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 Forum index » DIY Hardware and Software » Les Hall's Projects including eChucK
Oscillators and Related Circuitry
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6219
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Sun May 12, 2019 4:59 am    Post subject: Oscillators and Related Circuitry
Subject description: A Project Thread
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Let's play with oscillators! I was daydreaming about oscillators, logic, and assorted networks when it occurred that this topic would make a good electro-music.com project thread. So here we are.

I've purchased some parts and some more that fell through the cracks are on the way. The list includes breadboards, opamps, lamps, jumper wires and assorted "breadboard friendly" parts from Adafruit (pots, jacks, battery holders, etc.). Which, BTW, those breadboard friendly parts are golden because the tiresome task of soldering leads onto parts for breadboard use all but disappear.

So anyway, the plan is to make oscillators and hook them up in interesting ways, then play around interactively to discover something worth building. In other words, the usual interesting stuff.

So here we are at the beginning of yet another project thread and I'd just like to leave you with one thought. When you post to a project thread it motivate me. Probably the single biggest project killer is lack of interaction. So if you have a free moment, I'd love to read whatever strikes your fancy.

Here's to good times!
Les

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Last edited by Inventor on Sat Aug 31, 2019 11:17 am; edited 1 time in total
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Grumble



Joined: Nov 23, 2015
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Location: Netherlands
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PostPosted: Sun May 12, 2019 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

I am in the proces of building an Eurorack synthesizer:
http://electro-music.com/forum/topic-69485.html DIY Multichannel Midi to CV converter which I adapted for eurorack and has an USB midi input.
https://ornament-and-cri.me ornament and crime, speaks for itself.
https://www.muffwiggler.com/forum/topic-201663.html a dual adsr generator.
https://electricdruid.net/cem3340-vco-voltage-controlled-oscillator-designs/ I use the memory moog vco, one has a switch to lower the frequency even more in order to use it as a LFO, and two identical vco’s, so I have a total of 3 vco’s.
I made a three input VCA almost straight from the datasheet of the V2164 https://electricdruid.net/wp-content/uploads/2015/07/V2164.pdf
http://electro-music.com/forum/topic-70593.html Transistor ladder filter with input mixer.

If this is not what you are after I’m happy to remove this post.

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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6219
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Sun May 12, 2019 4:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sure Grumble, it's great to see the gear you have. You could chain those oscillators together to test out some ideas.

What I am doing is circuit level, where it's possible to evolve it into a pedal or enclosed PCB device. Maybe even a modular board.

I am sleepy so I'll write more later.

Les

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RingMad



Joined: Jan 15, 2011
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Location: Montreal, Canada
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PostPosted: Mon May 13, 2019 10:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice to see you again, Les.

Could you elaborate on what you envision? How would nets be connected together?

As for chains or loops, the first circuit I put in a box was based on the one in Nicolas Collins' book "Handmade Electronic Music" (the book that started me on this electronics adventure), wherein he proposed four NAND gate oscillators, each one gating the next one (and the last splitting into the output as well as a feedback pot going back to the first one).

Those of course are simply plugged directly.

Nets would need to involve something more elaborate, right? Resistor or diode mixers? Or maybe the interference or whatever the appropriate technical term is for when signals go backwards, affecting a circuit would actually give interesting results?

.:james:.
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Blue Hell
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PostPosted: Mon May 13, 2019 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

I think delays in the connection paths would make it Cool come alive Exclamation

Also this made me think of a performance Howard once did, 2003 I t hink it was, in London, for two oscillators ... so a very simple network which was played by turning knobs ... let me see if I can find a link ... yupsa Smile

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also .. could someone please turn down the thermostat a bit.
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RingMad



Joined: Jan 15, 2011
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PostPosted: Tue May 14, 2019 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
a performance Howard once did [...] for two oscillators ... so a very simple network which was played by turning knobs

Yes! Some very nice sounds in there.

I wonder if it gives anything to connect several pairs of oscillators in the same manner.

