about AY

Hello, Alexey! 20 Feb 2001 you wrote: > - what do the graphs of the envelope waves (C and E) actually look like? C - gradual increase in signal level over one period envelope from minimum to maximum value, after which a sharp jump to the minimum level followed by repetition the resulting signal shape in each envelope period: /|/|/|/|. E - gradual increase in signal level over one period envelope from minimum to maximum value, after which in the next cycle, a gradual decrease in the signal level to minimum value and then repeating the obtained waveforms: ////. In general, find out what a graph looks like for any shape envelope, you can do this: use the T-E sample at the value envelope divider #FFFF. You will clearly hear exactly how volume changes. The AY coprocessor has 16 gradations of signal level changes envelope, in YM - 32. Therefore, the sound is slightly different. > - what is the principle of mixing tone and envelope The tone generator generates rectangular pulses, their frequency depends on the note, and the amplitude is the fourth digit of the parameters notes (for example, for the note A-4 1F.F the amplitude will be #F). That's all for the case when the envelope is not used: ┌────┐ ┌────┐ ┌────┐ ┌────┐ ┌────┐│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ┘ └────┘ └────┘ └────┘ └────┘ └──── When the envelope is used, the amplitude is not taken from note parameters, but directly from the output of the generator envelope. Let the generator output a signal of this form (for simplicity, there are only six gradations in the figure, but in reality there are more): ──┐ ┌──────┐ └──┐ ┌──┘ └──┐ └──┐ ┌──┘ └──┐ └──┐ ┌──┘ └──┐ └──┐ ┌──┘ └──────┘ Then, combining these two graphs, we end up with this: ┌─┐ ┌─┐ │ └──┐ ┌──┘ │ ┌──┐ │ │ │ │ │ └─┐ │ │ ┌┐ ┌┐ │ │ │ │ │ │ │└──┐ ┌──┘│ │ │ │ │ ┘ └────┘ └──────┘ └────┘ └────┘ └──── > that is, for example, I have this sample 00 T-E ------------ 0 > looped to 00 and then I put the envelope number> corresponding to G-4 with tone G-1 - ~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~ The underlined is usually called the value of the frequency divider envelope. And the envelope number is the second number in note parameters, which determines the shape of the envelope. > soft bass is obtained, and the signal amplitude also fluctuates > why is this happening? This effect is similar to that which occurs when adding two oscillations with slightly different frequencies (or oscillations with “almost” multiple frequency - say, X and 2.01*X). B coprocessor, tone frequencies and envelopes do not add up, but as if “overlap” each other (see above), but the essence of the phenomenon remains the same. The phase difference between the oscillations relative to changes slowly, and because of this the volume and timbre of the resulting of the signal also change - so-called beats. By changing the frequency offset in the sample, you can observe changing the beat frequency and even achieving their complete disappearance - this will happen just when the frequency tone will become exactly equal to or a multiple of the envelope frequency. Why didn’t these frequencies initially turn out to be exactly equal? or multiples? The fact is that the frequency of the envelope is adjustable more coarsely than the frequency of the tone. Therefore you can definitely adjust the frequency of the tone to the frequency of the envelope, but not vice versa.> - what exactly does the envelope number indicate? As I understand it, you mean the value by the envelope number envelope frequency divider. In essence, this is her period, expressed in certain conventional units. Best regards, Ivan Roshchin.