PCB's FOR THE MOST POPULAR PROJECTS ON THIS WEBSITE. AVAILABLE HERE.
I have designed PCB's for the top visited projects on my website. The idea is to create some revenue to keep this website affordable for me because it has grown so much it's becoming a day job and it's not generating any income but I want it to remain freely accessible for all. So by purchasing a PCB you're not only guaranteed a successful build (PCB's are verified to work) but you're also helping keep this website afloat which will be very much appreciated.
I ship PCB's in aircushion envelopes which keeps shipping costs down. Shipping costs € 4,- world wide, If you order more than 3 boards shipping will be €6,-. There's no track and trace with this method but I never hear anyone not receiving their order and I shipped to locations over the whole world. If you insist on track and trace shipping you need to mention it and then shipping will be €10,- If your order weighs over 100 grams this will be the only option for shipping anyway but I'll inform you of that. (I only had two orders so far that weighed more then 100 grams so it's rare.)
US COSTUMERS PLEASE TAKE NOTE
For parcels to the USA you need to pay import fees. If you're in the US keep your order below $100 so I can send it under the 'gift' category. It can take a while before you receive it. Sorry about this but posting to the US is a bit weird at the moment.
Latest news:
I've made some changes to the procedure for ordering PCB's.
Please message me on Facebook to put in your order or email me directly to order. You can find a link to my email if you click on my profile underneath the menu.
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Sorry about the roundabout way of ordering but I'm afraid it's the only way I can do this. Please use the link below to my paypal account for payment of your order.
HOW TO ORDER:
You can order your PCB's by using this PayPal link for payment --- CLICK HERE ---
Just look below for the PCB(s) you want and if it's more than one, add the prices up and then add €4 to the total for shipping for up to 3 PCB's. If you order more than three PCB's then add €6,- to the total for shipping. Message your order through to me using Facebook messenger (or my email which you can find in my profile)
Please do not forget to mention the PCB(s) you want, how many you want and the address you want it to ship to. I do not automatically get your address so please don't forget it. Your email address will also be handy to have so I can message you. It will be deleted once you received your order.
Please contact me on Facebook Messenger or email me directly with your list of PCB's and your shipping address.. Please don't forget I'm in the Central European Timezone, so if you contact me from the other side of the world it might take a few hours for me to respond at certain times of the day.
I ship from The Netherlands. As mentioned before shipping to the united states will be problematic because of these @!# tarrifs. I'll let my US customers know when the situation changes.
Shipping times can vary a lot. For instance: I've had packages arrive in the U.K. in two days and others that took 10 days. For shipment to Australia expect the parcel to be in transit for about a month. I have had no reports of anything going wrong with shipping and I've sent PCBs all over the world.
FOR THE BILL OF MATERIALS FOR YOUR PCB's PLEASE VISIT THE ORIGINAL PROJECTS ON THIS WEBSITE. Each project has a bill of materials amongst the layouts.
HERE'S A QUICK OVERVIEW OF ALL THE STOCK WITH PRICE AND AVAILABILITY:
- Proj. 67: Kassutronics Precision ADSR € 10,- pp 13 in stock. Eurorack size panels for ADSR € 10,- pp 2 in stock
- Proj. 66: TB-303 filter. € 10,- 4 in stock.
- Proj. 57: Thomas Henry X4046 VCO € 10,- pp 1 in stock
- Proj. 56: Thomas Henry State Variable Filter VCF1 € 10,- pp 9 in stock.
- Proj. 50: Utility LFO € 10,- pp 4 in stock Eurorack panel for LFO: € 10,- 4 in stock
- Proj. 49: 8 Step Sequencer € 15,- pp 9 in stock. Kosmo sized panel for sequencer: € 15,- 2 in stock
- Proj. 43: Vactrol Filter € 5,- pp 2 in stock.
- Proj. 39: Moog Ladder Filter using CA3046 transistor arrays. € 10,- pp 4 in stock
- Proj. 37: Thomas Henry 555 VCO € 10,- pp 11 in stock
- Proj. 35: Resonant Lowpass Gate € 10,- pp 10 in stock.
