(working past each other a little here...)
Well, I want to make an electric drum set, so the sound has to start playing as soon the drum is struck - can't really have any latency. Each drum card would only play 1 sound at a time. Playing like 20 beats per second, need to hear the initial strike from each hit, so a new sound to start playback at 22.7uS rate every 50mS. I suppose that's enough time to add say 4 samples from different times together and send to the DAC? Vs having 4 DACs and mixing them in analog realm. I couldn't envision doing that before, too complex a design with discrete logic chips. Not sure how it would sound either. Snare drum dies out quick, but tom-toms go longer, might just turn into a long rumble. I suppose I could force ongoing sounds to be quieter quicker as a new one starts. Not really sure how best to take advantage of the 1284 RAM. You think each 1284 could control several DACs at one time? So maybe 2 or 4 sounds at one time? This is getting farther along than what I was thinking was possible with 8 bits at 16 Mhz. Every 22uS, (transfer 2 byte from SRAM, to 3 bytes into the DAC,) * 4, = at 0.5uS/byte raw speed = 10uS, and if add some math to combine the sound... Hmm ,that's not going to leave time to capture the input level and multiply it accordingly before doing the adding. If I do it simply, say 1 of 8 levels, that's just shifting the data to the right by a bit to cut the sound by 1/2 with each bit shift, yes?
These guys will purchase & install the little SMT chips onto DIP adapters for a couple dollars on top of the chip price. http://www.proto-advantage.com/store/product_info.php?products_id=2200091 I have no confidence I can solder the little pads of the SOT-23-8 and MSOP8 parts myself and have them be functional afterwards.
If you think the AD5662 can be a good match with an SD card for sampling playback (pair up with AD7680 to capture samples & listen to immediately, then play back with drum strike from SD card or from SRAM) I'll order a couple of each and have them mounted so I have something to start testing. The Vref chips too.