Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Analog Pitch Shifting
Analog Pitch Shifting
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 31st March 2007, 10:25 AM   #1
flashbandit is offline flashbandit  United States
diyAudio Member
Join Date: Mar 2007
Default Analog Pitch Shifting

I've heard this task is possible albeit difficult, but I was wondering how I might go about building an analog pitch shifter. I have a few conceptual ideas, but I like the electronics knowledge to start them and I was wondering if anyone could help. Here are two different ways I've considered pitch shifting:

1) Split an audio signal in two. Take one of the signals and run it through an oscillator so it starts at the right pitch, and then allow whatever control to bend the pitch of the oscillator. Then, add the two signals together. This isn't really efficient or effective pitch shifting since the original signal has timbre but lacks the bent pitch, and the bent pitch lacks timbre. This is just an effect, and may or may not sound good.

2) This idea is the one I really want to pursue because I think it has more potential. I was reading about sampling a signal and how you have to sample at 2 times the highest frequency you're recording inorder for it to sound right. If you drop your sampling rate below that, you get aliasing witch maintains the timbre of the signal, but alters the pitch. I was wondering if you could somehow manipulate this to achieve pitch bending

Any help would be greatly appreciated. I need to know what circuits would help me achieve this, schematics would be great. Thanks in advance!
  Reply With Quote
Old 2nd April 2007, 12:48 PM   #2
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
EC8010's Avatar
Join Date: Jan 2003
Location: Near London. UK
Analogue pitch shifting is done by modulating the signal with one carrier frequency but demodulating it with a slightly different carrier frequency. The famous example of this is the Dalek voice in Dr Who. You require two very stable carrier oscillators and two four-quadrant multipliers. No, I don't have a diagram.
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 2nd April 2007, 01:15 PM   #3
phase_accurate is offline phase_accurate
diyAudio Member
Join Date: May 2002
Location: Switzerland
What do you exactly want to do ? Do you really want to SHIFT frequency ?
Shifting means as mentioned by EC8010 that it is incresed or decreased by a fixed amount like making 315 Hz out of 300, 415 out of 400, 515 out of 500 ..........
Or do you want to multiply or divide ? And in this case it makes a huge difference if it is just a single frequency or a whole frequency band and if it is distortion-sensitive.


  Reply With Quote
Old 2nd April 2007, 11:01 PM   #4
flashbandit is offline flashbandit  United States
diyAudio Member
Join Date: Mar 2007
I basically want to make an electronic analog whammy bar. It doesn't have to have an actual "whammy bar" but I want to be able to bend notes full octaves on command with a potentiometer or something. Any ideas?

Oh, and I was also thinking of a third way to be able to bend notes non-digitally:

Take the incoming signal, split it up into discreet "packets" and speed up or slow down each packet uniformly. Changing the speed changes the tone, then you'd put each packet back together and its pitch would be changed.
  Reply With Quote
Old 3rd April 2007, 04:13 AM   #5
rcavictim is offline rcavictim  Canada
diyAudio Member
rcavictim's Avatar
Join Date: Jun 2004
Location: Next to an open wormhole NW of Toronto
You might try to find an old Radio Shack reverb box that used the analog bucket brigade chip. It was an analog level cmos shift register I.C. You change the frequency of the clock oscillator with a potentiometer and it will momentarily change the speed and thus pitch of the audio that tumbles out of the back end of the brigade chip. This is exactly the methodology you postulated in your previous post, but in an analog domain (audio not converted to digital signal). The effect is actually like seriously bad wow and flutter in a tape deck.

The box has a few slide pots and uses a 9 volt battery. Line level inputs and outputs. RCA jacks.

I have one still in the original box (somewhere) that could be pried loose if you cannot find something closer. Contact me off list if you want it.
"There are more worlds than the one you can hold in your hand." Albert Hosteen, Navajo spiritual elder and code-breaker, X-Files TV Series.
  Reply With Quote
Old 3rd April 2007, 11:57 PM   #6
flashbandit is offline flashbandit  United States
diyAudio Member
Join Date: Mar 2007
I just realized that octaver technology might help. An octaver basically doubles the incoming signal. Could you multiply the signal by fractions? And possibly control that from a pot? That just seems alot simpler.
  Reply With Quote
Old 5th April 2007, 03:15 AM   #7
neutron7 is offline neutron7  Canada
diyAudio Member
neutron7's Avatar
Join Date: Dec 2003
Location: Toronto Canada
an octaver usually multiplies the frequency by rectifying it, so you couldn't really have a fractional one.

what do you need it for and can you use a digital one? you could buy a boss pitch shifter guitar pedal on ebay for about $120 USD
  Reply With Quote
Old 5th April 2007, 03:48 PM   #8
RickshawRecords is offline RickshawRecords  United States
diyAudio Member
RickshawRecords's Avatar
Join Date: Jan 2007
If you're interested, there are currently some Radio Shack Reverbs on eBay going for ~$10 - $15 each:

- Rickshaw
  Reply With Quote
Old 12th April 2007, 01:28 PM   #9
eeka chu is offline eeka chu  United Kingdom
diyAudio Member
Join Date: Nov 2003
Location: England
I think EC8010's probably got the best idea for this.

I used to have an original Digitech Whammy pitch shifting pedal that costs a fortune.

They, and the newer ones, use digital sampling for the shifting I think. The originals were supposidely better because the shifting chip was produced by a company who specialised in custom firmware, whereas when it came round to making the new version Digitech decided to do it themselves and didn't do so well.

I've never tried one of the new versions, so I can't comment. But the original shifter I had was very slick and responsive. It's a tricky effect to subtly fit into a sound though, it's pretty in your face. The octave up sound had a kind of ring modulated, tinny, phased, flanged, chorusy side to it if you actually tried playing long passages through it. You can hear it on some of Audioslaves stuff - I think one tune is 'Like a Stone', but I can't remember for sure. The harmoniser effects could produce some extremely thick sounds. Like in the break in Cochise, also by Audioslave. I like the bit in Shadow on the Sun when Morello does the huge octave up sweeps with all the delay and funny noodling, I thought that was pretty innovative. I really like the sound in that solo. But the high pitched whistling effects get very tedious in a lot of their stuff and the tunes he did with RATM.

I'm guessing the original poster is asking about analog shifting because a lot of the digital shifters you can get now sound nasty. I expect he also wants a solder iron option, as opposed to coding.

I'm kind of interested in this as well, but as far as I know, you're not going to find a schematic for something EC8010 described for the studio in hurry, all of the variable shifters I've seen have been digital. Someone was asking about how to code a digital shifter on here I think, and I don't remember it coming out as easy. Besides, you'd probably just want to buy one if you go that way, unless you're already a coding genius.

Like Neutron says, pitch shifting effects like the Octavia rely on a blisteringly simple method of frequency doubling that will only double the frequency, you can't make it variable.

To go any further, I'd suggest reading around to see if you can find examples of the Darlek voice in Dr Who. You'll also find mountains of stuff on modulation with carriers by reading about radio electronics. Expect to read quite a lot is the only advice I can give at the moment about that. Introductions to basic radio should start discussing carriers early on. A lot of it is suprisingly easy to understand and interesting, for me anyway.

There's a site on the net somewhere called something like 'Radio school' with a load of PDFs on it about how radio works for the beginner. I remember that being an excellent read but can't find it again.

One good thing working in your favour here is that there are also tons of premade ICs for radio electronics that you might be able to hack into a pitch shifter. You might even be able to bust something out of radios, vcrs and tvs depending on how inventive you are.
  Reply With Quote
Old 3rd September 2009, 10:07 PM   #10
flavio81 is offline flavio81  Peru
diyAudio Member
Join Date: Sep 2009
Location: Lima, Peru
Originally Posted by EC8010 View Post
Analogue pitch shifting is done by modulating the signal with one carrier frequency but demodulating it with a slightly different carrier frequency. The famous example of this is the Dalek voice in Dr Who. You require two very stable carrier oscillators and two four-quadrant multipliers. No, I don't have a diagram.
That is FREQUENCY shifting, not pitch shifting. You are describing the "moog frequency shifter", invented by Dr. Harald Bode.

I have read somewhere that there existed a professional analog machine for pitch shifting without changing tempo, that used some kind of magnetic media that was read in a funny way. Something like a disc that spinned at some speed while a rotating head read a specific section of the disc. So if we wanted to double the pitch every X length part of the audio was read twice at twice the speed while the disc rotated at the "correct" speed.

NOTE: I did not understand how that latter device worked, i'm just guessing.
  Reply With Quote


Analog Pitch ShiftingHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Question concerning phase shifting in opamp xover taotao Multi-Way 2 8th May 2009 11:14 AM
Tuning of a cheap opto coupler (for gate driving/level shifting) mrx23 Class D 0 31st March 2007 07:12 AM
Level shifting for output rtarbell Class D 2 17th December 2005 02:26 PM
Mosfet Shifting Vth by Coil Current classd4sure Class D 2 13th February 2005 05:19 PM

New To Site? Need Help?

All times are GMT. The time now is 05:57 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio