Store real time sound reading in a memory

[Progg70]

I’m interested to find a diy project that store the spdif signal from the real-time reading CD-rom in a digital memory, perhaps about 3 min buffering before the DAC do the work and sends the signal to the amp… any ideas? I don’t wont to use a computer…

[mako1138]

A three minute digital delay?

Let's see how much storage you'd need:

180 seconds * 44100 samples/second * 2 bytes/sample
= 15876000 bytes = ~ 15 MB

You can get 64MB SDRAM for $5.

This system can be built around a microcontroller. The hard part is getting data into the microcontroller. After it's in, stick the data into SDRAM, and read it out three minutes later into an SPDIF out chip. (For SDRAM you also have to refresh the data every 64ms.)

As for getting the data into the microcontroller, I can't think of anything elegant. CS8420 -> serial-to-parallel random logic -> micro?

There are audio DSPs with built-in SPDIF, but they're overkill for this application.

Alternatively you can do the whole thing with just FPGA + SDRAM. Depending on your experience, it could be simpler.