- Proj. 26: Steiner-Parker Diode Filter € 10,- pp 13 in stock
- Proj. 18: Digisound 80 VCO € 10,- pp 12 in stock bi-polar version. 3 in stock of the old unipolar version.
- Proj. 17: MIXER w. Gain, Bias, Clip Indicator and Distortion. € 10,- pp 9 in stock.
- Proj. 12: Korg MS20 Filter € 10,- pp 11 in stock
- Proj. 10: Yusynth VCA € 8,- pp 12 in stock. Eurorack Panels for VCA € 8,- 6 in stock.
NONE SYNTH PROJECTS:
A - The original Transistor Curve Tracer with Transistor Matching Circuits for NPN and PNP. € 10,- pp 9 in stock
B - Original Transistor Curve Tracer with Matchers, same as the one above only made for use with ZIF sockets (DIP 14) € 10,- pp 9 in stock
C - New Transistor Curve Tracer with transistor matchers using @indepth_electronics improved circuit for the curve tracer which works very well. The PCB is to be used with 3 ZIF sockets. € 10,- pp 8 in stock
D - Original Curve Tracer board only, € 5,- pp 9 in stock
Please mention which PCB type you want, A,B, C or D when you order.
When something goes out of stock it is immediately re-ordered so if you check back in regularly you'll find items back in stock soon.
LISTING OF ALL AVAILABLE PCBs with descriptions and wiring diagrams:
(In chronological order just like the menu. Latest projects on top.)
PROJECT 67: The Kassutronics Precision ADSR.
Price: € 10,- per PCB 13 in stock.
I also have eurorack sized panels for these at € 10,- per panel (2 in stock)
Pre-assembled and fully tested ADSR Module € 80,- (+ €10,- shipping) 1 in stock.
You don't have to buy a panel with a PCB. It's purely optional.
A very small board of only 4,5 CM by 7,1 CM. It features the Rene Schmitz, gate input with manual trigger option and my attenuverter mod. I just built it up. It took me 45 minutes to solder the components in and an other hour to take the stripboard version out and solder this PCB back in behind the panel. It really works very well. It has a risetime of just 300µSec on the fastest Attack time. (250µSec faster than my stripboard version)
It has 2 LEDs. One to indicate the envelope is being generated and a second bi-colour LED connected to the attenuverter output, showing if there's a normal or inverted signal coming out of the attenuverted output. It's very useful and it looks cool too :).
The Precision ADSR with the VCA of project 10 mounted together in a Nifty Case. It looks great I think!
It took me 1 and ¾ hours to build it completely. So a great project for a rainy afternoon. The Envelope has an output voltage of 8 Volt. This is always the case with 7555 based ADSR's because that voltage is determined by pin 6. (see article 67 for more info)
I forgot to put a hole in the panel for the manual trigger button but I don't use that option much anyway. But if you want to include it, the PCB has a connection for a push switch and there's room between the sockets on the panel to put a momentary switch in. You'll just have to drill a hole for it yourself.
Wiring Diagram:
The PCB is only 45mm by 75mm. The panels are 12hp wide (6 CM).
The PCB is 47 by 92mm. Compact enough to go behind a Eurorack sized faceplate. You can build it up in one hour and I'm convinced the PCB sounds even better than the stripboard version. I am constantly surprised when I get new boards in and build them up, how good they really sound.
Here's the wiring diagram with all the errors corrected so it doesn't show the labels as they are visible on the PCB, but it shows the potmeters true functions and the correct location and signal for all outputs. Don't forget to use 100K resistors for R27 and R28 !!
PROJECT 66: TB-303 Filter
Price: € 10,- per PCB. 4 in stock.
An updated version of the TB303 Acid House filter.
WIRING DIAGRAM:
This filter needs at least 3 pairs of matched 2SC945 transistors and one matched pair of 2SA733 transistors. It also needs six 1µF non polarized capacitors, the red ones in the picture above.
The top and bottom pairs in the transistor ladder need to be matched but I matched all 5 pairs in my own module just to be sure.
