BUILD THE UniQuad

PHLAZEX

STEREO MODIFIER AND MATRIX ENCODER

Do you need any of the following audio functions?

  • Stereo Phase Inverter
  • Wide Stereo Generator
  • Mid-Side Converter
  • Stereo Blender
  • Solo Eliminator
  • Microphone Channel Phase Inverter
  • Matrix Surround Encoder
  • Matrix Surround Image Rotator
  • Matrix Surround image shifter

Then build the UniQuad Phlazex Stereo Modifier and Matrix Decoder.

UQ The Phlazex allows you to either adjust the level and polarity of each of the two stereo signals, or to cross-mix each channel into the other at an adjustable level and polarity. It does this with a minimum of passive components. No power supply is required.

Phlazex may be built into a project box, or into a rack-mount chassis for professional use. For convenience, several Phlazex stereo units can be combined into the same package. The signal connectors can be chosen to match the cables the Phlazex will be used with. And for more flexibility, Phlazex can be connected to a patchbay.

Materials:

You will need the following parts for each Phlazex:

  • Two 600 ohm 1/4 watt resistors*
  • Six 4.7 K 1/4 watt resistors
  • Two 4.7 K 1/4 watt resistors*
  • One 10 ohm 1/4 watt resistor
  • Two 5 K linear taper potentiometers ("pots")
  • One 4-pole 4-throw switch (Switchcraft A1040Z or equivalent)
  • One Radio Shack Ground Loop Isolator 270-054
    NOTE: You can substitute two 600 ohm to 600 ohm transformers for the ground loop isolators, but then you will probably want to build a circuit board for the transformers and resistors.
  • Two 4-terminal solder lug terminal strip
  • Hardware to mount the Ground Loop Isolator and the terminal strips
  • One chassis box or rack-mount box to build Phlazex in
  • Four connectors chosen to suit. If the box is metal, these must be the insulating type.
  • Two knobs for the pots
  • Shielded cable.
  • Number 20 solid hookup wire.
  • Small heat shrink tubing to fit the resistor leads and cable shields
  • Electrical Tape

* Not needed if the Phlazex will never be connected to balanced line equipment.

You will need the following tools:

  1. Screwdrivers
  2. Adjustable wrench
  3. Drill and bits
  4. Hand reamer or Greenlee punches to make holes to fit the shafts and jacks
  5. Soldering iron and solder

Construction:

  1. Lay out the locations of the fittings on the box. Be sure to leave space for a terminal strip near the terminal lugs of each of the pots. Also make sure the cables from the Ground Loop Isolator will reach the pots and terminal strips when the Isolator is mounted.
  2. Mark the box for switch positions, jack identification, and pot position. You can copy the template above.
  3. Drill the holes and ream or punch the shaft and jack holes.
  4. Mount the jacks, pots, switch, terminal strip, and Ground Loop Isolator. Make sure that all wires from the Isolator can reach the pots and terminal strips.
  5. If you have three-terminal jacks, connect the 600 ohm resistors from the "cold" terminals to the "shield" terminals of the input jacks.
  6. If you have three-terminal jacks, connect the 4.7 K resistors from the "cold" terminals to the "shield" terminals of the output jacks.

    In all of the following steps, when you connect up a cable shield, twist the strands of shield together and place heat shrink tubing over the twisted wires, so the shield can not short to other connections.

  7. Cut four pieces of shielded cables to easily reach from the pots to the jacks. Connect shielded cables to the jacks, with the center conductors connected to the "hot" terminals and the shields connected to ground terminals. Solder all connections to the jacks now.
  8. Connect the center conductors of the cables from the input jacks to the counterclockwise terminals of the respective pots, left and right. The left input cable should go to the left pot. Connect the shields to the terminals on the terminal strips that are closest to the counterclockwise pot terminals, and that are NOT connected to the chassis. See the note to the right on how to identify the terminals of the pot.

    NOTE: NO connections are ever made to any lug that is screwed to the chassis.

    NOTE: The left pot is the one on your right when looking at the panel from the back. It might help to put a big L on it with a marker.

