2 effects in 1 box: How do I power them from the same 9V?

Putting two effects in one box almost looks too easy, but you will save a lot of time reading the frequent questions before starting such a project...
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Post by eman »

I'm using two separate schematics (tyco oct and fuzz face) complete with 2 DPDT switches in one enclosure.

Newbie question: To power both, do I solder up each effect separately, then connect both to the same 9V power source?

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Post by briggs »

You connect each effect's 9v and ground connections to each other then to the power jack/battery connector.
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Post by bajaman »

You connect each effect's 9v and ground connections to each other then to the power jack/battery connector
I would prefer to isolate each stage by running a separate 100 ohm resistor to each effect from the + 9v supply socket or battery positive terminal and then drop a 220uf electrolytic(or larger if you prefer) from the circuit side of these resistors (2 electros required) to ground. By doing this you will decouple any signal voltage from travelling through the power supply rail between each effect and enhance operational stability by reducing or eliminating any intermodulation artifacts, particulary in the high frequency range. Make sure you connect the negative terminals of each electrolytic to ground.
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Post by modman »

--moved to the Workbench--
good topic though
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Post by gshapzira »

Hello, nOOb here...
bajaman wrote:
You connect each effect's 9v and ground connections to each other then to the power jack/battery connector


I would prefer to isolate each stage by running a separate 100 ohm resistor to each effect from the + 9v supply socket or battery positive terminal and then drop a 220uf electrolytic(or larger if you prefer) from the circuit side of these resistors (2 electros required) to ground. By doing this you will decouple any signal voltage from travelling through the power supply rail between each effect and enhance operational stability by reducing or eliminating any intermodulation artifacts, particulary in the high frequency range. Make sure you connect the negative terminals of each electrolytic to ground.
cheers
bajaman
can you please explain this issue to me? if you could make a simple schematic of this it would be great!
Thanks a lot.

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Post by bajaman »

Hello - is this clearer :) :?:

Add a 100 ohm resistor from EACH effect's +ve supply rail to the + 9v supply socket or battery positive terminal and then add a 220uf polarised aluminium electrolytic capacitor from EACH circuit's +ve supply rail to ground (connect the -ve pins of the capacitors to ground). This is a very old "trick" known as supply rail decoupling and it works surprisingly well, particularly when running effects from a common power supply adaptor. Many good designers already use this method of decoupling in their products - a schematic helps to identify this. :wink:
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Post by gshapzira »

Thanks a lot Bajaman! Sorry for my silly question :mrgreen: English is not my native language and sometimes I just don't get the terminology.

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Post by flood »

bajaman's method is probably the simplest and best - BUT - if you want to really overkill it, you could use something called a DC-DC converter - that's what we were taught is used in ECG front ends to decouple the patient side )the converters i used were isolating types, up to 2.5kVDC)... but for this purpose, you'd be really overdoing it - DCDC converters are large, expensive, and need noise suppression components.
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Post by rocklander »

bajaman wrote:Hello - is this clearer :) :?:

Add a 100 ohm resistor from EACH effect's +ve supply rail to the + 9v supply socket or battery positive terminal and then add a 220uf polarised aluminium electrolytic capacitor from EACH circuit's +ve supply rail to ground (connect the -ve pins of the capacitors to ground). This is a very old "trick" known as supply rail decoupling and it works surprisingly well, particularly when running effects from a common power supply adaptor. Many good designers already use this method of decoupling in their products - a schematic helps to identify this. :wink:
cheers
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so if I was looking at building a pedal that has 2X surpeaux in it, would you be saying that I should replace the 100uF cap there with a 220uF or adding another, and then put a 100ROhm between the two pedals supply rail (just before the last trim in this schem), or if it's on the same PCB would it be ok to leave the supply rail as constant?
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Post by bajaman »

Hi rocklander
You can probably leave the 100uf capacitor as it is on BOTH Supreauxs.
You will need to add TWO 100 ohm resistors (one in series FROM the supply +9v to the +ve 100uf electrolytic terminal of each Supreaux).
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Post by rocklander »

sweet as then. again, thanks! :D
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Post by rocklander »

so would this layout be what you're suggesting? (I'm trying to make the boards long and thing rather than short and fat as ROG has them - suits my applications better)
top right is the decoupling R+cap
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Post by bajaman »

NO!!!!
the +9v battery lead connects to the 100 ohm resistor. The other terminal of this resistor connects to the +ve terminal of the 100uf electrolytic and the +ve rail for the circuit, where the +9v battery terminal was previously connected.
The same applies to all the other circuit/s. In this way ALL the circuits are separated from each other's +ve supply rail by 2 x 100 ohm resistors.
Hope this makes sense.
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Post by rocklander »

clearly I'm not getting this then huh :oops:

so what you're saying is to put 100R between supply (9v battery and/or PSU) and (to all intents and purposes) the +ve rail for that particular effect.

then from that +ve rail (not the 9V supply) have an appropriate electrolytic to earth.
(apt. electrolytic is normally 220uF, but in the supreaux case it's 100uF)

is that it, or do I still have my dunce cap on?
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Post by bajaman »

yep - that is it!!
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Post by rocklander »

whew.. :lol: if that wasn't it I dunno how I was gonna get it
thanks again...
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Post by bobo »

I'm built 2 effects in one box. When I run by 9v battery no any problem. Once run by external power supply, it had sound like pop corn. I already put resistor 100ohm and capacitor 220uf per Bejaman advise. The problem is still unsolve. Anyone can suggest for this case.

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Post by timbo_93631 »

I drew this up in DIYLC. Does it look correct?
2 effects in 1 box power distribution diagram.png
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Post by euronymous0001 »

that is correct

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Post by Masuto »

Slightly different question here: any kind soul can suggest me a full offboard wiringlayout (since we are here.. including 9v single power supply) to have two pedals in one box? Ins, outs, cascading from guitar and outs including the final out to the amp?
Is my question silly enough/useless?

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