50kHz pitch shifter

[Magnus Danielson]

From: Toby Paddock <tpaddock at seanet.com>
Subject: 50kHz pitch shifter
Date: Sat, 10 Jun 2000 09:17:33 -0700

> Hello,
> A friend is doing a physics experiment for school and 
> one of the resulting signals is a 50kHz sine wave with 
> noise on it. The noise and ringing is one indication 
> of what is going on. We thought it might be worth 
> bonus points to be able to listen to it. 
> So we need a pitch shifter or divider.
> 
> Maybe a 1/100 divider. Sample one cycle and play it 
> back slow and do it again. Sync could be direct from 
> the clean sine source. The wave is periodic and fairly 
> repetitive, cycle to cycle. But the sample rate would 
> be pretty high.  
> 
> Maybe a ring mod (my favorite). Assuming the carrier 
> is a clean sine wave would the output have the same 
> waveform as the input. It would not need to be perfect 
> as long as you could hear the change. Any tips on 
> what ring mods like 50kHz inputs? 
> I have a sample AD633, but have never built a ring mod.
> 
> Ideas?

Ringmod with 49.5 kHz sine followed with a lowpass filter at say 1k
should do the trick. The lowpass filter does only need to be a single
RC section since the suppression will be sufficient.

Your AD633 should be fine.

Cheers,
Magnus