My Dream Sampler-Synth from DSI

Discussion about Dave Smith Instruments, upcoming and potentially-upcoming instruments.

My Dream Sampler-Synth from DSI

Postby Razmo » Thu Jul 10, 2014 10:35 am

Now that I've read so many thoughts on what the next synth from DSI should be, I thought; why not try and dream up a concept of my own? ... and then make a thread about this to see how many would find such a product a good idear? ... maybe chime in on the features and such... a kind of little "Let's dream we were Dave, and could design the next one" kind of thread?

It will have to not only be something that is possible in your dreams... it should also be possible in reality, trying to keep things like cost, parts, structure and such in mind at the same time, just like DSI would do it. Afterall, we don't want a synth that cost more than 2000 dollars, or fit technology only attainable 50 years ahead in time :)

What I would like to "design" in this thread is MY dream... a hybrid Sampler-Synth.

I've been thinking about the rough voice layout today, trying to keep the number af ADC/DAC's to a minimum, and keeping in the design philosophy of how the Curtis VCF/VCA seems to work (from looking at DSI's other products). It's a hybrid "digital front end with analog signal path thereafter" approach, simply because that's the only way to do a Hybrid Sampler-Synth.

I've not yet thought much about what goes into each module in the below diagram, but that will be my next step... later I'll be thinking about sample import/export, how to manage it all and stuff.

So basicaly, this thread is about designing a DSI type hybrid Sampler-Synth... if you have any idears, feel free to post them... it would be fun to see how many would really like to see such a synth from DSI in the future :)

Here is my current voice layout:

DreamSamplerSynth.jpg
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Re: My Dream Sampler-Synth from DSI

Postby Razmo » Thu Jul 10, 2014 10:59 am

One thing I'd like to know, if Chris or Carson could help me out, would be how the Curtis chip's signal path is internaly... exactly what features does it have... does it have both VCA/VCF in the same chip? ... does it have Panning internaly? ... what really goes into the chip, and what comes out.

Without knowing this, it's kind of hard to figure out, what is possible in a voice architecture using these chips... my above diagram may be incompatible or something.... I'm not expecting any greater explanation, just a few guidelines if they want to give them. :)

Personaly I'm a bit confused as to these chips panning options... is panning done "in chip" or is this additional components after the chip... so many questions :)

I'm trying to stick to ONE DSP chips on the digital front end, that should have a digital output to the DAC... and an input that could come from a DAC, so that the DSP can do the feedback path it needs to.... and then everything after that being analog all thru.

The only exeption is the optional digital FX in the above diagram... I suspect that might require an extra DSP chip and extra converters to accomplish which would raise the price... it might be more addequate to leave that out, and simply use external FX instead, though it's always nice to have some FX that can be appliead to preset design "in box".

The FX I'm thinking about are not Reverb and Delay... these are usualy best delivered externaly in my opinion, but FX like Distortion, Chorus, Stringer Ensemble, Phaser etc. that are not ambient FX.

The reason I have "Volume" in the Pan section as well is that it would be crucial to be able to turn down the volume of both FX and Analog path individualy, so that the FX path can be heard on it's own without the dry signal... some insert FX would require this.
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Re: My Dream Sampler-Synth from DSI

Postby Razmo » Thu Jul 10, 2014 11:10 am

Another goal of this design would be to avoid having to use USB for sample transfer between computer and device... mostly because it will require software development that I know DSI don't want to delve into (this has been said many times regarding editors, that DSI leave for 3rd party developers).

Therefore I think the wisest way (and the easiest to implement) will be an SD card slot for both saving and reading data, and for a fast working environment the sample memory should be static RAM, and not Flash memory that is slow to write and has a finite amount of times it can be written.

