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Post subject: Re: Feature suggestion for Possible Firmware update
Posted: Fri May 24, 2013 11:19 am
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captainc wrote:

I interpret that as a "limitation" of the dynamic range and not a signal limiter. I could be wrong, but I think if there were a brickwall limiter in place the issue wouldn't be so prevalent. However, if there is in fact some type of pre A\D limiter in the chain, I would imagine a firmware flash that raised the threshold to give more headroom and a clip light function might do the trick.


Yes! i think you're right: my hypothesis was right a limited dynamic range , let's say a not enough depth quantization to handle easily high input levels..
in theory you can expand the dynamic range, but in practice should depend on the resolution of A / D converter(s), and memory available to handle a momentary data stream bigger ...
in the case of a Wav file on the PC if for example you quantizes to 24 bits (not to mention 32 bits) and sample at 44.1 Khz , with equal format and duration of recording, you will obtain a file much larger, than the Wav at 16 bits, to store in hard disk.
In the case of digital effects you have to store nothing permanently but you need the same an adequate memory buffer to host that momentary stream of data..
And the real resolution of A/D seems to depend on amount of noise in input.. if there is too much noise (if the Signal/Noise ratio is low) the converter is unable to take advantage of full resolution (for example all 16 bits) so the dynamic range is pratically narrowed..


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Post subject: Re: Feature suggestion for Possible Firmware update
Posted: Fri May 24, 2013 3:38 pm
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frondizi wrote:
So, is it possible that the dynamic range is already limited in some way before the input signal goes into A/D converters? in the precedent message i was assuming that could be a problem caused by a not adequate dynamic range or quantization depth to handle higher input level from external effects or internal distortions as well.

Dimitri


I think the basic problem boils down to a couple of facts:

For decades, guitarists have gotten used to amps that you could hit with basically any input level, and whose gain stages could be overdriven at any level, and as you increase the levels, the sound got gradually more desirable ('warmer,' more harmonics, etc).
In pre-master volume days, and before the multitude of overdrive pedals were available, you needed hot pickups to help get more signal level.

Suddenly, with digital, as you increase the levels, the sound stays exactly the same with no change in tonality at all, until a certain point. From the noise floor up to 0dB, the sound is exactly the same. At 0dB + 1 bit, total disaster ensues. Hot input is no longer needed, or useful. And digital distortion comes on abruptly, with no warning.

It would be very useful if amp-makers, and pedal makers, would give MUCH better facilities to monitor levels at various points. But, it also going to take a different mindset from guitarists, who much realize that they have to stop merely pummeling input and preamp stages trying to get "warmth" and overdrive.

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Post subject: Re: Feature suggestion for Possible Firmware update
Posted: Sat May 25, 2013 5:21 pm
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thompal wrote:

Suddenly, with digital, as you increase the levels, the sound stays exactly the same with no change in tonality at all, until a certain point. From the noise floor up to 0dB, the sound is exactly the same. At 0dB + 1 bit, total disaster ensues. Hot input is no longer needed, or useful. And digital distortion comes on abruptly, with no warning.

It would be very useful if amp-makers, and pedal makers, would give MUCH better facilities to monitor levels at various points. But, it also going to take a different mindset from guitarists, who much realize that they have to stop merely pummeling input and preamp stages trying to get "warmth" and overdrive.


Yes, the 0 dB is a fixed limit that you cannot exceed (you could do it in the analog tapes) , but if you can have a dynamic range extended of several tens of decibels means to have the possibility for example to add at least a fuzz at highest gain in front a low/clean amp chanel without go beyond the limit and without get hard clipping.

Of course is not the task of the A / D converter (he needs to be able to handle high levels of analog signal) add warmth and overdrive but it is the task of the mathematical algorithms that runs in processors ..

I may be repetitive but there are excellent Fractal Audio digital processors that are showing that it is possible to eliminate all the disadvantages of digital (such as various types of aliasing, and of course hard clipping) and be able to deal with more and more amp models and effects in the same way as the real things.

Clearly there will be always the musician who says ".. but.. this model of the Big Muff is not exactly as powerful as the real thing .. you can improve the gain, the freq response, output level.." or "this model is fine but the output level is too low compared to the real amp.."
But these types of improvements are less important compared to having to improve the accurate simulation of a fundamental physical behavior of an amp..
Much depends on the power and goodness of the processors, the potential and the quality of A / D converters (and D / A) and the amount of memory to temporarily hold the amount of data .. (also first quality electronic components) and of course it takes a great software that directs the orchestra.

