Atari 7800 Stereo/discreet channels

[Rick Dangerous]

Does anyone know how many games in the 7800's library actually are stereo or even have discreet channel audio effects? Just wondering because I can't find much about it online, just pokey info and everything sounds pretty much mono to me.... Thanks.

[SoundGammon]

Actually, ALL the games are in stereo including all the 2600 games. All the games use both sound channels. The 7800 version of Asteroids is cool to listen to as some sounds get "pushed" from one channel to the other when a ufo comes out, sounds cool if you have it connected to a surround sound system!

[ColecoGemini]

In order to hear it in stereo, the video/audio mod needs to be wired as such, but I dont know which pins on the TIA to tap in order to facilitate this, plus you would need to mix it with the mono pokey sound, which could be confusing.

[SoundGammon]

Pins 12 and 13 are the audio pins. You could take a couple of resistors from the pokey chip and feed one to each channel and still keep the stereo sound and also feed the pokey audio to both left and right channels together!

[Dauber]

Two audio channels does not mean stereo. Only if each audio channel has something different.

[SoundGammon]

Can't think why a programmer would use both sound channels for one sound. One interesting thing is Atari's COMBAT has the left tank's sounds coming from the left channel & the right tank's from the right and M Network's Armor Ambush's sounds work the same way! The 2600's version of Asteroids has some sounds from one channel and other sounds like ufos on the other but sound better mixed to mono. You can try any 2600 game in Stella and hear it in stereo. Some early Beatle's recordings were only 2 channel recordings with the music on the left and the singing on the right! Better in mono. Early stereo recordings were referred as "Ping-Pong" stereo because the way the sounds were isolated from each other.

[Rybags]

Ideally a stereo mod would have a switch so you can choose between mono mixed and seperate stereo. Or maybe even have each channel on the "wrong" side as well but muted 50%

 

2 voices doesn't really give much scope for games to do stereo effects, playing a sound on both channels isn't really viable since there's potential for undesirable effects, e.g. on Pokey you can have 2 same sounds cancel each other out, not sure if it can happen on TIA. Plus doing sound on both voices means only 1 effect at a time.

 

At least TIA provides the seperate outputs - Pokey has everything on 1 pin. I guess that traces back to the original intent for the VCS to have the 2 inbuilt speakers.

Edited March 10, 2014 by Rybags

[Rick Dangerous]

Awesome thanks guys this has been really helpful. Anyone know if there is a thread or list of games that utilize the Pokey audio chip?

[Rybags]

The list isn't very long. Ballblazer, Commando and some modern day homebrews. And I think 1 or more old games have been modified to use Pokey sound.

Edited March 10, 2014 by Rybags

[Synthpopalooza]

If you were to wire POKEY for stereo, the recommended way, I think, would be to wire channels 1 and 2 to one side, and 3 and 4 to the other.

 

Reason being: This is necessary if you want to engage 16-bit mode (AUDCTL=$50 or AUDCTL=$80), where you combine channels 1 and 2, or 3 and 4 into a 16-bit channel to increase your note resolution. Strange results might happen otherwise.

[Rybags]

Pokey only has 1 audio out pin, so no stereo possible from a single chip.

 

Plus the triangle wave relies on interaction between voices 1/3 and to work well would need to be on the same speaker... although it's not exactly in common use anyway.