Save I/O input levels

[chris]

I noticed that I seem to clip the input a lot easier than I did on the Axe-FX II. On the Axe-FX II it was OK for it to hit the red but on the Axe-FX III I feel like if it touches the Red I hear clipping noises. The input levels seem to require lower levels also to avoid clipping around 40% for some of my guitars. I also noticed a difference in sound as I turn the input levels lower.

the manual comments on how the Clip light is a bit different on the III than the II. the input is also more sensitive with more headroom (dynamic range), so lower values are fine.

 

[stereotactic]

so you don't clip the input.

Yes, I understand that part, and I understand the idea of setting it for the highest output pick up guitar in the stable and allowing the downstream digital compensation to do the work of leveling all the lower output guitars. However, there is that issue to which I originally referred, meaning optimizing converter performance by setting the converter input level to "full scale". I think I hear a difference and would prefer to set and store each patch/guitar pickup output to optimize for a full scale level going into the converter. Either there is a discernible difference between the two methods of getting all guitars to the same level in the digital domain or there is not...

 

[chris]

Yes, I understand that part, and I understand the idea of setting it for the highest output pick up guitar in the stable and allowing the downstream digital compensation to do the work of leveling all the lower output guitars. However, there is that issue to which I originally referred, meaning optimizing converter performance by setting the converter input level to "full scale". I think I hear a difference and would prefer to set and store each patch/guitar pickup output to optimize for a full scale level going into the converter. Either there is a discernible difference between the two methods of getting all guitars to the same level in the digital domain or there is not...

sure. just to clarify, no one is arguing against your wish. that's a feature that many have wanted since the first Axe 10 years ago.

some of us are just explaining, perhaps, why it hasn't come to fruition as of yet.

 

[stereotactic]

sure. just to clarify, no one is arguing against your wish. that's a feature that many have wanted since the first Axe 10 years ago.

some of us are just explaining, perhaps, why it hasn't come to fruition as of yet.

OK thanks, didn't mean to be argumentative for the sake of it, just trying to make sure I am being understood properly.

So, does anyone know if this is any more possible to implement with the 3?

 

[Rex]

As I said above, I understand the clipping and noise issue...

Clipping and noise are the only issues.

...the question remains whether this compensation sounds any different when done digitally, or by adjusting the I/O for each guitar to achieve as close to "full scale" for best converter performance.

"Close to full scale" only affects converter performance in matters of noise and clipping. There is no other performance measure that it affects.

What difference to you hear between the two settings? More treble? Different volume? Or something else? More than once, I've been mixing a band and dialing in a vocal. I EQ it so it sounds just right, only to realize I've been tweaking the next channel strip over, and all those adjustments I was so proud of weren't actually doing anything.

 

[stereotactic]

I know, I think we have all had this experience. When I make these kinds of blunders, I go back and double check a/b to make sure, and I check with the engineer if I'm in the studio.

In my case, I would switch guitars, hear something wasn't right, look at the levels not hitting the red and realize I hadn't changed the instrument level to that guitar's optimal level. What I hear or think I hear, is less sensitive and less full, not by a lot obviously.

Of course, clipping and noise are the first order concerns for setting the converter levels to achieve full scale. However, what if what I'm hearing when below full scale is a second order byproduct of having a higher noise floor with less guitar info and more silence/hiss converted, which then creates a lower scale of guitar to noise which sounds less sensitive and full because...the guitar info is now in lower proportion to other parts of the converted signal and sounds like it has less detail and dynamic range?

One of the many things I love about the Axe as compared to my big rack, is the noise floor is so much lower, which means more guitar and effect information/detail is present in proportion to the noise/hiss. This certainly improves dynamics and clarity, especially because much of the music I play is very loud, like 2-4 4x12"'s and more than enough watts loud. And when you boost up a signal through big power amps and lots of speakers, that higher proportion of signal to noise ratio is even more noticeable and the increased clarity and dynamics more dramatic. Am I hearing things other than what I think I'm hearing? Maybe, but I think my explanation is valid and should be producing audible results, however subtle..

 

[hippietim]

I know, I think we have all had this experience. When I make these kinds of blunders, I go back and double check a/b to make sure, and I check with the engineer if I'm in the studio.

In my case, I would switch guitars, hear something wasn't right, look at the levels not hitting the red and realize I hadn't changed the instrument level to that guitar's optimal level. What I hear or think I hear, is less sensitive and less full, not by a lot obviously.

Of course, clipping and noise are the first order concerns for setting the converter levels to achieve full scale. However, what if what I'm hearing when below full scale is a second order byproduct of having a higher noise floor with less guitar info and more silence/hiss converted, which then creates a lower scale of guitar to noise which sounds less sensitive and full because...the guitar info is now in lower proportion to other parts of the converted signal and sounds like it has less detail and dynamic range?

