audio processing

[mischl]

hello all

i'm looking for a small solution which can control an audio signal as following :

- volume
- equalizer
- limiter

i would like to do that with a pic. but i don't know which one is fine for that. smust it be a dspic?

thanks for any help

[mister_e]

no need for a DSPIC.. TI and few other company already do some sounds DSP easy to use with I2C or SPI interface. Usually those chip are use in home theater sound system..

For the limiter.. no big deal. Use a PIC analog in, read the signal, compare to your own treshold, then play with the volume.

[mischl]

hi mister_e

thanks a lot for the answer

can you tell me some types from TI? this are only eq or also volume control include?

and i understood right for the limiter: read in the audio signal parallel to the TI (i think the audio signal must go trough the dsp) and then control the volume via I2C or SPI on the DSP?
or another setup?

thanks for helping a starter again

[mister_e]

http://focus.ti.com/paramsearch/docs...s&familyId=378
look for TAS3002 and TAS3004. Yup not as easy as ABC but i already used them and they gives decent results. TAS3002 will probably be the smartest choice. Of course you can find many other from aother company... google search dude

For the limiter, you're right. You read the signal in parrallel with the Audio Processor then you play with the volume VIA I2C bus. TAS3002 include a compression/expansion module but i can't comment on that section as i didn't used it.

Depending your skills, it willn't be easy to do, but really interesting project you have on hand now. Good luck!

[Sebastian]

Hi,

I just found your thread while searching for information on a TAS3002. I've some experience with microcontrollers (80C552, PIC) and know how to use an I2C bus.
My next project will be a midi controlled distortion unit (for guitar) and I'd like to use the TAS3002 for that.
However, I've got no idea of these "strange" filter coefficients that I need for the biquad filters (I need a 4 or 5 band parametric eq). Can you help me with some formulas or other calculation tools?

Thank you
Sebastian

Sorry for my English, I'm German.

[mister_e]

Yeah Biquads are a bit hard to figure out. TI have a software called ALE (Automatic Loudspeaker Equalisation) you sould aksed them and play a little bit with. It should be enough to give you some hints.

Now, do you really need all feature of the TAS3002? DRC, Mixer, Bass, Treble, Biquads and such?

If you just need a simple equaliser you should jump to the TDA7416.

But TAS3002 is a reaaaaallly cheap'n great Audio DSP