Today my small discovery was...

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pieter
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Re: Today my small discovery was...

Post by pieter » Sun Jun 14, 2020 4:35 am

LDT wrote:
Sat Jun 13, 2020 5:46 pm
For people with a bit more electronic knowledge, this is likely an obvious thing, but:
Today I discovered that it does indeed matter what way I go through a passive attenuator. I was sure that input and output are swappable, and to some extent they are. Only, the curve of the potmeter is all wrong, if you go the wrong way.
If by passive attenuator you mean the signal goes only through a potentiometer, then there should not be a difference. A pot is just a variable resistor, and resistors can be used in any orientation (unlike diodes or electrolytic capacitors).

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Re: Today my small discovery was...

Post by cptnal » Sun Jun 14, 2020 4:57 am

pieter wrote:
Sun Jun 14, 2020 4:35 am
LDT wrote:
Sat Jun 13, 2020 5:46 pm
For people with a bit more electronic knowledge, this is likely an obvious thing, but:
Today I discovered that it does indeed matter what way I go through a passive attenuator. I was sure that input and output are swappable, and to some extent they are. Only, the curve of the potmeter is all wrong, if you go the wrong way.
If by passive attenuator you mean the signal goes only through a potentiometer, then there should not be a difference. A pot is just a variable resistor, and resistors can be used in any orientation (unlike diodes or electrolytic capacitors).
True, but if the pot has an exponential response is the rate of change not faster at one end than the other? :hmm:

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LDT
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Re: Today my small discovery was...

Post by LDT » Sun Jun 14, 2020 5:01 am

pieter wrote:
Sun Jun 14, 2020 4:35 am
LDT wrote:
Sat Jun 13, 2020 5:46 pm
For people with a bit more electronic knowledge, this is likely an obvious thing, but:
Today I discovered that it does indeed matter what way I go through a passive attenuator. I was sure that input and output are swappable, and to some extent they are. Only, the curve of the potmeter is all wrong, if you go the wrong way.
If by passive attenuator you mean the signal goes only through a potentiometer, then there should not be a difference. A pot is just a variable resistor, and resistors can be used in any orientation (unlike diodes or electrolytic capacitors).
Well, that is what I thought, but my passive attenuators proved me wrong.
Going through left to right the response curve i just right. Going through right to left, the response curve is crap: From 7 o’clock to 8 o’clock you have 95% of the range.

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Re: Today my small discovery was...

Post by sbergen » Sun Jun 14, 2020 5:19 am

pieter wrote:
Sun Jun 14, 2020 4:35 am
LDT wrote:
Sat Jun 13, 2020 5:46 pm
For people with a bit more electronic knowledge, this is likely an obvious thing, but:
Today I discovered that it does indeed matter what way I go through a passive attenuator. I was sure that input and output are swappable, and to some extent they are. Only, the curve of the potmeter is all wrong, if you go the wrong way.
If by passive attenuator you mean the signal goes only through a potentiometer, then there should not be a difference. A pot is just a variable resistor, and resistors can be used in any orientation (unlike diodes or electrolytic capacitors).
That's not quite true. Quoting Wikipedia here, because it's so concise: "A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider. If only two terminals are used, one end and the wiper, it acts as a variable resistor or rheostat."

In an attenuator, you have one end at ground (0V), one end at the input, and the sliding contact is the output. How it works in reverse will depend on various things, like the output and input impedances of the connected devices.

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LDT
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Re: Today my small discovery was...

Post by LDT » Sun Jun 14, 2020 5:32 am

cptnal wrote:
Sun Jun 14, 2020 4:57 am
pieter wrote:
Sun Jun 14, 2020 4:35 am
LDT wrote:
Sat Jun 13, 2020 5:46 pm
For people with a bit more electronic knowledge, this is likely an obvious thing, but:
Today I discovered that it does indeed matter what way I go through a passive attenuator. I was sure that input and output are swappable, and to some extent they are. Only, the curve of the potmeter is all wrong, if you go the wrong way.
If by passive attenuator you mean the signal goes only through a potentiometer, then there should not be a difference. A pot is just a variable resistor, and resistors can be used in any orientation (unlike diodes or electrolytic capacitors).
True, but if the pot has an exponential response is the rate of change not faster at one end than the other? :hmm:
I think you are very much on to something here.

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Re: Today my small discovery was...