I also like the unpredictability. (Although playing a concert with it can be pretty scary... I remember with horror my most disastrous concert, using no-input mixing board).

Delays could be good too, although I admit that I don't know how those would be achieved (except maybe if only dealing with square waves).

Jan/Blue Hell, did you ever reproduce Howard/Mosc's patch on WREN? Would it be possible? Maybe I should finally try WREN.

.:james:.
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Blue Hell
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PostPosted: Tue May 14, 2019 1:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

RingMad wrote:
Jan/Blue Hell, did you ever reproduce Howard/Mosc's patch on WREN? Would it be possible?


No, I didn't ... in fact it's the first time now that I've actually looked at the patch .. Wren does not have the phaser module properly .. this could be patched with some delays, lfo's and mixers.

But let me not derail the thread too much Laughing

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also .. could someone please turn down the thermostat a bit.
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RingMad



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PostPosted: Wed May 15, 2019 4:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Wren does not have the phaser module properly

The phaser was just for "stereo-izing" the output, it seems. The heart of the patch is the cross-modulation of the oscillators, and is the part I think most interesting, and possibly applicable to this thread.

Anyway, that's what I want to try first, if I had time... I'm preparing for a solo concert, although... no, no, it's too risky to attempt a set with a hardware version of Mosc's thing.

.:james:.
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Stream Operator


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PostPosted: Fri May 17, 2019 9:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ty for the comments, also for the link. I used to be in such a hurry that I would not take the time to follow links and actually listen to the music of my friends. That was a mistake.

I enjoyed Howard's music well enough to call it inspiring because with only two oscillators a lot of different sounds were created. I was thinking of a similar idea. Take a look at the schematic of the Wien Bridge Oscillator (attached).

My plan is to lift up the ground terminals on the inverting and non-inverting sides and connect outputs from other oscillators in some creative way. Ideas for how to do so are forming now.

At the moment I have built an LM386 oscillator driving a small breadboard-friendly speaker, tested and working by mimicking a switch's "click" noise from silent to full volume, USB power input, and just beginning on the oscillators by creating a virtual ground.

Lets cross our fingers and hope for good luck!
Les


Wien Bridge Oscillator Reerence Circuit.jpg
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The Wien Bridge Oscillator Schematic (from Google image search)
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Wien Bridge Oscillator Reerence Circuit.jpg



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PostPosted: Sat May 18, 2019 5:19 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm not sure if I should post this here or in Howard/Mosc's old thread. I built a couple of 555 astable oscillators and cross-modulated them, but I don't get anything like the nice timbres Mosc did.

Specifically, for both oscillators, I took the output at pin3 and split it to its own pin5 as well as the other 555's pin5 (through a capacitor). I also took the output from one and put it into a bandpass filter, and then mixed that with the raw output of the other oscillator. So, I believe this is the essentials of what Mosc did, without the compressor or stereoization stuff. The sounds I was getting never had wild volume fluctuations, so compressing wasn't necessary.

Maybe there's something I'm missing.

.:james:.
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Stream Operator


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PostPosted: Mon May 20, 2019 8:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi James, maybe it's best to back off a little then move forward in steps.

You could connect one oscillator to the output and vary it's control(s) to observe the range of sounds that it normally makes. Then make a chain but do not close it into a loop, noting the changes in sounds that you can make. Finally add a connection to form a loop and see how you like that.

Les

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PostPosted: Mon May 20, 2019 2:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here is a quick update on my progress.

See "The Electrifried" speaker driver breadboard circuit. It is designed to receive power from the left, generate test signals in yellow wires and drive an 8-Ohm speaker on the right. It works pretty well.

More to follow.
Les


breadboard of speaker driver.jpeg
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"The Electrifried" speakervdriver
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AlanP



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PostPosted: Tue May 21, 2019 9:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very cool, Les Very Happy
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PostPosted: Thu May 23, 2019 1:32 am    Post subject: Reply with quote  Mark this post and the followings unread

AlanP wrote:
Very cool, Les Very Happy


TY Alan.

