Dear community,

Current mirrors keep on being the best circuit! Here is a two way current mirror design with just 6 components, excluding the load resistor.

Simple Two way Current mirror

The output current is actually inverted (mirrored you can say heh), so 1 mA into the circuit results in -1mA through the load, so the output voltage becomes negative and current goes from ground into the output. The output voltage is -(Input Current)*R.

To get a Two way current mirror without inversion you can chain two such circuits together. Using Opamp feedbacks, or another set of NPN / PNP transistors on the outputs you can have current amplification.

Here is the same circuit as above with stabilized virtual ground input, this removes the forward voltage drop on the first set of transistors.

https://preview.redd.it/5gipx7yywjge1.png?width=685&format=png&auto=webp&s=5d4262d541903d8b1946df1c930f1cf23cb6c817

Is the easiest way to do this with a boost converter IC?

I'm making a 4017/555 clock sequencer and have been intending to run it off it 9V. Issue is that if I want to take an external clock, those are typically 5V and that will not be enough to meet the threshold requirements of something running on 9V.

Yes, I could run the entire thing on 5V to get around this I suppose, but I kind of like the idea of doing 9V so that my CV range can be from 0-9V instead of 0-5V.

So, I figure, I could boost a 5V external clock to 9V somehow to allow the external clock signals to work.

Thoughts? What's the easiest way to increase the voltage of a clock signal?

I've designed a 10p front panel in KiCAD. No copper layers, only holes for pots, audio jacks, & mounting. I'd like it to have blue solder mask. PCBWay is having trouble with my soldermask layers. They say that "solder mask files are empty". They will not manufacture until I fix he problem.

I've done this before using JCLPCB to manufacture front panels. When I used JCLPCB, I kept all of the KiCAD settings at default values and JCLPCB manufactured perfectly. I look in the KiCAD settings. I see that I can specify no fewer than two copper layers. For the F. Mask & B. Mask layers, I can specify Material & Color, but I am not sure what to specify (my hunch is liquid ink). Slodermask color is selectable on the PCBWay order form, so that field seem immaterial.

Does anyone have experience ordering front panel "boards" from PCBWay? Thanks in advance.

Hey everyone! Just showing off my minimalist printed rack.
THe rails come from gie-tec and the printed side pannels come from here: https://www.thingiverse.com/thing:4923072
They are really nice give the designer some love!

https://preview.redd.it/z8k5i4dycige1.jpg?width=4032&format=pjpg&auto=webp&s=9f2f615d2571ecb27f8cffb9766558a4172e156d

https://preview.redd.it/140o33eycige1.jpg?width=4032&format=pjpg&auto=webp&s=c517df5bfb719385b3ea7cc620cb4d49eaa7f9ac

Hi there! I’m really interested in building a Radio Music module for my rack. I know the files are open source but printing them costs me like 90 dollars, and the Teensy 3.2 also isn’t cheap to find. Does anyone maybe have the PCB’s they want to sell on to a fellow DIYer? Located in Europe but also willing to pay shipping from USA.

Anybody know of some good polysynths to build? I dont mind between analog or digital, the few ive found out there just dont have a lot of documentation.

I noticed that Erica Synths released a device for saving one's patch routing for modular/semi-modular synths...looks like the matrix from their SYNTRX instruments. Basically four of those 8x8 LED matrixes arranged in a 2x2 grid with a microcontroller interface for saving your patch routing. I think calling it a 'Mixer' is a little less descriptive than 'Patching Matrix' or something, but it does offer a few attenuation levels and you can mix CVs with it.

Anyone have any ideas on what chip(s) they're using to handle the actual switching? Or are there some pics of the inside that show the chips hanging out somewhere that I haven't seen?

Or more generally - has anyone built something like this? If so, what ICs / what kind of setup did you use to handle the actual switching?

I've always figured that they're using one or more analog crosspoint matrix ICs; there are plenty of them out there. There are a handful that are DIP-types and could even be breadboarded, though I think that most are surface mount and would require a breakout board. Just interesting because I feel like a lot of synths with deep mod matrices are handling those signals digitally (or all of the pathways are just connected all the time and disabled as needed or have VCAs that are set to zero when not in use). Wondering how companies/people are handling switching of analog signals (if they are at all).

Just saw that they added an ability to save projects. Anyone considering making this device now has the option to save their work. A feature we've been looking forward to for years.

If anyone would like to buy a LMN-3 I have a special one for sale. Made by Floyd Steinberg himself.(upgraded with the help of his videos.) Dm me.

I am currently choosing components for my newly designed PCB.

My design features an input stage to my ADC and an output stage from my DAC.
I am attenuating 10Vpp input to 1.7Vpp, and vice versa on the output. so roughly a gain of 5
My input stage has a 1uF coupling cap. My output stage 10uF.
I am searching for the right dielectic material.
I heard MLCCs are really disadvised in audio applications because of piezoelectric effects.
Since this is my first design, i don't need to have hifi-top-notch-esoteric performance. It just needs to work and shouldnt sound like shat.

Can you recommend caps , that are usually used in Eurorack AC-coupling, preferably SMD?

