Hello !
I’m trying to build the PT2399 delay module (With Sam’s modifications). I’m new at this so I don’t quite understand schematics, but I try. Really hard. So the questions are : Where do I connect these parts (highlighted in red) on the main circuit ? And I thought modulars were +/- 12V, so why do I see +5V indications ? I tried to make sense of it by my own, but I can’t. Not cool enough. Alright thanks !
The thing I’m trying to build, but I want it on PCB (with EasyEDA).
This is a Eurorack style 10 pin power header:
And this:
connects wherever you see +12V marked, for instance here:
it’s providing power to a 5 volt voltage regulator (L7805), which is where the +5 V comes from.
(Not all modulars use ±12 V, ±15 V is rather common, but Eurorack and Kosmo use ±12 V; the Eurorack specification actually calls for +5 V to be supplied too, but usually Eurorack systems just distribute ±12 V and if +5 V is needed it’s done in the module with a regulator, like this.)
This:
tells you +12 V should be connected to pin 4 of the TL074, and -12 V to pin 11.
Here
you see +5 V (from the L7805) is to connect to pin 1 on the PT2399.
I think that’s it for the power distribution.
Except that there really should be some capacitors added to this circuit. Two 10 µF electrolytics, one from +12 V to ground and one from -12 V to ground, both located close to the power header, and three 100 nF ceramics, from +5 V to ground near pin 1 on the PT2399 and from +12 V and -12 V to ground near pins 4 and 11 on the TL072. Ideally they should be located right next to those pins. These are bypass capacitors and while the circuit will probably work okay without them, it’s best to add them.
to be precise for the second it’s more GND to -12V 
Thanks ! It’s really helpful 
Can you tell me if I got it right ? I’m no so sure about the capacitors. Did I place them right ?
No, ±12 V connect to pins 4 and 11 on the TL074, not the PT2399. And one 100 nF (not 100 µF) cap goes next to each of those pins connecting the power rail to ground — total of three caps, not nine. All the caps (10 µF and 100 nF) connect from the rail to ground, not in series on the rail.
ok ! I understand for the capacitors But I don’t see number 4 nor 11 on the TL074. Is it just me ?
I think I found the answer. The schematic I sent you was a simplification of this one. mmmh but even so I don’t see the U4E TL074… Well I’m still stuck haha
OK… I said TL072 because only two op amps are used. A TL072 contains two, a TL074 contains four. It’s kind of silly to use a TL074 here unless something else is being added to the circuit that uses more op amps. And in fact a TL072 is shown on the stripboard instead of a TL074.
Anyway, TL074:
There are five pieces to this one IC, here is one:
(pins 1, 2, 3); here is another:
(pins 5, 6, 7); there are two more not shown, pins 8, 9, 10 and pins 12, 13, 14, which are the two unused op amps, and finally there is this piece:
They’re drawn in different parts of the schematic (or not drawn at all) but all are part of one IC. Pins 4 and 11 are the power pins.
If you use a TL074 you should not leave pins 8, 9, 10, 12, 13, and 14 dangling. You should connect pin 8 to pin 9, connect pin 13 to pin 14, and connect pins 7 and 12 to ground.
Or you can just use a TL072 in which case there are only 8 pins and 1, 2, 3, 5, 6, and 7 are connected the same as with the TL074. +12 V connects to pin 8 and -12 V connects to pin 4.
Ok now I understand ! Thanks again I see what you meant, now that I look at the stripboard. Sorry to have bothered you, I should have looked into it earlier !
If you’re using EasyEDA (or pretty much any other EDA tool), you can use net flags and net ports to make sure things are properly connected. Use net flags for power connections:
All flags marked with +5V will be connected to all other flags marked +5V, etc.
If you use standard footprints for your integrated circuits, they usually come with the power pins clearly marked. Just add the right flags to them, and EasyEDA handles the rest.
You can also use ports; they work the same way, but are more often used for signals (but still work for power connections):
All ports and flags with the same name will be connected to each other.
See the “Wiring tools” section in EasyEDA Tutorial for more on this.
On a simple diagram, all circuits could be drawn directly, but it gets a bit of a mess when you have more complex diagrams. Hence the use of “Flags” and “Power” symbols to reduce the number of interconnects.
Thanks ! Didn’t know that. I might have other questions later on
First one : What’s the solution for when the pieces I need are not in the software’s library ? Like the power connector for example.
Which program are you using?
There are a couple of options for getting symbols/footprints. You can try finding them online and download/import them to your program.
Or, you can “build” them yourself from the datasheet dimensions.
Also the power connector should be there 
in kicad there is for sure
I’m using EasyEDA, but I’ll try Kicad !
Search for “header 2x5” and you’ll find various footprints that’ll work. The Eurorack connector is an IDC connector, but you don’t necessarily need that exact component; the pin layout is the important bit.
(searching for “eurorack” actually brings up a whole bunch of user-contributed components, but many of them only have schematics and no PCB footprint)
It looks like this, are you sure ? It’s not the same symbol as in the schematic. And they all pretty much look the same !
That looks fine to me.
The original schematics was done in KiCad, so it uses KiCad symbols.
But the one chosen by the author of that schematic is not a good choice IMO…
Question 2 :
Do I connect every +5V symbol to the 5V voltage regulator (L7805) ? And if so, why does +5V connects to +5V and +12V connects to -12V ? thanks
Yes
Where do you see +12V connected to -12V ? I don’t…
