As a musician I often need to learn new songs, and it can be difficult to hear individual instruments in recordings I want to study. I have often wished for an easy way to eliminate or reduce the vocals and isolate the instruments. Various hardware and software solutions exist but they tend to be expensive or inconvenient.  I wanted a cheap method that I could use anywhere, on any device with a 1/8″ stereo headphone jack.

Then, one night, I was fiddling with a pair of headphones with a defective plug. When moved a certain way, it gave exactly the vocals-canceling effect I had been looking for!

To understand what was happening, I did some research online, bought some components at RadioShack, and tested various wiring combinations. My son Nathan and I tested the final device.

In my research, I discovered that many songs are mixed down with vocals equally on both channels (Right and Left). This is called “Down the Center” because it gives an illusion that the vocals are coming from “center stage.”

Singalong Song Devocalizer Schematic

Now, when the ground (sleeve) on a tip-ring-shield (TRS) signal is disconnected, the hot wire from each signal (Left or Right) tries to use the opposing hot wire as its new ground. As a result, the signals are 180 degrees out of phase. Thus, anything that was mixed to both tracks gets cancelled out by destructive interference.  When this happens in a recording, anything mixed evenly to both right and left channels will magically disappear.

Many recordings are well-suited to create this effect. Depending on how a song is mixed, the instrument isolation effects using this technique can be quite remarkable. The device can also be set to send full right or left signal to both headphones for added isolation effects.

Sing-a-long Song Devocalizer

Steps

Step #1: Prep the enclosure.

PrevNext
Sing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song Devocalizer
  • Measure and plan placement of the switches and audio jacks. Blue painter's masking tape is handy for making easily seen and easily removed marks on the box's surface.
  • Drill holes in the project box for the switches and jacks. Drill through the tape, then peel it off and throw it away.
  • Mount the switches in the holes on the long side of the box, per the photos, using their bundled hardware. Soldering will be easier if you leave the jacks free for now.

Step #2: Wire the DPDT center-off switch.

PrevNext
Sing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song Devocalizer
  • NOTE: We will only be using one side of the DPDT center-off switch, i.e. only using three of its six contacts.
  • Solder a jumper wire from the center pole of the DPDT center-off switch to the ground (sleeve) connection on the "device" jack.
  • Solder a second jumper wire from the nearby pole of the DPDT center-off switch to the center pole of the SPDT switch.
  • Solder a third jumper wire from the remaining pole of the DPDT center-off switch to the ground connection of the "headphone" jack.

Step #3: Wire the SPDT switch.

PrevNext
Sing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song Devocalizer
  • Solder a jumper wire between the ring terminals of the two jacks, and another from one side of the SPDT switch to the ring connection of the "headphone" jack.
  • Solder a jumper wire between the tip terminals of the two jacks, and another from the remaining pole of the SPDT switch to the tip terminal on the "device" jack.
  • Carefully inspect and test these connections. Use the continuity testing function on your multimeter.

Step #4: Try it out!

PrevNext
Sing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song DevocalizerSing-a-long Song Devocalizer
  • Using the hardware bundled with the parts, mount the jacks into the holes drilled in the short end of the box, per the photos, and close up the box.
  • Label the HEADPHONE and DEVICE jacks. This step is important; the device won’t work if these are mixed up!
  • Plug one end of the stereo cable into the DEVICE jack and the other end into an iPod or other device audio output. Plug your stereo headphones into the HEADPHONE jack and try it out!

Conclusion

In the “off” position, the center-off switch should cause the vocal canceling effect. Switching it to one side should give you a normal stereo signal; switching it to the other side activates the SPDT switch, allowing you to choose between full-right channel and full-left channel effects.

Pick an older song (1960s or so) for your first test run. Many of the older songs are mixed with center vocals and isolated instruments in each channel, which works particularly well. For example, in “Help!” by the Beatles, the vocals disappear nicely with the switch in center position.

