I’ve completed designs for the Prophet 3000 I-627 rev B memory controller adapter in collaboration with Martin Day in the UK (thanks Martin!). Martin successfully upgraded his 2MB Prophet 3000 to a 4MB unit.
A bit of history: The first revision of the Prophet 3000 (most of which were shipped to Europe) had a first generation custom voice controller chip, the I-627. This chip takes the sound data from RAM and generates 8 voices worth of sample playback. The first generation chip (in a PGA style package) has problems using multiple banks of memory, which is why most Prophet 3000’s only have 2MB. After Yamaha bought Sequential in 1988, they redesigned the I-627 and changed the package to PLCC. The main PCB of the P3000 was redesigned for the PLCC I-627, and these units can be expanded to 4MB.
The corrected I-627 is available from Wine Country Productions; however until now there was no solution to retrofit the first generation Prophet 3000’s. Additionally, the schematics were updated for the new I-627 pinout on one page only, and the rest of the schematics refer to the old PGA I-627. Martin identified the pinouts for the PGA I-627 and cross checked the newer PLCC I-627. He constructed an adapter board for the newer I-627, but unknown to him, there are several errors in the schematics which prevented proper operation. Luckily I have one of each revision of Prophet 3000, and was able to find the errors. It appears as though there was a documenting error with the newly revised I-627. Two power pins were swapped (which Sequential solved by physically removing the PLCC socket contacts for those pins), and the RAM bank select signals were out of order (which they solved by cutting the PCB and using wire jumpers). With the newer units, they reassigned the banks so that banks 0 and 1 were on the PCB and banks 2 and 3 were on the memory expansion connector. I don’t know if Sequential ever made a memory expansion board, but if they did they are very rare.
I’ve completed a design for a memory expansion board which will require the I-627 rev B adapter board for older units. If all goes as planned, this set of boards can be installed without any soldering or modification of the main PCB. Stay tuned!
Fantastic News to start off 2013!!
does this project also open the road to the 8mb extension (unobtainium or urban legend ?).
“4Mb memory expansion board could be added to a 4Mb Prophet to create an 8Mb Prophet 3000 that offered 42.4 seconds of stereo sampling at 48kHz. The 8Mb Prophet’s largest single sample size was 4Mb, which meant that an 8Mb Prophet 3000 in mono could only allow for two single samples with a maximum of 4Mb each (not one 8Mb sample).”
The P3000 can only have 8MB total memory (4M words), so yes, that is correct. There are four banks of 16-bit x 1Mbyte.
Any news? Could you post documentation, pics, schematics and info, please…
I haven’t worked on the P3000 update for a while. I’ll post some pics if I get a chance over the next couple of weeks.
How does the p3k compare to the E3? I would imagine that’s it’s closest rival?
on paper the P3000 should be better as it has variable sample rate rather than DSP interpolation for transpose. But the EIII has that emu magic in the sound department and some great vca filters. EII has variable sample rate and companding.
Well, Syn-Fi, I think you’re wrong. Emulator III (and Emulator III rack) has variable sample rate and has 16 voices and 16 individual monophonic outputs plus one stereo output. Old design where every voice has it’s own DA than filter and ADSR and finally analogue voice mixing. Minus is monophonic outputs. Emulator 3X and later models (ESI32, EIV…) have DSP interpolation. All voices are digitally resampled to fixed sample rate inside DSP (EMU 8000 or similar), digital filters, envelopes and mixing. Plus is polyphonic outputs and digital I/O.
In my opinion Emulator III is best sounding machine of all in my studio. Btw, I have 30+ various synths, modules and samplers including EIII turbo, EIV Hollywood gold, Akai S3200, Akai S1000, Akai S950, Yamaha TX16, Roland S550, Ensoniq DMS8 and Prophet P3000 (plus various soft samplers…). Emulator III has most powerful sound, always impresses me.
I was going from memory and had not studied the service manual and theory of ops carefully enough, it seems. But your post has caused me to look again. The EIII departs from the EII, in that, it has a over-sampling DSP chip the ‘F-CHIP’ which feeds the DAC with the rate and its 2x over-sampling at any point and that digital signal is fed to the x16 DACS. Yes each 16 voices has a discrete audio path. The pitch data is not arrived by clock change from DAC alone, it is asynchronous per voice, so yes it is ‘variable shifting’ but it not the same process as the EII or EI because of this F-Chip. Its probably better, more refined, for this reason than the methods deployed in the EII and alike especially as its over-sampled.
This ‘F-chip’ could be the difference (amongst other things) between the EIII performance and the p3k. It probably has better resolution in the high-end with no discernible aliasing. The p3k also has a discrete chip that goes to each DAC but its difficult to see what it might be doing with out a detailed theory of ops.
Many thanks for your opinion over the EIII, you clearly have many samplers to choose from and form a view.
It would be really cool if someone could do a test with the say the (1)EI/ppg waveterm, (2)EII, (3)EIII, (4) Fairlight and finally a pure interpolating sampler like the EIV/ASR10.
what happens to the sound as it is transposed from low to high.
thanks for making me look at this again and i need to redouble my efforts to find a EIII, clearly!