DSP freq multiplier

"Jame Barlow"

Its called " digital pitch shifting " .

Say what you ACTUALLY want to achieve - or piss off.

........ Phil

A "shift" is an additive translation in frequency and not a multiplication by "10 or 100x," that would be a "scaling." The OP is out to lunch as usual.

If it's already a digital recording, just play it back at 10 or 100 times the original sample rate. If it's not a digital recording, digitize it.

"John O'F"

So 25 Hz becomes 25 kHz and 20kHz becomes 20MHz.

Or else, simply " frequency shift " the signal up by 25 kHz.

Then 25 Hz becomes 25,025Hz and 20 kHz becomes 45kHz.

Can easily be done in real time - by simple, analogue means.

....... Phil

That's a great idea. Let's assume the files are MP3.

But where would I source commercially a digital recorder that would allow the 1000x playback required?

Or, is there some way to modify a relatively low cost item, maybe by changing the clock crystal?

James Barlow

Go to the Goodwill or Salvation Army outlet store and pick up an old reel-to-reel tape deck for five bucks. Record your sound onto it at

Good Luck! Rich

That's a different thing- it's an encoded, compressed file, not a simple digital recording. You may find MP3 software where you can set the playback rate, but that's just the beginning...

... what are you going to play it back into? If it's ultrasonic, it won't be going into the air.

If you have the file on a computer, you can probably get it to play back to an output port at whatever rate you want by just programming. Maybe if you describe what you're trying to do overall, you could get more useful suggestions.

Your scheme doesn't save any bandwidth, so the exercise is pointless.

OK thanks, but it doesn't matter to me what digital format the signal is in. I can record it as WAV if required.

All I want to do is take advantage of a commercial audio editor's GUI and then record and "play it (the signal) back" at 1000x the original speed.

Can it be done? If so how?

James Barlow

You haven't answered the question about what you are trying to do. "Play it back", into what? And for what purpose?

-- John

What is the highest frequency in the result?

How long of a record do you need?

The biggest problem you are likely to face is finding an ADC and DAC that can output what you need and figuring out how to feed them. The sound card on a PC has a limited rate.

For the ADC, you could use you digital scope, if you don't need a huge number of bits or two long of a record.

For the DAC, you may have to build something.

James Barlow snipped-for-privacy@retrodyne.com posted to sci.electronics.design:

If you have a .wav file, reset the stated sampling rate. I believe that Audacity can do that for you. Maybe some other applications.