One of the many things I love about the Axe as compared to my big rack, is the noise floor is so much lower, which means more guitar and effect information/detail is present in proportion to the noise/hiss. This certainly improves dynamics and clarity, especially because much of the music I play is very loud, like 2-4 4x12"'s and more than enough watts loud. And when you boost up a signal through big power amps and lots of speakers, that higher proportion of signal to noise ratio is even more noticeable and the clarity and dynamics more dramatic. Am I hearing things other than what I think I'm hearing? Maybe, but I think my explanation is valid and should be producing audible results, however subtle..

Have you had a chance to try goosing the input when you switch guitars? I think you'll get what you're after sonically.

 

[stereotactic]

Have you had a chance to try goosing the input when you switch guitars? I think you'll get what you're after sonically.

Thanks for the reminder, have been preparing a lot for a gig on Weds, will definitely try it at some point. The gig only requires 2 guitars, one change, so no big deal if I have to adjust the instrument I/O level once during the gig...

 

[Rex]

...what if what I'm hearing when below full scale is a second order byproduct of having a higher noise floor with less guitar info and more silence/hiss converted, which then creates a lower scale of guitar to noise which sounds less sensitive and full because...the guitar info is now in lower proportion to other parts of the converted signal and sounds like it has less detail and dynamic range?

It’s true that if you’re not tickling the reds, you’ll have a lower signal-to-noise ration in the converter. But your guitar’s own noise will still be much stronger than the noise of the converter, so your actual signal-to-noise going into the grid will be exactly the same, because your guitar’s noise will still overpower the noise of the converter.

With a lower-output guitar, it will sound less sensitive and full because you’re hitting the Amp block with a lower signal and not driving it as hard. Turning up Input Level won’t change that, unless you’re at extreme settings. But if you turn up Input Trim in the Amp block, you can completely compensate for the lower guitar output. That’s not subtle at all. At that point, the only remaining difference is the voicing of the pickup, and wether it’s single-coil or humbucker.

 

[stereotactic]

It’s true that if you’re not tickling the reds, you’ll have a lower signal-to-noise ration in the converter. But your guitar’s own noise will still be much stronger than the noise of the converter, so your actual signal-to-noise going into the grid will be exactly the same, because your guitar’s noise will still overpower the noise of the converter.

With a lower-output guitar, it will sound less sensitive and full because you’re hitting the Amp block with a lower signal and not driving it as hard. Turning up Input Level won’t change that, unless you’re at extreme settings. But if you turn up Input Trim in the Amp block, you can completely compensate for the lower guitar output. That’s not subtle at all. At that point, the only remaining difference is the voicing of the pickup, and wether it’s single-coil or humbucker.

I think I understand the idea of the higher guitar noise going into the converter vs whatever noise is present from other sources, which is increased if full scale is not achieved, and the idea that it evens out downstream with digital leveling because the non guitar noise is lower. However, even within the guitar noise is information which can be important to the overall sound and feel. So, you are not just losing guitar/pickup noise, but some other information you might want, like some fret noise from a bend and some of the decay of that bent note, all of which will be further back if full scale is not achieved. Once that info is scaled down, you lose some measure of realism, and while that information may be brought back out to some degree by hitting the preamp harder than you would otherwise, from compression, it's not going to sound the same as a full scale signal going into the converter, then hitting the preamp with lower gain and all the information at the proper scale. That's how it seems to me, I might be wrong, but that's what I think I'm hearing...

 

[yek]

A/D Input Level does not include a noise gate, and does not affect fret noise etc.

 

[stereotactic]

A/D Input Level does not include a noise gate, and does not affect fret noise etc.

Yes, of course. But I am speaking of musical information which is almost at the same level as more non-musical information, like hum or hiss. So if the signal is not full scale going into the converter, it will be that much harder to discern from the guitar noise as it recedes further into the noise floor. Good information such as the overtones and decay of metal to metal fret noise from the bend as you wring out the last bit of sustain, receding into hiss or hum and becoming harder to distinguish from the proportionally rising noise floor. Scale is the right word.

I think of it this way, please tell me if this example is lacking or incorrect: I used to mix with a bus compressor, a very nice Neve. This is what I learned from guys who engineered platinum records. The trouble was the music I was making was far more dynamic than most of the pop music they mixed. I would wind up in mastering trying to get details out of the music which were impossible to highlight because of the amount of bus compression before we got to the mastering stage. I finally got it through my thick head that maybe we should try mixing with and without bus compression and then take it to mastering and see what the difference would be. Lo and behold, Spending a few more minutes trying to get a better balance and EQ of the individual tracks in order to increase intelligibility was much more fruitful than letting the bus compressor level out all the details, then attempt to surgically highlight things in the mastering....

