    Here are some circuits how to create a D/A convertor (mono or stereo)
    on your LPT port. The circuits are created by Mark Cox, and are extracted
    from a hardware.doc file written by him.


    HOW TO MAKE A D/A CONVERTER
    ***************************

    A simple circuit for HiFi quality sound needs only a few components (and
    this circuit will work with other software).   It even sounds better than
    a Sound Blaster for sampled output!

    You need:

    IC1 a ZN426E (about 3 pounds) (Ferranti or Plessey are UK manufacturers)

    C1 a 10micro-farad electrolytic capacitor (10V or greater)

    C2 a 4.7micro-farad electrolytic capacitor (10V or greater)

    R1 a 380ohm resistor (5%, 1/8W)

    CON1 a phono socket for connecting a lead to your amplifier

    CON2 a 25 way male D-type connector for your parrallel port

    A bit of 10 way cable - or 10 short wires.

    A +5v supply

                               Zn426e    +5V
                              Ŀ  
                  (2)  D0  Ĵ9     14Ĵ
                  (3)  D1  Ĵ10       
                  (4)  D2  Ĵ11         390
                  (5)  D3  Ĵ12       
                  (6)  D4  Ĵ13     5Ĵ
                  (7)  D5  Ĵ1      6Ĵ       +
                  (8)  D6  Ĵ2      4ĳĴ> TO AMPLIFIER
                  (9)  D7  Ĵ3   7             10F
                               +        (may not be needed)
                                    4.7F
                                         
                  (25) GND  GND



    GETTING A +5V POWER SUPPLY
    **************************

    Catalogues such as MAPLIN (uk) provide simple circuits for obtaining
    a +5v power supply (it only has to be 100mA maximum).  Alternatively
    you could tap +5v off the keyboard connector or use 3 1.5volt
    batteries (or even 4 1.5volt batteries with two diodes in series to
    drop the voltage).  In fact, anything that produces a voltage in the
    range 4.5  5.5 volts. (in fact you can even tap +5v from the game
    port).  Don't forget to connect the 0v of your power supply to the GND
    rail shown.


    ANOTHER D/A CONVERTOR
    *********************

    Here is a circuit to hear mods through the LPT port.
    You will only need 18 1% resistors, 2 capacitors,
    a male D-25 connector and a jack.


          Printer Port:

          signal   pin
                              20k   20k
          D0       2      >İİ0v
                              20k  10k
          D1       3      >İĴ
                              20k  10k
          D2       4      >İĴ
                              20k  10k
          D3       5      >İĴ
                              20k  10k
          D4       6      >İĴ
                              20k  10k
          D5       7      >İĴ
                              20k  10k
          D6       8      >İĴ
                              20k  10k
          D7       9      >İĴ
                              20k  10k  100nF
                                  Ĵ> TO AMPLIFIER
                                           
                                   10k      10nF
                                           
          GND      20     >>
                                  0v


    This circuit is an enhancement of the one that came with MPLAY200,
    so thank you Mark J. Cox for the original design.


    STEREO-ON-1 BOARD
    *****************

    You can use your stereo-on-1 board with other programs that require
    a single D/A on the port as follows:

    Find out what address your port is at (LPT1 = 0378, LPT2 = 0278) and
    add 2 (LPT1 = 037A, LPT2 = 027A).  Go into DEBUG and type
    o 37a,0       (replacing 37a with the port address)
    q
    Then all sound directed to the parallel port will come out of both
    channels.

                                ZN428
                                Ŀ         390
              Ĵ11           6ı+5v
               Ĵ12           7    
                Ĵ13           3NC    
                 Ĵ14                    + 10F
                  Ĵ15           5ĳĶ> Left out
                   Ĵ16                       0v>
      20 >0v       Ĵ1           10+5v 
                     Ĵ2            90v 
      14 >ĳĳĳĳĳĳĳĳĴ4            8    
                              
      11 >Ĵ          ZN428                   + 1F
                        Ŀ      Ķ0v
       9 >ĳĳĳĳĳĳĳĴ11 D7   VRIN 6
       8 >ĳĳĳĳĳĳĴ12 D6  VROUT 7 NC
       7 >ĳĳĳĳĳĴ13 D5     NC 3 NC
       6 >ĳĳĳĳĴ14 D4                 + 10F
       5 >ĳĳĳĴ15 D3    OUT 5Ķ> Right out
       4 >ĳĳĴ16 D2                    0v>
       3 >ĳĴ1 D1     +V 10+5v
       2 >Ĵ2 D0     0v  90v
       1 >Ĵ4 !EN    0v  8
      25 pin male D connector   


      Notes:

      Make sure all the 0v lines are connected together and connected to the
      0v line of your power source.  Also, make sure the +5v lines are
      connected together.  The lines marked 'NC' do not need to be connected.

      If a ZN428 is not available, any D/A with input latches will work -
      the D/A should latch the data bus when pin 4 (!EN) is low.

      ĳ = No connection,  = joined

      The above circuit (Stereo-on-1) is (C) Mark J Cox 1991, 29 Lundie Close
      Stenson Fields, Derby DE2 3AN; and is supplied for personal use only.
      For any other use, please contact the author at the address above. If
      this circuit is abstracted or incorporated into any other document or
      circuit then that document or documentation supplied with that circuit
      must contain this paragraph of text.  Any commercial use where not
      agreed by written contract with the author (Mark J Cox) is prohibited.



      This file is supplied with MEGAPLAY v1.0

      MEGAPLAY is created by Marco Koetsveld
                             W.v. Collenstraat 12
                             3621 CM  Breukelen
                             Holland