Sonsivri

Hi, looking for audio playback circuit example preferably using PIC and serial eeprom. Audio waveform stored in serial eeprom and using D/A to directly drive a speaker.

Any leads much appreciated. Thanks.

I guess you need a little fraction of a second of audio playback as this is all you can get with the configuration you provided! Roughly over 1 or 2 second with a 512kbit eeprom with much reduced quality rate. Try this for reduced quality:

http://www.romanblack.com/picsound.htm

Regards...

What type of audio? Music, speech or MIDI? There are orders of magnitude difference in the compression you can achieve, depending on the nature of the sound.

I'm looking at reasonably sampled music, say 11 or 22 kHz mono. With the current low prices of memory, you can store about 1.5 minutes of uncompressed waveform into a 8 Mb eeprom device. Do you think this will give better quality than audio stored into voice chips like ISD? Another possibility is to use MP3 chipsets - don't know about the price or quality impact of this choice.

From your site http://www.romanblack.com/picsound.htm - you could get 33 secs of sound from a 512 kb eeprom. Than's not too bad. I have to check the quality of the sound, though.

Thanks for the ideas.

I've used the ISD chips in a commercial design. They're actually analog storage technology. (The charge on the internal EEPROM gate bits is stored is varying levels to recreate analog from a basically digital device. Have a look at their data sheets. Very clever IMHO.) In my experience the sound quality is at the "AM Radio" grade. Very good for speech but for music...it would be a matter of opinion.

The ISD chips, at least a few years ago when I used them, have to be individually programmed with an analog source. And this is most important: The recording circuit must be carefully designed and be very quiet electrically in order to get the optimum sound recording quality.) I think ISD offered a dedicated programming fixture for sale but is was far too expensive for our project. The playback circuit doesn't matter much. It can be very low cost & low component count. But the recording for each device must be made very carefully. Check the ISD website and see if they've improved the chips, but my basic hunch is that they're still loaded with an analog signal.

Remember, the market for these chips is for toys and digital memo takers, not music playback.

What's your application, audio amplifier power and THD, proposed speaker, ambient background noise, budget, etc? There's no point using 16-bit 44 KHz PCM digital music, even if you could, if you're playing back on a 2 inch paper cone speaker in a plastic project box.

That's precisely why i'm looking for alternatives to the ISD chips - they don't cut it for music quality applications.

My application is for a high-quality audio playback device with 1 or 2 music clips each of about 2 minutes - sort of an advertising device that can be triggered based on time. Power output 3 watts or so, using a good quality speaker (not the paper cone types). Budget is approx USD 15 - 20 in volume. Audio clips will be prerecorded so there's no recording circuitry required.

Do you have experience with the MP3 chipsets?

For mp3 chips try:

http://www.pjrc.com/tech/mp3/sta013.html

But there is the same question where to store the audio data. You'll need lots of eeprom to store it even in a mp3 format!

Regards...

http://www.aplusinc.com.tw/    for APR9600 voice record chip

I was looking for a serial interface that allows a microcontroller to read and write data to files on a SD media card and I found it.

http://hittconsulting.com/products/sddatalogger/

I think it may help you.

Fábio André