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-- Ask me somthing DSP :-D

Posted by DJSentinel on Jun-21-2006 01:08:

Ask me somthing DSP :-D

Want to know how an effect or synth you use works? Just post your question here and I will answer you to the best of my knowledge.

Peace,
DJS

Posted by SPAWNmaster on Jun-21-2006 07:23:

this might be basic but since your offering...heheh...

roll effects (such as on the pio DJM800)...how does that work? is it just chopping a loop -> infinity?

Posted by No Left Turn on Jun-21-2006 11:50:

^^ It takes a sample of whatever you're playing at a selected quanitzation and loops it until the effect is disabled. On the DJM-909, you can set the FX to be controlled by the volume fader, hence the name 'Fader Roll'. At various points of the volume fader, the quantization will vary from not so small sizes (1/4 and 1/8 nearing the top) and the iddy biddy ones (1/64 and 1/128 when you slam the fader down).

Posted by DJSentinel on Jun-21-2006 16:46:

Well a Roll is just a sampler that plays a quantized and recorded sample of audio This gives the effect that a certain part of the music is repeating until the effect is released. Usually the roll has some type of beat detection where if picks up on amplitude spikes, whick are usually kick-spikes, and then set its tempo to that interval of time between two amplitude spikes. It then plays the recorded bit in the roller over and over at a defined division of two from the tempo until you disable the effect. This effect is also availiable in Traktor DJ Studio 3 and acts as a looper.

Help?

Posted by Low Profile on Jun-21-2006 23:03:

Explain convolution and it's purpose/usability in a short summary???

Posted by aquila on Jun-21-2006 23:51:

Formant-altering filters. How do they work?

Posted by DJSentinel on Jun-22-2006 00:46:

Convolution Reverbs

A convolution reverb is a reverb unit which is controlled by an impulse response. The reverb analyses an impulse response, usually taken from a natural space or other reverb units, and looks at its decay, harmonic content, and waveshape. It then changes the reverb unit to be tailored to that impulse response. This allows you then to apply the sound of a real physical space or other reverb unit to your own sounds. Most people use convolution reverb units to emulate a space they really like. An example is if a producer went to a club and loved the sound of the club, he could go to the club when its closed and empty and take an impuse response in the club, then he could use his Convolution Reverb to emulate that space to get that sound.

To take an impulse response you usually have the device which emits a very lound sound and a microphone on the other end or center of the space which records the sound moving through the space, its decay, and reflections of any kind. Which will ultamately tell the reverb unit what to apply to the input sound.

Convolution Reverbs in short allow you to emulate real spaces with hardware or software. Thye can also emulate other amplifiers or effects units, but not very well.

Posted by DJSentinel on Jun-22-2006 00:55:

Formant Filters

A formant filter is a filter which emulates the resonant shape of the human mouth. The human mouth makes different shapes to produce the 5 different vowel sounds "A, E, I, O, U" These vowel sounds are taken from a very dry sound that our vocal cord makes. A formant filter tries to emulate that resonant shape the mouth makes to produce tones we identify human tones. The formant filter is like any other filter you have used, but where it passes and cuts frequencies are very specific to produce the desired vowel sound. Formant filters use different methods to produce their effect but most of the time the filter is actually a set of panaramic equilizers that you smooth between to smoothly transition from the A - O vowels. You can emulate a formant filter by setting your panoramic equilizer up a cetain way, you will have to research it further yourself :-D

Posted by alanzo on Jun-22-2006 03:07:

Linear Phase Vocoding

Posted by DJSentinel on Jun-22-2006 03:52:

Phase Vocoding

Vocoding is a technique used to take an modulator signal's harmonic content and modulate a carrier signal's harmonic content "using band pass filters" to match the input signal's harmonic content. When this is applied using the human voice as the modulator and a harmonic rich waveform such as a sawtooth wave as a carrier signal, you get what is known as a "talking synthesizer."

Vocoding works by analyzing the harmonic content of a modulator signal, like a frequency analyzer would. It then, depending on how many bands a Vocoder features, takes the average amplitude of the frequencies around each of the Vocoders bands "or frequencies in the band's Q or width range," and stores those values. Then the value returned by each band is then used as the amplitude value of (insert number of bands) band-pass filters in the Vocoder. This cuts or boosts frequincies of the carrier signal using these band-pass filters. The resulting audio is the carrier signal with is harmonic content matching relativly with the modulator signal's harmonic content. The produces a formant effect that we recognize as speech. The more bands a Vocoder has, the more realistic and crisp the resulting carrier signal will sound.

You can think of it like this as well. The carrier signal is your vocal folds and the modulator signal is the shape of your mouth. Depending on the shape or your mouth your mouth "filters" away certain frequencies, giving you the different vowel and consonant sounds. Your mouth is sorta like a natural vocoder.

Throw me another one :-D

Posted by Derivative on Jun-22-2006 12:59:

What is phase distortion and why do assynmetric phase filters not exhibit as much phase distortion as non linear phase filters?

Posted by Aesthetic on Jun-23-2006 01:50:

Ask Jeeves aint got nothing on DJ Sentinel

Posted by DJSentinel on Jun-23-2006 03:55:

Phase Distortion

Phase distortion occurs when certain harmonic parts of a wave are delayed for whatever reason, whether intentional or not intentional. This modifies the waveform by repositioning certain harmonics at different places in the phase cycle. This produces harmonic distortion and can artificially resonate certain frequencies within any given waveform. I am not familiar with asymetric phase filters so I cannot answer your question on why one would give out more phase distortion. Since phase distortion works by delaying certain harmonic content in a wave, the difference may be associated with the shape and or slope of ether filter. I am not sure thought. I will have to read up more and experiment with phase distortion some more.