How to connect 2 circuits together ? [Beginner Question]

[seadi123]

Hello everyone So let's say i want to put 2 or more circuits on the same enclosure . So tell me if i'm correct , all i have to do is :
1. Connect the output from the 1st circuit 3dpt switch to the input of the 2nd circuit 3dpt switch
2. Connect all ground of both circuits together
3. Share the same 9v source together in parallel

So i have 2 questions . If i connect both circiuits ground , will the signal accidentally pass from 1 circuit to the other ? And 2nd question , if both circuits are sharing the same power source , does it mean they're using 4,5v each , or does each of them have its own 9v source ? Thanks

[GibsonGM]

Great questions, Sead!  Review the stuff on here, esp. the "two in one box" stuff.  This will help you sort it out 
http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=33&Itemid=27

Both circuit grounds should go to one common ground point (the battery, a jack, or something) rather than >board>board>battery.     IOW, a separate wire from each PCB to the battery....

If you run the + voltage to EACH board from the battery or a "9V spot" on a circuit board (called the power buss), they'll share 9V, no problem.   Good question again, tho!   If you ran 9V THRU something, then out, and into something else in series, yes, you'd see the voltage drop of the first *stuff*.    In our case, you're really putting them in parallel with the battery, so they have the same voltage and different current draws. 

[duck_arse]

it is better to think in terms of "a switch" rather than "the 3dpt" (which should be 3p for poles 2t for throws). you might come across a dpdt instead.

connect all the grounds at a common point. as above.

anything "together in parallel" must have the same voltage across them, as their circuit diagram will show.

if you are connecting 2 high gain circuits to the same voltage source, they may well accidently pass a signal between, on the power line. it is a good idea to seperate such circuits with a "power line RC filter" or two.

[seadi123]

Thank you very much guys

if you are connecting 2 high gain circuits to the same voltage source, they may well accidently pass a signal between, on the power line. it is a good idea to seperate such circuits with a "power line RC filter" or two.

Any article about this that is can read to understand better ? thanks

[Mark Hammer]

Many pedals will contain an assortment of components or subcircuits that are based on the assumption that THIS is the only pedal you own, or that any other pedals you own may have this or that particular area of risk not attended to.  As a result, there can often be things you don't need to include when combining two of your own circuits in the same box.  Conversely, there can be some things they leave out, that you DO need to include.

For example, because they use FET switching, instead of mechanical switching (whether true bypass or not), almost all pedals made by Boss will have a "buffer" stage before the switching FET at the input to the effect portion, and a buffer after the other FET switch on the output of the effect circuit.  The buffers are often not essential to the sound, but are only there because it uses electronic switching.  There isn't much point in having two consecutive buffers.

Of course, because all the switching is done on the "inside" of the circuit, and not between the input/output jack and circuit board, as you are likely to do, none of those electronically-switched pedals will have a "terminating" resistor between the input and ground.  If you try and copy them exactly (with the omission of the FET-switching part, you will hear popping whenever you switch because those terminating resistors are absent.  What makes absolutely perfect sense in the one context, causes problems in another.

So, I think, as you progress along, it will be useful for you to ask the more experienced folks here "I am going to run X into Y.  Is there anything I can easily leave off without affecting their functioning, or is there anything I need to add."  Nine times out of ten, the answer will be "No", but it's helpful to be open for advice on that 10th time.

One last thing.  Sometimes, you want to be able to turn on this part OR that part without accidentally changing/switching the "other" part.  So plan out the spacing of any footswitches or other switches with an eye towards how you plan to use them.  That includes things like whether you want/need to orient the chassis itself another way.

Happy building.

[duck_arse]

Thank you very much guys

if you are connecting 2 high gain circuits to the same voltage source, they may well accidently pass a signal between, on the power line. it is a good idea to seperate such circuits with a "power line RC filter" or two.

Any article about this that is can read to understand better ? thanks

go on the amz link at the top of the page, read everything there especially in the lab section. the page on "hum and noise" might be instructive.

[GibsonGM]

+1 on AMZ, and +1 Mark - I made an assumption that we're talking about DIY stuff and not something like a re-house of Boss pedals - good that someone pointed that out.

It's surely good practice to include an R-C network at the power supply to decouple, Duck caught me on that one.  I've never had trouble because of NOT having (more than) one, as I always am running EITHER this pedal OR that one.   If you wanted to house, say, an overdrive and a booster in one enclosure, and click in the booster after the overdrive so both are on at once, it does make sense that you could experience some oddity/noise without the RC.

All it is, is a resistor followed by a capacitor to ground. Power taken from the junction between the two.  This allows noise currents to pass harmlessly to ground rather than sneak into the next circuit. It's called "decoupling" from the power supply.  You'd have one of these babies on each board, where your 9V enters. 

http://www.muzique.com/lab/main.htm
http://www.muzique.com/lab/hum.htm