The circuit has been optimized for use in a Eurorack system (+/-12V). It has a 10 pin eurorack power connector but the circuit only uses positive +12V and +5V which is made on the PCB with the 7805 voltage regulator.
Some resistor values have been changed and some trimmers have been added. It works really well.
PROJECT 57: The Thomas Henry X4046 VCO with the famous Hard Sync sound. The best HS of all analog VCO's.
Price: € 10,- per PCB 3 in stock.
Wiring Diagram for this VCO:
This PCB is 58 by 113mm. It's fully verified and I found it easier to tune than the stripboard version.
PROJECT 56: The Thomas Henry State Variable Filter VCF1.
Price: € 10,- per PCB 9 in stock.
An awesome sounding filter with Lowpass, Bandpass and Highpass, each with their own outputs. The filter sounds like a Steiner Parker diode filter but I think it's a bit more musical in the resonance. I actually prefer this filter over the Steiner-Parker. It's the filter I use the most in my DIY synth. It's fully self-oscillating. Below you can see the mounted board. This is the old version. The new one is laid out a bit better with more sensible sized solderpads.
New version:
Here's the wiring diagram for the State Variable Filter PCB.
The value for C1 and C6 is not mentioned on the PCB but it's on the diagram below. C6 is 100nF and C1 is 10pF:
PROJECT 50: UTILITY LFO with extra DUAL VARIABLE WAVEFORM OUTPUT.
Price: € 10,- per PCB (4 in stock)
Eurorack sized panel € 10,- (4 in stock)
FUNCTIONS:
- Dual LFO (bi-polar) so the features listed below are in two fold
- Goes smoothly between Ramp-, Triangle- and Sawtoothwave with one potmeter (Shape control).
- Squarewave output.
- Pulsewave output with variable duty cycle (pulse width).
- Each LFO section has a Variable Waveform output that goes between Squarewave and Saw/Triangle/Ramp-wave.
- I added a mixer section that goes between the two Variable Waveform outputs, which means you can mix all the waveforms together making this LFO capable of outputting the weirdest waveform shapes.
My take on the Utility LFO by Ken Stone.
I built one up and everything works like a charm and it can output all the normal waveforms you'd expect in two-fold because it's a dual LFO. Each LFO has a variable waveform output going between squarewave and Triangle/Sawtooth wave. I included an extra mixer that mixes those two together with a potmeter that goes between the two vari-outputs. You get some amazingly weird waveforms with it.
Unfortunately I did make some mistakes with labeling the potmeters and the outputs.
Outputs that are numbered as 2 are in fact 1 and those numbered 1 are 2. The 'Speed-2' potmeter connection is the wrong way around so clockwise is faster and counterclockwise is slower. The potmeter labeled Vari-1 is in fact Vari-2 and vice versa.
But those are all just labeling errors and things you can take into account and correct when wiring it up, especially if you make your own panel for this module.
I've made a wiring diagram, posted below, that explains everything and shows what everything does and where it is located.
The two 47nF capacitors determin the frequency range of the LFO. In my own build I put in one 47nF and one 68nF making one LFO section run slower than the other, with some overlap, so I have a wider overall range. With a 47nF cap the LFO's max frequency is about 20Hz and min about one waveform every 5.7seconds. With a 68nF it's about 2 seconds to 10Hz.
PROJECT 49: 8 STEP SEQUENCER.
Price: €15,- per PCB 9 in stock.
Kosmo size panels: € 15,- per panel (2 in stock)
They are a bit more expensive than the other PCB's because they are quite a bit bigger and more expensive to have made but they work really well!.
A perfected version of the 8 Step Sequencer V2.0 in project 49. This sequencer has a comparator on the external clock input that changes any waveform into a useable clock signal. It works great!! It also has an Offset function for the CV output so you can transpose a sequence up or down. I also designed panels for this module in Kosmo size (20 CM high, 10 CM wide). I replaced my old stripboard sequencer with this module and it works so much better now. The old stripboard version was a mess of wires. Looking at it I was surprised it actually worked. This one however looks professional and feels like it too when you use it.
