frequencyband of the audiosignal of my soundcard. I don't want to control the LEDs by software (e.g. by Winamp Plugin), because i want to be independent of the player-software. So i thought i use the output-signal of my soundcard and use this to extract the frequencies from it. And there is my problem. I have absolutely no idea how i can do this. Do i need a DSP for that, in my eyes, easy task, or will it do some simpler IC which takes the input-signal and provides me with a couple of output-signals which represents the frequencies of the input-signal? Are there such analog chips that can do this or will there be only digital chips which needs further processing to extract the frequencies? I also don't know how to control a LED-matrix yet, but i think that's something i can figure out by myself. It would be great if you could tell me, which components i need for this project or if this whole thing is just a stupid idea. I would very appreciate it if you could help me out. Last edited by noxon; Jun 8, 2005 at 02:58 PM.

Jun 9, 2005, 10:33 AM	#4
Duranix DriverHeaven Senior Member Join Date: Jan 2005 Posts: 614 Rep Power: 0	just wondering..... why would you want flashing lights on your case for anyway?? oh, and whats the name of that song in the vid __________________

Jun 8, 2005, 04:01 PM	#2
Nappylady DriverHeaven Addict Join Date: Jun 2003 Posts: 257 Rep Power: 0	Frequency analyzers out of LEDs are a lot of work and a lot of circuits. Your most likely course of action will be to make a series of bandpass filters--one for each frequency band your LEDs will represent--and then to built a separate level meter for each band. (I do know of some ICs available that do the level metering for you.) See here: http://sound.westhost.com/projects-6.htm Projects #55 and #60 will be of interest to you. Please note that he mentions an analyzer he's planning, and that it will be posted "soon". It has said that exact thing for several years!

Jun 9, 2005, 02:19 PM	#6
Daniel Drummond DriverHeaven Senior Member Join Date: Dec 2002 Location: Brazil Posts: 1,137 Rep Power: 0	Maybe some info here may help you achieve what you want: http://www.ucapps.de/ and www.midibox.org __________________ www.palcomp3.com.br/ed