effects not playing nicely together

Downunderwonder · #1 12-03-2011, 05:11 PM

Strange noise problem, when I switch on Groove Regulator I get a whine, but only when my cool cat chorus is in the chain. It doesn't matter if chorus is on or off. Take away either of them and no noise, what gives?

keyofnight · #2 12-03-2011, 05:19 PM

Does it matter what order they're in?

Baron Von Vik · #3 12-03-2011, 05:25 PM

Maybe a voltage parity issue? From what I read, the Cool Cat is an 18-volt.

RickenBoogie · #4 12-03-2011, 07:17 PM

Most likely the power source. What are you using?

Downunderwonder · #5 12-03-2011, 08:57 PM

The cool cat is a 9V one, all powered off a one spot type. I don't get how noise from the power supply requires a particular (switched out, or switched in) pedal to make it audible when another particular pedal is switched in.

bongomania · #6 12-04-2011, 12:49 AM

It's all about ground planes and differences in potential. A ground plane is the common wiring, which acts as "zero volts", and it not only includes the common ground on the circuitboard and from the power supply, but also the neg connector of the in/out jacks, and very often the metal housing of the pedal itself, as well as any metal knobs and switches. Because the jacks are part of this, the ground plane of any one pedal is also in common with the ground plane of any pedal it's connected to via patch cords. Additionally since you're using a daisy-chain supply, all the pedals have their grounds connected that way too. So it's a big messy loop, with every pedal affecting every other pedal.

"Potential" is a difference in voltage, so for example the only reason a circuit sees 5V at one component is because there is a 5V difference in potential between that part at that moment, and the ground plane. There's actually no such thing as zero V in a powered circuit--it's just a reference point.

When two devices are designed so their ground planes are not identical, there is a potential between those two planes--even though internally to each pedal the ground is "zero V"! When the is a difference in potential between two planes, there is voltage, and this voltage has nowhere to go, and it takes the path of least resistance, which very often means it leaks into the audio path as noise.

Even switching a pedal on and off can change the potentials, as the path of least resistance changes. So a pedal can be silent when "off" and noisy when "on", or the other way around!

And as often as not, the pedal that acts noisy isn't even the one with a problem. Just because the noise leaked into the audio path of pedal A, it could still have been pedal B that had the odd-man-out ground plane among the various pedals on the board.

G3Mitch · #7 12-04-2011, 01:18 AM

+10 to post above. all of my noise problems were caused by power supply. fixed now

Downunderwonder · #8 12-04-2011, 04:09 AM

Thanks Bongoman, I'm thinking the cool cat has the problem since there is no problem when it's taken out. Can I force it to use the common ground?

RickenBoogie · #9 12-04-2011, 08:13 AM

No, you'll need to use an isolated power source.

jongor · #10 12-04-2011, 12:40 PM

Quote:

Originally Posted by G3Mitch

+10 to post above. all of my noise problems were caused by power supply. fixed now

How was it fixed?....batteries??....different power supply??

Quote:

Originally Posted by RickenBoogie

No, you'll need to use an isolated power source.

An isolated power source, not isolated power supply?

bongomania · #11 12-04-2011, 12:53 PM

Source = supply.

Plays_For_Dog · #12 12-04-2011, 12:59 PM

Sounds like the cool cat is bleeding interference from it's power circuit over to the grounding circuit.

Does the cool cat make the hissing sound when it's the only effect between your bass and amp? If so, you need a nerd to crack it open, check your solders and "shoot" your circuits.

Also, the one spot may not be providing the proper milliamps to the cool cat.

Baron Von Vik · #13 12-04-2011, 02:10 PM

Quote:

Originally Posted by bongomania

It's all about ground planes and differences in potential. A ground plane is the common wiring, which acts as "zero volts", and it not only includes the common ground on the circuitboard and from the power supply, but also the neg connector of the in/out jacks, and very often the metal housing of the pedal itself, as well as any metal knobs and switches. Because the jacks are part of this, the ground plane of any one pedal is also in common with the ground plane of any pedal it's connected to via patch cords. Additionally since you're using a daisy-chain supply, all the pedals have their grounds connected that way too. So it's a big messy loop, with every pedal affecting every other pedal.

"Potential" is a difference in voltage, so for example the only reason a circuit sees 5V at one component is because there is a 5V difference in potential between that part at that moment, and the ground plane. There's actually no such thing as zero V in a powered circuit--it's just a reference point.

When two devices are designed so their ground planes are not identical, there is a potential between those two planes--even though internally to each pedal the ground is "zero V"! When the is a difference in potential between two planes, there is voltage, and this voltage has nowhere to go, and it takes the path of least resistance, which very often means it leaks into the audio path as noise.

Even switching a pedal on and off can change the potentials, as the path of least resistance changes. So a pedal can be silent when "off" and noisy when "on", or the other way around!

And as often as not, the pedal that acts noisy isn't even the one with a problem. Just because the noise leaked into the audio path of pedal A, it could still have been pedal B that had the odd-man-out ground plane among the various pedals on the board.

I'm saving this post forever and ever. Muchos thank yous, Senor Bongo.

jongor · #14 12-04-2011, 03:17 PM

Quote:

Originally Posted by bongomania

Source = supply.

Okay....do you mean the wall-wart or the plug in the wall it's plugged into?

G3Mitch · #15 12-04-2011, 04:21 PM

Quote:

Originally Posted by jongor

How was it fixed?....batteries??....different power supply??

yeah, once i figured out which one it was coming from i took it and threw it in the river. felt great. haha.

so yeah just replaced it. was a frustrating 2-3 weeks as i thought it was coming from a pedal, or 2 pedals conflicting with eachother. it was a relief once i realised it was a power supply.

its a good idea to pay a little extra and get quality ones. one day ill get a dc brick or something similar.

jongor · #16 12-04-2011, 04:32 PM

What did you get?

G3Mitch · #17 12-04-2011, 04:37 PM

just one of the boss ones. the one that i threw out was some random brand id never heard of.. half the price of the boss type. never again.

bongomania · #18 12-04-2011, 04:47 PM

Quote:

Originally Posted by jongor

Okay....do you mean the wall-wart or the plug in the wall it's plugged into?

The wart.

Downunderwonder · #19 12-05-2011, 02:47 AM

Hang on a second, I thought the point of the epic post was that an effect pedal operating on a different "zero" potential feeds a noise into the common ground, thereby explaining my mystery noise appearing from an inactive pedal when a different pedal is operating.

If I talke away the cool cat, the noise, which occurs when the GR is on, goes away.

bongomania · #20 12-05-2011, 11:07 AM

Maybe I'm misunderstanding you, but it sounds like what you're saying matches what I was saying. No?