Where is the noise coming from and how to isolate?

Lol, okay. Still alive at this point and I intend to maintain that condition for a while.

What I do at the moment: I use a simple (grounded) consumer power extension cord that has a couple of (grounded) inputs. I connect my power amp to one WITH a grounded cord. I connect the AFX to another using a plug WITHOUT a ground pin.

If I connect both using grounded plugs I get a ground loop hum and I need to press a ground lift switch on the amp or AFX.

What do you advice? (sorry to hijack the thread)
 
I recommend one simple test. If you own a simple ohm meter or DVM, set it to measure ohms. If it has a beep setting for 0 ohms, enable it. Make sure the ground lift switches on everything aren't set to lift. On the Axe, plug a grounded cord into the IEC power receptacle on the back, but don't plug it into the wall. Connect one side of the meter to the ground lug, and touch the other to the sleeve of the Axe output to the amp. If it beeps / reads less than 5 ohms, you're grounded through the cable. The Axe is just as grounded as it ever was, through the shield on the cable from the Axe to the amp, and the amp is still the only thing connected to the safety ground, no loops. It is after all a safety / chassis ground, not the intended return current path. As long as the chassis is still connected to the one thing that IS connected to the safety ground, all should be good.

I used to do this for a living a lifetime ago - I learned grounding techniques doing live sound installations for the chief engineer at Showco (rip Showco) and studio installations as a design engineer at Harrison. The Showco dude, Howard Paige, used to run a seminar at NAMM every year on grounding and gain structure. This is how studios and touring companies ground stuff - except they don't trust the building ground... They drive their own pair of copper rods into the ground 8 feet apart, connect them together, and connect to that.

As always, advice is worth what you pay for it, and we each have our risk appetite - if you have a faulty cable between you and the wall, or somebody inadvertently lifts the ground in your ground path, you ARE at risk as Rex correctly points out. People have died getting this wrong.

Axe content- My AFXII finally arrived here in HK last week, upgraded to 2.00c, and I'm in a total state of awe and bliss. I used to write code for audio consoles, on these same processors - and I never imagined they could do what Cliff has accomplished. Now if only I had the talent to match the toys...
Cheers,
Kevin
 
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yek said:
Lol, okay. Still alive at this point and I intend to maintain that condition for a while.

What I do at the moment: I use a simple (grounded) consumer power extension cord that has a couple of (grounded) inputs. I connect my power amp to one WITH a grounded cord. I connect the AFX to another using a plug WITHOUT a ground pin.

If I connect both using grounded plugs I get a ground loop hum and I need to press a ground lift switch on the amp or AFX.

What do you advice? (sorry to hijack the thread)
Click to expand...

This is exactly how I am connecting the axe and amp to the power socket :)
I think I'm starting to understand the ground "loop" thing. That means I am in no danger as long as part of my equipment is grounded. I have a ground lift on my soundcard as well but It is not lifted when I play into my computer. Is this also safe? I'm still using the disconnected ground power cable.
 
Mike Snider said:
http://forum.fractalaudio.com/axe-f...nning-straight-into-guitar-amp-front-end.html

Here is another user same issue-
Click to expand...

That's me trouble shooting some ground issues with an AxeII!

To the OP - I would try a simple isolating "pedal" between your Ultra and the Amp. Something like the EbTech Hum Eliminator, or GigRig Hum Dinger.

The Hum dinger is working well for me and gives a more transparent sound as it's active (whereas the Hum Dinger works too, but is passive and seems to take some of the highs in the process).

I'm a little like you - really want to get the noise level down to where it's at with just the guitar plugged in while maintaining a unity guitar level. The Hum Dinger gets me there. My issue however is I'd rather not have to use it - especially with this new fandangled "humbuster" technology.

Be wary of some of the other "solutions" out there. There are some pedals that claim to be able to intergrate a rack into the front end of your amp, but lack any sort of ground isolation, which can actually make the problem worse. It's like A/B pedals that don't have a ground lift on one or both outputs - mostly useless if you're using two mains powered sources at the end of each output.
 
This device here was designed specifically to solve (correctly) your problem:

Radial X-Amp active re-amp amp-driver

It works - and addresses all the issues encountered when driving an amp input with a line-level source. Other methods only address a portion of the problem.

If you dig into the tech blurbs on the radial site you will see what's causing the problem. It's not the Axe.
 
yek said:
Lol, okay. Still alive at this point and I intend to maintain that condition for a while.

What I do at the moment: I use a simple (grounded) consumer power extension cord that has a couple of (grounded) inputs. I connect my power amp to one WITH a grounded cord. I connect the AFX to another using a plug WITHOUT a ground pin.

