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Axe Fx II can be "Microphonic"

Rex

Legend!
Crazy. How does it work? I don't understand how it's possible.
The Axe is digital, but the inputs and outputs are analog (if they weren't, you wouldn't be able to use your guitar or power amp :) ). If you whack any analog audio gear, you generate a tiny signal. Usually, those tiny signals are inaudible. But with the crazy amounts of gain available in the Axe, even a tiny unwanted signal can cause problems.
 

pauly

Fractal Fanatic
It's like it resonates more than feeds back - like it's emulating a circuit that resonates - one day they will find it - and I'm looking forward to that. It's very easy to duplicate but difficult to explain in traditional digital terms.

Pauly

The Axe is digital, but the inputs and outputs are analog (if they weren't, you wouldn't be able to use your guitar or power amp :) ). If you whack any analog audio gear, you generate a tiny signal. Usually, those tiny signals are inaudible. But with the crazy amounts of gain available in the Axe, even a tiny unwanted signal can cause problems.
 

greiswig

Power User
Capacitors in guitar amps that are in the signal chain sometimes become microphonic. I don't know if there are similar opportunities inside the AFX. Lower voltages, so safer to try to find them, though. ;-)
 

Rex

Legend!
It's like it resonates more than feeds back - like it's emulating a circuit that resonates...
That's the case that's ringing. If you put a stethoscope up th the case and tapped on it, you'd hear that resonance when you tapped the case, even with the Axe powered off. With lots of gain, that ringing gets amplified. With lots of room volume, that ringing can turn into all-out resonant feedback.
 

clarky

Axe-Master
I couldn't think of the right terms before… but I've just remembered them..
synth players talk about 'self oscillating filters'.. even in an all digital / modelling domain..
I'm no expert in this sort of thing… but I'm guessing that within the Axe, if you set up a preset with a ton of gain / compression, possibly with the addition of huge / strong reverb / delay, that you're setting up similar conditions for 'self oscillation'..

I've heard my Axe do this when I've been noodling with soloing tones..
even at low volume, monitoring thru cans etc.. so it's not feedback..
at least not in the regular " smokin' loud amp, stood in front of the cab, screaming noises, looking very cool and the crowd go wild" sense…
in my case it was a 5153Red set so hot it was radioactive, through a huge delay in a cathedral..
awesome tone.. but totally out of control..

I've seen many threads that refer to "high pitched feedback / squealing"..
and I reckon it's this oscillation thing..

out of interest, I just jacked into my Digitech 2120.. turned everything up to 11 and got exactly the same outcome..
low volume, thru cans, high pitched squealing..

so it ain't just the Axe..
 

Loquenau

Power User
I finally tried out the Kemper yesterday, and I was surprised to find I could hear the selector button clicking when I had the gain up and the gate down a bit. Sounded like a tapping it was so loud.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Anything with enough gain will be microphonic. It's primarily due to the circuit board and any ceramic capacitors. The ceramic caps are piezoelectric so they will convert any acoustical energy into electrical energy. The circuit boards flex (microscopically) which causes strain in the traces which is converted to electrical signals.

The Axe-Fx II strives to minimize this. The Mark II is comparable to most other modeler products. The XL has nearly completely eliminated this due to the use of PPS film caps in critical locations and a stiffer board mounting design.
 

Johnnyh64

Experienced
The Axe-Fx II strives to minimize this. The Mark II is comparable to most other modeler products. The XL has nearly completely eliminated this due to the use of PPS film caps in critical locations and a stiffer board mounting design.
Would it help to go ahead and dip it in wax then?

Kidding of course ;)
 

Womac911

Inspired
I noticed the same thing a few days ago when I set a pair of reading glasses on it and it went "clannngg"
Happend if I drag my nails across the top of the chassis as well. Currently patch loaded is "E Octaves of Fun"
I never noticed it before because I always had a monitor placed on top of the Axe..

Patch "Track Wah" and does it.. sounds like a hammer on wood...
:Synth Lead" produces some pretty odd sounds too...

Also happens if I tap on the desk the Axe is sitting on.

wierd.
 

Stratoblaster

Fractal Fanatic
My Orange Rocker 30 had the weirdest microphonic/mechanical interaction only on the high "D" note on either the E or B string until I changed out the offending tube. When I played that note, and only that note, a most bizarre oscillation occurred and it really did some sonic weirdness to the tone that sounded mechanical.

It's comforting to know the II will never be that microphonic...! That's one real tube amp 'feature' I don't need modeled.
 

GotMetalBoy

Power User
Anything with enough gain will be microphonic
Cliff, when you say "gain", do you mean the I/O page input or do you mean distortion turned up all the way?

I have an Axe-Fx II Mark I and my I/O front input set to 30 or less but my Layout gate opens when set to less than -60 whenever drums are hit and that's with no blocks in the grid, so my issue isn't being caused by I/O gain or distortion turned up.

FYI, I'm not complaining or bashing the AF2, I just want to make sure nothing is wrong with mine. My AF2 still sounds way better and is super quiet compared to my old TriAxis rig.
 

Rex

Legend!
...when you say "gain", do you mean the I/O page input or do you mean distortion turned up all the way?
"Gain" means amplification. Anything in your chain that amplifies your signal contributes to your gain. That means gain, compression and volume knobs in the amp block, compressors, drive blocks, or anything of a hundred parameters that can increase your signal.

I'm not sure why the drum hits are opening your gate. If anything, they should close the gate, not open it.
 
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