In the picture below you can see the LEDs next to the potmeters. I had to lengthen the LED wiring a little because they didn't quite reach the PCB. I then put yellow heatshrink tubing over the plus pole wires.
Wiring diagram:
The potmeters can be soldered directly into the PCB, so that saves a lot of wiring. Make sure you put them all in first with the PCB and screw them down hand-tight into which ever panel you made for it or my self designed panel. Then solder them in. This will prevent fitting errors.
If you use my panel then the LEDs need to have the legs lengthened by soldering short pieces of wire to them, otherwise they don't quite reach but that's not a big deal. It all came together great and everything worked straightaway. The ON/OFF switch only switches off the CV output and stops the CD4017 chip. This is to prevent an Offset voltage from remaining present on the CV output. So you have the option to switch that off. Once you switch off the sequencer will keep outputing Gate signals, only one LED will remain on (sequencer stops running) and the voltage on the CV output is cut-off.
The PCB is 78mm by 122mm. This module is my pride and joy since I designed the circuitry (and the panel) myself.
EDIT: I suggest a few resistor value changes. Change the feedback resistor R 12 from 100K to 150K for higher tonal range and lower the offset resistors R14 and R15 to 22K for better offset range.
PROJECT 43: VACTROL FILTER.
Price: € 5,- per PCB (2 in stock)
A very good sounding filter. It uses 2 Vactrols which you can easily make yourself just like for the Resonant Lowpass Gate. All you need is two 5mm red LED's and two LDR's.
The cutoff potmeter works the otherway around from normal filters and it is quite sensitive. That's normal for this filter.
It's a bit tricky to tune this filter for optimal sound. You need to get the balance right between the trimmers but that's just a matter of tweaking the circuit. The results are amazing though. This filter has a very good percussive sound if you feed it a pulse wave from an LFO. It sounds like a Techno bass drum.
I didn't make a wiring diagram for this one because it's pretty obvious what goes where. The 3 potmeters can go straight into the PCB or be connected with wires and that leaves an audio input and output and one CV input that comes with a Level control. If you want to add more CV inputs you must connect them with a 100K resistor to pin 6 of U3 (the left TL072) or to the top solderpad of R10.
PROJECT 39: MOOG LADDER FILTER.
Price: € 10,- per PCB. (4 in stock.)
This is the famous Moog Ladder filter and boy does it sound good with this PCB.
It's a straight forward build. It took me 1 hour and 20 minutes to solder all the components in and an other 45 minutes to change the stripboard for the PCB behind the panel.
You need a 50K Ohm reverse log potmeter for the Resonance but I used a 100K linear pot and put a 100K resistor parallel over pins one and three and then a 5K6 from pin 1 to pin 2. That gave me an approximation of a rev. log. pot. Anyway it works fine.
Wiring diagram.
The V/Oct potmeter can just be left in the middle position. I don't know anyone who uses their filter as a sinewave oscillator anyway.
You can use the Bill of Materials from project 39. You need one 500 Ohm multiturn trimmer and two normal trimmers, one of 10K and one of 1K. All inputs need level potmeters except CV-3 which is meant for the 1V/Octave connection. The PCB is 60mm by 96mm.
The three BC547 transistor pairs should be matched for the best sound although officially the only transistors that need to be matched are the ones that are inside the CA3046 transistor array chips. (That's why they are used) But it's best to have them all matched (but not necessary for the filter to work).
PROJECT 37: The Thomas Henry 555VCO
Price: € 10,- per PCB (12 in stock)
One of the best analog VCO's now on a small PCB of 55mm by 103mm
I took me 2 and a half hours to build it up and replace the stripboard with the PCB. Everything worked rightaway. You only have to set the ramp wave and the sinewave and tune the VCO.
Tuning the VCO took me about 15 minutes. You go between the HF trimmer for the high octaves and the V/Oct trimmer for the low and use the freq fine control on the front panel to tune inbetween.
Wiring Diagram:
This VCO has been optimized for use with +/-12V powersupplies. The changes made are as follows:
(The component numbering on the PCB is not the same as in the original TH Schematic)
Originally numbered R13 = R38 on the PCB was changed from 3K to 2K. Pulsewave output voltage divider.
