LED equaliser system

[Kane2oo2]

Hello
does anybody know where i can find some information on building a visual equalizer which can be connected to the computer and interfaced with winamp.
Like you see on stereo systems with the little bars showing each frequency!

ive searched google but lots of junk about winamp skins came up!

all i know is that i need to seperate the frequencys somehow, then have like a led-vu meter or something to show the strength right?

i would also be interested to hear if anybody hear has done such a thing as well

Thanks
Kane

 

[crust]

There is a application specific part to do this. It is an LM3916, and National still makes this part. Here is a link to the datasheet
**broken link removed**

 

[Kane2oo2]

thanks for the information

but i am still very much a beginner to electronics and could do with a circuit which i can follow to build what i am wanting

Kane

 

[crust]

What you are asking about is referred to as a "Spectrum Analyzer." The data sheet has a one-channel circuit on page 15, "0V to 10V VU Meter with Smooth Transitions" You build this, plug the output of your sound card into this circuit and you have your meter. If you want to make a couple of different ones for each frequency band, you'll need to build a very simple band pass filter for each of the different frequency bands.

Winamp has a spectrum analyzer built in. I have seen plugins that seem to access the values from the analyzer and use them to control a color organ. If that is the case, it may be possible to write a plugin which then just outputs a signal from one of the PC ports telling your external system which light on each band to light up. I realize this description is vague, but it seems if you are not that experienced, this one might be even more difficult -- though I suspect it would take less parts. I have never written a plugin for winamp myself, so I dont know how easy/hard that part would be.

The example on the internet is known as at **broken link removed**

 

[Kane2oo2]

I have seen plugins that seem to access the values from the analyzer and use them to control a color organ.

thanks for the info .... this is just what i needed to know ....i was searching for the wrong thing all along



iv'e managed to find this spectrum analyzer circuit **broken link removed**
(attached below)

however it has only 3 bands/channels ... is there a way to increase the number of channels?
and the channels are not set at a specific frequency eg. 15Khz ... is there a way to achieve this?


Kane

 

[crust]

You can have as many channels as you like, but each channel other than the lowest and highest will need two filters -- a high and low cutoff so that you are only picking out a select band in the middle. Depending on how many you want, it is probably going to be much easier to implement a discrete Fourier transform in software and use the software to illuminate the proper lamps. How many channels do you want to use?

In the diagram you posted, each of the three amplifiers on the right hand side of the page is usually referred to as a multiple feedback bandpass filter. It is govered by the following equations (for the top right amp).

f0 = (1 / (2 * pi * C)) * sqrt((R7 + R10) / (R7 * R10 * R13))
BW = 2 / R13 / C
Q = f0 / BW

BW is bandwidth, f0 is center frequency, Q is the "quality" of the filter

 

[Kane2oo2]

How many channels do you want to use?

ideally around 10-20 channels to get a full range of the spectrum

Kane

 

[crust]

Well, in that case you can use 10-20 band pass filters, or use software to perform the discrete Fourier transform on a set of samples and drive the LEDs from a microcontroller. I think the latter is easier. In addition, I have not looked at winamp much, but I would guess that they are doing an FFT in software and "drawing" the spectrum.

 

[Kane2oo2]

thanks everyone for the information

i think i now have everything to start trying to build such a device!

i will report back soon when i run into problems :lol:

I have not looked at winamp much, but I would guess that they are doing an FFT in software and "drawing" the spectrum.

to begin with the system will jus plug into a normal music output and then i can eventually modify it to suit needs

Thanks
Kane

 

[Exo]

There are plugins for winamp that output the current spectrum analyzer view of winamp to the parallel port... Add an grapic lcd and your off...

You see a lot of these on casemodders site's

**broken link removed**