Synth's Controls Affect On Oscope Waveforms

Discussions about anything analog, digital, MIDI, synth technology, techniques, theories and more.
robrob
Newbie
Newbie
Posts: 7
Joined: Thu Apr 03, 2014 10:38 pm

Synth's Controls Affect On Oscope Waveforms

Post by robrob » Fri Apr 04, 2014 3:15 am

I did a youtube demo video showing how the Arturia MicroBrute analog synth's controls affect the basic waveforms' shape, tone and timbre using an oscilloscope. You can see and hear the triangle wave distort as the VCF, LFO, pitch wheel, etc. are applied.

The video is here: How an Analog Synth Distorts Waveforms on Oscilloscope

I think it might help some understand what we're doing when we twist those synth knobs ;D

Video Discription:
Analog synthesizer connected to an oscilloscope so you can see how the synth's controls distort the triangle, sawtooth and rectangular waveforms' shape, tone and timbre. As I move a control its name is shown in the screen's top right.

I demo the VCF in Low Pass, High Pass and Band Pass with resonance, Brute Factor and Envelope Amount. I show how the LFO effects pitch, how the ADSR Envelope effects volume, how the Glide control and Pitch Wheel effect pitch. I also show the rectangular waveform and how Pulse Width changes it's shape and tone. The same is done with the sawtooth waveform.

The synth is an Arturia MicroBrute and the oscilloscope is a DS203. Sound is run through an Alesis MultiMix16 Firewire mixer with a direct stereo connection to a Canon HF100 full HD camcorder.
Rob

User avatar
Stab Frenzy
Moderator
Moderator
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Gear: Eurorack, RYTM, Ultranova, many FX
Location: monster island*
Contact:

Re: Synth's Controls Affect On Oscope Waveforms

Post by Stab Frenzy » Fri Apr 04, 2014 4:14 am

You realise that the waveform isn't distorting don't you? (Well apart from when the filter feedback is turned up).

I think this is a great example of why time/amplitude graphs don't do a great job of describing sound compared to frequency/amplitude graphs. And also how using an unmodulated triangle wave for subtractive synthesis is a bit pointless. Next time when you're trying to show what a filter sweep does on a scope try using a saw or square or something with a few harmonics. ;)

User avatar
Bitexion
Synth Explorer
Synth Explorer
Posts: 4230
Joined: Fri Apr 15, 2005 7:43 pm
Gear: Alesis Andromeda A6
Roland D-50
Creamware Minimax
Yamaha DX7s
Analogue Systems modular
Ensoniq SQ-80
Waldorf Blofeld
Location: Drammen, Norway

Re: Synth's Controls Affect On Oscope Waveforms

Post by Bitexion » Fri Apr 04, 2014 6:44 am

Yeah, a sine/triangle wave doesn't contain any harmonics so it will just look like you're turning the volume knob on an oscilloscope when you filter it.

robrob
Newbie
Newbie
Posts: 7
Joined: Thu Apr 03, 2014 10:38 pm

Re: Synth's Controls Affect On Oscope Waveforms

Post by robrob » Fri Apr 04, 2014 1:30 pm

Yea, I should have used the sawtooth for the filter demo. I was thinking the symmetric straight lines of the triangle wave would be easier to see distort and didn't consider the lack of harmonics. I may redo the video with the sawtooth.

User avatar
Stab Frenzy
Moderator
Moderator
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Gear: Eurorack, RYTM, Ultranova, many FX
Location: monster island*
Contact:

Re: Synth's Controls Affect On Oscope Waveforms

Post by Stab Frenzy » Sat Apr 05, 2014 12:15 am

Square wave also looks pretty cool when you close a LPF on it too, try that out. Has your scope got a frequency/amplitude mode as well? It would be worth running the same signal through that to show what it does.

User avatar
Jabberwalky
Synth Explorer
Synth Explorer
Posts: 2164
Joined: Fri Apr 01, 2005 6:03 pm
Gear: A hybrid of vintage and modern junk
Band: Variar
Location: Pgh, PA
Contact:

Re: Synth's Controls Affect On Oscope Waveforms

Post by Jabberwalky » Sat Apr 05, 2014 12:48 am

I put a scope on my Dx21 once and that was, by far, the most interesting looking read out I've ever seen. FM is incredibly animated.

robrob
Newbie
Newbie
Posts: 7
Joined: Thu Apr 03, 2014 10:38 pm

Re: Synth's Controls Affect On Oscope Waveforms

Post by robrob » Sat Apr 05, 2014 1:55 pm

Has your scope got a frequency/amplitude mode as well? It would be worth running the same signal through that to show what it does.
No, oscilloscopes don't have frequency/amplitude mode. Frequency is inversely related to a waveform's time period (the higher the frequency the lower the time period) so I don't know what would be different anyway.

