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Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!houxm!vax135!cornell!uw-beaver!ssc-vax!fluke!tonjon
From: tonjon@fluke.UUCP (Tony Johnson)
Newsgroups: net.analog,net.audio
Subject: Frequency Shifter with no practical application makes funny noises!
Message-ID: <49@vax2.fluke.UUCP>
Date: Sat, 17-Nov-84 17:49:34 EST
Article-I.D.: vax2.49
Posted: Sat Nov 17 17:49:34 1984
Date-Received: Wed, 28-Nov-84 03:33:29 EST
Distribution: net
Organization: John Fluke Mfg. Co., Everett, WA
Lines: 29


	Hey...remember that article in EDN of October, 1982 about the audio
	frequency shifter?  I built one.  To refresh your memory, the circuit
	performs a sin(A+B) = sinAcosB+sinBcosA identity electroncally with
	two phase delay networks, two multipliers and a summing amp.  I went
	down to Radio Shack and picked up an 'electret mike element', and built
	a simple mike amplifier which became my 'A' signal with an Interstate
	function generator providing my reference 'B' signal.
	Now people around my work area are blessed with phrases like 'testing,
	testing, one, two, three...' shifted in frequency by various amounts.
	The interesting thing about the system (somebody pointed this out in
	a reply to an inquiry a year or so ago) is that an additive shift of all
	the frequencies in an audio signal does NOT sound like changing the
	speed on your tape deck as the additive shifter preserves the bandwidth
	when the audio band is shifted up (if you double the speed of your tape
	deck, you automatically 'create' twice as much bandwidth, right?) Thus,
	when I whistle 'I left my heart in San Francisco' into the mike, the
	output is an 'additively' transposed (and therefore horribly out of 
	tune) version of the original.  At lower reference frequencies (10 Hz or
	so) the output sounds like a 'beating' version of the original.  Placing
	the function generator on sweep gives an even more dramatic effect.
	Now, if somebody could just tell me what I can use this thing for...

						Tony Johnson,
						John Fluke Mfg. Co. Inc.
						Everett, WA

	That's it!!!  Send it up in the Shuttle!!!  I should be able to get a
	couple hundred thou in government grants for THAT!!!