  9. Connect the center conductors of the short cables from the Ground Loop Isolator to the counterclockwise terminals of the respective pots, left and right, after cutting off the RCA plugs, separating the cables back a few inches, and stripping the ends. The cable that had the white plug must go to the left pot. Connect the shields to the same terminals on the terminal strips the input shields are connected to.
  10. Connect the center conductors of the long cables from the Ground Loop Isolator to the clockwise terminals of the respective pots, left and right, after cutting off the RCA plugs. You may shorten the cables, but do not mix up the left and right cables. The cable that had the white plug must go to the left pot. Connect the shields to the terminals on the terminal strips that are closest to the clockwise pot terminals, and that are NOT connected to the chassis. Solder the connections to the clockwise pot terminals.
  11. Connect the center conductors of the cables from the output jacks to the indicated common terminals of the switch, left and right pairs. Connect the shields of these cables to the same terminals on the terminal strips that are connected to the long cables from the Ground Loop Isolator. Solder the center terminal connections on the switches. See the note on how to identify the switch terminals.
  12. Connect the 10 ohm resistor to the same terminals on the terminal strips that are connected to the long cables from the Ground Loop Isolator, with one end connected to the left channel strip and the other end connected to the right channel strip.
  13. Connect one end of a jumper of hookup wire to the terminals on the left terminal strip that the input shields are connected to. Connect the other end to the terminal on the same terminal strips that is connected to the long cables from the Ground Loop Isolator. Repeat this on the right channel. Solder all terminal strip connections.
  14. Connect up the 4.7 K resistors to the counterclockwise and center pot terminals, and the switch terminals as shown in the schematic. Solder all remaining connections.
faceplate

Fig. 1: Faceplate and operation table

NOTE: How to identify the terminals of the pot: Hold the chassis so the shaft points away from you and the terminals point down, as in the diagram. The terminal on the left is the clockwise terminal, the one on the right is the counterclockwise terminal, and the one in the middle is the wiper terminal. On the schematic, the clockwise terminal is identified by a minus sign because that terminal is reversed in phase.

wiring

Fig. 2: Sample wiring diagram to match faceplate

NOTE: How to identify the switch terminals. Each column of three terminals is one section of the switch. The section closest to the left pot is the one at the top of the diagram, and the sections are in the same order on the switch as they are on the schematic. The common terminal of each section is the one in the middle of the column of three. The terminal that is switched to the common terminal whenever the switch is flipped up is the terminal that is farthest down, and vice versa.

schematic

Fig. 3: Phlazex schematic diagram

Testing:

Connect Phlazex into any stereo signal line. Play a mono source and set Phlazex to the soloist elimination setting (see below). You should be able to null out all but noise and distortion from the program. If no mono source is available, play a recording with a centered vocalist, and try to remove the vocalist.

If you cannot null out the mono source or the center vocalist, then you will have to perform the operation in the note below:

NOTE: It is possible that Radio Shack may eventually discover and remove the phase inverting property of its Ground Loop Isolator. If this happens, and only if this happens, you will have to perform surgery on the unit as follows:

Unmount the Ground Loop Isolator (you can leave it soldered into the circuit). With a hacksaw, carefully cut one end cap off of the Ground Loop Isolator's plastic case. Go around the edge, being careful not to cut to deep. Otherwise, you will damage the cable or the circuit board inside. Slide the cut-off end cap down the cable, and then slide the circuit board out of the case.

Do all of the following operations at the end of the circuit board facing the cap you cut off and slid down the wire. Do not do them at the other end of the board:

  1. Mark the two terminals the cable shields are connected to.
  2. Unsolder the both the center conductor and the shield of ONE cable of the stereo pair from the circuit board.
  3. Solder the center conductor to the marked terminal you just disconnected the shield from.
  4. Solder the shield to the unmarked terminal you just disconnected the center conductor from.
  5. Repeat steps 2, 3, and 4 for the other cable of the same stereo pair.

Now slide the board back into the case, slide the cap into position, and tape it in place with electrical tape. Test the unit as shown above.

Connecting to the studio:

How you connect Phlazex into your studio depends a lot on which function you intend to use it for. If it is to be used for multiple functions, a patchbay is suggested.

In short, connect Phlazex into the audio chain at the point you wish to make the modifications.

Using Phlazex:

Use the following table to make settings.