User avatar
meatballfulton
Moderator
Moderator
Posts: 6126
Joined: Wed Apr 13, 2005 9:29 pm
Gear: Logic Pro X

Re: Synth's Controls Affect On Oscope Waveforms

Post by meatballfulton » Sat Apr 05, 2014 1:57 pm

Yeah, it's fun to look at waveforms but I never thought it helped much to understand what's going on.

What you really want is a spectrum analyzer to see the harmonics :hifi:

Use the harmonic series, Luke!

Image
I listened to Hatfield and the North at Rainbow. They were very wonderful and they made my heart a prisoner.

User avatar
Synthetech
Junior Member
Junior Member
Posts: 185
Joined: Sun Oct 07, 2012 4:28 pm

Re: Synth's Controls Affect On Oscope Waveforms

Post by Synthetech » Sat Apr 05, 2014 2:48 pm

Jabberwalky wrote:I put a scope on my Dx21 once and that was, by far, the most interesting looking read out I've ever seen. FM is incredibly animated.

Back in the mid 90's, when laser diodes began to become cheap, I built a small laser light show using mirrored galvonometers driven by simple op amps.
I hooked my DX100 up to it and made some very interesting spirograph shapes on the ceiling. Very animated indeed.

User avatar
Stab Frenzy
Moderator
Moderator
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Gear: Eurorack, RYTM, Ultranova, many FX
Location: monster island*
Contact:

Re: Synth's Controls Affect On Oscope Waveforms

Post by Stab Frenzy » Mon Apr 07, 2014 2:54 am

robrob wrote:
Has your scope got a frequency/amplitude mode as well? It would be worth running the same signal through that to show what it does.
No, oscilloscopes don't have frequency/amplitude mode. Frequency is inversely related to a waveform's time period (the higher the frequency the lower the time period) so I don't know what would be different anyway.
Traditional scopes don't but newer digital ones often do. Your comment about the frequency being inversely related shows you don't understand what's going on there, as a waveform display like on a traditional scope is an amplitude/time graph. It's showing the amplitude of the voltage on the Y axis and the time on the X. Amplitude/frequency has the amplitude on the Y still but the X is frequency, so you can see the amount of the harmonics in each wave. The spectrum analyser that Meatball's talking about is an amplitude/frequency graph. It's actually useful for seeing what's going on and understanding how synthesis works and you would have realised right away that the triangle wave through the LPF wasn't going to do anything interesting sonically.

Ears don't measure amplitude/time, they measure amplitude/frequency. :idea:

robrob
Newbie
Newbie
Posts: 7
Joined: Thu Apr 03, 2014 10:38 pm

Re: Synth's Controls Affect On Oscope Waveforms

Post by robrob » Mon Apr 07, 2014 3:47 pm

Stab Frenzy wrote:
robrob wrote: Traditional scopes don't but newer digital ones often do. Your comment about the frequency being inversely related shows you don't understand what's going on there, as a waveform display like on a traditional scope is an amplitude/time graph. It's showing the amplitude of the voltage on the Y axis and the time on the X. Amplitude/frequency has the amplitude on the Y still but the X is frequency, so you can see the amount of the harmonics in each wave. The spectrum analyser that Meatball's talking about is an amplitude/frequency graph. It's actually useful for seeing what's going on and understanding how synthesis works and you would have realised right away that the triangle wave through the LPF wasn't going to do anything interesting sonically.

Ears don't measure amplitude/time, they measure amplitude/frequency. :idea:
You are describing a spectrum analyser which is a totally different (and much more expensive) animal than an oscilloscope. You will not see the waveform (triangle, square, etc.) on a spectrum analyser so it would be a totally different demonstration.

