Synthcart ACTION (longish)

[herr professor]

llo,

 

I got back into playing the Atari again after 17 yrs because of Paul Slocum's Synthcart. Its a fucking blast and looking at all the mods available for the Atari it got me thinking, why cant I hardwire a small casio style keyboard to replace the keypads. I could get a small case, an atari jr and modify down into a pretty mean synth. The case would leave enough room to add a vcf or lfo, or maybe delay and ring mod moduals. I would want the cartridge slot available to allow "upgrading" to possible future versions of synthcart or Paul's sequencer program. All I need to do is figure out to do it!

 

The way I understand how the keypads work is that they are scanned by the atari. It checks the pad for depressed keys (by columm then row), so all you have to do is make a pcb that has the 12 contacts spread lengthwise underneath the keys of a small trash casio style keyboard (actually mine is a yamaha). I guess I need to better understand how the keyboard controller pcb works... So I'm asking for help.

 

I've setup an yahoogroup at synthcart@groups.yahoo.com. You can subscribe byemailing synthcart-subscribe@yahoogroups.com, or visiting http://groups.yahoo.com/group/synthcart. I am gonna put up pics of the equipment as i build it so other can comment and do it themselves. Once the keyboard controller is compleated I will to figure out some more things:

 

*Individual audio outs - This would be handy to adding a vcf or whatever to the melodic sounds or a delay unit to the drum sounds to mix up the variety a bit. Is this possible? I would need to find out if the intelligent audio driver just uses whatever voice is available or does drum sound stay slaved to one voice or the other. If it isn't slaved would this mod be even worth it?

 

*Moving the switches on the atari jr to the front of the "synth" - I see some links on the webs to some of the switchs (like on the portable vcs site) but some are unknown to me... any links on how to move all six switches?

 

*Finding cheap model kits for sound modulation units- Paia mostly?

 

Once I started thinking about this my mind started wandering to other crazy ideas like:

 

*footswitch controller to trigger at least one pad's worht of sounds. good for triggering drums when your playing guitar or something.

 

*A atari joystick with presaved appegiator sequences on it (hang in with me for a second). triggering either axis or the buttons starts a loop of a note sequence that feeds signal through the controller port on which note to play. You could add a serial port to program the seqs from a pc and have bank switching to have multiple banks of data. Aside from looking really cool on stage(at least to someone like me) it would seem alot harder than a cv/midi type interface. But what price vanity?

 

As you can see, I've got my work cutout for me (I don't even own a soldering iron at the moment) but I plan to most of next month working on it. As I collect data I plan to mirror it on the yahoogroup for others. Let me know what you guys think.

 

Peter Swimm

[Paul Slocum]

I got back into playing the Atari again after 17 yrs because of Paul Slocum's Synthcart.

 

Glad you like it!

 

The way I understand how the keypads work is that they are scanned by the atari. It checks the pad for depressed keys (by columm then row), so all you have to do is make a pcb that has the 12 contacts spread lengthwise underneath the keys of a small trash casio style keyboard (actually mine is a yamaha). I guess I need to better understand how the keyboard controller pcb works... So I'm asking for help.

 

Probably the easiest way to do it would be to use the circuit from an existing keyboard controller. I also have a schematic of a keyboard controller somewhere that I can scan if you need it.

 

*Individual audio outs - This would be handy to adding a vcf or whatever to the melodic sounds or a delay unit to the drum sounds to mix up the variety a bit. Is this possible? I would need to find out if the intelligent audio driver just uses whatever voice is available or does drum sound stay slaved to one voice or the other. If it isn't slaved would this mod be even worth it?

 

If you take the audio straight out of the TIA chip you can get each channel separately, but I haven't actually tried this. I don't know the pin numbers, but you can probably find them with a little searching. I've heard of people doing the mod and they say it's cool. It's been a while since I've looked at the voice management code, but I think that the left keypad will tend to use one oscillator and the other keypad will tend to use the second oscillator.

 

*A atari joystick with presaved appegiator sequences on it (hang in with me for a second).

 

That's a neat idea.

 

-paul

[Rob Mitchell]

If you take the audio straight out of the TIA chip you can get each channel separately, but I haven't actually tried this.  I don't know the pin numbers, but you can probably find them with a little searching.  I've heard of people doing the mod and they say it's cool.  It's been a while since I've looked at the voice management code, but I think that the left keypad will tend to use one oscillator and the other keypad will tend to use the second oscillator.

 

The TIA chip puts out the sound on pins 12 and 13. One is left and the other is right. This can be checked by plugging in Combat and firing each of the tanks!

 

Here is the original post by Kevin Horton:

 

Rob Mitchell, Atlanta, GA

 

 

From: khorton@tech.iupui.edu (Kevin Horton)

Date: 21 Jan 1996 02:20:11 GMT

 

Also, it's confirmed: You *can* get stereo out of a 2600!!! Both sound

channels exit the TIA seperately. To get two seperate audio outputs from

a 2600:

 

Lift pins #12 and #13. Tie each to 5V through a 2K resistor. Attach

two .1uf caps to the two joins formed by the pin and resistor. Attach

two audio cables to the free ends of the caps and ground the shields

of the audio cables. I suggest adding a switch to short the two

pins together (that's what was done in the 2600) for mono sound. You'll

need mono for things like Pitfall ][, unless you like your music in one

side and all the sound FX in the other! :-)

[herr professor]

I got back into playing the Atari again after 17 yrs because of Paul Slocum's Synthcart.

 

Glad you like it!

 

 

Probably the easiest way to do it would be to use the circuit from an existing keyboard controller. I also have a schematic of a keyboard controller somewhere that I can scan if you need it.

 

Thats what I was thinking. I would like to see that schematic if it isn't too much trouble. I'll put it on my site so other can check it out.

 

 

*A atari joystick with presaved appegiator sequences on it (hang in with me for a second).

 

That's a neat idea.

 

-paul

 

 

seems like it would be "easier" than having rom memory on a catrdige. Just have something else feed the program info...

[Paul Slocum]

Actually, I found a scan of that schematic on here:

 

http://www.atariage.com/2600/archives/sche...sories_Low.html

 

-Paul

[gulag picture radio]

I couldn't find the yahoo group that you were speaking of at the top of this thread. Is it still active?

[oesii]

I couldn't find the yahoo group that you were speaking of at the top of this thread.  Is it still active?

 

 

there's an extra period in the above url, here's the right one:

 

http://groups.yahoo.com/group/synthcart/

 

Four other guys are waiting for you there

[gulag picture radio]

Yep. I signed up earlier today. I seem to be there under my old handle "blackhula". My soldering iron is ready... bring on the brilliance!