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Old 17th May 2015 | Show parent
  #84
Lives for gear
 
Quote:
Originally Posted by Jon Hodgson ➡️
I know, I've been looking at them

http://www.elby-designs.com/webtek/m...schematics.pdf

I can't say for certain about the 002 (the 008 is the VCO synth, I assume that was just a typo on your part), but look again at the monowave schematics.

Each oscillator has its own DAC, the input of which is fed from a 64K byte RAM.

The top 8 address bits come from an 8 bit latch, this corresponds to the 256 different waveshapes the manual says are availabe.

The bottom 8 bits come from a counter, they have to be incrementing sequentially, no sample jumping can occur (other than the hirez switch forcing the lower two address bits to zero which reduces the wavetable size to 64 steps rather than 256).

The bit that seems to be missing off that schematic is where the clock to the wave position counter (the CD4040 on the oscillator sheets) comes from, it shows it is the same as A0 for the wave memory, but not where it comes from. However if you look just above it you see a CD4024 counter being used for octave division, with the octave outputs going to a switch, but nothing indicating where the output of the switch the goes to... I'm reasoning that this is A0 for the wave memory and the clock for the wave memory pointer.

So, in the monowave at least it would appear that no sample skipping ever goes on. It's a variable sample rate architecture, whether there is any jitter depends on how the clock input to that CD4024 is generated in the ATTiny2013.

This is very different to an ESQ1.
Yes it's different from the ESQ1 but you missed the main point in i'm addressing the 002 design difference to Monowave by looking and comparing the 002 PCB with the Defender PCB and Monowave and by what Paul have said so far regarding all these 3 designs, then 002 seams to be quite different then Monowave and a lot more like the Defender. It certainly don't make it easier to figure out when Modal is redefining aliasing and using terms as NCO.They could as easily have said DDS, right!

I assume typo, you meant AT2313.

My take is this, Monowave appears more to be the tradition of a simplified PPG osc using external counters and ROM if you then compare that to Defender and 002 they don't have these externals as far as i can see on the PCB's, combine that what Paul said about having problem with high end fizzle (i recall from the other thread) this suggest Defender/002 is of different design then Monowave add to that i recall Paul once said he was reluctant when something is variable rate or not and since he never replied back regarding high end fizzle in the other thread we cant know... so far.

In the case of Monowave (i recall Paul in a old sdiy thread said they where phase acc's) bit toggling/missing as we know is translated into clock jitter which propagates into the wave read out , but then is LPF filtered by the inclusion of the wave readout counter.

So 002 and Defender with it's non existent counter and ROM parts "appears" to be phase acc's run directly to Flash/SRAM at high speed and assuming 32bits wide with no BLIT is as far as i understand from literature fixed sample rate, why else would Paul have problem with audible high-end fizzle/jitter in the 002? a problem he would not have with a "true" variable rate system.

There seams to be some bugs in the Elby schematics , but the clock you
cant find i suggest is the MSB of frequency generator in the 2313.