If I connect both using grounded plugs I get a ground loop hum and I need to press a ground lift switch on the amp or AFX.
Click to expand...
Yek, this should NOT cause a ground loop if both devices use grounded plugs.... as both are on the same circuit using the same ground wire. It's the same thing as connecting the amp to a wall outlet in your home, then powering the Axe from the next one over. In most homes, a single room is on the same circuit, so the ground wire on both outlets, is the SAME ground wire!

You might be seeing (hearing) RF interference isolated in the power extension you are using. I use a (self-built) 4-outlet box, with a common/shared ground on the end of 50 feet of 12 gauge with a grounded 3-pin 20-amp plug on the wall end.

Used it just last night - subbing for a band - and ran my 50w Atomic cab, Axe-II and G90 wireless off a single outlet. Axe was in 1st (of the 4 outlets on the box), G90 in 2nd and Atomic in 3rd. NO NOISE ! In fact I had to keep checking that eveything was still "ON" it was so noise-free. Single, common ground.
 
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kraebs said:
Connect one side of the meter to the ground lug, and touch the other to the sleeve of the Axe output to the amp. If it beeps / reads less than 5 ohms, you're grounded through the cable. The Axe is just as grounded as it ever was, through the shield on the cable from the Axe to the amp, and the amp is still the only thing connected to the safety ground...
Click to expand...
I wish that were true. It would make life much simpler. :) The problem is that if if a short circuit occurs, it can dump a whole lot of current through the ground connection. Your audio I/O and signal cables aren't designed to carry that much current. Under those conditions, they can pop open like a fuse; now you no longer have a safety ground, at the exact moment when you need one.

Defeating the ground pin on your power connector is flat out dangerous.
 
calleballe11 said:
I think I'm starting to understand the ground "loop" thing. That means I am in no danger as long as part of my equipment is grounded.
Click to expand...
Nope and nope. Sorry to keep beating on this, guys, but if one person gets zapped because he's not using the ground pin, and I could have spoken up and didn't, I wouldn't sleep well at night.
 
s0c9 said:
Yek, this should NOT cause a ground loop if both devices use grounded plugs.... as both are on the same circuit using the same ground wire. It's the same thing as connecting the amp to a wall outlet in your home, then powering the Axe from the next one over. In most homes, a single room is on the same circuit, so the ground wire on both outlets, is the SAME ground wire!
Click to expand...
True, it's the same ground wire, but unfortunately, there's no such critter as a zero-impedence conductor. If a ground current exists, that conductor's impedence will cause a voltage difference to occur between one end of the ground wire and the other end. That voltage is your ground-loop hum—even if both devices are plugged into the same ground wire.
 
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Sound like it could be polarity issue between the output and input on the two devices.
 
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Rex said:
True, it's the same ground wire, but unfortunately, there's no such critter as a zero-impedence conductor. If a ground current exists, that conductor's impedence will cause a voltage difference to occur between one end of the ground wire and the other end. That voltage is your ground-loop hum—even if both devices are plugged into the same ground wire.
Click to expand...
True, no argument with that. However, there SHOULDN'T BE any measurable voltage differential - at least not enough to cause hum - between the devices when connected like that - at least not power supply generated. If there is noise, it's probably something else, possible induced by pickup sensitivity, to much gain on a preset or.... ?? <pick something user induced>.

And.. to add to your prior post, I can't repeat this often enough..

NEVER USE A GROUND-LIFTER PLUG ON YOUR GEAR, YOU MIGHT SAVE YOUR LIFE.

Especially if you use tube amps!!! I've posted vehemently on this subject before.. just because it's often a quick-n-dirty solution to ground loops, I see musicians using lifters as part of their rig all the time. On some devices, like the AxeFx, the power consumption is almost nothing. Mostly solid state, etc. But in tube amps, there's a boat load of high voltage roaming around that circuitry and they have HUGE capacitor/condensors inside. In either case, improperly grounding a device can cause the current/voltage to go to ground thru you - given the right circumstances. It's not the voltage that kills you, it's the current. A FULL 15 amps is a HUGE jolt.. and 1 amp is more than enough to take you out.

To be sure, I've had folks use these on an ongoing basis and tell me they are completely safe and no need to worry. Truth is, it might be fine 9 out of 10, or 99 out of 100 times. But relying on "house power" being perfect is risky. Assuming the wiring is 100%, grounding is good and nothing is wrong is also risky. But the potential REALLY exists when you use a lifter, and it would really SERIOUSLY ruin your day if you got killed that one time.

Please do not use them...unless you know what you are doing.
 
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