Originally numbered R27 = R34 on the PCB was changed from 39K to 22K. This is the resistor in series with the Sine Roundness potmeter.
Originally numbered R33 = R24 on the PCB was changed from 100K to 130K (opamp feedback resistor determining gain)
PROJECT 35: The Resonant Lowpass Gate.
Price: € 10,- per PCB (10 in stock)
Panels €10,- a piece (out of stock)
My favourite module on the website. Just an amazing sounding VCF/VCA combination using Vactrols. This module really sounds awesome when built on PCB. These are newly designed PCB's designed to go straight behind a panel with only the switches and in- and outputs to be wired up. I also have panels for these PCB's. My first self designed front panels and they look amazing!
These Lopass Gates really react well to slow working Vactrols. Vactrols with slowly reacting LDR's in them. I've been experimenting and I built two of these now from the V3.0 PCB's and using the panels and different DIY Vactrols and they are just the snidy-est, synthy-est sounding things ever. I really love this one (can you tell?) If you pair it with a digital oscillator like the Klavis Twin waves for instance, oh man are you going to get a surprise. With two sawtooth waves mixed together with a phaser on top going into the LPG you get that ripping the fabric of the universe synth sound with bass elements in them that you feel in your stomach. Just amazing.
The size of the PCB is 56mm by 97mm.
The latest version PCB's also have complete text on the backside in case components are soldered in on the backside to make mounting behind a faceplate easier.
This is the latest version (V3.3), I have the RLPG connected to the Klavis Twinwaves mkII digital oscillator. The Klavis outputs a quadruple sawtooth wave with phase shifting effect. The melody is created entirely by the Utility LFO going through a Doepfer Quantizer and then into the Klavis and then into the Resonant Lopass Gate. Turn up the volume and bass! This sounds phenominal!
Wiring diagram for versions 1.0 and 1.1 of this PCB (the old versions):
Top 3 potmeters seen from the back. CV-1 level pot seen from the front.
Here's the wiring diagram for version 3.0 and upwards:
The actual working of the 3 pole switch is reversed from what is shown in the wiring diagram. Just keep in mind: The respective function of the LPG (VCF, BOTH or VCA) is active if their switch setting is open. I know that sounds counter intuitive but that's how it works,
The first two batches of these PCB's sold out very fast. I have new stock though. The newly designed version V3.3 circuitboards just came in. These are optimized for eurorack but can of course just as easily be mounted behind a Kosmo sized faceplate. I've already built two of these for my own use. The boards also have writing on the backside so you can have certain components on the back, like the trimmers and vactrols, for better access.
I now have front panels for sale for the Lowpass Gate. They are Eurorack size and 12hp wide (6CM). With the normal mounting method (PCB at 90° to the faceplate) the resulting module will be 5.8 CM deep.
As you can see a very clean build with just a few hook-up wires.
Here's an alternative PCB mounting method. This will make the depth about 4 CM and make it fit a Nifty Case for instance. In the picture below you can see I put the power connector, the trimpots and the vactrols on the backside of the PCB which allows for easy access and makes it easy to experiment with different Vactrols. Just leave some wire in the holes and you can solder Vactrols to them easily.
The picture below shows the copperwires soldered to the potmeters but not yet soldered to the PCB.
In the pictures above you can see how I mounted the board flat behind the panel. Solder 1 mm thick copperwires to the potmeter pins at a 90° angle to the potmeters so they stick up if the faceplate is flat on a table. After soldering all the components into the PCB, mount it by lowering the PCB over the potmeter copperwires sticking up, and solder them in. Make sure you mount the trimmers, Vactrols and the powerconnector on the backside of the PCB so you can get at them if you use this method.
On the other side from the potmeters I soldered a copper wire to the ground of the sockets. With sandpaper I made a clear copper patch on the PCB near the lower mounting hole and soldered the copper wire to it. Now the board is solid as a rock.
PROJECT 26: The STEINER-PARKER DIODE FILTER.
The size of the PCB is 53mm by 91mm
Price: € 10,- per PCB. (13 in stock).
