1184 quad mixer vca (AKA 1183)

ok that explains the dynamic clipping! which is fine good for this module but yes I will for the matrix mixer which is equally for voltages… Quite excited about the matrix module, as I have made it in such a way thats its modular within itself, each row is a separate board, so you can make a matrix module as big or as small as required, then I have 2 different panels 1 that houses 4 columns or one that houses 10 columns. but because its in a setup that suits the mixing of control voltages too. I will revisit the above.

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I see you’re all coming over to the dark modular modular side :smiley:

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aaah! yeah nice! they working good???

Works perfect in isolation, and in small configs. Still missing some modules for my larger (still rather vague) plans so remains to be seen if this is a good idea in the long run, but as I’ve mentioned earlier arbitrary and rather silly constraints is a huge part of the fun for me (*). I’m the first to admit that they’re not all the most practical way to do things :smiley:

*) main constraint being “how can I organize this kind of circuit so the important bits fit on this tiny PCB without going all SMD, and how can I make the circuit and the PCB more generally useful while doing that”; I’m especially fond of PCBs that can be used in multiple ways, or for that matter orientations :upside_down_face:

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Im just glad someone went farther than i did with the modular modular idea. Especially when its someone that can actually see it through n stuff.

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OK, it looks like @fredrik and you sorted it all out while I was sleeping. Good.

The 100k resistor could cause clipping for high level signals and high gains, but if you like it that way in this design, leave it like that, it can easily be replaced for those that don’t want the clipping.

If 10V peak-to-peak is to be the recommended “normal” signal level (which makes sense to allow for headroom etc), I’ll add that to the Kosmo Specification Wiki

Glad to see that we agree that the 2V Zener is not necessary on the signal input.
Given the voltage divider before the linear control voltage input, a 2V Zener diode is not necessary there either.

While analyzing the circuit to determine if a 2V protection Zener diode was necessary on the CV input, I noticed that the switch labeled “INV” doesn’t actually invert the effect of the control voltage as I expected it would, but it just adds an offset equivalent to about 5.6V on the CV input jack so it will just increase the output volume (and can be used with a negative going envelope to cause a drop in volume, but the envelope would need to have been inverted before being applied to this module’s CV input).

What is the expected voltage range out of an envelope generator?
Or said differently, what is the expected CV input range for this module for a normal envelope?
What does the #1157 Mini ADSR put out?
What do Eurorack envelope generator modules typically put out?

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the inv switch yes doesn’t technically invert its function, inv probably is a tiny bit misleading, its function. well its a couple of functions.

the module this module was replacing in my synth was the module at the bottom right of the synth cabinet at the end of 3 voices. 1 of those voices comes out of 1 of the vca’s and into another one of the vca’s with the inv usually turned on, this offsets it to like you say 5.6. the reason 5.6 well because 220k was a common round about value. It serves 2 purposes practically. in this mode an inverted envelope generator acts as a side chain going into it. but also going into it is an accent envelope generator too.

the other purpose is originally In the old vca mixer it was set to full power, in a gig in order to figure out where a problem is in the synth voice live I would need to bypass the vca, initially when I flicked the inv switch on this it would go full volume and blow peoples socks off. so I changed it to about half power (originally 100k resistor, then halved it pretty much, funnily enough I seem to recall in a van in a driveway in Hamburg! but also to add with the 100k at the time it was making it louder than what the envelope generator was powering it so it was making it loud loud.

the 1157 puts out 10v. Eurorack I have seen some put out 10, some out more than that! most less. so rather underwhelming ones closer to 5v. its all over the shop. the 1157 has an inverted output too.

usually going into the vca with inv mode in my instance there are two envelope generators going into a mixer, one inverted and one none inverted, one for side chain wired to a sum of the kick and snare input, and also an accent trigger for a bit more volume whilst keeping under 10v.

then the vca before that vca is wired with 1 envelope generator

as for the other 2 voices going into that mixer vca, thanks to the normalled jacks, are isolated from the above 2 vca’s and these two voices go to the mix out. (well not anymore actually they both go off separately now as its evolving)

I hope that makes sense. its a sort of middle ground. to allow for sidechaining and accenting. and also trouble shooting on completely closed VCA’s without blowing peoples socks off.

in the dual VCA this is just replaced with an offset knob, instead of a switch.

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I did have a plan to do a video on these VCA’s when I put them out but one thing lead to the other and it didn’t happen. then it sort of slipped my mind, however because of a mod I spoke about further up the thread (for bypassing the normalling of the jacks) ill be doing the video this week hopefully. I’ll talk about all the stuff we have been speaking about too. and possible mods. including increasing this inv/offset/bypass switch if people feel its not setup for their needs.

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Thanks for the detailed explanation ( and historical note :slight_smile: ), I think I got most of that.
The video should confirm (or correct) my (mis)understanding.

