Have you ever listened to a CD on a good stereo system and noticed that it seemed like stuff was going on at the edges of the stereo field beyond the width of the speakers? Have you ever wondered how they created that effect? Lots of expensive, sophisticated boxes have been marketed to do “spatialization”—but you can do a form of it yourself for free.
Do I have your attention? I must point out that the “free” method will tie up eight channels of your board to do it right—but you can get that number down to a manageable two or four simply by building and using the Great Phase Phlogger.
Phun with physics
We all know what happens when you reverse the polarity of a signal and combine that with the original signal: the two signals cancel each other out. By adjusting the level of either of the two signals you can almost get the resultant signal to disappear. That fact forms the basis of this cool mixing trick.
Notice that I used the term reverse the polarity instead of the more mellifluous flip the phase. Strictly speaking, the phase of a cycle has to do with where it is in time (see Figure 1 on the next page). Compared to the sawtooth waveform in diagram a, the waveform in diagram b is 180 degrees out of phase. It has been delayed exactly one half cycle in time.
If you tried to cancel signal A by combining it with out of phase signal B you would get signal C—not what you want. To cancel signal a effectively you need the reverse-polarity signal D. I know, the button on your console says phase reverse. Well, they’re wrong.
So why do I call this a Phase Phlogger instead of a Polarity Phlogger? It just sounds better.
Plot to kill M
Imagine you’re mixing a song. For simplicity let’s pretend all the ingredients in the mix are panned either hard left, hard right, or straight up the middle. Let’s call any information that appears only on the left L. Let’s call any information that appears only on the right R. And let’s call any information that appears equally on both the left and the right M (for Middle).
So the left side of your mix contains L and M information, and the right side of your mix contains R and M information. (We’re going to use a little simple algebra here—don’t get scared.) We can represent this as:
Left = L + M
Right = R + M
If you reverse the polarity of the left and right sides, this can be represented as:
-(Left) = -(L + M) = (-L) – M
-(Right) = -(R + M) = (-R) – M
Now, here’s where the fun begins. We can make all that M information disappear by reversing its polarity and adding it back into itself. If we were to add the left side of a mix to a reverse polarity version of itself, we would get:
Left + -(Left) = L + M + (-L) – M = no sound
Obviously that doesn’t work, so the trick is to add one side of the mix to the reverse polarity version of the other side. This gives us:
Left + -(Right) = (L + M) + (-R) – M = L - R
Right + -(Left) = (R + M) + (-L) – M = R - L
Notice that the Ms cancel and what we are left with is left-only and reverse-right-only information on the left, and right-only and reverse-left-only information on the right.
By itself this sounds pretty weird. But added into your mix it can create the illusion of spaciousness. The best part is that when your mix is collapsed into mono the effect disappears:
Mono = Left + Right = (L – R) + (R – L) = no sound
That means you don’t want too much of this stuff in your mix. It’s easy to get carried away, only to be surprised by the relatively boring sound of your mix in mono. You want your mix to sound great in mono, then add just a hint of this effect to make it sparkle.
Here’s how to create this effect on your console, assuming that you have four spare input channels and four spare groups (see Figure 2). Route your mix to the Left and Right Main outs of your board, as you would normally do. Then take any channels you have panned hard left or hard right and assign them to groups 1 & 2.
Percussion, acoustic guitars, drum overheads, and the like make good candidates for this. The effect is actually more striking when you don’t send everything through it. Just a few things jangling out at the edges is all it takes to sell the effect.
Groups 1 & 2 are not sent to the Left and Right Mains along with the mix. Instead they are routed to inputs 1 & 2 of your board. They are panned left and right and assigned to groups 3 & 4.
Take an insert send (pre-fader) off input channel 1 and route it to input channel 3. Take a send from channel 2 and route it to input channel 4. Reverse the polarity of input channels 3 & 4. Pan channel 3 hard right and pan channel 4 hard left. Assign input channels 3 & 4 to groups 3 & 4.
Groups 3 & 4 will contain the effect. Assign them to the Left and Right Main outs. Their faders will control the amount of the effect in your mix. The faders on input channels 1 through 4 control the blend of normal and reverse polarity signals. You need to adjust them so that the center information (M) disappears.
The easiest way to do that is to hit Solo or PFL (pre-fader listen) on groups 3 & 4 if your board is so equipped. This works if your Solo or PFL is mono (not solo-in-place). Otherwise, pan groups 3 & 4 straight up and temporarily un-assign the mix from the Left and Right Mains. Listen as you adjust input faders 1 through 4 to achieve the quietest signal. Then pan groups 3 & 4 left and right. Re-assign the mix to the Left and Right Mains.
