Korg Poly800 oscillator chip - M5232

[Circuitbenders]

I don't suppose by some freakish chance anyone knows where i could get hold of an M5232 do they? Its the oscillator chip used in the Korg Poly 800 mk1 & 2 but apparently it was also used in loads of arcade machines from that era. I can find very little information on it let alone find a replacement chip.

Anyone know of something else that might have one of these in it that might be easier to get hold of?

[gmeredith]

Ranger electronics claim to have them in stock - you could try giving them a buzz:

http://www.candisc.com/ranger/parts.htm

email:

sales@rangeraudio.com


Ranger Audio Enterprises
3703 - 1st Street N.E.
Calgary, Alberta
Canada, T2E 3E1

Cheers, graham

[Circuitbenders]

Unfortunately they appear to have a minimum order of $100, or about £50.

Although given the price of a working Poly 800 mkII that still might be cost effective if i can't find anywhere that will sell me just one.

[gmeredith]

I guess you could buy $100 worth of them and then sell the spares off to people for whatever you see fair - I reckon you'd have a pretty good chance of shifting some.

Cheers, graham

[Circuitbenders]

Well, if anyones interested i just bought a Korg M5232 from www.vintageplanet.nl for about £35, which is a bit pricey for a single chip but there doesn't appear to be anywhere else on the planet that would sell me one. Ranger electronics didn't actually have any and neither did anywhere else, which is a bit odd when you consider that it was used in so many arcade machines. I have discovered that it was called the OKI MSM5232 in most arcade machines but i can't find much information on that either, apart from people making software emulators.

Anyway i can recommend Vintage Planet if you are looking for some hard to find old synth components. Senso (if thats actually someones name) is a helpful guy and they have a lot of useful stuff available

[Gordonjcp]

So if there are emulators out there, we must be able to find out how it works.  Perhaps some sort of FPGA then?

[Circuitbenders]

Theres a lot of mentions of MSM5232 emulation on google but i can't seem to get any kind of solid information about it, although this could well be because it appears to be a rather specialist and / or obsessive field. I've never been entirely sure why people would want to emulate ancient arcade machines and i'm still none the wiser. 

To be honest i've never been that impressed by the sound of the 5232, or its use in the Poly800 anyway. Its always sounded a bit weak to my ears and the fact that you can barely hear an audible difference between the saw and square waves isn't much help.

[Gordonjcp]

On the Poly-800 the saw wave was generated by feeding the four octave outputs into an R/2R ladder.  So, to actually sound like a saw wave you'd need to have all four octaves turned on, otherwise you'd just get different levels of saw wave.

[korgpolyex800]

The pin outs, internal logic and description of the MSM5232 are available in the Poly-800 service manuals. The datasheet is available in the "Common" section of the files area of the yahoo group "korgpolyex".

[Gordonjcp]

Just on that note I'd recommend that has a Poly 800 or related synth to join the Yahoo! group anyway, even if they don't want the sound chip datasheet.

[YashN]

Here's a datasheet for the MSM5232 chip. http://www.citylan.it/wiki/images/3/3e/5232.pdf

Found it through a very roundabout route: first I searched for MSM5232 +arcade, stumbled on some code for the MAME emulator, saw that the chip sometimes had the RS suffix to it, searched for MSM5232RS +pdf +datasheet - voilà !

To add to what GordonJP was saying, I'm afraid it's Squares all the way down. It's a subset of Walsh functions called Rademacher functions. There are some Walsh harmonics missing that you could re-create by using the existing Square harmonics and EXORing them but... see below.

So, there's no real Saw output at all, the only thing you'll get is that the harmonics have a special amplitude configuration so that a mixture of those squares approximates a Saw...

Theoretically, Walsh synthesis is as versatile as Fourier synthesis (which does a similar thing with Sines), but for more flexibility, you'd need a good set of harmonics (i.e. 8 or 16 of them).

Once you have these, of course, you'd also need to be able to manipulate each harmonic's amplitude in a flexible way, i.e. either manually or automatically, and find some way of storing these settings.

So, it becomes a problem of control.

In truth, instead of going this route with the Poly-800, it's probably much simpler to mix in your DIY OSC circuit into the filter to augment the Poly-800's limited Osc section. You could tap into the MIDI OUT and route that to your new OSC(s) to get tracking.

[ScissorFeind]

There is one in the Korg PSS-50 also if you have a way of desoldering it...

[ScissorFeind]

Actually, speaking of which; Unless you think it wouldn't be helpful, can I see the documentation for the 'Polybeast' mod, I am curious if any of that will work on the PSS-50.