I finally got some good working, verified PCB's for this very popular filter. It's certainly one of my all time favourites. This is from the original Yusynth schematic. I built it up in just under an hour. It sounds amazing. In the stripboard version I could never really hear how the All-Pass mode worked but with this PCB version you can hear it clearly.
There are three trimmers on this board. The lowest one (blue multiturn trimmer) is for calibrating the throw of the Cutoff potmeter. I set it to it's middle position before soldering it in and frankly I didn't have to adjust it afterwards. The second one, just above the Cutoff potmeter connection, is the one that balances the the two sides of the diode ladder. Adjust simply by ear. Set it to what sounds best but don't put it all the way clock- or counterclockwise and check on a scope for offset voltages. If you get an offset voltage use this trimmer to correct it.
The third one is one I put in myself, as a replacement for R18. This is to help calibrate the Resonance potmeter. Set it in such a way that you get the best reaction from the resonance potmeter. That's usually just a few hundred Ohms.
The Resonance potmeter should be a 50K reverse logarithmic potmeter but I think few people have those so check the original article for the Steiner Parker to see how you can make your own reverse logarithmic potmeter if you don't have one. (It's simply a matter of soldering a 100K resistor between pins 2 and 3 of the 100K linear potmeter.)
Here's the wiring diagram for this filter. Be accurate in copying the wiring of the rotary switch! Especially the connections between the pins on the switch itself. The way I wired it is the easy way, and saves a lot of soldering but you can connect every point on the switch with is corresponding point on the PCB. Then you wouldn't have to make the connections between pins on the switch itself. That's the hard way to do it, and it's not necessary.
As you can see you only need to connect 4 wires to the switch solderpads on the board. One for the switch wiper and one each for LP, BP and HP. The Allpass mode is done with the wire on the switch itself going from pin B4 to pin A1. It connects Lopass and Highpass together creating Allpass.
Again, copy the wiring of the rotary switch accurately like you see it here.
Put the diodes in with the black band upwards, folding the leg on that side over. The anode goes in the round hole with the circle printed around it. The cathode side (with the black band) goes in the hole with the square solderpad with the K printed next to it. (K for Kathode). The diodes don't have to be matched really. Just make sure they all come from the same batch of diodes. You can buy a 100 diodes for a few dollars. The two BC547 transistors do need to be matched. I simply matched them by comparing their Hfe factor with my multimeter. You should really use the Ian Fritz method for matching. It can influence the sound significantly if they are not well matched. However I later de-solder the transistors and tested them with the Ian Fritz method and they were as good as matched. So just using the Hfe measurement works well enough.
I have PCB's with transistor matching circuits on them for NPN and PNP. See bottom item.
EDIT Aug 2025: I have designed new PCBs for the Steiner-Parker filter which more closely follow the PCB layout of YuSynth's original design. The boards are more square in shape, as you can see in the picture below (left PCB is new one). They are a bit bigger overall but much better laid out. I have designed a new footprint for the 3 trimmers so you can use either multiturn trimmers or the normal tripod single turn trimmers. They both fit in the same solderpads. I also added a 100K resistor on the board so you can use a normal linear 100K potmeter for Resonance.
The one on the left is the new PCB.
Wiring diagram for the new version V5.0 and upwards:
Short demo of the Steiner-Parker filter (new PCB):
PROJECT 18: The Digisound 80 VCO with the AS3340 chip.
Price: € 10,- per PCB (3 in stock of the original VCO design with 0-10V outputs
and 12 in stock of the new bi-polar version that has +/-5V outputs.
Please mention which type you want: Original or Bi-polar).
If you don't specify the type you want I'll send the Bi-Polar one by default.
This PCB is suitable for Eurorack modules. It's 54 by 104mm and it has been optimized for use with a dual 12V powersupply. (The original design is for dual 15V).
Above you see the PCB compared to the stripboard version.
Below, the classic version of the PCB:
Below is the new bi-polar version board. For this version you can use the original bill of materials from the stripboard article and add one extra multiturn trimmer of 100K and two 470nF capacitors. I made special footprints for the 470nF caps so you can put in caps with 5mm or 7.5mm leg width.
