Radio FOXX

[jonathan perez]

My FOXX Tone Machine is picking up radio stations. i LOVE the way the octavia sounds...but the unit picks up radio stations.

why do you think that could be, and what can i do to fix it?

[mmadscientist]

Check the FAQ- something about adding a cap?

[leonhendrix]

I posted pretty much the same thread a while back http://www.elixant.com/~stompbox/smfforum/index.php?topic=22052.0

I got rid of the problem by putting it a different enclosure, it was in a fuzz face enclosure.

leon

[jrc4558]

a ferrite bead on the wire that goes to the circuit from the input will solve your problem.

[jonathan perez]

id like to put it in another enclosure, BUT PURPLE VELVET ROCKS!!!!!

sorry, but i like it. 

i think ill try the ferrite bead. will that really work? haha i dont understand its physics.

also, i think ill need to get me a couple 1k resistors and 47µF....where can i just get a couple?

[rockgardenlove]

^Radioshack should have them

[jonathan perez]

ill try and go in the morning.

i think the tone of it ROCKS...but time for new tires, so...i wonder what gets done first?

[jonathan perez]

*bump*

sorry in advance for this one 

whats the ground? i just happen to have crapload of 1k and 4.7µf in a box with all my wah stuff. the input is obvious. but where the ground? i just dont wanna connect them to anything they shouldnt be. 

[jonathan perez]

whats the "ground?"

[Transmogrifox]

In a 9V operated pedal, "ground" is usually the common connection that is referenced to the "-" terminal of the battery.  We arbitrarily call this "zero volts".

If you think of your guitar cable, there is a tip and a ring.  The tip is the signal connection, and the ring is "ground"  It is the "0" volt reference for the signal that is "read" from the tip. 

So for reducing radio noise, here are some options:
Ferrite bead on the wire that connects to the part of the jack that the "tip" contacts.
Small capacitor (like 47pF) from between the tip and ring connections on the circuit board.
Large capacitors (like 47 uF) accross power supply rails.  This would be "+" side of capacitor to part of circuit that connects to battery positive, and "-" side of capacitor to battery negative (ground).

The reason "ground" is called ground comes from power systems.  The three wires used (most simple single phase) are "hot", "neutral", and "ground".  The hot and neutral are the current carrying conductors.  Somewhere out at the utility transformer that feeds your house, there is probably a big long piece of metal driven deep into the ground (called a ground rod).  This conductor called "ground" is connected to the ground rod.   This then comes up into the transformer where "neutral" is defined.  "neutral" is the conductor that is bonded to ground at that place.  Neutral is not bonded to ground anywhere else, however, by bonding it to "ground" at this point makes it a zero voltage potential between the ground you are standing on and itself.  Therefore, in a building that is well grounded and the electrical system is designed to code, you could very well shove a paperclip into the wall outlet on the neutral plug (the larger of the two) and it would do nothing to you.  If you touched onto the hot, you'd experience something exciting. 

***Now do keep in mind that I don't recommend sticking metal objects into wall outlets!***

The reasons being:
1. Not every power system is built to code.
2. You may guess the wrong side of the outlet and connect to the hot.

Now for the "ground".  This ground conductor is typically brought into a building and tied to all of those "ground" pins.  The chassis of your electrical appliances, then, are connected to ground.  As long as ground does not carry much current (ideally none), then the appliance you're touching is referenced to the same potential as the ground you're walking on.  That way you do not get shocked when you walk over and touch your refrigerator.

So...for your 9V pedal, all of your wall warts for power supply and such are isolated from ground, so there is no physical connection.  Likewise to the power system, your audio system should only have one reference to the real ground you walk on.  Otherwise you get noise problems due to ground loops, where the big loop between the two points you have connected to the wall ground becomes an antenna for radio. 

Your amplifier is typically where you reference "ground" to the ground pin in the wall, which is connected (hopefully) physically to ground somewhere.  This makes it so your guitar does not shock you.  I have played guitar through some amps that shock me because they are not properly grounded, or have a ground lift switch.  The ground lift switch is used to disconnect from ground only if you have multiple connections to ground in your system and are suffering from noise problems due to ground loops.  Otherwise, the ground lift switch can be dangerous.

In the end the grounds in all your system should look like a single continuous wire from the "ring" connection on your guitar, through all the pedals, to the amplifier, and into the ground pin on the wall through the amplifier's ground.  You should have no more and no less than one connection to physical ground, and nowhere in your system should there be a a ground branch that reconnects somewhere to form a loop.

[Coriolis]

Good post Transmogrifox!
I never quite understood the concept of ground loops until now. 

C