In “Ticket to Ride,” you’ll hear a nice example of what I call “reverb ghosts.” In this case the original vocals disappear, but the reverb trails are left behind, giving a ghostly echo effect, like you are standing with the band playing the instruments but the vocalists are down the hall.

To demonstrate the channel separation feature, try “Magical Mystery Tour.” Use the SPDT switch to hear the beautifully isolated bass, brass and some vocals in the right-hand channel. The left-hand channel has the drums, the guitars and the remaining vocals. Also the piano part at the end of the song is mostly isolated on this side..

After trying many songs by different artists, my experience is that about 20% of songs have a fantastic vocal cancellation effect with instruments clearly isolated. You could use these tracks for Karaoke with no problem. In 50-60% of songs, the effect is less pronounced, but you can still hear instrument parts you’ve never heard before, which should be useful if you are an instrumentalist trying to learn one. About 15% of songs tried have minimal effects, not enough to make the effort worthwhile. Finally, some 5% of songs have a fascinating, totally unexpected digital audio sound that is difficult to describe. Large parts of these songs have a bizarre robotic sound that occurs where large “swaths” of instruments disappear, but some parts have been left behind.

So experiment! Have fun and let us know if you find any songs that have especially pronounced or weird effects!



  • joe

    You can do this for free buy splitting stereo into individual mono tracks, inverting one half, then remixing (search youtube for audacity vocal removal). Albiet, this box is much more automated simple way of doing it.

    • Jeff Goller (article author)

      Joe, you’re definitely right that this can also be done with Audacity. However, the idea of this project was to build something that I could use on the fly or with DRM protected songs and without having to involve my PC to transfer/ copy/ process or convert files. Its also nice to have something you can use at 3 AM on a whim without having to fire up my PC.

      I believe Band in a Box also will strip vocals if you are looking for a software solution as well as other third party programs . I agree that Audacity is a really elegant solution if you are looking for something software based.

  • http://gravatar.com/bigjohn30 bigjohn30

    Wouldn’t it be safer to add a resistor between the center pin of the SPDT and the pin of the DPDT instead of just shorting the power from the device straight to ground.

    • https://www.facebook.com/matheuslps Matheus Lopes

      Good eyes!! I agree with you. I resistor there would be nice.

      • Rachel

        Yes, what size?? I just got the parts to make this today!

    • http://gravatar.com/ericfmyers Eric F. Myers

      What size resistor would this need?

    • docree

      Even in some high end systems, the center pin is just sent to ground. This is so that “excess” audio signals, or stray electricity goes directly to ground. Typically no “power” is sent over speaker cables. [With a few exceptions on powered speakers. And this device would not be for powered speakers. ] Placing a resistor / capacitor on the ground in this project will most likely add noise to the audio. [Ground loop hum.] It could possibly damage the speakers, as well.

  • http://jakespurlock.com/ Jake Spurlock

    What a cool project!

  • https://www.facebook.com/seth.meyers.969 Seth Meyers

    And this explains why, sometimes when an audio cable or headphones cable starts to go bad de to internal shorts, I guess, this weird effect happens where the vocals sort of disappear — you still get instrumental sound from both channels but the vocals (and maybe some other stuff) are gone. Excellent.

  • xaris papasideris

    Reminds me an old discovery (suggestion) of Brian Eno (late 70’s). You take the center signals from an stereo amplifier output (the “red” cables), and you connect an extra smaller speaker to them. You place that speaker opposite from the main speakers and you have a kind of surround sound in the room. I still use it at home and its beautiful becouse you listen everything wherever you stand! :-)

  • computer_freak_8

    Note: It’s not 180 degrees out-of-phase, it’s just polarity flipped. There is a big difference – phase implies a reference to time, whereas polarity is time-independent. The question to ask when something is said to be “out-of-phase” is always “at what frequency?”.

    • Jeff Goller (article author)

      Good point. Nice technical language pick up!