Post by sbergen » Sun Jun 14, 2020 6:06 am

LDT wrote:
Sun Jun 14, 2020 5:32 am
cptnal wrote:
Sun Jun 14, 2020 4:57 am
pieter wrote:
Sun Jun 14, 2020 4:35 am
LDT wrote:
Sat Jun 13, 2020 5:46 pm
For people with a bit more electronic knowledge, this is likely an obvious thing, but:
Today I discovered that it does indeed matter what way I go through a passive attenuator. I was sure that input and output are swappable, and to some extent they are. Only, the curve of the potmeter is all wrong, if you go the wrong way.
If by passive attenuator you mean the signal goes only through a potentiometer, then there should not be a difference. A pot is just a variable resistor, and resistors can be used in any orientation (unlike diodes or electrolytic capacitors).
True, but if the pot has an exponential response is the rate of change not faster at one end than the other? :hmm:
I think you are very much on to something here.
The response curve of the pot has very little to do when you wire things the wrong way around. You are essentially forming this circuit:
>----|
    | |
    | |  output impedance
    | |
     |<-------------------------|
    | |                        | |
    | |  "left half" of pot    | |  "right half" of pot
    | |                        | |
     |                          |----------> what the device "sees"
     |                         | |
    GND                        | | input impedance
                               | | 
                                |
                               GND
The thing is, that while attenuator pots are usually around 10 kOhm, your output impedance is usually around 1k, and input impedances around 100k. So most of the "action" is happening between the output impedance and the "left half" of the pot, because the output of a voltage divider depends on the ratio of the resistors.

You essentially have a 'x / (1 + x)' response on the "left side", going from 0 to 10: https://www.wolframalpha.com/input/?i=p ... om+0+to+10

On the right side, you have a '100 / (100 + x)' reponse (but in the other direction) https://www.wolframalpha.com/input/?i=p ... om+0+to+10
Notice the limited range!

So even with a linear pot, the overall response will be something like this: https://www.wolframalpha.com/input/?i=p ... om+0+to+10

Now, if you'd want to see how it responds with different output and input impedances, you can substitute the 100 and 1 in those equations. Things get especially interesting, if you make the output impedance 0 (which it ideally should be in theory, ignoring all practical matters). In this case, you only get a gain range from about 0.91 to 1.0.

I know this isn't the DIY forum, but WTH, I was bored :hihi:

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DCDanno
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Re: Today my small discovery was...

Post by DCDanno » Mon Jun 15, 2020 2:19 pm

paoling wrote:
Sat Jun 13, 2020 4:20 am
A telephone pickup coil into Ears makes for an incredible drone when you go around scouting through your modular system. A few digital modules with a screen (like Maze) can be a source of little melodies. This, with the Rossum Panharmonium can provide a nice melody that can be tuned with the rest of your modular patch.
Nice! Was just going through a box of misc electronic stuff and found a telephone pickup. Pulled it thinking I would use it for something. And then I see this. Thanks.

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Re: Today my small discovery was...

Post by gelabs » Tue Jun 16, 2020 12:39 pm

Working with an oscilloscope (even a cheap one, like a DSO Nano) is not only fun and interesting but also super useful, especially when combining modulations.
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Dr. Sketch-n-Etch
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Re: Today my small discovery was...

Post by Dr. Sketch-n-Etch » Tue Jun 30, 2020 1:54 pm

Today my small discovery was...

that EVERY zener diode must be tested.

I have built my Sketchy Labs 5U Frequency Shifter for a fellow Wiggler, and it involves a (simplified) dual-core Rubicon VCO. Upon testing the device, I noticed that the two cores were producing waveforms with significantly different voltage levels. I thought something was seriously wrong, and did a massive search for solder bridges, replaced quite a few chips, etc, etc, and nothing helped. Then I checked the levels coming out of the core comparators and they were both more or less exactly 20Vpp, as designed. That means that the problem had to be with the zener diodes.

Each core requires a single zener diode within a zener bridge to set the voltage level of the waveforms. I use 3.9V zeners for this (1N4370) since there are two diodes in each direction in the bridge and they each add about 0.5V (in fact, the diodes I bought in bulk from Digi-Key are extremely consistent, and measure 0.533V to 0.537V -- assuming an average of 0.535V, that means that the zener should be 3.93V to give 10Vpp waveforms). I replaced one zener, and it got worse. So, I thought, I'll replace them with 1N4371s (of which I had 3) which are 4.3V -- I measured them as well, and they measured around 3.0 to 3.1V -- more than a volt low! So, then I thought, what if I measured some 1N4372s (4.7V) -- the first two diodes I pulled out of the bag measured 3.9V almost exactly (which is what I wanted), so I installed them and VOILA the damn thing works perfectly. (A third 4372 measured 4.4V, so they are not consistently WAY too low -- some are just too low.)

So, going forward, my new policy is to measure every zener diode and put them in bin bags to the nearest 0.1V, regardless of their denomination. Then I will have a collection of precision zeners that I can pull out and use as needed. What a bore!
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Re: Today my small discovery was...

Post by sd_falter » Wed Jul 01, 2020 9:13 pm

Ive been naively treating my drum modules as mostly self contained in that a gate goes in, drum sound comes out to either the mixer or an effect. Hadn't really considered using the various tools on hand to further shape transients.

Anyway I was a bit frustrated that the attack and general timbral qualities of my prok bass drum wasn't gelling with the patch I had set up, it was too upfront, static and digital. Rather than take the module out to edit the drum presets I figured I'd see what I could do to the shape in my modular. Running the same drum thru a low pass gate, with an AD envelope where the attack and decay times were ever so slightly modulated gave it this gorgeous dynamic, silky feel.

