Front vs. Rear Input Question

sampleaccurate said:
Our band uses a pre-programmed mix and pre-programmed effects processing. When we set up each time, we go through a methodical calibration procedure that involves inserting a test tone into the input used by each instrument and selecting a special patch that's flat with enough gain to cause the level of the tone to match a certain benchmark.
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And there is no reason not to do precisely the same with the Axe-Fx. It is only when the test tone is not representative of the signal from a guitar that problems will occur. A viable calibration procedure for any type of gear will by necessity take into account the nature of the intended signal. You got the level too hot. Not only did I tell you about that quite some time ago, the manual warns against doing that. Why you continue in an attempt to lay blame elsewhere for your own error is something of a puzzle to me. It's an easy error to make, but it is an error nonetheless.

We assume LINEARITY of the response,
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Which you have, given the appropriate signal level. That's what you were missing. It is disclosed in the manual, and I warned you about it when I first noticed the errors in your cab sim responses. If you apply THE CORRECT SIGNAL LEVEL, you will have LINEARITY.

and we make sure things like tube preamps are in a zero distortion linear mode when we measure the total gain of each signal path.
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If the signal you use to calibrate the guitar signal chain is low enough in level to keep a tube amp in "linear" operation (which is not fully achievable), it will not cause problems with the Axe-Fx

If I didn't know that the AXE uses a frequency dependent limiter between the input jack and the meter
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It does not. It has an HF boost filter in front of the limiter. The limiter itself is not frequency-dependent. The only reason it appears to be is that you are looking at it with a sweep, which only contains one frequency at a time. When a broadband signal exceeds the limiter threshold, the limiting action is not frequency-dependent.

The entire procedure is dependent upon our assumption of the linearity of the response.
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And that assumption is perfectly valid, given the correct signal level at the input.

Some of us do need to know stuff like this.
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What you really need to know and act upon - that the Axe-Fx front input requires an instrument-level signal - is fully disclosed in the manual.
 
Jay -

I have an O.T. question:

If you happen to be using active pickups and also an onboard pre-amp ( ie; EMG, w/boost ) through the front input, what would the "sonic" difference be ?

And how would you know if you're driving the input into self limiting, if you're' not actually clipping the input ?

TX -
 
R.D. said:
If you happen to be using active pickups and also an onboard pre-amp ( ie; EMG, w/boost ) through the front input, what would the "sonic" difference be ?
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It would depend on how much level you're applying to the input.

And how would you know if you're driving the input into self limiting, if you're' not actually clipping the input ?
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I can only guess that it would begin to sound squashed.

If your guitar puts out a line level signal, it would seem to me to make sense to just use the rear input and avoid the issue altogether.
 
Man, reading through this thread gave me a headache.

I've never used the rear input, but maybe my take away from this thread is I should try it out when using active pups.
 
Jay I could really use some help. I am running a Warr guitar with active Bartolinis into a SoundSculpture SwitchBlade 8B and then into the rear inputs and I never seem to get enough level. I couldn't clip the input if I wanted to. Its a different story in the front input. So what I need to know is should I crank my Bart preamp gain and continue to use the rear inputs on the axe or should I go in the front? Please help.
 
Sterling said:
Jay I could really use some help. I am running a Warr guitar with active Bartolinis into a SoundSculpture SwitchBlade 8B and then into the rear inputs and I never seem to get enough level. I couldn't clip the input if I wanted to. Its a different story in the front input. So what I need to know is should I crank my Bart preamp gain and continue to use the rear inputs on the axe or should I go in the front? Please help.
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If there is a unity gain setting on the guitar preamp, my guess is that it would be safe to use the front input with that setting. GIven that an active circuit is going to have a different noise spectrum than passive guitar pickups, I'm not sure if the encode/decode ("special sauce") will be of any benefit to your guitar, but it won't hurt, as long as the signal from your guitar is no stronger than what you'd get from passive pickups. Can you do a side-by-side comparison with a passive guitar and compare levels? I'd recommend doing that if at all possible.
 