I'm working on a Max4Live frontend for Ambika, and there's a couple parameters I can only reach through Sysex.

I have MIDI CC control: https://i.imgur.com/3qDCS5P.png

and I have NRPN control: https://i.imgur.com/rm1Bvpy.png

The parameters I can't reach are voice part allocation and BPM. I assume there is a message I can send to MIDI out that would set them, but I don't understand the instructions in the manual ( https://medias.audiofanzine.com/files/ambika-user-manual-mutable-instruments-476409.pdf ) for how to get that information. Could someone give me a hand? Happy to share the maxpat file, and I'll be posting it for free on maxforlive.com when it's finished

Pardon the naive beginner question but… Is it a worth replacing the tempco resistors if the leads have been cut? Building the MFOS sound lab mini synth mkii and realized after populating the pcb and cutting all the leads that rays instructions specify FULL LEADS on the tempcos that are in combination with the transistors. Again, thanks for indulging the novice.

Built default Minidexed as per the github using USB.

Works with controller but is not recognized by Mac or PC.

Last time I played with midi, it was an old MT32.

Thank you.

Hi guys, I don’t know if this is a stupid question or not, but I’d like some help to clear my doubts. I would like to build a basic 4 voices analog synth but I am a bit confused on how voices assignation works. For example, imagine I have already 4 keys pressed, how do I make sure that an eventual 5th keys pressed doesn’t play and doesn’t affect any voltage signal that is being sent to the oscillators? In wider terms, how do I connect every key to the 4 oscillators?

I received an Erica Synths Bassline pcb and panel for Christmas, which is awesome, but I'm having a hard time finding the LM337LZ/NOPB. It's obsolete and not on Digikey, Tayda, or Mouser. The only places that have it either have $100+ minimum order requirements or want $10-20 for it. They're listed on Amazon, but I don't trust them for anything I can't test quickly. Anyone know where to get this part or know of a substitute? Thanks!

I saw this post back in October:

https://www.reddit.com/r/arduino/comments/1fenu0y/midified_an_old_set_of_organ_bass_pedals_using_a/

Surprisingly, my brother and I had already made plans to get together the following weekend to do pretty much exactly what this fellow had done. I had a set of bass pedals from a Farfisa Compact combo organ, and was fortunate enough to have a parts organ as well from which I harvested the female pedal connector, then an Arduino, an Adafruit 7-seg display, some off-the-shelf parts and a project box, some programming time and voila! It's a lot cheaper than a new MIDI bass pedalboard and I can still use the pedals with the organ if I want to.

Here's the result:

https://youtu.be/K9BUOJILgAM

I'm making a synthesiser using a teensy 4.1 with the audio shield, it's powered using a lipo battery. I have a little speaker with a pam8403 amplifier.

When the teensy and the speaker are powered by different batteries, it works fine - the speaker plays the audio as expected.

However, when they're both connected to the same battery, the audio is very feeble and noisy.

I've read online before that a lot of people do use separate batteries for the speaker and the synthesiser - however, I've made a few synthesiser projects in the past - using the same teensy 4.1 and pam8403 amplifier. In the past, I've connected them both to the same battery and it's been fine.

So my question is, what might I be doing differently here, and how can I wrangle it to use the same battery for both?

Hello folks! I'm finishing my sound studies and I have to make a final project and I decided to make a synth by myself (analog or hybrid i don't care). I don't know where to start, don't know what components to get or anything about electronics. If someone could help me with maybe recommending me videos/books or any other type of information source i'd be so happy. Thanks :)

I'm working on building a standalone kick drum synth. After initially planning on using a VCO for the synthesis and looking over several schematics, I ended up deciding to use a pinged resonating filter to generate the sine wave instead.

I'm fairly certain I already have the components lying around for an MS20 style filter or a modified Wasp filter (modified to allow for self-oscillation) or the Thomas Henry VCF-1, but I figured I'd ask for other opinions so that I have some options.

So what are some of your favorite filter schematics to make kicks?

I just wrapped up the conceptual part of the design of a Eurorack Optical Compressor circuit. I haven't prototyped this yet, it is all theoretical, but the main features are:

• RGB Led - in theory, the different wavelengths should affect the LDR behavior differently, so the ability to mix between each color should offer a lot of flexibility in terms of the gain reduction transfer curve. It will be interesting to test!
• Envelope follower circuit instead of a single capacitor parallel to the LED to set the timing
• Adapted the linearization of Trevor's design to blend between local or global feedback
• Precision full wave rectifier rather than just a half wave or full wave bridge

https://preview.redd.it/16d7wwnmuefe1.png?width=1514&format=png&auto=webp&s=6b45cd5a4dafad2bd00d3c800d35de13c79f31fa

Here's the Falstad Sim... note that the LEDs don't actually couple with the LDR, it just has a resistance/brightness slider.

Any initial thoughts or... ahem... feedback? I might pair down some of the parameters if it looks like some are redundant or not very important once I get it on the breadboard. I suspect the linearization blend might not be very useful, but we'll see!

The irony is not lost on me that Europeans cannot legally make this Eurorack design due to cadmium restrictions :(