Controlling Phoenix Sound Volume with
Aristo Craft's Revolution Receiver
Revised 10-24-09 - 9-08-16

The Phoenix 2K2 sound cards can be easily interfaced to Aristo Craft's Revolution receiver so that two of the auxiliary control buttons can increase or decrease the sound unit's volume.

The newer Phoenix sound card, the PB9, uses a different method of adjusting volume and needs an interface board so that the Revolution can control volume.

The Revolution's six auxiliary outputs are "open collector" outputs that pull the output pin to ground when activated. 

The Phoenix sound card's volume adjust pin is pulled low (to ground) or pulled high (to +5 volts) to change the volume.

The interface changes the open collector outputs on the Revolution so that they can apply the proper voltage to the volume adjust pin.


PB9 Volume Connections

P5 Volume Connections




Volume Switch


Volume Level


Volume Switch


Volume +3V


Volume Switch


This schematic is the one from Phoenix.

This schematic is just my reproduction of the Phoenix schematic.  Note that the transistor is a 2N3906 rather than the recommended 2907.  Internally they are almost identical.

2N3906 (available at Radio Shack for $2.59 for 15)
1K resistor (available at Radio Shack for $0.99 for 5)

Results with this circuit:
Input voltage A active B active Neither active
5 volts 4.97 volts 2.5 millivolts 0.94 volts
3 volts 2.9 volts 2.5 millivolts 0.94 volts
This circuit is so simple that construction on a piece of prototyping board should only take a few minutes.
  1. Place the PNP transistor with it's flat side oriented as shown here:


  2. Connect the 1000 ohm resistor to the base (center lead) of the transistor with the wires connecting and being soldered on the bottom of the board.


  3. Connect the other end of the resistor to the blue wire from the Revolution's Aux Interface.
  4. Connect the green wire from the Revolution's Aux Interface to the transistor's collector (the left pin in this photo)
  5. The collector also connects to the output pin that goes to the Volume Adjust pin in the Phoenix card (shown here in yellow)
  6. The red wire goes to the emitter, the pin on the right of the transistor

  7. Please note that the two black wires only connect to one another - they DO NOT connect to any other devices on the board!
Making Connections

The four wires at the bottom of the photo go to:
  • black - Revolution's Aux plug - common (black) wire
  • green - Revolution's Aux plug - output "b" (green) wire
  • red - Phoenix card - pin marked either Volume +3V or Volume +5V
  • blue - Revolution's Aux plug - output "a" (blue) wire

The two wires at the top of the photo go to:

  • black - Phoenix card - pin marked ground - it is next to Volume Level
  • yellow - Phoenix card - pin marked Volume level
    IMPORTANT - if you don't connect these wires the interface will not work - note that these wires are NOT shown on the schematic

In the description above I used the blue and green wires from the auxiliary interface - that allows you to increase or decrease the volume with buttons 1 and 2.  If you want to use two other buttons simply use two other wires from the auxiliary interface.

Note that the black wire to the Phoenix card may not be necessary and could cause a ground loop.  If you experience any problems try removing it.


The completed, trimmed board is shown here: