tonjon@fluke.UUCP (Tony Johnson) (11/18/84)
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!!!
crandell@ut-sally.UUCP (Jim Crandell) (11/28/84)
> Hey...remember that article in EDN of October, 1982 about the audio > frequency shifter? I built one. To refresh your memory, the circuit ... > Now, if somebody could just tell me what I can use this thing for... Hmm.... Sounds like good sound effects material, no? How about this: make some excuse to take a trip to Hollywood and scour the landscape for some bozo making a flick about a novice short-wave listener who is just learning to tune in SSB.... -- Jim Crandell, C. S. Dept., The University of Texas at Austin {ihnp4,seismo,ctvax}!ut-sally!crandell
cspencer@bbncca.ARPA (Clifford Spencer) (11/29/84)
Approximately ten years ago, frquency shifters were quite trendy for
electric instruments, in particular the fender rhodes piano.
check out "red baron" on billy cobham's "spectrum" lp for
a nice example. Also Todd Rundgren's "born to synthesize" on
his "Initiation" lp has some nice shifted vocals.
cliff
--
{decvax,linus,ima,ihnp4,wjh12}!bbncca!cspencer
cspencer@bbncca.ARPAdon@oakhill.UUCP (Don Weiss) (11/29/84)
[post no bills] In 1968 or 1969 Dr. Manfred Schroeder of Bell Labs lectured at the University of Illinois on his recent research in digitally simulating acoustic environments. A result of his early simulations suggested that there was a "fine-grained" structure to the frequency response of a typical room that had not previously been discovered by traditional room-measurment methods. Upon investigating with new kinds of measurments, this fine grained "sawtooth" in the room response was found in some real rooms. Now, this frequency-domain sawtooth had a periodicity on the order of a few hertz, which explained why it hadn't been remarked on before. Dr. Schroeder then proposed that this characteristic could be exploited in sound reinforcement systems to increase gain-before-feedback by freqency shifting the input from all live microphones by half of the room periodicity, which would amount to a shift of only a hertz or three. The idea, of course, was to effectively cut down the loop gain of the feedback mechanism, without cutting down the actual forward gain of the sound reinforcement system. Interesting idea; I haven't heard any more about it since the lecture.
doug@terak.UUCP (Doug Pardee) (12/04/84)
> Hey...remember that article in EDN of October, 1982 about the audio > frequency shifter? I built one. > > Now, if somebody could just tell me what I can use this thing for... Sell it to local ham radio operators who operate Single Side-band (SSB) using transceivers without Receiver Incremental Tuning. Somewhere over 99% (no joshing) of all SSB operators mis-tune when listening, always in such a manner that the received voice sounds higher-pitched than it really is, usually by 50-100 Hz or so. When two hams are communicating and neither has RIT, there is inevitably a waltz whereby ham B tunes in ham A's voice a bit high-pitched, then when ham B is talking ham A tunes him in a bit high-pitched, etc. and they slowly walk up the band. (With a transceiver without RIT, changing the received frequency also changes the transmitted frequency). With the shifter, a ham can transmit his voice shifted high enough that the other ham will tune properly. Or even better, the other ham will tune so that HIS voice sounds higher-pitched to the ham with the shifter! Of course, a more direct but less interesting approach would be to simply use the shifter as if it was an RIT, shifting the incoming voice up to the desired pitch. Doug Pardee -- Terak Corp. -- !{hao,ihnp4,decvax}!noao!terak!doug
tonjon@fluke.UUCP (Tony Johnson) (12/08/84)
> > Hey...remember that article in EDN of October, 1982 about the audio > > frequency shifter? I built one. To refresh your memory, the circuit > ... > > Now, if somebody could just tell me what I can use this thing for... > > Hmm.... Sounds like good sound effects material, no? How about this: > make some excuse to take a trip to Hollywood and scour the landscape > for some bozo making a flick about a novice short-wave listener > who is just learning to tune in SSB.... > -- > > Jim Crandell, C. S. Dept., The University of Texas at Austin > {ihnp4,seismo,ctvax}!ut-sally!crandell *** REPLACE THIS LINE WITH YOUR MESSAGE *** This is a follow-up to the follow-up. Just a note to say I saw 'Star Wars' on the tube a couple of days ago, and noted the sound of the voices 'over the intercom' during the last fight sequence to kill the death star (you know...you see Princess Leia and other folks at the rebel base looking at the map and you hear some distorted voice in the background). The voice over the speaker sounded a lot like mine over my frequency shifter when I put in higher frequencies (1 kHz). Neat huh? Tony Johnson John Fluke Mfg. Everett, WA
gnome@olivee.UUCP (12/10/84)
Could someone out there send me a copy of the schematic for the frequency shifter. Let me know who has one and I'll send a SASE if needed. Thanks. Gary (hplabs,allegra,ihnp4)oliveb!olivee!gnome