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Working on a 3-voice 40106 oscillator. Need help...

Alec_t

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I assume that you're saying that it doesn't matter which way I wire up a pot to the voltage input to play with 'voltage starve.' Am I correct?
No. My comment was about the output of the IC, not its supply voltage.
Re: your first file: I do hear an amplitude shift on the middle tone. I.e, that one sounds lower in volume to me than the other two. But, the highest tone sounds quite loud and audible.
Then your perception of the tones now doesn't correspond with the reduced perceived loudness of higher frequencies which you reported earlier. That suggests something wasn't/isn't wired exactly as you thought it was.
I like the sound of the 3rd file. But, I'd need to see a redraw of that part of my schematic to understand how you produced it.
Redraw not needed. Circuit was the same as in Post #16. I simply recorded the voltage at pin 9 of the IC.
Also, did you plug in the resistance values that I have in my schematic above the first 3 oscillator pots?
Yes.
And FYI: I have no idea what “gating” means.
In the present context it means turning an oscillator on/off by forcing its input high (or low) via the diode.
Btw, from this article it seems the chanter waveform should consist of the fundamental plus several harmonics, with strengths increasing with harmonic number up to the fourth harmonic. I don't see how you can get that by the successive gating arrangement you are currently using.
 
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bertus

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Hello,

Do you know this page?

Perhaps it gives you more ideas.

Bertus
 

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”Then your perception of the tones now doesn't correspond with the reduced perceived loudness of higher frequencies which you reported earlier. That suggests something wasn't/isn't wired exactly as you thought it was.”

(Sorry. I can’t figure out how to get quotes in boxes.)

I thought we already talked about that though. Your simulation, in that case, was just of one oscillator, not a string of them. So, it may’ve behaved differently. Do all 3 of those tones in that first file sound equally loud to you, Alec? Or do you think my ears may have a problem with certain frequencies?
——-
“Redraw not needed. Circuit was the same as in Post #16. I simply recorded the voltage at pin 9 of the IC.”

So, you knocked one oscillator out of the mix? But, left in the last cap that’s part of that oscillator circuit?
——-
“In the present context it means turning an oscillator on/off by forcing its input high (or low) via the diode.”

Can I take out the diodes? That was one of the things I was asking about at the very beginning—whether they are necessary to protect the chip. Because, I’ve seen at least 3 similar circuits with them inserted differently (either reverse- or forward-biased). That made me question whether or not they are even doing anything.

Thanks!
 

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“Btw, from this article it seems the chanter waveform should consist of the fundamental plus several harmonics, with strengths increasing with harmonic number up to the fourth harmonic. I don't see how you can get that by the successive gating arrangement you are currently using.”

I have no idea how that graphic can help me. Sorry!
——-
And Bertus, yes, I’ve seen the Andres Siagian page, but that’s definitely not the sound I’m going for. That’s like fingernails on a blackboard, except about 10x worse, IMO!

:)

 

Alec_t

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Do all 3 of those tones in that first file sound equally loud to you, Alec?
No. I'm older than you so the third tone is weaker to me :).
So, you knocked one oscillator out of the mix?
No. It was still running.
Can I take out the diodes?
Yes. But increase the value of the resistor coupling adjacent oscillators.
Here's a test simulation circuit for 2 stages, plus the resulting sound file.
nodiodesdemo.png
 

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bertus

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Hello,

As far as I know a bagpipe consists of a bag with a couple of fixed pipes (drones) and a plpaying pipe (chanter)

You could adapt the Andres Siagian:
40106-hex-oscillator-schematic as bagpipe.png
Bertus
 

Alec_t

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Here's another approach for a chanter sound attempt, using one '40106 oscllator and a '4013 forming two divide-by-two stages :
The second divider, first divider and oscillator generate the fundamental tone, the second harmonic and the fourth harmonic. respectively. These are mixed by R2/3/4/5. C2 blocks DC.
PipesTest.png
Attached is a wav file for the simulation output where the pitch was increased at 2-sec intervals by changing R1..
 

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Explorer

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THANK YOU SO MUCH Alec_t and Bertus! I’ve got these last suggestion in my “Bagpipe” file on my desktop, along with all of your audio files, Alec. I’m going to end this thread here and get back to the workbench and start messing around again.

However, one last note, in case it helps someone else out. With regards to ‘voltage starve’ and using diodes to drop voltage, I made this little box over the weekend with a rotary switch and a series of 1N4004 & 1N4007 diodes in it (10, in all):

28533264-7467-42BB-8242-50278847E238.jpeg

While my digital multimeter measures an average of a .54-volt drop across each diode, in circuit the drop averages only .24-volts. And, when I say ”in circuit,” I mean with a wall wart putting out 8.44V hooked up to the terminals on the left and 6.02 volts measured by my DMM at the terminals on the right, with the switch at the end of the 10-diode chain.

I thought I’d get a much greater range out of the box, as an experimental aid, or just to modify whatever wall wart I might have on hand that doesn’t quite match what I need for power. A bit of a bummer...

Adios for a while, everyone!
 