I just built this new version and everything works beautifully. Tuning is a breeze.
Here's the wiring diagram for the classic version (potmeters seen from the front, shaft facing you):
You can use the above wiring diagram for the new version too, only the new version has normal potmeter connections for the Fine and Coarse potmeters. The bi-polar version has one extra trimmer and you use that to center the pulse wave output around the zero volt line using an oscilloscope.
This PCB also includes the Pulse Width Modulation mixer which enables you to have an external Pulse Width Modulation signal come in and still change the Pulse Width with the panel control too.
I made quite a few improvements on this new version. As I mentioned, it's bi-polar now. I also changed the Frequency and Coarse connections to straight potmeter connections. I just finished building this latest version and everything worked straightaway. Tuning was very straight forward, following the procedure in the original article for project 18. On a dual 12V powersupply I had it tuned over 5 octaves within 10 minutes with only a few cents between the octaves. It's the best tuning experience of any VCO I ever built. When you switch this VCO on, the waveforms start out as 0-10V and then in about 2 seconds drop to normal +/-5Vpp operation. Not a problem, it's just the caps charging.
BTW, you can easily change the bi-polar VCO back to 0-10V operation by putting 1K resistors in the place of the 470nF capacitors and setting the offset voltage for the squarewave to +5V with the trimmer.
PROJECT 17: MIXER with GAIN, Clipping Indicator and DISTORTION Effect!
Price: € 10,- per PCB (9 in stock)
This is a more feature rich version of the simple mixer used in project 17. I included the clipping indicator with adjustable threshold level and I added a DISTORTION effect using two diodes and an extra output opamp. It all works great. The distortion boosts the level up quite a bit you can turn that down again with the input level control. The distortion is most effective when you use it with sawtooth waves. The mixer also has a BIAS control, which is an offset function so you can trim the signal to the correct zero Volt line.
Below is the wiring diagram:
This is V1.0 of this board so there are two tiny little errors. The audio LED doesn't work because I was dumb enough to connect the opamp buffer that drives the LED to the virtual ground of the input opamp. Beginners mistake @___@. To set this right I have cut the track going to pin 5 of U3 (on all PCBs) and I've drawn in the connection you need to make between pin 5 and the left leg of R8 (1K) (seen from the top of the board). I've drawn it in with white pen so it's easy to correct. All you need to go is solder a wire between those two points. I made the change and tested it and it now works fine.
I also forgot to put in the 10K input resistor for the distortion but we can easily mount that on the switch, like the wiring diagram shows. Be accurate when wiring the switch up and use the exact positions shown in the diagram and don't forget the little wirebridge at the bottom of the switch. Btw, the original schematic has a 100K resistor there but I thought 10K sounded better.
PCB mounted with a single L-Bracket behind a Kosmo sized panel, before wiring up.
Bill of Materials (add one 10K resistor to the list):
PROJECT 12: The KORG MS20 FILTER with HIGHPASS and LOWPASS mode.
Price: € 10,- per PCB (11 in stock.)
Finally a PCB for this filter. This is the number one visited filter article on my website.
I built one up myself and it sounds great, see video below.
The PCB is very very small. Only 39mm by 93mm so ideal for eurorack. It only took me half an hour to solder all the components in. You can solder one potmeter straight into the board and use that to mount the board at 90° behind a panel. Then you can connect the rest of the controls and sockets with hook-up wire..
Wiring diagram for this PCB. (potmeters seen from the backside):
Here's a short demo video of the filter in action. The audio for this filter needs to be attenuated. This filter can not handle high audio levels straight from the oscillator because this will drown out the resonance. This is a well known issue of this filter. So if you build this project make sure you include a level potmeter for the audio input and put a level potmeter on at least one of the CV inputs aswell, so you can regulate the ADSR input to the filter. (I'd would recommend level pots for all but the V/Oct input)
PROJECT 10: The Yusynth VCA
Price: € 8,- per PCB 11 in stock.
Eurorack sized panel (6hp) € 8,- per Panel (5 in stock).