As for the switches that I had to spread the pins of, I believe it is these ones:

What surprised me is that you didn’t use the same pin spacing for the SPDT and DPDT switch footprints.
The SPDT fit fine in the DPDT footprints as they have the same pin spacing as the DPDT.
This is how the SPDT (right) and DPDT compare, with and without spread pins.
image

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ok! well since the brand of switches I usually use do fit into both ( I just checked) I made them different size as the dpdt some of them fit snugger than others which was a bit weird so I adjusted those and never came up against it with the SPST so they stayed snugger… from now on ill make the SPDT footprint the same. ill update it. and also if of use ill share the footprints for both.

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So…Sam…one question (or anyone who can answer please) and one request please…

Question… If you use 2k resistors instead of 1k then the LED’s would not be as bright, yes? Is it possible to switch out the 1k resistors to 2k on the daughter board so my LED’s won’t be as bright or will that screw up something else in the module if I did that? I’d like them not so bright but wanted to use the ones I have.

Request please… Seeing as how I am new to synth DIY and I am a modular idiot, I’m still trying to figure out…

A) what all of these modules do
B) whether or not I have built them correctly

I wondered if you could make a video for the modules that just shows what happens when a single signal is plugged into each audio jack and another one for each CV jack? For example, what happens when you just have a square wave input to the LFO? What do the knobs do when you turn them with that square wave in? For example, I’ve built the LFO but I don’t know if it is working the way it is supposed to because I am not sure what to expect to hear when I turn each knob and/or flip the switches, if that makes any sense. If I had a reference for testing so I knew how to verify that it’s working correctly it would be extremely helpful. I know a lot of people have gotten into synth DIY because of you and I think there are many of us who could benefit from something like this. Just an idea that I thought would be helpful to me and others. :slight_smile:

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you can maybe open a new thread for this :wink:

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Question… If you use 2k resistors instead of 1k then the LED’s would not be as bright, yes? Is it possible to switch out the 1k resistors to 2k on the daughter board so my LED’s won’t be as bright or will that screw up something else in the module if I did that? I’d like them not so bright but wanted to use the ones I have.

yeah 2 things you can do. try a 2k however they won’t turn on lower voltages. the other option is to get less bright LED’s. which led’s do you have? if they are standard they are pretty dim anyway! but super brightsl… well haha the name suggests.

yep of course! my aim is to do more videos on the modules on the more serious channel. this week im touching on the the 1184, and ill work along from that! hope thats ok.

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i begining this thread

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I changed the title. Let me know if I got it right. I also tried to change some of the text into more idiomatic English. This is very useful.

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yeh thanks a lot :slight_smile:
i make a wiki for that

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Okay, so using 2k would make them less bright but it will also not allow them to turn on with lower voltages. Is that what you’re saying? That doesn’t sound like that will work then.

I have several different LED’s, but the ones that I want to use are like yours where they are clear but turn red when in use. I found some that said they were just “bright” but not “ultra bright” but they were .49 a piece. So I was hoping that I could use the ultra bright ones that I have, which are .02 a piece, and just use a different resistor to control the brightness.

Yes, starting with the 1184 is absolutely fine. Whatever order you want to do is no problem. I only mentioned it in this thread since you had already commented on making a video about the 1184 and mods for it. Thanks for doing this. It will really help myself and others. Not knowing if I made a mistake in the build process can be frustrating.

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There are two sets of LEDs in the #1184 VCA.
The “mute” LEDs have a fixed brightness so you can directly control their brightness by changing their current limiting resistors.
The “CV level” LEDs vary in brightness with the CV level, they don’t actually “turn on” at a specific voltage, but they have to reach a certain level of brightness before we see that they are lit. If your LEDs are brighter than average (or your environment darker) you will notice them being lit at a lower CV level. Increasing the current limiting resistor to reduce the maximum brightness may just bring the point where you notice the LED being lit back to the same level one would notice it with “less bright” LEDs or in a brighter environment.
But in fact, the 1k current limiting resistor only controls the maximum brightness that occurs only for high CV levels. At lower CV levels the current through the LED (and thus its brightness) is mostly controlled by the 100k resistor at the base of the transistor.
So you can increase the 1k resistor to limit the maximum brightness and reduce the 100k resistor to increase the brightness at lower CV levels (don’t go too low though, down to 33k should still be OK).

You could temporarily solder in pots on wires, or try it on a breadboard to find the brightness level you like.

To quote a wise man (or was he a wiseguy?): “Don’t be scared to try it!”

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This is really good information to have. I might try 2k on mine.

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Thanks Antoine! I’ll try putting in a 2k and then reduce the 100k to 47k and see what happens.

“To quote a wise man (or was he a wiseguy?): “Don’t be scared to try it!””

Damn that quote! LOL Yeah, that “wise guy” is what got me into this mess in the first place :laughing:

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