Alec_t

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in circuit the drop averages only .24-volts.
It depends on how much current flows through the diodes and your measuring circuit. At very low currents the voltage drop will be much smaller than the ball-park figure of 0.6-0.7V normally quoted for a silicon diode.
Adios.
 

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So, if I actually have a circuit connected to the right-hand terminals, rather than just my DMM, I might see something closer to a .5-volt drop? It might actually be useful?

I was wondering if I could've damaged the diodes when I soldered them. The lugs on the rotary switch didn’t want to heat up very quickly, but I had little copper alligator clips on the diodes, both sides, as I was soldering them. I don’t see any reason why the diodes can’t be tested one at a time, while connected to the rotary switch. I’ve just gone over them once again with the DMM on the diode function. I get “OF” in one direction on all of them, and about .55V in the other direction. And, with a good 9V battery connected up, I measure closer to a .3V drop at each switch position.
 

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I’m sorry, Alec. I’ve got one more question for you: If I take the diodes out of my circuit, do the resistors between the oscillators really need to be as high as 220K? Just wondering how you arrived at that value. I’ve never worked with a simulation program. Did the program recommend that value or tell you that the chip would crash and burn with a lower value? Or, your a wiz, I expect, at reading data sheets? :) :) :)
 

Alec_t

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So, if I actually have a circuit connected to the right-hand terminals, rather than just my DMM, I might see something closer to a .5-volt drop? It might actually be useful?
Yes. A few mA through a diode is enough to get a decent voltage drop, ~0.6V for a normal silicon diode such as a 1N4148 or 1N400x. Don't forget you will need some current-limiting resistance in series when testing.
If I take the diodes out of my circuit, do the resistors between the oscillators really need to be as high as 220K?
The coupling resistance (Rc) needs to be considerably higher than the oscillator's timing resistance (Rt), otherwise the oscillation will stop.
Just wondering how you arrived at that value.
Consider this example:
gate.png
The hysteresis (voltage difference between the upper and lower switching thresholds) of a '40106 Schmitt gate is about 10% of the supply voltage. The thresholds are equally spaced about the mid-supply voltage.
Supply voltage = 10V. Mid-supply = 5V.
Upper threshold = 5V+ 5% of 10V = 5.5V.
Lower threshold = 5V - 5% of 10V = 4.5V.
The coupling resistor Rc must be large enough in value to allow the '40106 input b to go higher than the upper threshold and lower than the lower theshold, regardless of the input voltage v(a) to Rc. Note that Rc and Rt form a voltage divider.
Suppose the timing resistor Rt is 100k and Rc is also 100k. If v(a) is high (10V) and v(c) is low (0V) (or vice versa), then v(b) will be 5V. That's no good. If Rc is instead 125k then with v(a)=10V and v(c)=0V (or vice versa), v(b) will be either 5.55V or 4.45V respectively, which is theoretically ok (just). Making Rc at least 150% of Rt gives a good margin for component tolerances.
 

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“Don't forget you will need some current-limiting resistance in series when testing.”

OOPS! Well, I didn’t do that...

THANKS SO MUCH FOR ALL THE HELP!

Happy holidays, everyone!
 

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Serious packaging skills. WOW.

ak
THANKS! The nice blonde boxes come ready-made from Michael’s Crafts and aren’t very expensive. I’ve noticed that this holiday season, they’ve got a lot on their shelves. The one above, enclosing my diode box, may’ve possibly come from Hobby Lobby though. (It’s got a different hinged top.)

The mint green plumbing washers, beneath the nylon screws, on the ‘bagpipe’ box cover up a drilling error. (First hole I drilled in the box was the wrong size. Aaarrgghh! I used two washers to make it symmetrical. I’ve got my power cord attached to those nylon screws, and then going elsewhere.)

The keyboard was a very tricky build. Mostly, poplar hobby wood from Home Depot. 2 circuit boards at right angles to each other. The horizontal board has 9 enclosed, carbon pad, silicone rubber switches that I finally found on Amazon. (And I can dig up that link if anyone wants it. I haven’t seen them anywhere else.) Sitting on top of them are 9 brass bullet shells from a pile that I cleaned up from a path in some woods. There’s some kind of Hillman hardware-thing inserted snugly into them, possibly screw inserts that hold license plates to cars? Or maybe flanged nylon bushings? I forget now. Then, buttons epoxied to them. The bullet shells have an O-ring in the groove around the bottom of them, to keep them from falling out of the box.

The vertical circuit board, beneath the back, raised, removable section, has 9 multi-turn trim pots on it, with all of the tuning screws aiming upward, so that they’re easy to adjust. 7 of them are nice Allen & Bradley 100Ks from Electronic Goldmine.

If I ever get the project to be more musical, I’ve also been working on an extensive PDF (including bagpipe info and a few pieces of sheet music), will put it up on my mediafire page, and will post a link here. Hopefully, by the end of this winter... ???
 

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I’ll just add it... Here’s what you need to look for on Amazon, for the little silicone switches:

E15C6AC1-A4B0-43F7-BD52-EAAFBFA0C3C9.jpeg
 
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