User avatar
Stab Frenzy
Moderator
Moderator
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Gear: Eurorack, RYTM, Ultranova, many FX
Location: monster island*
Contact:

Re: Synth's Controls Affect On Oscope Waveforms

Post by Stab Frenzy » Tue Apr 08, 2014 5:46 am

robrob wrote:
Stab Frenzy wrote:Traditional scopes don't but newer digital ones often do. Your comment about the frequency being inversely related shows you don't understand what's going on there, as a waveform display like on a traditional scope is an amplitude/time graph. It's showing the amplitude of the voltage on the Y axis and the time on the X. Amplitude/frequency has the amplitude on the Y still but the X is frequency, so you can see the amount of the harmonics in each wave. The spectrum analyser that Meatball's talking about is an amplitude/frequency graph. It's actually useful for seeing what's going on and understanding how synthesis works and you would have realised right away that the triangle wave through the LPF wasn't going to do anything interesting sonically.

Ears don't measure amplitude/time, they measure amplitude/frequency. :idea:
You are describing a spectrum analyser which is a totally different (and much more expensive) animal than an oscilloscope. You will not see the waveform (triangle, square, etc.) on a spectrum analyser so it would be a totally different demonstration.
Yes, that's what I've been saying the whole time, an amplitude/frequency graph is different to a waveform display on a scope and actually gives you useful information about the sound that's being produced. I've been suggesting a totally different demonstration would be much more useful.

As far as them being more expensive, I've got one on my phone that cost $10, one on my computer that came with my audio interface and you can build one with raspberry pi and bitscope for around the price of the cheapest analogue scope available. Even the $250 Dave Jones O'Tool module has an amplitude/frequency display. :thumbright:

robrob
Newbie
Newbie
Posts: 7
Joined: Thu Apr 03, 2014 10:38 pm

Re: Synth's Controls Affect On Oscope Waveforms

Post by robrob » Tue Apr 08, 2014 12:33 pm

Stab Frenzy wrote: As far as them being more expensive, I've got one on my phone that cost $10, one on my computer that came with my audio interface and you can build one with raspberry pi and bitscope for around the price of the cheapest analogue scope available. Even the $250 Dave Jones O'Tool module has an amplitude/frequency display. :thumbright:
Are you talking about a live, animated spectrum analysis or just a static graph? My oscilloscope can create a static spectrum graph but not a live display.
Stab Frenzy wrote: Yes, that's what I've been saying the whole time, an amplitude/frequency graph is different to a waveform display on a scope and actually gives you useful information about the sound that's being produced. I've been suggesting a totally different demonstration would be much more useful.
Then do it. Why not just do it instead of telling me I should have done it?

User avatar
Stab Frenzy
Moderator
Moderator
Posts: 9723
Joined: Tue Jun 06, 2006 5:41 pm
Gear: Eurorack, RYTM, Ultranova, many FX
Location: monster island*
Contact:

Re: Synth's Controls Affect On Oscope Waveforms

Post by Stab Frenzy » Tue Apr 08, 2014 2:28 pm

robrob wrote:
Stab Frenzy wrote: As far as them being more expensive, I've got one on my phone that cost $10, one on my computer that came with my audio interface and you can build one with raspberry pi and bitscope for around the price of the cheapest analogue scope available. Even the $250 Dave Jones O'Tool module has an amplitude/frequency display. :thumbright:
Are you talking about a live, animated spectrum analysis or just a static graph? My oscilloscope can create a static spectrum graph but not a live display.
Live of course.
robrob wrote:
Stab Frenzy wrote: Yes, that's what I've been saying the whole time, an amplitude/frequency graph is different to a waveform display on a scope and actually gives you useful information about the sound that's being produced. I've been suggesting a totally different demonstration would be much more useful.
Then do it. Why not just do it instead of telling me I should have done it?
Why did you post here if you didn't want anyone to discuss your video? I guess you're pretty new here, but this is a discussion board and you get a whole range of opinions here, some of which might not match up with your own. If you're not prepared to have people critique with what you've done (filter sweep on a triangle wave? Priceless :lol:) then you probably should post your videos here, especially seeing as there's already a thread for posting synth videos.

robrob
Newbie
Newbie
Posts: 7
Joined: Thu Apr 03, 2014 10:38 pm

Re: Synth's Controls Affect On Oscope Waveforms

Post by robrob » Tue Apr 08, 2014 3:21 pm

I was just trying to post an instructional video to help people visualize what their synth's controls are doing using an OSCILLOSCOPE--that's what's in the thread and video title. I do appreciate the critique of using another wave form for the demo and as I said I may redo the video using another wave form.

It's one thing to critique the video and another to suggest I should have done a completely different demo video and then insult me with your "priceless" comment--and you're a freaking moderator. Thanks for the warm welcome to your forum. :shakingheadindisgust:

Post Reply