[sdiy] Novation peak NCOs

[Richie Burnett]

I think confusion is caused by the use of the term "oversampling" in the online article. It's not *oversampling* anything, it's just *the sampling rate* like you said Tom.

-Richie, 

Sent from my Xperia SP on O2

---- Tom Wiltshire wrote ----

>I've watched the interview and read the article again, and they're pretty explicit about saying that they're generating the oscillators and the envelopes and LFOs at 24MHz. They describe that as the "sample rate" several times. They do say that it's converted to a 1-bit output, but that's just the output - (probably downsampled at that point?)
>
>So, no, I don't think it's a 375KHz or similar sample rate, although I was convinced briefly there for a moment. They say clearly it's 24MHz, so it's 24MHz. Richie's right.
>
>Tom
>
>
>
>On 22 Apr 2017, at 00:25, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
>
>> James J. Clark wrote:
>> 
>>> Regarding the 24MHz issue, the documents that I have read on the Peak 
>>> (https://uk.novationmusic.com/peak-explained) only say that the DAC is 
>>> oversampled to 24MHz, which is pretty typical for sigma-delta style audio 
>>> DACs these days. Its a way to get high bit widths - typically 16 or 24 
>>> bits. It does NOT mean that the signal processing is done at 24MHz.
>> 
>> Have a listen to the interview with one of the Novation designers about Peak on the Sonicstate website from Superbooth. He reveals more details and states that the oscillators and LFOs run at 24MHz.
>> 
>>> In 
>>> fact the "peak-explained" document specifically says that the wavetable 
>>> waveforms are band-limited before being stored in the table, to avoid 
>>> aliasing. This wouldn't be necessary if the signal path was running at 
>>> 24MHz.
>> 
>> I think you misread the document you linked to. It states that the waveforms *don't need to be band-limited* in Peak because they are being generated at 24MHz. Quoted below from the Novation website:
>> 
>> " On a conventional digital wavetable-based synthesiser, the waveforms are band-limited before being stored in the table. This is to avoid unwanted aliasing. With the New Oxford Oscillator design there is no need for band limiting; the extreme oversampling means that the aliasing problem is pushed way out of the audible frequency spectrum enabling Peak to utilise mathematically pure waveforms."
>> 
>> -Richie, 
>> 
>> ---- James J. Clark wrote ----
>> 
>>> Regarding the 24MHz issue, the documents that I have read on the Peak 
>>> (https://uk.novationmusic.com/peak-explained) only say that the DAC is 
>>> oversampled to 24MHz, which is pretty typical for sigma-delta style audio 
>>> DACs these days. Its a way to get high bit widths - typically 16 or 24 
>>> bits. It does NOT mean that the signal processing is done at 24MHz. In 
>>> fact the "peak-explained" document specifically says that the wavetable 
>>> waveforms are band-limited before being stored in the table, to avoid 
>>> aliasing. This wouldn't be necessary if the signal path was running at 
>>> 24MHz.
>>> 
>>> I would guess that the signal path is running at whatever the DAC sample 
>>> rate is (which is not 24MHz - that is just the master 1-bit clock rate).
>>> 
>>> They call this the "New Oxford Oscillator". I don't see what is 
>>> particularly new about this. Maybe there was an old Oxford oscillator?
>>> 
>>> In any case, the Cylonix Cyclebox (and the Cylonix-Intellijel 
>>> Shapeshifter) is an FPGA design and DOES run the signal path at 24MHz and 
>>> has all the nice properties that other posters have mentioned, such as 
>>> inaudible aliasing and ability to do artifact-free FM (and also 
>>> complicated nonlinear operations which would otherwise cause heaps of 
>>> aliasing). And this was released back in 2010...
>>> 
>>> Regards,
>>> Jim
>>> www.cylonix.com
>>> 
>>> 
>>> 
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