Paul Slocum's website

Synthcart is a cartridge I developed for the Atari 2600 game console that turns it into a basic synthesizer with an argeggiator and built-in rhythm patterns. The controls are designed so that it is possible to use without a TV, allowing it to function as a stand-alone synthesizer. Synthcart requires a pair of Atari keyboard controllers or video touch pad controllers, which can be found on eBay.

Synthcarts can be purchased from The Atariage Store.

FEATURES:
● Play an assortment of familiar Atari sounds
● Use two different sound types at a time, one assigned to each controller
● 8th, 16th, and 32nd note arpeggiator
● Beat Box with many pre-programmed beats and fills
● Play two beats simultaneously to create custom beats
● Two tremelo settings
● Four attack/release settings
● User interface designed so that a TV is not required

● Easter egg: light show mode that displays color patterns based on sound output. To activate, put the scale on "major" and put the left keypad on "pitfall" or "saw" and play the notes: 4 7 8 9 8 9.

Audio Samples:

Synthcart bass with beat
Synthcart square arp
Synthcart with Pitfall sound and drum beat

Synthcart 'Light Show Mode' Examples:

Which controllers work with it and where do I get them?

Keyboard Controllers, Video Touch Pads (Star Raiders controller), and the Atari Kid's Controllers will work. I usually use the Video Touch Pads which you can get on Ebay. The Kids Controller is also good and looks great, but is usually a bit more expensive (about $20-$30 for a pair.)

What all do I need to use Synthcart?

An Atari 2600 w/ power supply, TWO keyboard controllers, and a TV (or a VCR that includes a TV tuner and audio out).

Which Ataris will it work with?

It will work with all Atari 2600's including the Junior model (black and silver). It also works on the Atari 7800. However, the 7800 doesn't have a B&W/Color switch. So the 7800 will not be able to access all the sounds unless the B&W switch mod is done (install a switch/toggle in place of the 7800's momentary Pause button).

There are PAL and NTSC versions, but not a SECAM version.

Is there a sequencer or drum beat editor on the Synthcart?

The beats cannot be easily edited. There are 33 beats and they are hard coded in the cartridge. There's not enough memory to have any proper sequencing. The Atari only has 128 BYTES of RAM which is already filled.

However, since I've released the source code (see above), if you like to hack, you can modify the beats and re-assemble the ROM into a version with your own beats. Then you can run that on an emulator, krokodile cart, or cuttle cart 1 or 2, or get Atariage to make a custom Synthcart.

What generates the sound?

The sound is generated by the Atari 2600's built in sound chip (the TIA). The cartridge doesn't have any special sound generating hardware, and it is just a regular Atari 2600 cartridge.

How do I get a direct audio out?

You can do the modifications yourself: you just solder two wires to the Atari board and then connect them to a RCA or a 1/4" connector.

Check out Ben's how-to page to figure out where to solder the wires. On Ben's page go to "How do get composite video from [whichever Atari you're using]?" and it'll show you where to solder the audio wire (just do the audio mod, ignore the video portion). Solder the other wire to any ground point.

There's also this mod to get audio-out with a stereo option (one output per oscillator).

And there's also the new A/V mod kits from 8bitdomain which are quite a bit cheaper than the Cybertech mods that I use (which are no longer in production). I haven't tried these A/V kits yet, but I've heard good things about them.

Other easier options are to get a VCR and use its tuner and A/V outputs or get a video demodulator.

Do I have to have a modified Atari to use it?

No, you can just use your TV. Or you can hook it up to a VCR with A/V out to get the audio.

Is there a way to sync the Synthcart to my gear?

Not automatically, but if you set your gear to the same tempo as the Synthcart and start them at the same time, they will stay in sync since the 2600 clock is very accurate.

Some limitations that musicians should be aware of:

- The pitch on the Atari is very limited. I’ve set up a sound table of 12 notes from a major scale for each sound type. While these notes are reasonably in tune with each other, some sound types do not use a standard tuning. For example, the bass sound is in C# major at -35 cents. You will have to tune your other sound modules accordingly or use a pitch shifter to compensate. I have not found this to be much of a problem.

- The tempo is only adjustable in large increments. The Atari demands a lot of the processor’s time to draw the screen. To have a fine tempo adjustment would require me to update the tempo counter, arpeggiator, beat box, and voice manager many times while drawing the screen, which is just not feasible.

Tempo values in BPM on the NTSC version are: 224.71 179.77 149.81 128.41 112.36 99.87 89.88 81.72 74.90 69.14. The values are calculated from the Atari's clock frequency, so they are very accurate.

- Although Synthcart works with NTSC and PAL Ataris, it does not fully work on European SECAM Ataris since the B&W/Color switch doesn't work the same way on those models. Half of the sounds will be inaccessible on SECAM models.