 

[Rex]

Yes, of course. But I am speaking of musical information which is almost at the same level as more non-musical information, like hum or hiss. So if the signal is not full scale going into the converter, it will be that much harder to discern from the guitar noise as it recedes further into the noise floor.

Once the information you want drops below the noise floor, it's lost. The Axe's A/D converters have a lower noise floor than your guitar, no matter where you set Input Level. So all that information gets buried by your guitar's own noise long before the noise of the converter becomes an issue.

Good information such as the overtones and decay of metal to metal fret noise from the bend as you wring out the last bit of sustain, receding into hiss or hum and becoming harder to distinguish from the proportionally rising noise floor. Scale is the right word.

It's an A/D converter. There's no scaling involved, and no "proportionally rising noise floor."

I think of it this way, please tell me if this example is lacking or incorrect: I used to mix with a bus compressor, a very nice Neve. This is what I learned from guys who engineered platinum records. The trouble was the music I was making was far more dynamic than most of the pop music they mixed. I would wind up in mastering trying to get details out of the music which were impossible to highlight because of the amount of bus compression before we got to the mastering stage. I finally got it through my thick head that maybe we should try mixing with and without bus compression and then take it to mastering and see what the difference would be. Lo and behold, Spending a few more minutes trying to get a better balance and EQ of the individual tracks in order to increase intelligibility was much more fruitful than letting the bus compressor level out all the details, then attempt to surgically highlight things in the mastering....

That's a good story, but it's all about compression — not signal conversion or noise.

 

[stereotactic]

Once the information you want drops below the noise floor, it's lost. The Axe's A/D converters have a lower noise floor than your guitar, no matter where you set Input Level. So all that information gets buried by your guitar's own noise long before the noise of the converter becomes an issue.

To be clear, I was referring to musical information just above or at the same level as the guitar noise floor. I was positing that if the level going into the converter was not Full Scale, then the ability to differentiate between quieter musical details close to the guitar noise floor would be lessened by the then relatively higher Axe analog input circuitry noise, and to a much lesser degree, converter noise. Any noise, no matter how low scale, takes away from the dynamic range in some small degree, this is why we care about things like aliasing, which are all the way down at -60 dB, right? That is an actual question, not trying to be argumentative..

Further, I was positing that the ability to hear the last little bit of a bended note sustain overdrive guitar sound would continue to fade down to the Axe analog input noise floor at a slower rate if at Full Scale, than if it were a lower level going into the converter.

It's an A/D converter. There's no scaling involved, and no "proportionally rising noise floor."

As I said above, there is an Axe analog noise floor, however low, which comes from the circuitry before the converter, as well as the converter noise itself, right? I thought a "Full Scale" input level was the maximum level you could safely go with any particular instrument before clipping, which is the same idea as an analog input, in terms of the input being scaled up maximally for best signal to noise ratio. If that's not what Full Scale means then what does it mean? Please let me know if I'm misunderstanding anything.

That's a good story, but it's all about compression — not signal conversion or noise.

The idea of the story was to relate the issue of scale in bus compression. Buss compression flattens out the scale and makes it harder to discern details because the ratios of peak to nominal are less than what was input.

I havent had a chance to try increasing the preamp drive to simulate what I'm hearing when a lower input guitar is played through the same I/0 block input setting vs a Full Scale setting for the same instrument. Do you or anybody else know how much I should increase preamp drive for a 35 step I/0 difference? I don't know what those numbers represent, hence the question...

 

[Rex]

To be clear, I was referring to musical information just above or at the same level as the guitar noise floor. I was positing that if the level going into the converter was not Full Scale, then the ability to differentiate between quieter musical details close to the guitar noise floor would be lessened by the then relatively higher Axe analog input circuitry noise, and to a much lesser degree, converter noise.

I get what you're saying, but that's not how it works. Once a desired signal sinks below the noise floor, it gets swallowed up by the noise. You might be able to barely discern a single-frequency signal that's 1 or 2 dB below the noise floor, but beyond that, it's gone. Lower noise floors from other equipment will have no effect on the end result. It works in the same way that a dog hair lying in the road constitutes a speed bump. It might change the trajectory of the car in some microscopic way, but you you will never perceive its existence.

Any noise, no matter how low scale, takes away from the dynamic range in some small degree...

