I would like to modulate continuous white noise with an audio sinewave, by modulating the low pass cut-off of an in series active filter.
Can anyone please advise me regarding the best practice for this? \\
The type of fliter most suited, how to feed the modulation signal, etc.
Many thanks,
Stuart Kendall
One *cannot* "modulate" with a linear device, period.
Voltage controlled LP filter?? ssssssssswwwwwwwwwwWWWWWWWWW :)
My guesses... switched capacitor filter IC program a PC sound card? music store effects rack/box ADC's, DAC and a DSP chip. Op amp active filter with opto conductors A capacitor,photoresister and a LED
D from BC
Resistances that are near ground voltage and/or transconductances are the easiest to electronically control. If your control was digital, I'd suggest a DAC be used. There are some chips that do a multiply function.
How good of a filter do you need this to be? How wide of a range does it need to be able to vary over?
What, exactly, is your definition of "modulate"? If not "modulate," what WOULD you call what the OP wants to do? It seems to me that what he wants to do meets a reasonable definition of modulate: to change a characteristic of one signal under the control of another signal. He's suggesting to change the spectral content and the total energy of one signal, in response to another signal. Modulation. Period.
Perhaps a filter with a signal input and a cutoff-frequency input is not a linear device...
Cheers, Tom
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