Relationship between sound envelope, and Measures on Amps (Part-1)

[AP2]

I believe the time is ripe, to analyze the sound of some musical instruments and then see what parameters are needed for an amp, so they play with good realism.
1) will be excluded sources and speakers at this early stage.
2) No commercial product, which is mentioned will be.
3) Some special tools or methods to measure non-standard, will only serve to get, and show all the parameters of a sound. I mean, this does not mean that current devices (such as Audio Precision), is not good.
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the first step, the analysis will contain up to four musical instruments (with steps) up to simultaneously (as in reality). analysis will be done with the four signals in the Graphic Overlay. This will make us see the rise times that a sequential amp will follow. (this speed, of course, affect the bandwidth required).

Please, not post a comment for now. (for clearance,i show first graph)

Roberto P.

[pieter t]

Roberto,

May I suggest to have your English checked and edited by a person who can do this for you?
People loose interest when they don't understand what you want to tell.

[AP2]

Thanks Pieter t, yes, someone will help me to translate the article.
(I was hoping the introduction was clear) ... maybe the last part is not..

[AP2]

Hi,
We are preparing the documentation for the thread.
Just a little preface:

The first mistake is, to evaluate the bandwidth (eg 22Khz) in relation to periodic signals with constant speed, and also assume that if a sound has a frequency of 22Khz, we can decide that the bandwidth can therefore be 22Khz. (This is absolutely wrong, if you play a musical envelope).
Or, 22Khz can be valid, if (or adjusted only by extension of the harmonic spectrum), if we use a system composed of an amp. for each musical instrument. (I do not think we use this system)
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The bandwidth must be seen as a result of slew rate,need to play sound envelope.

Why is speed so necessary?
Because live music and speech are both essentially made of transients. And transients are only sounding accurate when they are rebuilt into the ear with exactly the time coherence they had initially. Only extra-large amplifier bandwidth can rebuild time coherence accurately.
The audible effect ? A real frequency-balanced time response brings Intelligibility which is extremely important for the ear to recognize musical instruments, and understand speech.

Regards
Roberto P.

[AP2]

A perfect audio component will maintain the coherency of a signal over the full range of frequencies. Phase distortion can be extremely difficult to reduce or eliminate. The human ear is largely insensitive to phase distortion, though it is exquisitely sensitive to relative phase relationships within heard sounds. The complex nature of our sensitivity to phase errors, coupled with the lack of a convenient test that delivers an easily understood quality rating, is the reason that it is not a part of conventional audio specifications.
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A system may have low distortion for a steady-state signal, but not on sudden transients. In amplifiers, this problem can be traced to power supplies in some instances, to insufficient high frequency performance or to excessive negative feedback. Related measurements are slew rate and rise time.
Distortion in transient response can be hard to measure. Many otherwise good power amplifier designs have been found to have inadequate slew rates (ref to a module of sound envelope from real instruments).
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The next step, the speed necessary to play (4) real instruments sound.
these are: percussion, bass guitar, piano, violin (medium).
instruments chosen to provide a complete envelope, in terms of sub-modulation, the dominant modulation and harmonic content.
In this case, the slew rate is dominant to calculate the bandwidth.
This has nothing to do with the frequency response).

Regards
Roberto P.

[ChocoHolic]

Slew rate discussion always needs the information at which voltage levels reproduction is required.
A system with 100V output will naturally need 20 times the slew rate of a 5V system...
With respect to this, I prefer to talk about rise times.
Which rise times would you need in order to reproduce a base drum properly?
Which rise times for a snare drum?

[AP2]

Originally Posted by ChocoHolic

Slew rate discussion always needs the information at which voltage levels reproduction is required.
A system with 100V output will naturally need 20 times the slew rate of a 5V system...
With respect to this, I prefer to talk about rise times.
Which rise times would you need in order to reproduce a base drum properly?
Which rise times for a snare drum?

Hi,
Certainly, this parameter is important.
having (tr), we can calculate the slew rate of 60Vpeak (medium power amplifier).I think it will not be a surprise for you (the value of tr),perhaps for other.
the charts soon.

Regards

[elevator]

Hi AP2,
so would you suggest using square waves as test signals, in place of sines?
E

[AP2]

Originally Posted by elevator

Hi AP2,
so would you suggest using square waves as test signals, in place of sines?
E

Hi,
In this article I will try to demonstrate that standard measures are not sufficient to understand if the amp is able to play with the right definition, especially in high-frequency sound, or in the presence of complex envelope (as a symphony orchestra). This requires a much higher speed than the rise time measured.(for an indirect reason)
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as a sound envelope is composed of transient, if you want to develop a good amplifier, the rise time and linearity are the most important thing.
From these two parameters can give you all the others. This has always been my philosophy.

Regards

Roberto P.

[ChocoHolic]

Originally Posted by elevator

Hi AP2,
so would you suggest using square waves as test signals, in place of sines?
E

Square wave evaluation everywhere, no matter if we look to the F5 or to multiple classD threads.
It is the most natural thing to do during amp design.