[sdiy] FPGA digital audio

[Magnus Danielson]

From: Grant Richter <grichter at asapnet.net>
Subject: Re: [sdiy] FPGA digital audio
Date: Sat, 12 Jan 2002 13:05:43 -0600

> Are there any other designs for digital oscillators besides the classic
> indexed accumulator?
> 
> I was thinking a digital implementation of a counter wavetable driver. It
> seems like with 1 nanosecond clock speeds, a high resolution variable
> divider driving a counter would allow sub-hertz resolution.

Surely you could do that. If you have a counter running at 200 MHz
(feasable by cheap FPGAs of the shelf) you can do alot of neat
tricks. However, you do use up the hardware pretty lousy. An phase
accumulator running for a number of registers and a common accumulator
reuses the hardware very efficiently and you can with moderate clocks
get many, many oscillators and high sample rate and the silicon will
also not run red hot (which is an issue for an DIYer not being an
expert on power line decoupling and cooling).

> A high resolution successive approximation A/D could also be realized in the
> FPGA. From the outside it would look like an analog oscillator, the the
> wavetable could be extremely wide range and stable.

Indeed.

The one thing that I lack on the music instruments is the 10 MHz
reference clock input such as I have on my measurement
instruments. ;O)

Cheers,
Magnus