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Modulate noise w/ LPF

S

Stuart Kendall

Jan 1, 1970
0
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
 
R

Robert Baer

Jan 1, 1970
0
Stuart said:
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.
 
D

D from BC

Jan 1, 1970
0
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

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
 
M

MooseFET

Jan 1, 1970
0
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.

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?
 
T

Tom Bruhns

Jan 1, 1970
0
One *cannot* "modulate" with a linear device, period.

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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