Start your mix with the faders on groups 3 & 4 low, then adjust the mix until you are happy with the balance. Then slowly bring up the faders on groups 3 & 4 until you hear the effect. You may have a tendency to over-use the effect at first, so it’s important to drop the faders on groups 3 & 4 (or de-assign them, or pan them both straight up) periodically to check your mix for mono compatibility.
What if you don’t have four spare inputs and four spare groups on your board? There are various ways to get creative depending on the flexibility of your board.
If you have two unused post-fader aux sends you can route the mix to them instead of groups 1 & 2. This frees up two groups and has the advantage of allowing varying amounts of send for the individual tracks. That way the shakers can get a lot of it and the bongos only a little.
The downside is that the auxes on some boards are not as sonically pure as the groups. Try it both ways and see which way sounds better on your board. Also remember not to send any of the channels to both auxes—M information gets lost along the way.
This wiring scheme makes operation a little tricky to set up, but it can eliminate the need for groups 3 & 4. Instead of sending inputs 1 through 4 to groups 3 & 4, then sending groups 3 & 4 to the Mains, inputs 1 through 4 can be sent directly to the Mains. It’s harder to set the input channel faders so that they achieve a null—and do so at the right relative level in the mix—but sonically it may even be superior, as groups 3 & 4 are out of the signal path.
There’s a way to do this trick using only two input channels. Send groups 1 & 2 (or the auxes in Plan B) to two input channels set up like inputs 3 & 4 in figure 2. Route them to groups 3 & 4. Any input channels in your mix that get sent to groups 1 & 2 (or the auxes) also get sent to groups 3 & 4.
Listen to groups 3 & 4 in mono as you adjust the faders on input channels 1 & 2 until the signal disappears. In theory it should work; I tried it and wasn’t completely happy with the results. Things seemed to get louder but not really wider.
If you don’t have four spare input modules on your board, you could always use a small external mixer, as long as it has polarity reverse switches on the input channels. Not every small mixer does.
Plan 9 from outer space
I don’t know about you, but I use all the real estate on my board when mixing. Tying up six or eight channels seems like kind of a waste to create this effect.
That’s why I designed and built the Great Phase Phlogger (see Figure 3). It frees up those four input channels for more creative things like eq and effects returns. This box performs the tasks of polarity reversal, cross-panning and blending, and provides a Low Cut control in case you somehow end up with too much out-of-phasey bass buildup in your mix.
I never tried to design an electronic circuit before. Fortunately, I had a little help from my friends Jack Orman (www.muzique.com/amz) and T.J. at Advanced Musical Electronics in West Los Angeles. They patiently endured my bogus design revisions and guided me along my path of discovery.
This project taught me how to wire a polarity-reversing op amp and how to build a summing network. I was able to get a signal to phase-cancel with itself at the turn of a knob. That’s true happiness, and you too can achieve it.
Let’s get phlogging
Start by mounting the terminal strips to the perfboard. I recommend that you lay out your terminal strips in a manner similar to Figures 4 and 5. You can use a small nut and bolt to secure them, or glue them if you prefer. Then cut a strip of white tape and attach it to each terminal strip. Use a felt tip pen to label the lugs A through P and X, Y, and Z.
These lugs represent locations on the schematic diagram with the corresponding letters (see Figure 6). Don’t worry—you don’t need to know how to read a schematic to build this project. It is included only for those of you who like to know what’s going on inside the box.
I used a 4" x 2 3/4" piece of perfboard and the whole assembly fit neatly in a box measuring 4 1/2" x 4 1/2" x 2 1/4". Of course there’s no reason you can’t use a bigger box, or even mount all of the electronics on the back of a 1U blank rack panel.
Use a jeweler’s loupe to inspect your solder joints. And get the best parts you can—quarter-watt 2% resistors and mylar or polyester plastic film capacitors. Also be sure to get sturdy 9-volt battery terminal connectors. The cheapies break too easily.
Refer to Figure 4 for the following steps. Connect R1 between lugs B and C. Connect R3 between lugs C and D. Connect R5 between lugs D and E. Connect R11 between lugs F and G. Connect R13 between lugs G and H. Connect R9 between lugs E and G. Inspect your work.
Connect R2 between lugs J and K. Connect R4 between lugs K and L. Connect R6 between lugs L and M. Connect R12 between lugs N and O. Connect R14 between lugs O and P. Connect R10 between lugs M and O. Inspect your work.
Insert one end of R8 through a hole in the perfboard near lug B. Connect the other end to lug B. Put some thin tubing over the end of R8 poking through the perfboard and route it so it’s away from where the chip sockets will be. Connect a wire from this end of R8 to lug N. Tape the connection between the wire and R8 so it doesn’t touch anything.
Finally, insert one end of R7 through a hole in the perfboard near lug J. Connect the other end to lug J. Put some thin tubing over the end of R7 poking through the perfboard and route it away from the chip sockets. Connect a wire from this end of R7 to lug F. Tape the connection between the wire and R7 so it doesn’t touch anything.
