Swept Monophonic Octave Generator (SMOG)?

EBK · June 30, 2017, 12:10:46 AM

Started working on banging together a proof of concept circuit. At least if this idea doesn't pan out, I'll have the beginnings of a kickass modular synth!

EBK · July 03, 2017, 10:20:01 PM

Starting to look complicated now.

The vast majority of those parts are just for the LFO and VCO!

Hanging out at the bottom, just left of center, is an AD633 analog multiplier that will become my mixer. I was originally going to use a MC1496 modulator chip, but I decided to upgrade for ease of implementation.

On the right, mounted on the green adapter board is a THAT4316 Analog Engine, which will be my VCA.

In the lower right corner is a TL072, which will probably go with the VCA (it is just hanging out there so I don't lose it or use it elsewhere in the meantime).

Missing from the board is the AS3320 VCF I have ordered, which will (hopefully) allow me to control the resolution (LPF bandwidth and resonance), as a function of sweep rate, fairly automatically.

So far, the LFO works, but I haven't tested the VCO.

Still, I'm having fun, and I'm prepared to learn all that this crazy academic lark will teach me.

pinkjimiphoton · July 04, 2017, 02:06:24 PM

so far above my paygrade eric, just waiting to see what happens munching on some popcorn

EBK · September 04, 2017, 11:13:50 PM

Just going to add a micro update here with the hope that it will inspire me to pick things back up and make some more progress (sort of kicking myself in the rear after a long break from this project

).

The VCO is set up (basically speaking) to sweep its frequency inversely to the control voltage. I have the VCO sweeping with a ramp LFO, and it produces an amusing retro-sci-fi "JOOM JOOM JOOM" laser cannon sound when the rate is high.

I've haphazardly hooked up the modulator in a rush to more results, and I've received an audible reminder to slow down and balance things out carefully to get more of the products I want, and less of a wall of everything.

Im not going to work on the filtering until I feel the modulation has been decently balanced, but I might take a slight detour and get the VCA working.

(I have WAY too many ongoing projects. This is just one crying for my attention.)

EBK · January 23, 2018, 04:05:14 PM

Well, that last micro update didn't give me the boost I had hoped for.

Anyway, now that my design/build/rebuild queues have gotten entirely out of hand, and I've thoroughly convinced myself that I can't resist starting new stuff anyway, it is time to move some old stuff forward or abandon it. I did abandon a microDSP project by giving the parts away, bringing happiness to both myself and the recipient.

This project, however, will go on. In its dormancy, I've noticed that things often got physically piled on top of this circuit, which has been occupying most of my largest breadboard with long component leads carefully, yet fragily (sp?), balanced to provide function without unwanted short circuits.

To give this project a better chance, I've decided to buy another breadboard and rebuild it, this time more compactly and more robustly. This is where I'm at so far (I haven't quite caught up to my previous progress):

This breadboard is translucent, which I'm enjoying the look of.

stringsthings · January 24, 2018, 12:30:34 PM

Wow. Just came across this thread. Very interesting project!

I'm always impressed with people who can take breadboards and come up with something different.

EBK · January 28, 2018, 04:11:10 PM

This micro-update is just to prove (mostly to myself) that I am making a tiny bit of progress. In 2018, I'm trying to advance or officially abandon all my older projects.

Next, I'll verify that the VCO is working again, then I'll get that analog multiplier working in a nice, balanced manner.

EBK · February 04, 2018, 02:58:45 PM

I've got the multiplier wired up with its offset trimmers. I've got to do something about these trimpots though. They won't stay in the breadboard holes. Any suggestions?

maartendh · February 04, 2018, 06:12:59 PM

Change the orientation of the pins on the trimmers by 90 degrees using a pair of pliers.
I also do this to position pots on the breadboard. Hope this will help,
Maarten

EBK · February 04, 2018, 06:26:11 PM

Quote from: maartendh on February 04, 2018, 06:12:59 PM
Change the orientation of the pins on the trimmers by 90 degrees using a pair of pliers.
I also do this to position pots on the breadboard. Hope this will help,
Maarten

Thanks! I'll give that a try. I was about to resort to making tiny veroboard trimmer-to-header-pin adaptors. Your method sounds much simpler.

Aph · February 08, 2018, 05:04:39 PM

Quote from: EBK on February 04, 2018, 02:58:45 PM
... I've got to do something about these trimpots though. They won't stay in the breadboard holes. Any suggestions?

I bought a bunch of these to use on breadboards:

They fit perfectly. A little expensive, but I bought a bunch of different values just for breadboarding.
Nidec Copal Electronics CT-6 series.

EBK · February 08, 2018, 05:58:19 PM

Another great suggestion. Thanks!
I will take a look at those next time I am ready to order parts.

Kipper4 · February 08, 2018, 06:46:59 PM

Even easier to work with on the breadboard are theses (from Tayda. Other sellers are available.)

Just snip the pcb lugs off. BOOM.

https://www.taydaelectronics.com/media/catalog/product/cache/1/image/500x500/9df78eab33525d08d6e5fb8d27136e95/a/-/a-1850.jpg

Following this with intrest.

EBK · February 08, 2018, 07:09:35 PM

I have yet to place my first Tayda order.

I have ordered lots of Chinese bargain parts through Amazon though, so perhaps it is time.

bluebunny · February 09, 2018, 06:13:29 AM

Quote from: EBK on February 08, 2018, 07:09:35 PM
I have yet to place my first Tayda order.
I have ordered lots of Chinese bargain parts through Amazon though, so perhaps it is time.

Get Nathan to place a really big order first - then they'll issue a discount coupon shortly afterwards.

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Swept Monophonic Octave Generator (SMOG)?