Something new I built - fun with decade counters

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devinw1
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Re: Something new I built - fun with decade counters

Post by devinw1 » Wed May 13, 2020 11:11 pm

Got the proto boards (4067 based) in and built them up. First time I've had a first-shot PCB design where everything worked 100% right off. Woohoo! I played with it a bit in the sound sample below. Lots of harmonics to be had with this thing. The very begnning is a really severe (square) LFO modulating all the segments so it sounds fairly harsh. Listen through though and you can hear there are plenty of musical sounds to be had.

Some initial sounds:
https://soundcloud.com/saywaht/ts0-prototype-test

The PCBs:
ts0proto.jpg
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Re: Something new I built - fun with decade counters

Post by guest » Wed May 13, 2020 11:30 pm

that sounds great. the modulation works really well, especially when its at a harmonic of the fundamental.
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Re: Something new I built - fun with decade counters

Post by EATyourGUITAR » Thu May 14, 2020 7:39 am

devinw1 wrote:
Wed May 13, 2020 11:11 pm
Got the proto boards (4067 based) in and built them up. First time I've had a first-shot PCB design where everything worked 100% right off. Woohoo! I played with it a bit in the sound sample below. Lots of harmonics to be had with this thing. The very begnning is a really severe (square) LFO modulating all the segments so it sounds fairly harsh. Listen through though and you can hear there are plenty of musical sounds to be had.

Some initial sounds:
https://soundcloud.com/saywaht/ts0-prototype-test

The PCBs:
ts0proto.jpg
this project sounds great and looks great. very very well done. perfect 10
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Re: Something new I built - fun with decade counters

Post by devinw1 » Thu May 14, 2020 10:12 am

Thanks guys!

One thing I realaized is I did screw ONE thing up. I wired the wrong pin of the 2nd counter up so my "sub octave" square ouput is actually a sub-sub octave (1/4 freqency). Whoops!

Something I've been thinking would be really cool is to be able to have each segment get a random CV that would change with a LFO or something. I think this would take 12 separate S&H circuits though, wouldn't it? Probably a monstrosity :D.

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Re: Something new I built - fun with decade counters

Post by guest » Thu May 14, 2020 10:53 am

a random CV instead of the slider setting? or mixed with it? since each slider is only active on a step, you could just add it to the final mix and change it for each step, so a single S/H would work, but the random voltages would have to repeat. a microcontroller would work well here. or you could make a digital shift register random number generator, and that could be made to repeat the same random pattern.
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Re: Something new I built - fun with decade counters

Post by Whelm » Thu May 14, 2020 11:09 am

This is very cool! You're productivity is off the charts.

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Re: Something new I built - fun with decade counters

Post by EATyourGUITAR » Thu May 14, 2020 11:57 am

having a 1/4 frequency out with no 1/2 out may actually be preferable to some users. I would leave it in.
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Re: Something new I built - fun with decade counters

Post by devinw1 » Thu May 14, 2020 1:18 pm

Or both? :) They are basically free with the counter.

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Re: Something new I built - fun with decade counters

Post by devinw1 » Thu May 14, 2020 1:20 pm

guest wrote:
Thu May 14, 2020 10:53 am
a random CV instead of the slider setting? or mixed with it? since each slider is only active on a step, you could just add it to the final mix and change it for each step, so a single S/H would work, but the random voltages would have to repeat. a microcontroller would work well here. or you could make a digital shift register random number generator, and that could be made to repeat the same random pattern.
I guess I was thinking random CV mixed in to each summer for each segment, so you could theoretically zero each slider if you wanted, and set to S&H, and have a completely random waveform shape that varied with time.

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Re: Something new I built - fun with decade counters

Post by guest » Thu May 14, 2020 2:47 pm

i see, so it could also act as a record/playback as well if the input waveform was timed to the step rate.
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Re: Something new I built - fun with decade counters

Post by devinw1 » Thu May 14, 2020 3:22 pm

guest wrote:
Thu May 14, 2020 2:47 pm
i see, so it could also act as a record/playback as well if the input waveform was timed to the step rate.
Indeed!

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Re: Something new I built - fun with decade counters

Post by Tonescape » Fri May 15, 2020 6:41 am

Freakin' cool. SOme really interesting sounds in that demo!

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Re: Something new I built - fun with decade counters

Post by devinw1 » Fri May 15, 2020 12:32 pm

Was thinking more about how to do the S&H idea strcitly analog, but I think indeed I would need 12 S&H circuits. The LF398 is cheap enough, but 12 of them starts to add up and take up space. There are quads but they are like $16+ each.

Seems like digital might be the only way that makes sense here. I needed a reason to get back into learning Arduino I guess. Ha.

