[sdiy] Novation peak NCOs

[Tom Wiltshire]

That Novation Peak is an interesting synth. Thanks for bringing it to my attention. They're obviously actually proud of what they've done that's different given how much info is published about it:

https://uk.novationmusic.com/peak-explained

Ultimately, this is an 8-voice polysynth in an FPGA, with everything running at 24MHz (they claim even the LFOs and Envs, if I'm not mistaken). The signal path is the usual digital-analog hybrid, with digitally-produced sources going out through analog filters and VCAs.
I was interested to see that they've even done the effects section in the FPGA, and typically for this type of machine, the effects are "wet only", so you can claim you've got a analog signal path from the oscillators all the way to the output (the clean signal is never digitised).

Frankly, this is an amazing time to be into this stuff. We've got the re-release of analog chips that everyone thought were long dead, we've got incredible digital power making very powerful synths realistically priced, and we've got all kinds of interesting mixtures of the digital and the analog.

Tom

On 21 Apr 2017, at 00:45, Scott Gravenhorst <music.maker at gte.net> wrote:

> 
> Interesting discussion.
> 
> My first FPGA subtractive synth was a 4 osc with naive waveforms.  I did that because the
> DAC was capable of 1 MHz sample rate which I used.  Harmonics above 500 kHz are so low in
> amplitude as to be negligible.  I could portamento without siren fear.  The drawback was
> that it's 1 MHz DAC was also only 12 bits (the Spartan 3E Starter Kit board).  However, the
> 12 bit-ness didn't really seem to degrade it's sound.  But still, aliasing is aliasing and
> a good high sample rate is one of the cures.  It allows the simplicity of generating
> waveforms in a naive manner.
> 
> Tom Wiltshire <tom at electricdruid.net> wrote:
>> Ok, so let's just have a look at that for a moment.
>> 
>> Assume a highest output frequency of 20KHz (I wouldn't even be 
>> able to hear this). We've got a nyquist frequency of 12MHz. That 
>> means that only anything that goes far enough over 12MHz to alias 
>> all the way back down below 20KHz is actually going to be 
>> audible. So that's 23.98MHz before we get audible aliasing. 
>> That's equivalent to the 1199th harmonic of 20KHz ramp wave. 
>> 
>> It's a high enough frequency they can ignore aliasing, even for 
>> naive waveforms, and even for tough cases like ramps and squares. 
>> 
>> It does seem like overkill, but FPGAs are cheap these days, and 
>> running a few (or a lot of) NCOs isn't even going to make one 
>> break a sweat. 
>> 
>> Yeah, why not? I like it. Simple, direct, does the job.
>> 
>> Tom
>> 
>> On 20 Apr 2017, at 18:20, Richie Burnett <rburnett at richieburnett.co.uk> wrote:
>> 
>>> An interesting direction Novation are taking with the use of 
>> FPGA based NCO oscillators on their new hybrid polysynth. There's 
>> a video from Superbooth about it on sonicstate. It uses a sample 
>> rate of 24MHz to generate classic analog saw, pulse, tri waves, 
>> etc, then feeds them through conventional analog VCF, VCA, etc. > 
>>> Seems like a bit of a brute force way to crack the old aliasing 
>> nut, but I guess it gives them the ability to do some wacky audio 
>> rate modulation stuff with reduced aliasing too. > > -Richie, > > 
>> Sent from my Xperia SP on O2 > > 
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> 
> -- ScottG
> ________________________________________________________________________
> -- Scott Gravenhorst
> -- http://scott.joviansynth.com/
> -- When the going gets tough, the tough use the command line.
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