You should now have a cute little assembly. Double check everything.
Ground is commonly needed at various places in a circuit, so we want to have lots of ground lugs at our disposal. Connect a wire from lug X to lug I. Connect a wire from lug I to lug A. Ground is now available on lugs X, A, and I.
Next, we mount the chip sockets. Use needlenose pliers to carefully bend out pins 1, 3, 5, and 7. Pins are numbered counterclockwise, starting at the upper left, when you are looking down on the top side of the chip with its notch or dot at 12 o’clock (see diagram).
Insert the unbent pins 2, 4, 6, and 8 through the holes in the perfboard and secure the chip socket by bending the pins flat on the underside. Don’t put the chips in the sockets yet—all your soldering might cook ’em.
Next, we provide the chips with power: +9 volts, -9 volts, and ground. We use two 9-volt batteries to provide +9 volts and -9 volts, giving our chips 18 volts to play with. The venerable NE5532 can take a 40 volt swing so we won’t be needing any heat sinks or cooling fans. Note that +9 volts is available on lug Y and -9 volts is available on lug Z.
Connect a wire from lug Y to pin 8 of IC1. Connect a wire from lug Y to pin 8 of IC2. Connect a wire from lug Z to pin 4 of IC1. Connect a wire from lug Z to pin 4 of IC2.
The chips require ground on pins 3 and 5. Connect a wire from lug I to pin 3 of IC1. Connect a wire from lug I to pin 3 of IC2. Connect a wire from lug A to pin 5 of IC1. Connect a wire from lug A to pin 5 of IC2.
This is a good time to inspect your work. Your wiring should look something like Figure 4.
Refer to Figure 5 for the following steps. We are going to solder eight wires to complete the connections to the chip sockets.
Connect a wire from lug L to pin 1 of IC1. Connect a wire from lug K to pin 2 of IC1. Connect a wire from lug C to pin 6 of IC1. Connect a wire from lug D to pin 7 of IC1.
Connect a wire from lug P to pin 1 of IC2. Connect a wire from lug O to pin 2 of IC2. Connect a wire from lug G to pin 6 of IC2. Connect a wire from lug H to pin 7 of IC2.
Carefully insert IC1 and IC2 into their respective sockets, noting that the small dot on the top of the chip is closest to pin 1.
Congratulations! If you got this far in one day you’re doing pretty well. Now unplug your soldering iron and call it a day. You’re about half done at this point.
Wake up. Plug in the soldering iron. Make some strong mocha java. Take one more long look at the solder joints you did yesterday. Double-check the wiring. If everything appears in order, it’s time to hook your little assembly up to the rest of the world.
I configured my box as shown in Figure 7. The four pots are located across the center, the switch is in the lower right corner, and the four jacks are mounted close to the top surface to allow room for the two 9-volt batteries positioned below them. The perfboard assembly is located under the pots.
Start with the 9-volt battery clips. Connect the red wire (+) of one clip to lug Y. Connect the black wire (-) of that clip to pin 1 of the switch (see figure 5). Connect the red wire (+) of the other clip to pin 2 of the switch. Connect the black wire (-) of that clip to lug Z.
When connecting components like the pots, the jacks, and the switch, it’s important to position them close to where they will ultimately be located when cutting the wires that will connect them to the perfboard assembly. Put the switch near its position and connect a wire from lug X to both pins 3 and 4 of the switch.
Next, position the left input jack and connect a wire from its tip (+) terminal to lug B. Position the right input jack and connect a wire from its tip (+) terminal to lug J. We’ll do the output jacks later.
Going to pot
Position the left Trim control in its virtual spot and connect a wire from lug 1 (as seen from the knob side) to lug E. Connect a wire from lug 2 to lug I. Connect a wire from lug 3 to lug F.
Position the right Trim control and connect a wire from lug 1 to lug M. Connect a wire from lug 2 to lug I. Connect a wire from lug 3 to lug N.
Get the Low Cut pots. Ideally this would be a dual-ganged pot requiring only one knob, but my local electronics store had none on hand. So I opted for the 2-knob method. Connect a wire from lug 2 to lug 3 of the left Low Cut control. Do the same for the right Low Cut control.
Connect C1 across lugs 1 and 3 of the left Low Cut control. Connect C2 across lugs 1 and 3 of the right Low Cut control.
Connect a wire from lug 1 of the left Low Cut control to lug H. Connect a wire from lug 1 of the right Low Cut control to lug P.
Position the left output jack and connect a wire from its tip (+) terminal to lug 3 of the left Low Cut control. Position the right output jack and connect a wire from its tip (+) terminal to lug 3 of the right Low Cut control.
Finally, connect a wire from lug X to the ground lug on the right output jack. That grounds the box. Take a few minutes to admire your work. I know, it looks like a mess with all those pots and jacks flopping around.
