HOW DO I MOD MY 1040 STfm For 3 Channel Output?

[DEADBEATBLAST]

Hey, I wanna do a "pro audio" type mod on my 1040STfm, with all three channels being separated.

Can anyone point me towards some thorough documentation on how to do this? I've seen a couple peoples "tutorials" but they're worthless.

Also possibly doing this to a 1040STE as well. Looking to add either 3 rca jacks, or 1/4 inch patch cords to run to a mixer.

If anyone can help me thankyou!

[DarkLord]

Don't know how much you can find out about it, but the Tweety Board did this, I think.

Here is a description:

"Practical Solutions debuted Tweety Board at a recent Atari Fest in Glendale, California. Tweety Board is a solderless upgrade that enables any ST to produce stereo sound. A hardware adaptor with three RCA phono jacks connects to the RS-232 port on the ST; you can add two speakers for conventional stereo sound or three for full surround-sound capability. The adaptor also includes a pass-through that lets you connect other RS-232 devices to your ST. Tweety Board is expected to cost $49.95. Contact Practical Solutions at 1930 East Grant Road, Tucson, AZ 85719, (602) 884-9612."

Of course they are long since out of production. I don't know if maybe you can pick one up off of a dealer, ebay, or maybe some user somewhere.

Good luck, and let us know how it goes!

PS that description looks like an external model - there is an internal one as well.

[DEADBEATBLAST]

Hmmmmm... Not really what I'm looking for. I want to do this myself with a soldering iron and some wires.
A schematic of the YMs sound output would be more helpful. I know there's people out there who have done this before.
ungh... If I figure this out I am going to make THE DEFINITIVE 3 Channel output mod tutorial. That way no one else will have to suffer.

[DarkLord]

Hmmmmm... Not really what I'm looking for. I want to do this myself with a soldering iron and some wires.
A schematic of the YMs sound output would be more helpful. I know there's people out there who have done this before.
ungh... If I figure this out I am going to make THE DEFINITIVE 3 Channel output mod tutorial. That way no one else will have to suffer.

Yeah, I figured it wasn't - if someone had the schematics of the Tweety board, that might be helpful as well.

I look forward to your tutorial.

[wongck]

is there such a thing. Only mod to stereo 2-channel output can be easily found in this forum.

I remember I had a small PCB that plugs into the parallel port of my STFM and drive a speaker.
Sort of digial sound from parallel port but I cannot remember which program I was using.
But I think you're not looking for this.

[Awol]

There's this video...

I haven't done the mod, but it seems fairly simple. From what I understand (again: I haven't done the mod, this is just from a brief viewing of that video, and I could be wrong), you should just be able to find a pinout of the YM2149 chip, and look up the 3 pins that correspond to each of the 3 YM voices, which are normally soldered together and mixed on the motherboard. I think you just have to cut the trace by each of the 3 pins in order to disconnect them from the motherboard and each other, and then just solder an audio jack to each of the 3 pins (and of course connect the appropriate tabs on the audio jacks to a ground spot as well). The video I linked to mentions a possible 5-channel mod on an STE... I think he is probably referring to adding an audio jack to each of the 2 channels on the STE's DMA sample playback chip. STF/STFM computers don't have this additional DMA chip and must playback samples through the YM chip as a "digidrum" effect (which I think is supposed to sound more lo-fi and be more CPU-intensive).

However, be warned that (apparently) if you perform the 3-channel mod, the sound will be slightly different, and you may have trouble playing digidrum samples:

gwEm asked that I inform watchers, that if you perform a similar mod on your ST, that you be aware that you may encounter difficulty with 8bit sample playback through the YM (ie: ProTracker) as this requires an even mono mix of the channels for reliable recreation of the sample playback. Additionally, the stock YM setup achieves a bit of natural compression that is lost due to the channel separation. You have been warned, if you value the stock characteristic sound, proceed with caution!

[wongck]

why.... that idea is so simple.
Just get directly from the chip pins.

[DEADBEATBLAST]

Well thanks anyways for all the ideas, i guess I'll just start with a chip pin diagram and work from there. Not to worried about messing up any sample playback/digidrums, i think they'll sound ok as long as i mix the 3 lines back together. Either way, I got an extra 1040 in case I mess one up. And I wouldn't even bother doing it to an STE. Anyone have an idea for isolating the audio input line?!

[Stefan jL]

You don't have to worry about the music using the "digidrum" effect... the "drums" will sound ok when played on each channel, it is only 8bit samples playback that is messed up when splitting the YM channels.

[Ayreon]

Here you can find a way to do the stereo "upgrade". It should be easy enough to mod it to a 3 seperate channels circuit or make it switch between normal, stereo and 3 channel .

http://www.xs4all.nl/~rdemming/Atari/index.htm

[Xerus]

You have to make a mod where you can choose the position of tracks or to mix them together, otherwise the music will not always pleasant to listen...
Ex: ABC, ACB, BAC ...
It seems there is a similar mod in the French magazine ST Mag.
It comes from Rodolphe Czuba but I could be wrong...

[Stefan jL]

I just made the three YM2149 channels seperate on my ST, it was just a test to see if it worked and not to make something that looks "good"
I dont have much knowledge in this stuff... i just tested what worked aand what did not work (dont worry nothing got broken).

You need three phono connectors for this.

First the audio out pins of the YM2149 must be seperated from the PCB as it gets mixed there, i soldered of the YM and put a socket there and then i carefully bended out the three audio pins so they were not in the socket and then soldered wires to each one of them... i also soldered a wire from "pin 1" to get ground from there.
If you dont want to add a socket then you can just cut of the three audio pin legs of the YM (as close to the PCB as possible) and then bend out them, just so they have no connection with the PCB.

The ground wire needs to be connected to the audio signal wires thru a 22k resistor (one resistor for each channel) and after that so added i another resistor for the audio signal to pass thru because the volume was so loud... i used a 47k resistor... you can choose another value if the volume is too loud or weak.
And then just connect the wires to the phono connectors and you have three seperate cahnnels from the ST.... if you do this on an STE so do you get 5 seperate channels , 3 YM and 2 DMA.

The circuit certainly needs optimisation, this is how my looks right now:



Overview:



Closeup of the socketed YM with bended legs:



If you did not understand the text and photos so have i done an even more confusive drawing here: http://www.ym2149.com/ym2149_3/ym_3channel_setup.png

also i did some recordings of the seperate channels and also mixed them for mono and stereo using Audacity... you find them here:
http://arcade.ym2149.com/pcbupdate/atar ... el_ym2149/

[Stefan jL]

Now i modded my STE for 5 seperate cahnnel outputs and it worked fine.

A pic of a recording showing all 5 channels (from Lethal Xcess music excerpt)



The YM channels are a bit low in volume compared to how they are mixed in the Atari, DMA is unchanged and still sound loud.
get the Audacity project files here if you want to check out the recordings (also stored as OGG files so you dont need Audacity to hear them) STE_5channel_recording_audacity_project.zip

[redhawk668]

I remember I had this kind of mod on my 1040 STfm, remember running Ex BIG demo in stereo.... Absolutely great! By the way, I'm new here....

[redhawk668]

I remember I had this kind of mod on my 1040 STfm, remember running Ex BIG demo in stereo.... Absolutely great! By the way, I'm new here....