I was having some issues with powering the board due to lack of parts in my workshop. No battery holders, no wall power cube jacks, no usb power connectors - all stuff I normally have suddenly missing. So what to do?

Order new parts then look more. So long story short, lots of power parts are on the way. This includes some pleasantries such as a 2.1mm jack in-line power switch, very handy and very safe. Also some panel mount USB power input parts for the final design.

Then I searched more thoroughly, and on top of the refrigerator was a box in a box that had a jack and plug of 2.1mm size! The female one was what the circuit needed so I hooked it up, plugged in a 12VDC transformer found earlier, and and suddenly crisp, loud (loud enough) tone came out of the speaker!

So long story short, problem solved. I played a bit with the frequency knob of the oscillator and was able to get bird calls out of it even! Happy day!

Les

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kkissinger



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PostPosted: Sun May 26, 2019 1:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Les. Look forward to seeing and hearing your results!
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PostPosted: Mon May 27, 2019 2:43 am    Post subject: Reply with quote  Mark this post and the followings unread

kkissinger wrote:
Hi Les. Look forward to seeing and hearing your results!


Hi Kevin, it's great to hear from you! I find myself typing messages and erasing them - well what can you say? How about just "back to the project at hand..."

I have managed now to coax some bird chirps and other typical oscillator sounds from the breadboard circuit that I've been describing. Next I'm planning to add one or more Wien Bridge Oscillators and see what lovely tones I can create with them. I'll have to record some audio!

Les

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PostPosted: Sun Jun 23, 2019 4:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Friends, checkout this photo of my latest test circuit. It's got my latest test circuit. The idea is to make a "Mr. Microphone" that shifts the burden of the audio output to an AM radio. This is cool because its small and simple which saves space and complexity. An equivalent circuit (single supply and LM386 speaker output with artificial ground) with more typical setup took an entire breadboard and had wires all over the place!

Below and attached to the underside of the breadboard are a pair of 6V battery holders creating Vcc and See. I like this arrangement because it eliminates the virtual ground and does not glue me to a test bench where a bench supply delivers power.

The circuit is simple: just an oscillator that oscillates in the AM band. When it's on and all tuned uo I can hear a frequency from it that drifts or warbles. It h as no antenna yes so I'm surprised that it works that well. I have t here pots: negative feedback, upper RC and lower RC. I chose this arrangement to study how the circuit works.

It's fun to listen to the frequency drift when t he power is switched on. I figure it's due to the lamp warming up (or probably al of the parts). I am currently working on removing harmonics due to the slew rate limit of the opamp of 11 Volts/microsecond. The test for that is to set the oscillator at a low frequency and scan for a harmonic at twice that frequency, then adjust the feedback pot to minimize the upper frequency. I have better pampas on order soon, but this one is what I have for now so I'm working within its limitations.

The transmit distance is about 0 to 4 inches so. At 8 to 12 inches in any direction the signal is completely lost. Of course that is without an antenna. Next up: build an antenna!

I'll post another update soon (I hope).

Les


oscillator testing.jpeg
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oscillator test circuit
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AlanP



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PostPosted: Mon Jun 24, 2019 11:45 am    Post subject: Reply with quote  Mark this post and the followings unread

is that a neon lamp? I've got some, but not messed around with them yet
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PostPosted: Wed Jun 26, 2019 3:57 am    Post subject: Reply with quote  Mark this post and the followings unread

It's a lamp, yes. I'm not sure if it's neon or incandescent or whatever else a lamp can be. I got it from Digi-Key. I'm not sure if it's the right lamp for the job and some kids claim to have damaged half of my stock of 10 lamps including this one. The kids are pranksters. Grrr but not that much!

This lamp reads 100 Ohms when off. I heard it mentioned that sometimes the lamp glowed and other times it did not glow in this application, dependent on the setup. Or it can glow below the visible threshold in daylight and room lighting.

The way it works is the lamp has a positive temperature coefficient meaning that when it heats up it gets higher in resistance. So what happens is the amp starts out with harmonics in it's spectrum then the lamp warms up from all the signal applied to it and this causes the gain of the lamp to lower then the reverse happens, etc. (or the other way around, anyway it stabilizes). This creates a clean sine wave.