This is only true of the strongest noise in the system. It's true that noises add. But if you take a noise that's -50 dB and add another noise that's -70 dB, the result is very close to -50 dB.

...this is why we care about things like aliasing, which are all the way down at -60 dB, right?

We care about things like aliasing because we want to make sure they're smaller than other sources of noise, because that makes them irrelevant.

... not trying to be argumentative..

I know. Neither am I.

Further, I was positing that the ability to hear the last little bit of a bended note sustain overdrive guitar sound would continue to fade down to the Axe analog input noise floor at a slower rate if at Full Scale, than if it were a lower level going into the converter.

It will fade down at the same rate, regardless of where you have Input Level set to. If it didn't, you'd have compression going on.

I thought a "Full Scale" input level was the maximum level you could safely go with any particular instrument before clipping...

Correct.

...which is the same idea as an analog input, in terms of the input being scaled up maximally for best signal to noise ratio.

The idea is to get the signal as far above the noise floor as you can, to maximize the S/N ratio. But here's the rub: when you turn up Input Level, you're also turning up the noise that your guitar makes. Your guitar is the dominant source of noise, so you're not affecting the actual S/N ratio unless you've got Input Level set extremely low. That's why it's okay to set it for your loudest guitar, and then leave it there.

The idea of the story was to relate the issue of scale in bus compression. Buss compression flattens out the scale and makes it harder to discern details because the ratios of peak to nominal are less than what was input.

But changing the level isn't the same as compressing the signal. If it were, every volume knob would be a compressor.

I havent had a chance to try increasing the preamp drive to simulate what I'm hearing when a lower input guitar is played through the same I/0 block input setting vs a Full Scale setting for the same instrument.

Use Input Trim instead of Input Drive, because it won't affect amp EQ. You owe it to yourself to try this. The difference will be dramatic compared to anything you could possibly be hearing when you adjust Input Level.

Dial it in to where it sounds and feels best, not by a formula. Different guitar = different sound, and quite possibly a different sweet spot for that particular guitar.

 

[stereotactic]

I get what you're saying, but that's not how it works. Once a desired signal sinks below the noise floor, it gets swallowed up by the noise. You might be able to barely discern a single-frequency signal that's 1 or 2 dB below the noise floor, but beyond that, it's gone. Lower noise floors from other equipment will have no effect on the end result. It works in the same way that a dog hair lying in the road constitutes a speed bump. It might change the trajectory of the car in some microscopic way, but you you will never perceive its existence.



This is only true of the strongest noise in the system. It's true that noises add. But if you take a noise that's -50 dB and add another noise that's -70 dB, the result is very close to -50 dB.



We care about things like aliasing because we want to make sure they're smaller than other sources of noise, because that makes them irrelevant.



I know. Neither am I.



It will fade down at the same rate, regardless of where you have Input Level set to. If it didn't, you'd have compression going on.




Correct.



The idea is to get the signal as far above the noise floor as you can, to maximize the S/N ratio. But here's the rub: when you turn up Input Level, you're also turning up the noise that your guitar makes. Your guitar is the dominant source of noise, so you're not affecting the actual S/N ratio unless you've got Input Level set extremely low. That's why it's okay to set it for your loudest guitar, and then leave it there.



But changing the level isn't the same as compressing the signal. If it were, every volume knob would be a compressor.




Use Input Trim instead of Input Drive, because it won't affect amp EQ. You owe it to yourself to try this. The difference will be dramatic compared to anything you could possibly be hearing when you adjust Input Level.

Dial it in to where it sounds and feels best, not by a formula. Different guitar = different sound, and quite possibly a different sweet spot for that particular guitar.

Ok! Will do, I think I understand all you've said, it's a question of what am I actually hearing, and I'm sure you are right. Thanks for your patience and time!

 

[Rex]

Ok! Will do, I think I understand all you've said, it's a question of what am I actually hearing, and I'm sure you are right. Thanks for your patience and time!

No worries. Let us know what you discover.

 

[Rex]

...to just turn up the Output Level of the Input block!!!

How did I miss this? One tweak — instant new preset for another guitar.

 

[pauly]

Personally, I like the idea!
For those that want the optimum sn ratio, it's a great feature.
Thanks
Pauly

Yes, I understand that part, and I understand the idea of setting it for the highest output pick up guitar in the stable and allowing the downstream digital compensation to do the work of leveling all the lower output guitars. However, there is that issue to which I originally referred, meaning optimizing converter performance by setting the converter input level to "full scale". I think I hear a difference and would prefer to set and store each patch/guitar pickup output to optimize for a full scale level going into the converter. Either there is a discernible difference between the two methods of getting all guitars to the same level in the digital domain or there is not...