Analog Noise/Distortion Present When Nothing is Plugged In

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DrPhatteus

Member
Hey folks, I've noticed something very strange on my Axe FX III.

As a test, I have a microphone plugged into the left input of Input 2.
I have nothing plugged in to the right input of Input 2.

If I route the right channel of Input 2 to an analog output, I hear distortion when signal is present on the left channel.

The issue is present on the analog outputs and in the headphone jack of the Axe FX III.
The issue is NOT present on the USB inputs to my computer.
This happens whether or not the USB is connected to a computer (I thought maybe it was the USB connection introducing the noise).

I have created some videos to demonstrate the issue.

ISSUE IS PRESENT (analog outputs):



ISSUE IS NOT PRESENT (USB outputs):
This is the same video as above, but the audio is recorded via USB and the issue is not present here.





Is this issue "by design", am I doing something incorrectly, or is there a fix or workaround for this?
 
So my guess would be that using the input set to stereo while nothing plugged into the right side is the cause.
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I would agree with that assessment, thanks- but I don't think a device as well-engineered as the Axe FX III would demonstrate this type of issue. If there's no signal at the input of the right channel, where is the noise coming from?

I am hoping there is a solution for this.

I am also wondering if this is "normal" behavior for an Axe FX III or if my unit is defective.
 
It's normal. Input 2 jacks are not "normaled" because the combi-jacks do not have normaling contacts. With nothing plugged in the input impedance is extremely high because they are designed to also be used for instrument inputs. You're not hearing distortion, you're hearing noise, which is normal because there is nothing plugged in.
 
FractalAudio said:
It's normal. Input 2 jacks are not "normaled" because the combi-jacks do not have normaling contacts. With nothing plugged in the input impedance is extremely high because they are designed to also be used for instrument inputs. You're not hearing distortion, you're hearing noise, which is normal because there is nothing plugged in.
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Thank you for the explanation. This makes sense and reassures me that this is by-design.


mr_fender said:
Would a shorting plug be helpful to ground out the unused input?
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I wish I had thought if that before posting! Great idea and seems to address the issue 100%. I don't know if there are other issues that might arise because of the short (I don't know, phasing issues or something esoteric - most of you posters are way more technical than me!) but can't think of any. This is the solution I'll use going forward as it is simple to manage and troubleshoot. Thank you!


unix-guy said:
Why not just setting it to Left on input mode?
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I appreciate the "keep it simple" essence of your suggestion. The real preset I'm working with has some additional capabilities for other instrument inputs. However, in different scenarios not all instruments are connected at all times. I toyed with the idea of making a separate preset for each scenario, but then when I made a change (let's say MIDI control of a specific parameter) in one preset, I would then have to apply that change to all the similar "separate" presets. I am hoping to create a minimal number of master presets that are dynamic enough to accommodate different scenarios. So far so good, except for this particular exquisite little inconvenience.... which, thanks to this amazing community, has been addressed in less than 24 hours :smiley:
 
DrPhatteus said:
Thank you for the explanation. This makes sense and reassures me that this is by-design.



I wish I had thought if that before posting! Great idea and seems to address the issue 100%. I don't know if there are other issues that might arise because of the short (I don't know, phasing issues or something esoteric - most of you posters are way more technical than me!) but can't think of any. This is the solution I'll use going forward as it is simple to manage and troubleshoot. Thank you!



I appreciate the "keep it simple" essence of your suggestion. The real preset I'm working with has some additional capabilities for other instrument inputs. However, in different scenarios not all instruments are connected at all times. I toyed with the idea of making a separate preset for each scenario, but then when I made a change (let's say MIDI control of a specific parameter) in one preset, I would then have to apply that change to all the similar "separate" presets. I am hoping to create a minimal number of master presets that are dynamic enough to accommodate different scenarios. So far so good, except for this particular exquisite little inconvenience.... which, thanks to this amazing community, has been addressed in less than 24 hours :smiley:
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Sounds like you just need to use global parameters.
 
Budda said:
Sounds like you just need to use global parameters.
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In some cases this could suffice, but if I wanted to introduce a new effect, or adjust routing or block sequence, or tweak an EQ, its easier to do that in one preset, rather than half a dozen - I realize there are mechanisms for making the process easier, but overall the fewer presets I need to tweak, the better.
 
DrPhatteus said:
In some cases this could suffice, but if I wanted to introduce a new effect, or adjust routing or block sequence, or tweak an EQ, its easier to do that in one preset, rather than half a dozen - I realize there are mechanisms for making the process easier, but overall the fewer presets I need to tweak, the better.
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That's what the global parameters do. Any preset with that block will get the change, no matter which preset you're tweaking at the time. You'd only have to tweak 1 preset.
 
Budda said:
That's what the global parameters do. Any preset with that block will get the change, no matter which preset you're tweaking at the time. You'd only have to tweak 1 preset.
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Hey, I may heave learned something new today (in addition to yesterday)... Will have to read up more on this as it may save me a LOT of work - thanks!
 
unix-guy said:
Well... The setting I mentioned originally IS a global setting ;)
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I totally get that- but if possible, I'd rather just plug something in if I need it, rather than navigate through menus to make a change on the fly, although I can see the argument in the other direction, too. It's just that when I'm at a gig, I'd prefer to make physician connections, instead of putting on my glasses and tweaking menu settings that I might forget etc... :) Tomato tomahto!
 
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