Maybe you can add the credit/source, a title, and “verified” on your pic
look here
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The credits as well as all other relevant documentation, including pictures of the completed built module is available in the linked post on my website. I’ve intentionally left out stuff like a “verified” stamp and the BOM from the picture to prevent people who run into it in image search from building it without looking up the context.
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On the forum we prefer that everything is on the image because if someone downloads the image alone, there is no information (and then when you have lots of images like that in your files it’s complicated)
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I’m sorry but I don’t think downloading just the image of the stripboard layout to your computer is a good idea and it’s not a use case I intend spend time on supporting with my layouts. There is vital information regarding the module in the article my website including:
- The schematic
- What it is based on
- A link to an article by the original creator that explains how it works
- A list of all the changes I’ve made to the original circuit along with explanations for why I’ve made them
- The BOM
This won’t all fit in a single .png and I would very much prefer that if someone decides to build my module they have all the context they need. If you’re downloading layouts because you intend to build them somewhere without an internet connection or you want to have a local copy in case my website disappears one day, you can hit ctrl+P in your web browser to download the article as a .pdf (and remember to download Electric Druid’s article as well).
Should I not include an image at all when posting in this thread and only include the link to my article? I tried that but the forum doesn’t display rich link previews, which made the post very easy to miss so I added the picture to the post.
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It’s best not to get too hung up on rules. The recommendations of information to include in the layout image were intended to mitigate the fact there are people who do an image search for some circuit, find a stripboard layout, and grab that without knowing anything else about it; unlabelled images therefore pollute the internet with unverified layouts, layouts without proper attribution, and so on. But a layout that has a URL on it where all that information can be found is as good as, or better than, a layout that has that minimal information on it directly. The point is not “you should have this information on the layout”, the point is “your layout should provide this information”, and the URL does do that. And if you have a file folder full of printouts of layout images and nothing else, well, it’s on you to label them.
Of course, unverified layouts still should be labelled as such.
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I am leaving this belated reply in case anyone is interested… If you are looking to boost the inputs then this is definitely the wrong circuit! The AI Harmonic Mixer is supposed to mimic the old Moog mixers, at least in the PNP/NPN transistor topology. You are supposed to get clipping on the sine and triangle waveforms, a boost on the fundamental of sawtooth waveforms, and a small boost in the square waveforms (more on less, but don’t quote me). The issue with not getting an overall boost in the signal is that the mixer inputs are not buffered, so apart from the cross-talk (which is part of the character I guess?) any boosting that you get on an individual input will be cancelled by an attenuation on the other inputs, so there is no overall boost. If you are looking to amplify individual signals you are better off with op amp designs with buffered inputs, or if you would like to go the transistor route, you can try North Coast synthesis transistor mixer which, again, provides buffered inputs (all in a very simple discrete design).
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Hello folks I’m looking for a way to get a few channels of line level signal from my soundcard up to eurorack level, this looks like it could be just the ticket but I think I might need a bit more gain and also to be able to adjust the gain.
Please could anyone direct me as to which resistor I should change to increase the gain?
Thanks
It’s the Simple line amplifier x4 circuit I was looking at
That’s just a pair of non inverting amplifiers:
https://www.electronics-tutorials.ws/opamp/opamp_3.html
In this case the gain is (1+R1/R5) = (1+30k/10k) = 1+3 = 4 as advertised.
To increase the gain you can increase R1 (and R3) or decrease R5 (and R6). To make it adjustable you could use a potentiometer, preferably in series with a fixed resistor. For instance if you added a 50k pot in series with R1 the minimum gain would be 4 and maximum would be (1+(30k+50k)/10k) = 9.
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Great, thank you! I will have to build up a few channels of these
This one is semi-verified: I have built it on my custom protoboard but I am posting a layout adapted to a more normal breadboard (mine has 3 rails on the edges and a central ground rail). Pass up on this one if you don’t feel capable of cross-referencing the schematic as you build.
This is the Skull & Circuits Vactrol VCF-1, probably as simple as a usable VCF circuit gets.
I used a pair of 1N4148 for the filter diodes instead of LEDs - actually I added both to my board so I can rewire it later. Both sound different. The LEDs do not light up when used as part of the filter.
The LED I put on my panel connected to the audio output with a signal diode antiparallel instead.
Also I used a single TL074 instead of two 72’s. Ok actually I used a TL084 if you wanna be all technical about it. Works all the same.
Edit: The TL074 is upside-down!! Sorry I didn’t make it more obvious in this version of the picture. Pin 1 is in the top-right.
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I made one of these, and plan to make many more. Really fun and simple on top of sounding great! Nice to take a break from massive stripboard layouts for a second.
Given the toxicity of X, I would welcome a repost of this material here.
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I am not usually into the laser cut acrylic look, but that is sweeeeeeet!
It has already been posted here. 
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Here’s a simple mixer.
The schematic, BOM, DIYLC project file, panel template and a video where I explain the circuit, build the module and demo it can be found here: Making a Simple Eurorack Mixer | Sandelinos' website
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The layout has (I overlooked that) but not “the original circuit diagram [they] found on Modwiggler, some build pics, and a video of the quad LPG in action”
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I believe this is the link to the Modwiggler thread:
https://www.modwiggler.com/forum/viewtopic.php?t=107006
Taking into consideration this schematic published by @RocketMermaid on Twitter/X and also posted on the Modwiggler thread:
Here are some build images posted by @RocketMermaid also on Twitter/X:
Some videos I found on the Modwiggler thread:
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One change one might want to make: The two LEDs, the one in the Vactrol and the indicator, both are exposed to whatever control voltage is applied. Most LED datasheets specify an absolute maximum reverse voltage of around 5 V. Granted, you don’t get larger negative voltages all that often in a modular, but you can. To protect against such large negative voltages you could:
- Add two 1N4148 diodes, one antiparallel to each of the LEDs (cathode to anode and vice versa), or
- Add a 1N4148 diode in series after the CV jack, cathode toward the LEDs. That requires only one diode instead of two, but will diminish the voltage at the LEDs, so you’d probably want to reduce the values of the resistors to compensate.
Another thing: This being a passive LPG, there could be an issue with the low input impedance. If a +5 V CV comes from an upstream module via a 1k current limiting resistor, that will sag to about 4.5 V here. Probably not an issue most of the time but something to bear in mind. Likewise if the pot is turned toward the low end and the CV is high, the impedance on the IN input will be low and that voltage also could sag; and a 100k downstream load in parallel with the 25k pot could distort the output voltage, but again most of the time you probably wouldn’t care.
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