bipolar (BJT) transistor families for audio power output stages

AX tech editor
Joined 2002
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Do you ever feel embarrassed about commenting on matters that are beyond your understanding?

You must know how it feels ;)

Hi,
the Fourier transform will analyze pure sine waves perfectly representing a well-defined frequency. The Fourier transform may be useful for analyzing other signals in different applications fields, but music signals are very far from sine waves, it just has to give up pretty quickly.

Fourier analysis is perfect to analyze a complex signal; it shows you in one view all the frequency components. Ever seen the freq display of an equalizer? That's Fourier analysis for you, live, on music signals.

OTOH, doing a Fourier analysis of a single sine wave is pretty irrelevant.

jd
 
Bonzai,
You seemingly have rejected the message. Abstracting the abstract in the long run can give a more clear revelation of ikko, kakko, taiko, shoko, kokiriko, along with shime-daiko, tsuri-daiko, den-den daiko, furthermore sasara, bin-sasara, ita-sasara, not to mention tsuzumi, otsuzumi, san-no-tsuzumi, also shaku and last but not least kagura suzu.
 
Bonzai,

You seemingly have rejected the message. Abstracting the abstract in the long run can give a more clear revelation of ikko, kakko, taiko, shoko, kokiriko, along with shime-daiko, tsuri-daiko, den-den daiko, furthermore sasara, bin-sasara, ita-sasara, not to mention tsuzumi, otsuzumi, san-no-tsuzumi, also shaku and last but not least kagura suzu.

:eek:
 
Bonzai,

You seemingly have rejected the message. Abstracting the abstract in the long run can give a more clear revelation of ikko, kakko, taiko, shoko, kokiriko, along with shime-daiko, tsuri-daiko, den-den daiko, furthermore sasara, bin-sasara, ita-sasara, not to mention tsuzumi, otsuzumi, san-no-tsuzumi, also shaku and last but not least kagura suzu.
Kampai! :drunk::p
 
Of course, FFT analysis is a lie. That is to say it is not a true representation of a continuously changing music signal because it assumes an infinite repeat of your sampled waveform, both backwards in time and forwards in time. This causes trouble with discontinuities at the joins of the samples adding spurious spectra. Then there is the sampling resolution that adds inaccuracy.
Having said that, I think the technique is accurate enough if you choose a sympathetic waveform and sufficient resolution, and you know what you are looking for.
 
traderbam,

Infinite sine waves, although kinda monotonous for my taste...

Hi Lumba,

Use of the Fourier Transform (AKA spectrum analyzer) is by no means limited to sinewaves. While it is limited to signals that repeat over some long interval, that allows for some extraordinarily complex waveforms that can bring out misbehavior and all sorts of distortions in an amplifier.

One example is the 19+20 kHz CCIF test, where the rep rate is at 1 kHz and where you get to see an enormous array of IM products. People who know what they are doing can look at the result and make some very useful conclusions about an amplifier.

Another example, which I am sure you will like being a no-feedback lover, is the DIM test for TIM developed by Matti Otala. That test employs a very complex waveform rich in harmonics and fast transients. The evaluation of TIM with the DIM test relies fundamentally on spectral analysis, which is usually done these days with an FFT.

Cheers,
Bob
 
Are there news about audio BjT power devices?

Burr/Brown - TI, Analog Devices, Linear Technology and National Semiconductor create an real inflation of audio operational amplifiers.
But where are the new discrete power semiconductors for audio applications ?
In opposite to the audio OP Amps the range of audio BjT discrete POWER devices is relatively small.
 
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