I'm not saying that in those processors is impossible to exceed the limit of 0 dB ..
indeed the proper settings of input level is an important step suggested for optimal results .. (and if you do wrong tweeking of advanced parameters you can get unwanted behaviours included distortion) everything that follows after works wonders.

I beg to talk about these things because am a passionate of course, but other than that, because for the moment no one seems to be able to solve this kind of problems and it is good to know that there are ways to solve them .. logically the limit may be due also and especially to the budget invested in designing and building in order to target to a range of users.


Last edited by frondizi on Sat May 25, 2013 5:34 pm, edited 1 time in total.

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Post subject: Re: Feature suggestion for Possible Firmware update
Posted: Sat May 25, 2013 5:32 pm
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frondizi wrote:
thompal wrote:
Yes, the 0 dB is a fixed limit that you cannot exceed (you could do it in the analog tapes) , but if you can have a dynamic range extended of several tens of decibels means to have the possibility for example to add at least a fuzz at highest gain in front a low/clean amp chanel without go beyond the limit and without get hard clipping.

Of course is not the task of the A / D converter (he needs to be able to handle high levels of analog signal) add warmth and overdrive but it is the task of the mathematical algorithms that runs in processors ..

I may be repetitive but there are excellent Fractal Audio digital processors that are showing that it is possible to eliminate all the disadvantages of digital (such as various types of aliasing, and of course hard clipping) and be able to deal with more and more amp models and effects in the same way as the real things.


I think there are two things concerning the Fractal. One, which is a big one, is that the Fractal costs 6 or 7 times what an entire Mustang III costs.

But, more to the point, Even 16 bit digital has far more dynamic range than a guitar is bound to use. I suspect what most digital units do when it comes to metering, it not make digital max at 0dB on a meter. I suspect that 0VU (or the threshold of a clip LED) is actually at -30dB or so, so it LOOKS like you're close to digital overload, but in reality, there is headroom left. That way, if you accidentally light the LED (or hit 0dB on the VU meter, there's no digital distortion. It would make absolute sense from all standpoints. It doesn't take a larger bit depth, and it still pleases the guitarists who think that "just a little more input level" = "better."

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Post subject: Re: Feature suggestion for Possible Firmware update
Posted: Sat May 25, 2013 6:24 pm
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thompal wrote:

I think there are two things concerning the Fractal. One, which is a big one, is that the Fractal costs 6 or 7 times what an entire Mustang III costs.

But, more to the point, Even 16 bit digital has far more dynamic range than a guitar is bound to use. I suspect what most digital units do when it comes to metering, it not make digital max at 0dB on a meter. I suspect that 0VU (or the threshold of a clip LED) is actually at -30dB or so, so it LOOKS like you're close to digital overload, but in reality, there is headroom left. That way, if you accidentally light the LED (or hit 0dB on the VU meter, there's no digital distortion. It would make absolute sense from all standpoints. It doesn't take a larger bit depth, and it still pleases the guitarists who think that "just a little more input level" = "better."


In fact, for what regards the first thing i talked about budget for that reason. Here in Europe you can pay a Mustang 3V2 between 270 and 335 Eur , Axe Fx2 from German direct distributor would costs even about 2350 Eur.. (and in Italy there is not a guitar shop where to try and buy it )

for the second thing.. in the days when I did, an apprenticeship in the studio recording my teacher explained to me that the old high quality 16-bit converters used to their full potential are better than new converters with Higher bit depths which are only partially exploited.

So it is my belief that the converters on our amplifiers are forced to work with a depth of less bits and then the dynamic range is less than the potential ..

by the way.. Axe FX2 has these specifications:
A / D conversion : sampling rate 48 khz, bit depth: 24 bits , dynamic range : >110 dB

and this is another interesting, and clarifying information on my opinion, i found in G66 web site (european distributor):

DESIGNED FOR UNITY GAIN

The Axe-Fx II uses digitally controlled potentiometers to operate as a unity-gain device irrespective of the input trim controls. Simply set the input trims such that the input LEDs indicate optimum operation and you are done.
Another benefit of this technique is that Amp and Drive blocks are unaffected by trim settings.


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Post subject: Re: Feature suggestion for Possible Firmware update
Posted: Sun May 26, 2013 9:26 pm
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A clip light could be cool.

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