Re: Analog Pitch Shifter

bharat pathak schrieb:
Jerry,

I do not have analog background. So i do not know what can
be achieved and what cannot. By the way are there any good
"analog signal processing" books out there?

Hi Bharad,

No book suggestion. You may want to have a look at analog computers and modular synthesizers.

In short you can do the following mathematical operations using analog electronics:

- add
- subtract
- multiply
- tanh
- exp
- square

If you add an opamp you get:

- divide
- log
- roots

You can approximate other functions like sin or cos either using polynomials. For sin the tanh function can be directly used for small angles.

That's enough to do quite a bit of math. All the essential stuff is there. Some of the functions are hard to build in practice if you need high precision and low noise. Temperature compensation is not easy to get right as well.

You can do delay using BBD chips or allpass/dome filters. That'll give you some memory if you need it. Not exactly high precision but it works.

So an analog-pitch shifter is definately possible, but it will be huge, expensive and most likely it won't sound better than a digital implementation.

A more practical way would be to go the electro-mechanical way. You could use a old video recorder (the one with multiple rotating playback-heads). Add some electronics and you get some crude pitch-shifter out of it. AFAIK that's how they did the slow motion playback in the early home-video days.

Nils
.

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