Thank you for purchasing the Synthrotek DLY Eurorack module kit!
ATTN: Please follow the BOM and these instructions and don’t populate from the PCB alone. Also sometimes we cannot get the exact pictured components, so please look over your parts and check the codes first.
If you’ve received your parts and ready to build, the first thing you should do is to check to make sure you have all the parts. Check your kit against the DLY BOM. If you’re missing anything we’ll send it to you free of charge.
First up is the resistors. Populate them according to the BOM, and then flip the board over onto a flat surface, then solder and clip your leads. Using a flat rigid card or another PCB can help hold the resistors in place as you turn the board over.
ATTN: R13 is optional, the circuit will not be affected if that resistor is not soldered in.
Next up are the Diodes. Insert them into their proper places according to the BOM, with the stripe (cathode) of the diode matching the direction of the stripe on the silkscreen. Diodes are polarized components and can cause big issues if not soldered in properly.
Now the IC sockets can be populated. Insert them into the board, making sure to align the notch, or the side with the ‘U’ shape in it, with the side of the silkscreen that has that same marking. Then flip over onto a flat surface and solder. One way to keep the IC sockets from falling out is to slightly bend one leg, or two legs on opposing corners.
Ceramic capacitors are non-polarized, so it doesn’t matter which direction they go in their spots, just that they make it into their proper spots. The PT2399 chip is very particular about which value caps it has in which spots. Once they are all populated, flip over onto a hard surface and solder. One tip for getting these guys a little flatter is to only solder one leg first, then you can move them a little, and solder the other leg in place. Clip all your leads afterwards.
Next up are the Electrolytic capacitors. Unlike the Ceramic versions, these are polarized and can do some damage to themselves or the circuit if installed improperly. On the PCB’s silkscreen, there is a little ‘+’ symbol next to one of the solder pads. When placing the Capacitors, make sure that the longer lead goes through the solder pad with the ‘+’ next to it, and that the stripe is pointing away from that side. Once you have all the Capacitors in place, flip over and solder your leads.
Transistors and Voltage Regulator
When inserting the transistors into the board, align the flat side of the transistor with the flat side on the matching silkscreen, like in the picture above. The voltage regulator is going to be populated in the same way. Then flip over and solder your components.
Next up are the two trim pots. Align them so that the flat sides match the flat part of the silkscreen, then flip over and solder them in place.
Eurorack Power and Vactrol
We are now ready to insert the Vactrol (Resistive Opto-isolator). Warning: You MUST use the vactrol provided with your DLY kit or PCB/Panel set. If you do not, or use any other vactrol or opto-isolator, your circuit may not work. When inserting the vactrol into the board, align the dot on the side of it with the dot on the silkscreen. Put the shorter set of legs through the solder pads inside of the circle, so that the body of the vactrol sits in the circle, and the longer legs stretch out to the other two holes.
Next, align the notch on the 10 pin Eurorack power connector with the notch in the silkscreen, like shown above. Flip the board over and solder everything in place.
Jacks and Potentiometers
After trimming the nubs on your pots (if they are present), place the pots in the board first, turn the board over with the pots in place, and then solder ONLY THE CENTER PIN to the PCB. Do likewise for the jacks now. Place the the jacks in and on a flat surface ONLY THE CENTER PIN to the PCB.
Once you have all the jacks and potentiometers attached, you can test fit the front panel to make sure that all of your components fit into the front panel, and that everything is straight. If it is, go ahead and solder the rest of the legs on the jacks and potentiometers.
Next, insert the ICs into their proper sockets, making sure that the notches on the ICs match the notch on both the socket and the PCB silkscreen.
Place all the nuts onto the potentiometers and the threaded parts of the jacks, and hand tighten first. Then go back with a 10mm and 8mm socket, respectively, and tighten the nuts so the front panel is snug.
DO NOT OVERTIGHTEN, it may damage some of the components and put undue stress on the PCB.
Calibrating and Testing Procedures
First thing to check is if the DLY will self-oscillate. Set the RATE knob fully counter clockwise, set the FEEDBACK knob fully clockwise, and set the MIX knob fully clockwise.
Slowly turn the FB MAX trimpot clockwise until you start to hear the DLY self-oscillate. Rotate the FEEDBACK knob to 3 o’clock and see if the oscillation will stop. From here you will want to dial the FB MAX trimpot to taste. We typically aim for the DLY to self-oscillate around 3 o’clock on the FEEDBACK knob (when the RATE knob is fully counter clockwise and the MIX knob is fully clockwise).
—-CALIBRATING DELAY RANGE—-
Just like you did above, set the DLY up to self-oscillate. This time, turn the RATE knob fully clockwise and slowly turn the DELAY RANGE trimpot clockwise until the delay goes as slow as possible before “getting weird.” That’s usually about 1.13 seconds. You may want to dial the DELAY RANGE trimpot to taste. We set the DLY up to go as slow as possible before the delay starts to break up and freak out.
Set all knobs to noon and take an audio source (preferably non drone based) and plug it into IN. Make sure that the audio is passing through and is being delayed.
Take a Bipolar (-5/+5V) Envelope, LFO, Offset, or Sample & Hold and plug it into the DLY input. You should be able to hear the speed of the delays change from fast to slow and vice versa. Unplug the DLY CV source.
Take a Unipolar (0-10V+) Envelope, Gate or an Offset and plug it into the FB input. This input is vactrol based and will only respond to Unipolar voltages. At 10V+ you should be able to hear the module self-oscillate. Take note that the FEEDBACK knob sets the starting point for CV over feedback!
By now you should be able to confirm that the DLY is working correctly.
Congratulations! You just successfully just built a DLY module from Synthrotek! You can check out all the info on the module, watch a demo video, or read the quick start guide over on the product page.
Thanks for choosing Synthrotek!