The good news: with any luck you’re done soldering. You have built the beast. Now you have to build it a cage.
Take a break
That’s right, take a break now because you’ll need your wits about you for the next step: playing with power tools. At this point you are no doubt eager to finish, but this is no time for shoddy craftsmanship. You get one shot at laying out the locations for the holes, so don’t blow it.
Carpenters have a saying: measure twice, cut once. Be careful when planning the drill holes so that the components don’t interfere with each other when mounted. Remember to leave sufficient room for the batteries.
Mark the locations of the holes for the switch, the pots, and the input and output jacks. Be sure to drill the right sized holes for the components you use. The switch I chose required a 7/16" hole, the pots required 5/16" holes and the jacks needed 3/8" holes. Your holes may vary.
Attach the assembly to the box one component at a time. First do the switch. Then do the pots. Then do the jacks. Make sure the switch is off and connect the batteries to their clips. Give it one last visual inspection to make sure there are no loose wires or places where the terminal strips are touching the box. Use foam or electrical tape to isolate anything that could short out.
Connect the batteries. Then seal the box. That’s right, no testing this time. It’s all or nothing. Mine worked the first time, so yours has a very good chance. Put the knobs on the pots in a position that seems close. We’ll calibrate them later.
Turn on the Phase Phlogger’s power switch. If at any time you smell anything funny—like burning components—turn off the power immediately and invoke your backup plan. You do have a fire extinguisher, right? Somewhere over by the soldering iron?
Connect the outputs of groups 1 & 2 of your board to the left and right inputs of the Pha se Phlogger. Connect the outputs of the Phase Phlogger to the inputs of groups 3 & 4 of your board. Send a tone (or any musical signal) equally to groups 1 & 2.
Listen to group 3 as you adjust the left Trim control. There should be a place in the center where the signal is almost completely eliminated. Then listen to group 4 as you adjust the right Trim control. Find that null spot.
You are now calibrated. If you want, you can carefully re-set the knobs on the Trim controls so that they point straight up. Disconnect the tone generator (or whatever) and set up to play a CD. Send it to the Main outs of your board as well as to groups 1 & 2. Assign groups 3 & 4 to the Main outs.
Play the CD. Adjust the faders on groups 3 & 4 until you hear the effect. Remember to pan them hard left and right. They cancel each other out in the center.
The Low Cut controls have a subtle effect on the sound. If you somehow end up with a profusion of unwanted out-of-phase bass you can roll some of it off. At their maximum settings the Low Cut controls produce a 10 dB dip at 30 Hz, a 6 dB dip at 60 Hz, a 3 dB dip at 100 Hz, and no appreciable effect above 500 Hz.
When you are satisfied that your box is doing some serious Phlogging—or even if it’s not—now is the time to take the circuit out of its box so you can label the controls and spray a nice clear lacquer finish on top. (I didn’t want to make you wait for this step before trying out your new toy.)
Art supply stores have black rub-on lettering in various fonts and sizes. Label the switch, the knobs, and the input and output jacks as you like. Make up a name for it if for some reason Phase Phlogger is not your cup of tea. Spray a few coats of clear paint over the lettering to keep it from scratching off. When dry, re-assemble with love and care.
If your unit is malfunctioning you have my sympathy. Remove the chips and check all your interconnections for continuity with an ohmmeter. Use that loupe. Test it out of the box—it might work. Maybe something was shorting out against the box. Make sure the proper voltages are really getting to the places they need to go. Did you wire the switch correctly? Check all the grounds. Double-check everything.
Chances are that if you were careful putting this new toy together, you are well on your way to mix-Phlogging pleasure. And once you’ve mixed with the Phase Phlogger, there’s a good chance you will never mix without it. Now that I have my Phase Phlogger, I’m finally ready to mix my album, Orcastra.
Jon Bare is the author of ‘Recording The Electric Guitar—It's All About Tone,’ available from www.recordingmag.com. He may be contacted via firstname.lastname@example.org.
C1, C2 .1uF
IC1, IC2 NE5532, LM833, NTE778A, or equivalent
SW1 DPST switch
VR1,2 L / R Trim—10k linear
VR3,4 L / R Low Cut— 50k linear
J1-4 Mono 1/4 inch jack
T1, T2 8-pole terminal strip
T3 3-pole terminal strip
B1,B2 9-volt battery terminal
You will also need:
2 8-pin IC chip sockets
4 inches of thin plastic tubing
15 feet of hook-up wire
aluminum box (approx. 4 1/2" x 4 1/2" x 2 1/4")
clear spray paint
15-watt soldering iron
regular pliers or vise-grips
perfboard (2 3/4" x 4")
8X jeweler’s loupe
4 small knobs
3 small nuts and bolts (or glue)
2 9-volt batteries
and a partridge in a pear tree