FUNCTIONSWITCHLEFT
KNOB		 RIGHT
KNOB		CONNECTIONSUSAGE
Stereo Pass Through Encode+1+1 Use the connection you are otherwise using. This is sort of the "do nothing" setting on Phlazex. Use it when you wish to temporarily stop using a Phlazex function without disconnecting Phlazex.
Phase Invert Encode-1-1 Insert Phlazex into the signal line(s) you wish to reverse the phase of. To cancel phase inversion, turn the knob to +1.
Encode Surround Left-Biased Encode+1-1 Normally Phlazex is inserted into the bus 3 and 4 insert jacks of a 4 bus mixer. Buses 1 and 2 encode front sounds, and buses 3 and 4 encode back sounds, all with constant-level panning and normal pan positions. See the section on Encoding below.
Encode Surround Right-Biased Encode-1+1 Normally Phlazex is inserted into the bus 3 and 4 insert jacks of a 4 bus mixer. Buses 1 and 2 encode front sounds, and buses 3 and 4 encode back sounds, all with constant-level panning and normal pan positions. See the section on Encoding below.
Encode Surround Front-Biased Phlaze-.4-.4 Insert Phlazex into a pair of bus insert jacks, or into the insert jacks of the mixer's stereo output. It can also be placed between the mixer and the master recorder. Pan positions become (left to right) LB, L, LF, F, RF, R, R. 300 degree pan pots point to the real encoded direction. Constant-level panning is IMPOSSIBLE in this mode.
Phlazex Wide Stereo Phlaze-.2-.2 Inserted into the insert jacks in the stereo output of a mixer, or connect between the mixer and the master recorder. This makes the stereo image seem to spread out beyond the speakers themselves. It affects constant-level panning, but not as much as the encoder function above does.
Mid-Side Converter Phlaze-1+1 Insert Phlazex into the channel inserts of the two channel strips with the mid and side mics. The left Phlazex channel is mid. Converts a mid-side microphone set or a mid-side transmission into normal stereo. Also generates a mid-side transmission from normal stereo.
FUNCTIONSWITCHLEFT
KNOB		 RIGHT
KNOB		CONNECTIONSUSAGE
Stereo Blend Phlaze+B+B Insert Phlazex into either a pair of buses or the mixer's stereo output. Settings control how much blend takes place. Setting both controls to 0 gives stereo, +1 gives mono, and settings B in between give various amounts of blend.
Stereo Pass-Through Phlaze00 Use the connection you are otherwise using. This is the "do nothing" setting on Phlazex. Use it when you wish to temporarily stop using a Phlazex function without disconnecting Phlazex.
Surround Image Rotate Left Phlaze-A+A Insert Phlazex into the stereo output of the mixer. Rotate left: Set left knob negative and right knob positive.
Make sure settings are equal but opposite.
Rotation (degrees) = dial setting A times 90.
Surround Image Rotate Right Phlaze+A-A Insert Phlazex into the stereo output of the mixer. Rotate right: Set left knob positive and right knob negative.
Make sure settings are equal but opposite.
Rotation (degrees) = dial setting A times 90.
Soloist Elimination Phlaze-1-1 Insert Phlazex into the lines carrying the stereo program to be modified. Adjusting controls removes undesired sound from only ONE of the two outputs. Since the result is always in mono, use only that output and ignore the other one.
Mono Phlaze+1+1 Insert Phlazex into either a pair of buses or the stereo output of the mixer. Changes a stereo signal into a mono one. Useful for testing for phase cancellation.

Encoding Surround Sound:

Using the Left-Biased or Right-Biased Encoding Functions:

Normally you can choose either the left-biased or right-biased mode of encoding with no perceptible difference between them. Sometimes mic interactions or continuous pannings have a bearing on the choice.

Normally, you use a 4-bus mixer. Buses 1 and 2 are used in the normal way, and buses 3 and 4 have Phlazex connected into their bus inserts.

Phlazex can be used as the encoder in the following page by selecting the Encode Surround Right-Biased mode: Encoding Surround Sound with your Mixer

To encode mixer channel strips into matrix surround sound, use the bus assign buttons to select whether the channel strip is to be panned to the front or to the back of the surround sound image. For front, assign buses 1 and 2. For back, assign buses 3 and 4. Then pan the sound within that half of the image with the pan pot.

The pan positions of buses 1 and 2 are (in pan order):

The pan positions of buses 3 and 4 are (in pan order):

Constant-level panning is retained in these modes if the mixer has constant level panning.

Using the Front-Biased Encoding Function:

This operates in a different manner than the two other surround encoding modes. It changes the range of the pan pot to pan the signal to include (in pan order):

Thus, only two buses are needed to encode most sound sources.

There is one drawback to this method. Constant-level panning is no longer possible. The signal is much stronger at the back positions than it is at center front. So it must be used for static pannings, not sources that must be panned around during the piece. Adjust the signal level after you set the panning.

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