Ready made, pre-assembled and tested VCA module € 60,- + € 10,- shipping (1 in stock)
I call this project 'The Best Little VCA' because that's what it is. Of all the VCA projects on my website I still like this one the best because it works so well and is so easy to calibrate.
The original VCA inverted the output signal but I put in an extra Dual Opamp that turns the signal back to normal and I use the other opamp to drive a bi-coloured LED to give an indication of the signal the VCA receives. I did this with other VCA's and it turned out to be a very useful feature.
The PCB is 36mm by 93mm
It's still a good idea to use a 90° connector as shown below but it is no longer a necessity.
Wiring diagram will follow shortly but really, it's so simple you don't actually need one. You only need to wire up 3 sockets and a LED. The potmeters solder straight into the PCB.
The TRANSISTOR CURVE TRACER and MATCHING CIRCUIT.
A - Transistor Curve Tracer (original version) with Transistor Matching Circuits for NPN and PNP. € 10,- pp 9 in stock
B - Transistor Curve Tracer with Matchers, same as the one above only made for use with ZIF sockets (DIP 14) € 10,- pp 9 in stock
C - Transistor Curve Tracer with transistor matchers using @indepth_electronics improved circuit for the curve tracer which works very well. The PCB is to be used with 3 ZIF sockets. € 10,- pp 8 in stock
D - Curve Tracer board only (original version), € 5,- pp 9 in stock
Please mention which PCB type you want, A,B, C or D when you order.
(Bill of Materials is at the bottom of this text.)
The PCB's with original curve tracer and transistor matchers, with solderpads for the different connections so you can choose your own method for that:
Here's how I match transistors with this PCB. I soldered some pinheaders, with wire, to the Emitter, Base and Collector pads on the PCB for transistors A and B. I stick those in a small breadboard and use the breadboard as socket for the transistors under test. Leave one transistor in and keep changing the second one until the volt meter reads 000.0mV in both switch settings. Then you have matched transistors. The switch swaps the 100K resistors connected to the emitters of the transistors, that's why those resistors must have the same value. I found that measuring the 100K resistors with one digit behind the comma was enough for good functioning of the matchers. (Mine were both 97.3 KOhm)
New PCB's with the improved Curve Tracer and matching circuits and this one is set up to use ZIF sockets (Zero Insertion Force). You can buy these sockets from AliExpress for like € 0,50 a piece. They are very cheap and boy does it work well with these circuits!! Matching transistors is so much easier. This is definitely a must have for any electronics work place geared towards synthesizer projects. Especially ladder filters and VCA's that need matched transistors.
The back of the PCB has a complete explanation of how to measure the transistors.
These PCB's are 60mm by 197mm
MAKE SURE THAT INSTEAD OF 4,7 OHM RESISTORS FOR R25 AND R26 YOU PUT IN 15 OR 18 OHM RESISTORS.
ALSO MAKE SURE TO CHANGE C5 AND C11 FROM 100nF TO 120nF (FOR 6 TRACES) OR 150nF (FOR 8 OR 9 TRACES IN THE DISPLAY.)
You put two transistors you want to match in the ZIF socket and connect the wires with banana plugs to your multimeter. As the transistors cool down from being handled with warm hands, you'll see the voltage on the meter drop. If it stops at 00,0mV. you flick the switch and if it's still at 00,0mV then the transistors are matched.
Using the switch will swap the two emitters. Transistor A will now be connected to 100K resistor B and vice versa. This is done to eliminate the resistance difference of the two 100K resistors, from the equation. You take both measurements and subtrackt A from B (not forgetting the minus symbol) and divide the outcome by 2. That's your mismatch value. (Average value)
You can also leave one transistor in place a swap out the other one and if you get two transistors that show the same numbers then they are matched.
Here's a video demonstration of the new PCB:
Here's the bill of materials for the New Improved CurveTracer with Matchers.
You can disregard numbers 20 and downwards because they refer to connections to the board. All you need for that is a Eurorack 10 pin male connector or some pinheaders. The scope probe connections I leave up to your own imagination. I used copper wires to clamp the probes onto, as you can see in the image above. I used wire with banana plugs for the matchers voltmeter connections.