Jay Mitchell said:
If there is a unity gain setting on the guitar preamp, my guess is that it would be safe to use the front input with that setting. GIven that an active circuit is going to have a different noise spectrum than passive guitar pickups, I'm not sure if the encode/decode ("special sauce") will be of any benefit to your guitar, but it won't hurt, as long as the signal from your guitar is no stronger than what you'd get from passive pickups. Can you do a side-by-side comparison with a passive guitar and compare levels? I'd recommend doing that if at all possible.
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Jay,

I'm having trouble digesting all of this ..., in "layman's terms", what would the "special sauce" do to my tone if the signal from my active pickups were to strong a level ?

Or ..., if I "tweaked" my patches for an active pickup guitar ( using the front input ), and then switched to a passive pickup guitar, what would the patch sound like ?

Sorry to be so dense :?
 
Thanks for responding Jay. That is a good idea. I will try it with my guitar player. The front does seem noisier but I think that is just because of the increased signal. There is a dimmer in the room so I attribute it to that.
 
R.D. said:
I'm having trouble digesting all of this ..., in "layman's terms", what would the "special sauce" do to my tone if the signal from my active pickups were to strong a level ?
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It would cause some amount of compression.

Or ..., if I "tweaked" my patches for an active pickup guitar ( using the front input ), and then switched to a passive pickup guitar, what would the patch sound like ?
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Who knows? Almost certainly different. If you played a Strat through a preset that was built for a Les Paul, it would sound different as well. The difference between pickup designs is far greater than the difference between active and passive electronics.
 
I can't believe this discussion is still going. I don't know how many more ways Jay can explain the same thing...

PS - Seven pages and no rear input jokes? :shock:
 
One comment.........is "rocket science" really the most complicated thing in our universe?

I hear that phrase a lot...."it isn't rocket science." And it cropped up in this thread as well.

Sometimes that phrase is used around some rather heavy/technical talk. Really, I guess it's what a person decides to focus their time and energy on. To a rocket scientist, I would imagine rocket science would become easier with time. In technical arguments, they probably say, "hey this isn't.....uh, well.....it isn't........uh........well, it isn't.......easy."

Sorry for the totally OT post. I'm now gonna go plug my guitar into my Ultra's front input and have some fun.
 
Chad said:
One comment.........is "rocket science" really the most complicated thing in our universe?

I hear that phrase a lot...."it isn't rocket science." And it cropped up in this thread as well.

Sometimes that phrase is used around some rather heavy/technical talk. Really, I guess it's what a person decides to focus their time and energy on. To a rocket scientist, I would imagine rocket science would become easier with time. In technical arguments, they probably say, "hey this isn't.....uh, well.....it isn't........uh........well, it isn't.......easy."
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Well, it's not exactly brain surgery, is it?
 
Awesomely informative thread you got going here guys.

Sorry to jump and kinda go a little O.T., but I'm using EMGs on all my guitars, and since they're active pickups with a built-in preamp, I'm scratching my head wondering if I should plug into the front or the rear.

The Input LEDs almost never go to red and I'm running the input 1 pot at noon. Would this mean they output line level signal? Wish I had a more precise way of measuring the output, any software recommendations?

Best,

Alex
 
Alex EShadow said:
Awesomely informative thread you got going here guys.

Sorry to jump and kinda go a little O.T., but I'm using EMGs on all my guitars, and since they're active pickups with a built-in preamp, I'm scratching my head wondering if I should plug into the front or the rear.

The Input LEDs almost never go to red and I'm running the input 1 pot at noon. Would this mean they output line level signal? Wish I had a more precise way of measuring the output, any software recommendations?

Best,

Alex
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Which EMGs do you use? According to EMG's specs, the H series active pups (EMG-H, HA, 58, 60, 60A, 81, 85) aren't quite at "line level" output (either -10 dBV or +4 dBu).
 
60 and 81 mainly. So they've got the same output as passive eh? So I guess the high end sizzle I can't seem to reduce is indeed a EMG problem alone, and not something made worse by the Axe. Plugging in the rear makes it sort of go away though, but it also looses a lot of gain.

Guess I have to buy a new guitar so I can have one with EMGs for metal and one with some sort of PAF-style pickup for classic and hard rock.
 
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