On Tue, 28 Aug 2001 02:42:12 +0200 (CEST) Ãlvaro Castro alvcastro@yahoo.es wrote:
Hi all!!
Some days ago I posted an e-mail asking for help for building an equalizer. I didn't get many help, that's the reason I write again. If I'm writing to the wrong list, please tell me. I just want to know the basics of an equalizer so I can start working. As you see, I'm a beginner, but I don't know how to start.
the main reason you probably haven't received much help is because this is not really a pd question but a general dsp question. so ideally you would look into some dsp resources, where you will find that you need to know a fair amount about digital filtering to make an equalizer, then maybe you would get some help on building filters in pd.
I choosed to learn PD instead of other sound programs or programming languages because I thought it was very powerful and not very difficult to learn. But when I started working with PD I discovered that one of the most important things for me (the low and high pass filters) don't work very powerfully. I tried filtering a sample and I realized that the filters didn't cut TOTALLY the frequencies they just decreased the amplitude a little bit.
this is common with digital filters... to get a really sharp roll off you normally need a more complicated filter... you can also try recursively applying the same filter...
Finally, I would like to know what's the best way to work with pure (or almost pure) frecuencies. That's the reason I want to build an equalizer. I would like to add, increase, delete or decrease specific frecuencies. Is that posible with Pure-data??
well, adding frequencies is easy... [osc~] and [+~] :)
Thank you very much for your time! I will appreciate any answer, because I don't know what to do now!!
there is a dsp book available for download at www.dspguide.com, it's reasonably accessible as an introductory text.
pix.