It would not need an enormous amount of RAM anyway... I don't want this to be a full fledged sampler, but rather a Sampler-Synth... it's meant to be used for making synth sounds using sample building blocks like small looped textures, single cycle waveforms... not huge multisampled instruments... leave that for the true samplers and workstations instead. :)

With building blocks I'm thinking looped textures, transient sounds... small well prepared snippets of sampled sounds that can be sculpted into totaly different tones and mangled like crazy using a typpical DSI engine.
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Re: My Dream Sampler-Synth from DSI

Postby Razmo » Thu Jul 10, 2014 1:43 pm

OSCILLATORS:

I've been thinking about what would be needed for some flexible sample oscillators, and I came up with the following parameters:

OSC Sample Number (Off, 1...255)
OSC Sample Start (Random, 1...100%)
OSC Sample Loop Mode (Off, On, Gated)
OSC Sample Trigger Mode (Normal, Legato, Latched)
OSC Coarse Tune
OSC Fine Tune
OSC Glide (Off, 1...255)

Maybe more could be added, especialy in the loop department, but for now I asume that loop start, end etc. is hardwired in the .wav/.aif files that could be saved on an SD card.

Most manufacturers use the simplest level of control for an SD card, which leaves you to only save up to 512 files in the root of the card. As this is the easiest to implement, I'm thinking this could do it... of course a full fledged FAT32 format would allow for much better usage of the SD card, but for now I asume this simple way.

Thus, 255 .wav/.aif files could be saved independently to an SD card in the root, and when the synth reads a bank of sound data, the samples could all be easily loaded into static RAM... files could be named with numbers, indicating their position.

I think 255 samples would be more than enough for a single bank project. 16bit samples of course.

OSC Sample Start has a random setting, to allow the oscillators to start the same sample at different positions. With sustained textural samples and single cycle waveforms, this would be the equivalent to having free running oscillators, if the Sample Trigger Mode is also set to "latched" so that it never stops playing.

The Sample Loop Mode's "Gated" setting would allow for the loop of a sample to only loop when the voice is gated... and when the voice is released, it would continue playing the loop till the end, and then continue to any sample data left behind the Loop.

The rest is self explanatory...
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Re: My Dream Sampler-Synth from DSI

Postby chysn » Fri Jul 11, 2014 2:53 am

A DSI sample-based synth is something that I've never even thought about. I like the idea of loading in resources and then bringing DSI's modulation capabilities into the mix.

Without supporting multi sampling, you'll run into huge aliasing problems over a really short keyboard range. Maybe the innovation of a sampler-synth would be an anti-aliasing algorithm that can "smooth out" waves as the playback sample rate is lowered.
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Other Synths: Moog Little Phatty Stage II (Red), Arturia MicroBrute
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Re: My Dream Sampler-Synth from DSI

Postby Razmo » Fri Jul 11, 2014 8:31 am

chysn wrote:A DSI sample-based synth is something that I've never even thought about. I like the idea of loading in resources and then bringing DSI's modulation capabilities into the mix.

Without supporting multi sampling, you'll run into huge aliasing problems over a really short keyboard range. Maybe the innovation of a sampler-synth would be an anti-aliasing algorithm that can "smooth out" waves as the playback sample rate is lowered.


You are right about aliasing, though it could be done... Have you ever heard an E-MU Ultra sampler in action?... but they also use intermediate-sample interpolation algorithms to smooth things out.

But in general, being able to make multisamples would not be a problem, just require more coding and such... if one does not want to use it, you could just leave it alone I guess :)

Other things I've been thinking about is that maybe granular sampling could make up a bit for that, and the ability to stretch samples. It would make the thing more complex, but it would be a nice addition.

The whole idear of making such a synth is the ability to use small snippets of sustained textures as building blocks... that is what makes it different, because the signal path is not much different to DSI's usual signal path in their synths... the only new thing I've thought up is the "Oscillator Intermodulation" part that I'll write about soon... but in general the ability to modulate the four oscillators with each other in different configurations and algorithms... a bit like "algorithm" with an FM synth, just a load of other types of algorithms... like for example:

Ringmod
Frequency Modulation
Sync
Diverse logical operations between oscillators like AND, OR, XOR etc.
Clean Mixing

The thought is that these algorithms could always be expanded upon as new features, and that a set number af controls would be available to tweak the algorithm.... say four control parameters that change behavior with each algorithm.

In general a feature that allow you to mangle the samples together to form copletely new tones to work with before it goes into a digital multimode filter.
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