    • docree

      Computer_freak_ 8, you are correct to an extent. To an electrician it is just flipped polarity. To a sound tech, the audio signal is “out of phase”. Phase is still a reference to time in audio. After flipping polarity the audio signal becomes out of phase. To explain it simply, the signal is folded in half along the middle “center channel”. And whatever matches timing within that fold gets cancelled out.

      The speaker membrane [cone] can vibrate inward or outward. But not at the same time. So by folding the signal, the “center” frequency matches phase telling the speakers to vibrate in and out at the same time. Which makes the “center” null and void. That’s in the most simplistic terms.

  • Ty Tower

    So the device is whatever is playing the MP3 is it and the headphone is where you listen ? Is this correct?

    • Jeff Goller (article author)

      Yes, Plug your iPod (or whatever) into the “Device” jack and the headphones into the other jack.

  • Rachel

    I made this over the weekend, it’s fun to experiment with. Of the songs I tried- most “new” songs have the reverb ghost, and sounds pretty much the same on full left/right. The Beatles are good to listen to in full left/right, you can hear the differences in each.
    Is there a way to isolate the vocals instead of instruments? (like this, not using software)

  • coolaew

    Where do you guys get all these handy project boxes?
    I can’t find any here in Norway :/

    • Sean Michael Ragan

      Well, these all come from RadioShack, which is a big retail chain here in the US. Electronics enclosures are widely available online, but as for brick-and-mortar retail options in Norway I am sorry to say I don’t really know. :(

  • http://gravatar.com/d5s5 d5s5

    Nice project. Would this devocalizer work on the video presented here to eliminate the distracting music in the background?

    • Sean Michael Ragan

      Try it! Let us know! =)

      The human race is weirdly divided on the question of background music. Some people find it irritating and distracting. Some find it calming. The former group, of which I too count myself a member, seem to be in the minority.

  • Ray

    Where can I buy all the parts in Canada (not shipped from USA caz the shipping is ridiculous) ?

    • https://plus.google.com/+AllenMar Allen Mar

      You can try finding the old Radio Shack stores in Canada, rebranded as “The Source”. Or search for a local electronics parts dealer in your area. For example, I just googled this (non-definitive) list of Canadian suppliers: http://members.shaw.ca/roma/suppliers.html. Good luck.

  • Christopher Love

    Awesome, Thanks for such a cool project. Cheap and easy. Made it today.

  • Brian Turner

    I followed the schematic exactly, but there is no affect on the sound and the SPDT does nothing. Troubleshooting tips, anyone?

    • bbroome62

      It could be out of gas.

      • Brian Turner

        Your wit is overwhelming.

        • Glitch

          Hey Brian, The effect is caused by disconnecting the grounds from each signal but still connecting left to left and right to right, follow the signals and see if your ground wire is interrupted.

          You could also make a devocalising plug by grabbing a male and female audio jack and just connecting right and left signals,not the ground,then put it between your headphones and your audio source.

  • sahiba

    Can u name the song that is suitable for the project?

  • Jacob Baca

    Could someone explain the 180 phase shift in more depth?
    I do not understand how the removal of the input ground achieves this phase shift

    • Eric

      The sound for each channel is the difference between that channel’s voltage and some reference voltage. Normally if the reference voltage is “ground” and presumed to be unchanging — all the difference comes from the audio signal. Instead of the fixed ground reference, you use the other channel’s audio as the reference. If both channels are in sync with each other, their voltages will track exactly, and the difference between them will be zero — no sound. The headphones don’t know (or care) whether ground is a fixed signal or a varying signal — they only respond to the voltage difference between the signal and reference. In the more complicated stereo audio signals, the left and right voltages will be different. The part of that signal that’s in common between left and right channels will be canceled out.

      • Jacob Baca

        Thank you! I really appreciate it

  • Declan Embury

    is the spdt a ON-ON or a ON-OFF

    • slango20

      ON-OFF-ON, or center off, where the two other positions are different effects