Variable frequency of analog signal

Thread Starter

acheron

Joined Apr 11, 2016
5
Hi guys, so one generic question. Lets say that i have voltage f=1kHz and i want to be able to drop it with potentiometer all the way to f=100Hz and all the frequencies in between, and amplitude has to stay the same. Maybe it is stupid question but I don't know if it is even possible?
 

jpanhalt

Joined Jan 18, 2008
11,087
Yes it is possible and has been for quite awhile. It is even quite easy to do today with a modern DDS chip. Check out the AD9850 as just one example of such chips.'

You could use your relatively low frequency source as a clock, but it might be easiest just to buy a module with a clock crystal and synthesize all of the frequencies you need. Here is an example I posted last last year: http://www.electro-tech-online.com/articles/demo-assembly-code-ad9850-dds-signal-generator.755/

John
 

AnalogKid

Joined Aug 1, 2013
10,986
Is there amplitude or phase information in the incoming sine wave that must be preserved or reproduced, or can the incoming sine wave be used as a clock for a waveform generator or synthesizer?

If the latter, then there are several digital techniques that will achieve this, including some with a tracking output lowpass filter to re-establish the sine shape.

If the former, then you are looking for frequency subtraction (heterodyne), like the front end of a radio receiver only at much lower frequencies. As the ratio of the output and input frequencies changes from 1:10 to 1:1, this goes from difficult to impossible.

ak
 

GopherT

Joined Nov 23, 2012
8,009
Hi guys, so one generic question. Lets say that i have voltage f=1kHz and i want to be able to drop it with potentiometer all the way to f=100Hz and all the frequencies in between, and amplitude has to stay the same. Maybe it is stupid question but I don't know if it is even possible?
Why not start out with a simple DC voltage, you can create a frequency of your own from 100 to 1000. What exactly is your goal. Do you want to feed in any frequency and get something that is a given fraction lower? Do you want it to retain the same wave shape (square, triangle, sine, human voice, ...). I think you have some more explaining to do.
 

Thread Starter

acheron

Joined Apr 11, 2016
5
Ok, so I'm planning here to do pedal for guitar. My plan is to give pedal a signal with specific freq and to be able to drop it to approx 100 Hz. I'm guessing the numbers here. here is the link so you can see what i mean(bomber effect).
 

jpanhalt

Joined Jan 18, 2008
11,087
If you have an unknown frequency and you want to drop it a fixed amount, say 100 Hz, then looking into "mixers." They will give you the sum, which you don't want, and the difference, which you want.

John
 
Top