Posted By
SukkoPera
on 2022-11-03
18:25:28
|  Re: Let's remake the DigiBlaster!
Yeah, we all see the Ferranti (U3 in my board reproduction), but that would be the DAC. The Digiblaster is supposed to also have an ADC onboard (say a sampler), but it's definitely not visible in the pictures. It must either lie below the SID (my guess, just like the 74LS245 on the SIDcard) or ADC conversion must be done with one channel of the opamp (U4) a lot of help from software (TLC's hypothesis).
I have been trying to guess how address decoding is done (that's what the 74HC20 and 139 are there for) and I *think* that it's so convoluted because two Chip Select signals need to be generated, one for the DAC and one for the ADC. I think it could be done more simply if only the one for the DAC was needed but it's all speculation of course.
So the Digiblaster is a rare thing, I didn't expect that! There are quite a lot of people talking about it here and there plus it is emulated almost everywhere, which surprises me a bit if emulator coders never even had access to one!
Anyway, if that's the case, it's one more reason to make a replica! If anyone has one but doesn't feel like doing the job, I am also keen on taking care of everything if they ship it to me. I will also be glad to return it along with a few presents  .
EDIT: Hey, look at this smaaaall pic from Solder's page, it's the only one I found of a Digiblaster without a SID plugged in:
I know it's tiny but... Do you see what I see, right in the middle of the SID socket? ;)
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