Newb stuff but sometimes you really need reinforcement that the tools to shape your sounds are right there in front of you if you focus on the outcomes you desire.

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Re: Today my small discovery was...

Post by transistorresistor » Wed Jul 01, 2020 11:58 pm

Dr. Sketch-n-Etch wrote:
Tue Jun 30, 2020 1:54 pm
Today my small discovery was...

that EVERY zener diode must be tested.
long ago I got in the habit of measuring *every* component before installing it in circuit and you sure do learn a myriad of things, get a way better window into a manufacturers tolerance too. Oddly, this tiny extra time on the front end yields huge time savings on the back end troubleshooting why something doesnt work on the first power application.

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Re: Today my small discovery was...

Post by electricanada » Thu Jul 02, 2020 12:03 am

sd_falter wrote:
Wed Jul 01, 2020 9:13 pm
Ive been naively treating my drum modules as mostly self contained in that a gate goes in, drum sound comes out to either the mixer or an effect. Hadn't really considered using the various tools on hand to further shape transients.

Anyway I was a bit frustrated that the attack and general timbral qualities of my prok bass drum wasn't gelling with the patch I had set up, it was too upfront, static and digital. Rather than take the module out to edit the drum presets I figured I'd see what I could do to the shape in my modular. Running the same drum thru a low pass gate, with an AD envelope where the attack and decay times were ever so slightly modulated gave it this gorgeous dynamic, silky feel.

Newb stuff but sometimes you really need reinforcement that the tools to shape your sounds are right there in front of you if you focus on the outcomes you desire.
Can sometimes go the other way—use a drum module as a filter.
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Re: Today my small discovery was...

Post by moremagic » Thu Jul 02, 2020 12:45 am

Paranormal Patroler wrote:
Sat Jun 13, 2020 4:26 pm
Exactly. In most occasions you can reapply the knob so that it points at 12, and then 7 to 5 will, once again, be min to max.
in euro? found many more D shaft pots than slotted ones ime, and you cant just put the pointer wherever you want with them

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Re: Today my small discovery was...

Post by Paranormal Patroler » Thu Jul 02, 2020 1:50 am

moremagic wrote:
Thu Jul 02, 2020 12:45 am
Paranormal Patroler wrote:
Sat Jun 13, 2020 4:26 pm
Exactly. In most occasions you can reapply the knob so that it points at 12, and then 7 to 5 will, once again, be min to max.
in euro? found many more D shaft pots than slotted ones ime, and you cant just put the pointer wherever you want with them
Get an inverse D Shaft pot then, or a non D shaft pot with a screw. That's not a problem now, is it? The solution applies regardless.
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sd_falter
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Re: Today my small discovery was...

Post by sd_falter » Thu Jul 02, 2020 2:26 am

electricanada wrote:
Thu Jul 02, 2020 12:03 am
Can sometimes go the other way—use a drum module as a filter.
You mean like sending audio rate signal thru the gate input or something else? interesting 🤔

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pieter
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Re: Today my small discovery was...

Post by pieter » Thu Jul 02, 2020 4:19 am

If you modulate a filter cutoff frequency (on, say, a square or saw wave input) with the audio waveform of the drum module I imagine you'd get some vocoder-y drum sound. Gotta try this!

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Re: Today my small discovery was...

Post by tigersi » Thu Jul 02, 2020 10:31 am

This might be basic for most people but S&H makes for perfect basslines. What a moment it was when I patched that :omg:
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Re: Today my small discovery was...

Post by helix » Fri Jul 03, 2020 7:28 am

S&h to what parameter? Pitch? I prefer my basslines to be a little more regular usually. But link it to a filter cutoff or to an FM amount and now you're talking

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Re: Today my small discovery was...

Post by rayultine » Fri Jul 03, 2020 9:47 am

Last night I realized that the CV Recorder in O_C Hemispheres is VERY powerful. I can use Shades->quantizer to manually dial in CV for a step (buff mult to the synth I would be triggering), then can use a button gate (Pulp logic FSR) to manually iterate through the steps. Boom instant musical two track 2 to 384 step sequencer.

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Re: Today my small discovery was...

Post by tigersi » Fri Jul 03, 2020 11:00 am

helix wrote:
Fri Jul 03, 2020 7:28 am
S&h to what parameter? Pitch? I prefer my basslines to be a little more regular usually. But link it to a filter cutoff or to an FM amount and now you're talking
Clock in
Quantiser of main sequence multed into s&h
Out of s&h into OSC.

I’ll have to try the filter and FM tricks thank you.
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Re: Today my small discovery was...

Post by AbundantChoice » Tue Jul 14, 2020 12:40 am

... that when faffing around making drones for future pad use, an E370 + an Enosc can sort of give you the equivalent of *48* oscillators in one system (You can't address them all *individually* for modulation of course, but I still ended up mostly tapping out a Hypster a Triple Sloths & a Batumi before I ran out of VCAs).

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