[sdiy] Analogue hardware simulations in LTspice

rburnett at richieburnett.co.uk rburnett at richieburnett.co.uk
Mon Oct 14 14:48:39 CEST 2019


Yes, LTI is textbook stuff to model digitally with well established 
techniques: bilinear transform, frequency pre-warping, etc...

It's the non-linear stuff that is interesting to me.  All but the most 
simple circuits are non-linear to some extent for sufficiently large 
signals.

-Richie,



On 2019-10-12 22:19, rsdio at audiobanshee.com wrote:
> It is an “interesting” idea, but I’ll take a risk and say that it’s
> rather pointless, at least for linear, time-invariant (LTI) systems.
> The math behind the Fourier Transform is centuries old, and gives a
> full model of an LTI system. I suppose that if you’re modeling the
> distortion characteristics of real analog filters, then some other
> tool besides the FFT is needed. i.e. distortion is non-linear, so
> there might be some benefit to fuzzy analysis. On the other hand, even
> distortion can be modeled directly from the circuits without resorting
> to buzz words.
> 
> I do believe that it was someone like Yamaha who built a robot that
> could hit each key of a grand piano with 128 different velocities and
> gathered all of that data for analysis. This was decades ago, before
> the better digital piano synths were released.
> 
> In either case, I think it would help a lot if humans provided some
> intuitive input to the modeling algorithms, at least if we care about
> the energy needed to recreate the sounds after the learning process
> has completed.
> 
> Brian
> 
> p.s. But, most of all: Thanks! to Richie for sharing these LTspice 
> models!
> 
> 
> On Oct 11, 2019, at 6:19 AM, Rutger Vlek <rutgervlek at gmail.com> wrote:
>> Interesting idea to create an (IR) of hardware without having access 
>> to the actual hardware. I recently read that the digital filters of 
>> the ASM Hydrasynth were modeled after real analog filters (including 
>> Ian Fritz' threeler!) using machine learning on data (test signals) 
>> from the original hardware. Doing the same thing through Spice could 
>> also be potentially interesting! It allows to bring a non-real-time 
>> Spice model into (almost) real-time applications. The question is, how 
>> complex a machine learning model would you need to capture the essence 
>> of the Spice circuit in sufficient detail.
>> 
>> Oh and speaking of it... has anyone ever tried doing this with the 
>> Yamaha DisKlavier? That could also potentially be used to generate a 
>> very nice set of training-data from which ML techniques could learn to 
>> predict the signal resulting from a key strike (the input to the 
>> model).
>> 
>> Regards,
>> 
>> Rutger
>> 
>> Op do 3 okt. 2019 om 16:26 schreef Ingo Debus <igg.debus at gmail.com>:
>>> > Am 03.10.2019 um 15:20 schrieb Richie Burnett <rburnett at richieburnett.co.uk>:
>>> >
>>> > For anyone interested in simulating analogue hardware, I've put the LTspice schematics for three bits of classic hardware on my website for download here:
>>> 
>>> Thank you, Richie!
>>> 
>>> Speaking of LTSpice, does anyone know a simple way to get an impulse 
>>> response of a circuit other than sending a narrow pulse into it? I 
>>> mean, LTSpice can generate the frequency response of a circuit, so 
>>> there should be a simpler way, no?
>>> 
>>> Ingo
> 
> 
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