Winner, Name that Ware October 2023

The Ware for October 2023 is a Seiko DS-250 keyboard synthesizer.

Nobody guessed the exact make and model of the keyboard, but it was really entertaining to see the comment thread puzzle through the design. The dual 8049’s caught my attention too, as well as the lack of obvious DACs. I have some partial photos of the associated I/O board, and it also lacks an obvious DAC — mostly just generic mixer/amp/analog switch components on there, so I’d agree with the idea that the DAC could be integrated into one of the big Toshiba chips (or perhaps they are doing something with PWM).

I’ll give the prize to Cary Roberts for being the first to guess the general class of ware (congrats and email me for your prize!). Lots of attention to detail to what I had accidentally left in the background after the crop, I didn’t even notice the rollover diodes in the background until someone pointed it out!

Thanks again to JeffreyO for contributing these photos!

2 Responses to “Winner, Name that Ware October 2023”

  1. Andrew McNamara says:

    I’d still love to know what they’re using that PLL for in the lower left.

    • bunnie says:

      Hmm interesting. I took a quick look at the datasheet and they aren’t using it in the configuration recommended for any of the RF stuff — pins 2 and 3 should be connected to a crystal, and it’s not. So they are likely driving the reference frequency directly from some other chip. The phase comparator and frequency divider are definitely used, however. Hmm…and it looks like the 8049’s each drive one PLL chip (and interestingly enough there is a provision for a shared 2764 ROM).

      Ah looking at some of the capabilities of the device, it can do both “digital and additive”, and an article seems to reference that the additive features are at least partially implemented using analog capabilities. I wonder if the 8049s + PLLs aren’t responsible for the additive synthesis?

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