Yes... A real Atari does the same thing! That's what the processor and the other chips produce when the machine is started with no ROM to be executed.
I tried to implement the emulation at the hardware component level as accurately as I could. It happened spontaneously!
When the processor tries to read the game program from the empty cartridge slot, it ends up reading random bytes from the data bus. Its like a random program commanding the video and audio hardware!
Thats an amazing observation mjn!!!
I knew a little about the Nyquist frequency, but I didn't really hear much aliasing during development. Surely that is a good point to improve!
Thanks.
To be fair it's not really a show-stopper in the context of Atari emulation, just a "nice to have". Most of the Atari's sounds are so noisy to begin with (e.g. the famous Combat tank rumble) that the aliasing is much less noticeable than if you're digitally emulating simpler waveforms, like the ones from analog synthesizers.
The most-used 2600 emulator, Stella, doesn't do bandlimited synthesis either, without many complaints. I believe z26 is the only Atari emulator that does, so listening to differences between how things sound in z26 and other emulators might be a way to figure out if it really matters. Though as far as implementation, z26 is 100% asm, so not very easy to use as a reference.
Please, when possible, update to the latest version (0.92), and always check for updates.
A "Powered by Javatari" crediting on your page with a link to the emulator website would also be great! ;-)