Anyone want to help build a "DSP Student Synth"?

[jcsquire]

Is there any interest in building a synth to help EE students learn about filters (and maybe get them interested in SM building themselves)?

I teach courses to undergrad EE majors in both continuous time and discrete time signal processing. They love the interactive demos I’ve coded in C#, and when one asked last week what different filter types would sound like, I realized SM might offer a whole new world of creative demo possibilities for them, and possibly for many other students (my demos are becoming shared among several universities...some are on my website at http://www.jimsquire.com). It’s surprising how little intuition most signal processing textbook authors give to students; it seems a good venue for a SynthMaker synth.

Their needs as students are a little different than most new synth builders. They are familiar with oscilloscopes and with frequency (Bode) plots, but lack the intuition about what filters do and how harmonics sound. I’d love to see a simple SM .osm that is patterned after the default tutorial (the two oscillator synth with the ADSR amp and filter), but with
1) an added oscilloscope and spectral plot that can be set to either just before or after the filter, and
2) a small added filter Bode plot that’s dynamic (ie it shows how the ADSR changes the magnitude of the transfer function for each new voice).

Is this possible in SM as a stand-alone-VST? I’m not sure if a spectral plot component is available, and if it is, if it compiles into a VST. If someone finds this interesting, I could give them a small honoraria (and bragging rights as the developer, FWIW!) if we can keep everything open-source so the students who feel so inclined can download the .osm version and play around with it themselves.

[Disco_Steve]

SM can do bode plots
and what you sugest sounds relitively easy.
there isn't an 'open source' collection of filters to cycle through so one will need to code them. but from your c# examples that should be relitvely straight forward.
i.e. would you be willing to post the filters you would like coded in SM speek (including all coefs and maths, I know they are easy to find but give and take is always good ) and then I can whip them up for you

I would be happy to help, after xmas, I have some time before uni starts again. and I dont have any exams at the start of the second semester this year (YES!!!)

I've never made a synth before I just make funky sound algorithms
and would love to learn myself, and teaching others along the way is aways a bonus. (dont worry I have good SM skills and know about synth concepts, they just dont interest me as much as DSP)

[MegaHurtz]

if we can keep everything open-source so the students who feel so inclined can download the .osm version and play around with themselves.

hihi

If not this is one of the best programs to do yust that.
If you have the time for a bit of research seek out Dozius filter pack "on the forum"
Although 99.9% of the digital representations are filters based on ye good ole biquad.

[Disco_Steve]

I didnt think dozius wanted non paying members to use thoes filters? and they are all optimised. generic slow code will be more usefull to students?

[jcsquire]

Thanks for the feedback! I'm sorry; I was unclear about the filters. The filters I meant are the same ones as in the already-published demo synth that first pops up by default when loading Synthmaker. It comes with a lowpass, highpass, bandpass, bandreject, and peaking filter. If for some reason those aren't available for public distribution, I have no problem designing the IIR or FIR coefficients to implement them, however.

The musical community intuitively knows what these filters do, but my students lack that understanding; they only "know" them by the sight of their Bode plots, not by their sound. If they could see a little Bode plot underneath the filter choice at the same time they hear the sound, the relationship would be clear.

So I'm really suggesting "just" (and I appreciate how difficult "just"s can be) adding three plots to the already-available demo synth: a small Bode plot under the filter choice, and a combination oscilloscope/frequency magnitude plot of the signal that can be switched to tap the signal either before or after the filter. My impression is that some of the plot components don't compile into a stand-alone VST well, but maybe I'm mistaken.

[Disco_Steve]

yea the filters in the generic synth are for all to use.

shouldnt be too hard.
how pritty do you want it!
because if you want it to look like sex I'm not the best guy for the job!
if you dont mind it being 'ugly but practical' then I can whip you somthing right up. although knowing this forum, someone will have done it before I get home!!

[MegaHurtz]

I have to go now but if you give me a coulpe of hrs ill make you something nice tonite.

[trogluddite]

I built a scope a while ago (Thread Here) that you're welcome to use.
It will display multiple colour coded traces simultaneously by attaching the small 'probe' modules anywhere you like in the signal chain.
At the moment the vertical range is 'autoranging' (may not be so good for amplitude comparisons), but if you think it's suitable for you, I'd be happy to make a few adjustments.

[jcsquire]

I love working across timezones!

Disco-Steve: My students are engineers; their theme song (besides various Monte Python excerpts) is "we're engineers: sex can wait until we graduate". Would love to see whatever you come up with. I have a small honoraria for this that I'd be happy to distribute among whoever helps, although the really cool part is knowing you may help quite a few students get that "snap, that's what it means" moment. I'll put all contributor's names on it, of course, and if we can get it working well it may enjoy a healthy distribution among students from many universities.

You'd be surprised to see how many textbooks teach filter design purely using equations and plots, and how few attempt to use audio, even though we process visual images in the space domain, but hear in the frequency domain.

[jcsquire]

Oh, and thanks Trogluddite; your scope is beautiful!

[trogluddite]

Thankyou, glad you like it.
I'll give it a little check over at the weekend - should be easy to make the scales properly calibrated and add a few grid lines, so that amplitude comparisons between traces are made easier - something I always meant to do (SynthMaker is so versatile that I often go off on a tangent mid-project.

purely using equations and plots, and how few attempt to use audio

"Writing about music is like dancing about architecture" (Elvis Costello) - though I do rather have a soft-spot for some of the onomatapeoic neologisms used by the reviewers of audio hardware/software - I bet even Shakespeare would have found it challenging to describe the sound of an "Acid Techno" filter sweep in wprds.

[jcsquire]

Thanks Trogluddite. I don't understand SM graphics at all, but I think I recall that certain graphic plots don't translate well when the "compile to VST" option is checked. I hope yours works!

[trogluddite]

Must admit I've never tried it at a VST - I use the scope mainly for schematic 'de-bugging' etc. The main display is basically the same graphics routine as my goniometer design (LINK). and that has always exported OK.
Only source of problems I can think of would be the display resizing etc. (SMs VSTs always have fixed window size) - but let me know how you get on - I'm always glad of any feedback that can help improve my designs.

[jcsquire]

Thanks for the feedback Trogluddite! I'll let you know whatever I discover in the process. It is a beautiful scope you've made - cool to find programmers with artistic talent.

Is there anyone interested in wiring up Trog's scope and a spectral meter (and I appreciate the fact that there isn't a spectral meter component available!) to do this? Although I've been a SM member since beta times, and I've used it to code some simple frequency-generator components for non-audio uses (if interested this is an example of such a use) I really don't know anything about its graphics. Since synth development is not a hobby of mine (not that it doesn't look like fun, but it's too close to my day job of teaching DSP...like a friend of mine who's a game developer who won't touch a playstation) I'm not keen on learning a new language to create one demonstration.

If there's anyone interested in wiring something up like I've described, I can assure you it would expose a lot of young adults to SynthMaker in particular, and hopefully get a few more motivated to learn more about DSP. I realize there's not much fame in that, and that having your name on an open-source synth doesn't exactly pay the bills. I can say that demos I've made or organized do get a wide readership; only US universities so far, but they've been used by profs at MIT, BU, Arizona State, VMI, and others...so it's not like you'd be helping just one random guy, but rather potentially many teaching many, many others.

[Disco_Steve]

can it wait till after xmas day?

if so I can definatly whip you somthing up.
if not I dont think I have time sorry