When I play with it I see signs of this happening by tuning the lamp so that harmonics exist up and down the AM dial. Then when I tune the feedback resistor (I make it a 10k Ohm pot) I notice the effect. In no case do I not notice the feedback. I think this is because the trimmer pots I am using are 10k Ohms and the resistor is 100 Ohms, so I plan to use a smaller resistor parallel with the pot to get more sensitivity. That or get a 1k Ohm or 100 Ohm pot.

Anyway, it's really fun to play with and the goal is worth the effort. Stay tuned!

Les

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PostPosted: Wed Jun 26, 2019 4:51 am    Post subject: Reply with quote  Mark this post and the followings unread

"Oh man, he's writing a book!" Well, just skim it - it's not all that much.

I just wanted to make note of the purpose here and good intentions at this point. I made an LM386 circuit with a speaker and it worked pretty well. I could adjust amplitude and hear it well. It required lots of breadboard space and a big rat's nest of wires (I used jumpers instead of the neat freak technique). This worked out OK.

Then we have the simple opamp voltage follower driving a 3.5mm or 1/2 inch jack (or both for widest possible compatibility). That's OK too.

Then I got to thinking and it occurred to me that If I used an AM/FM radio as the output device, then I get hearing quality output from the board into speaker(s), headphone jack output also, and all manner of adjustments if purchased such as filtering, on/off button, volume control, etc. This I called the Mr. Microphone approach after the early 1980's product.

So basically I'm planning to try the Mr. Microphone approach! This is good for the final circuit and also for test and design because it should be easy to tap a signal on the board with a voltage follower driving some simple circuit adjustment and get both test signals and final output signal as required.

So that's the plan.
Les

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PostPosted: Thu Jun 27, 2019 1:38 am    Post subject: Reply with quote  Mark this post and the followings unread

I just improved the transmit distance from about a decimeter to a full meter (early tests of me playing around show this). First I would an inductive antenna, then I made calculations for a matching resonant capacitor. The website for calculating the inductance value is here:

https://www.eeweb.com/tools/coil-inductance

I invite you to have a try at the calculations so we can discuss the matching technique in-depth.

Les

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PostPosted: Sat Jun 29, 2019 5:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Results! The attached 17 second file shows the oscillator being switched on (at 4 seconds or so) and then warming up as it moves in frequency space to it's final frequency (or nearly so). This shows that the circuit works.

At this point the device functions as a Mr. Microphone without the microphone, just the output transmitter. How useful is that? Well all joking aside, it is very useful. I'm thinking of steering this project thread to a fun project of a DIY kit including PCB that is breadboard friendly and helps us with audio output and signal monitoring. Such a circuit could be available fairly soon.

What do you think about that?
Les


Proto 1 Test 1.m4a
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Warmup of Oscillator Frequency

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PostPosted: Fri Jul 19, 2019 3:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey, just a quick update here. I spent a week or two prototyping the new circuits and achieved only very limited response. I was able to transmit very poor but discernible voice from a short distance of about one foot. Also I randomly made a squelcher that worked within the same short distance.

Overall the brief exploration into Wien bridge transmitting was only partially successful. The next time I take a jaunt down this lane I plan to build an audio oscillator first, add vocals next, and radio with some new pampas I've selected. Hopefully things will go better next time.

Les

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PHOBoS



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PostPosted: Sun Jul 21, 2019 7:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Have you tried connecting the GND to actually earth ?
Not sure if that would make much of a difference and it's not very practical but maybe worth a try.

Also came across this which actually looks more like FM to me.

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Blue Hell
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PostPosted: Sun Jul 21, 2019 8:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Maybe not a 'real ground' but things could improve from using a metal plate connected to the circuit ground. A guy at work recently stressed on using ground planes ... sooo ... anyways .. I found http://www.csgnetwork.com/antennagpcalc.html when googling for: minimum ground plane size
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