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Re: Something new I built - fun with decade counters

Post by guest » Fri May 15, 2020 1:21 pm

you could use 12 opamps and another 16x1 mux. the advantage to digital is that it can hold the data forever.
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Re: Something new I built - fun with decade counters

Post by KSS » Sat May 16, 2020 1:23 am

Consider how vintage poly's implement multiple S/H's. An S/H -when refreshed often- is a cap.

edit: and a follower, but how many are needed is variable depending on end point(s).

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Re: Something new I built - fun with decade counters

Post by devinw1 » Sat May 16, 2020 12:24 pm

Well, it's a cap, an op amp, and a switch or FET (or MUX) to sample. So 3 things :). But yeah, I suppose it's not unsurmountable by any means. If I keep it Thru hole I'll probably have to expand it to a 3rd board. Could continue to do it all on 2 boards as it is now if I made it all SMT.

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Re: Something new I built - fun with decade counters

Post by devinw1 » Sat May 16, 2020 12:58 pm

So enteraining the MUX idea, I guess I could take the same clock as the main MUX and supply it to this secondary S&H MUX, and then basically have a signal to the "enable" pin on the MUX which would come from a pulse generator which pulses long enough to set all the S&Hs in the frequency range we are using. That pulse could either be generated by hitting a sample momentary button, and also hooked up to a jack which could take an LFO or something. The S&Hs themselves could be either fed from a noise source or from one of the incoming modulating signals, so as to "learn" the waveshape. What you guys think?

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Re: Something new I built - fun with decade counters

Post by guest » Sat May 16, 2020 7:47 pm

that sounds like it would work. id be interested to hear what you thought of the droop on the sample capacitors. it wouldnt take much to prototype up a channel or two and do some sampling. the amplitude of the signal probably isnt so critical since its used as an oscillator and not a CV, so the droop might be ok. i wonder how lossy a bucket brigade would be. i suppose an amp could be put in the feedback loop to make up for the loss.
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Re: Something new I built - fun with decade counters

Post by devinw1 » Sat May 16, 2020 8:27 pm

I still have a 3 channel proof of concept boarded up so I just tried it and it totally works . I'll have to see how it does just sitting there running as it leaks down. I did it as a TL072 buffer to the common port on another Mux506 and then each output goes to another TLP72 buffer with a 10n PP film cap to ground.

I also hooked up a basic noise source to it and you can hit the sample button and get a random wave shape. I hooked up an inverter from the S&h signal to the original MUX's enable port so that you don't hear the noise or sample wave for the split second it does the sampling. This seems to work well.

So all in all it works great, but yeah the droop will be the deciding issue of analog vs digital. Having a VCO that gradually looses amplitude while it's running is not so good!

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Re: Something new I built - fun with decade counters

Post by KSS » Sat May 16, 2020 11:14 pm

devinw1 wrote:
Sat May 16, 2020 8:27 pm
Having a VCO that gradually looses amplitude while it's running is not so good!
Call it the Fade, Climate Change, VCO Economy or Entropy, and it'll be fine. ;)

Actually, as long as it had a reset, the loss of amplitude could be a feature, not bug, Better if selectable probably, but I've been feeling a little backlash recently against 'perfect' modules.

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Re: Something new I built - fun with decade counters

Post by devinw1 » Sun May 17, 2020 5:42 pm

Lol KSS. You might be onto something!!

So it turns out the bleed is fairly substantial. About as high as I could go and still sample voltages to 5V from the noise was .1u and even with these, they leak down in about 45 minutes. Not so great. I'm sure it would be better with polystyrene, but I don't know how much.

So digital might have to be the way. The way I'm thinking about this, I believe I will need a 12 channel DAC, right? Or I guess one DAC and another MUX. Would be sweet in Arduinos had a DAC on board but they only can fake it with PWM.

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Re: Something new I built - fun with decade counters

Post by guest » Sun May 17, 2020 5:47 pm

you can just have a single DAC, and change what it outputs with the clock. just send it to the final mix. you could use an arduino if you make your own R/2R ladder on the output. the PWM DAC wouldnt be fast enough.
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Re: Something new I built - fun with decade counters

Post by devinw1 » Sun May 17, 2020 6:29 pm

Hmmm, good idea on the R-2R DAC. That is nice and cheap and easy.

On a different note, I was just looking again on the S&H idea, and perhaps maybe all I need is different caps and op amps to get acceptable performance. Bob Pease's article on cap leakage shows him getting some pretty spectacularly low leakage using PP caps and the LMC662 as the follower. The Ib is waaaay low on that thing (.002pA vs 65-200 pA for a TL072).

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Re: Something new I built - fun with decade counters

Post by EATyourGUITAR » Sun May 17, 2020 7:16 pm

lmc662
Ultra Low Input Bias Current:2 fA
pretty amazing stuff for $1.50
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Re: Something new I built - fun with decade counters

Post by guest » Sun May 17, 2020 7:38 pm

the leakage will be dominated by the MUX.
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