ZX-News #16 26 ноября 1996

Железо

Covox - The description and diagram Covox'a. Covox'a connection to Scorpio. Covox'a connection to the amplifier.

           Super digital music



          (C), Alexander Mayorov



             Covox. Part II.


  COVOX - it is nothing like the most common digital-analog 
converter, for short - DAC. He is engaged in that converts data 
from digital form into analog.



  Appears at the DAC output voltage,
proportional to the number filed at the entrance
DAC. Feeding the DAC the various numbers, we can
generate sounds of different frequencies (depending on 
processor speed) and different volume (depending on the bit 
DAC). In our case, there are 256 levels of loudness and the 
maximum frequency depends on program, and the CPU clock 3.5Mgts 
can reach 150 kHz .... 


  In addition to the simplest scheme COVOX'a there is a 
so-called SounDrive - it may other than the four COVOX'a - two 
on the left channel and two on the right ... 


  Generally speaking, the ZX already has three ADC
(This volume controls AY'shki), but they
have only 16 shades of volume and time
access to them is too great. Although Digital
Music on AY sounds good, but even single-channel COVOX sounds 
better! (Imho) 


  Well, now for the scheme COVOX'a.


  The cheapest and simplest is
scheme based on the resistor matrix R-2R:


                            > SOUND


    C0 R2 R1

                          0.1Mkf



    C1 R2 R1



    C2 R2 R1 Resistance

                      resistor R2 in

                      twice

                      than the resistance

    C3 R2 R1 resistors R1


                      The less resistance
                      resistance, the thunder
    C4 R2 R1 Th sound, but the pain
                      above the noise!


                      The optimal

    C5 R2 R1 is:


                      R1 = 7.5 K

                      R2 = 15 K

    C6 R2 R1



    C7 R2 R1



  Signals C0 ... C7 are removed from the output of the printer 
(CENTRONICS). 


  The inclusion of DAC chips instead of the matrix
R-2R is not quite justified, because despite the simplicity of 
(m / s ADC + m / OC) is required to submit a lot of stress (+5, 
-5 or -15, +10.24 ...)



  And the fact that the matrix R-2R creates some
distortion - the use of resistors
7.5K/15K these distortions completely invisible.


  If your computer has no printer port, then collect the 
following scheme: 


                       555IR23


                    13 D RG Q 12

      Z80/14 R 0 0 C0 D0

              And 17 16

      Z80/15 H D1 January 1 C1

              A 18 19

      Z80/12 D2 February 2 C2

              A June 7

      Z80 / 8 A March 3 D3 C3

              H 2 March

      Z80 / 7 N D4 April 4 C4

              Since 14 15

      Z80 / 9 H, May 5 D5 C5

                     May 4

      Z80/10 D6 June 6 C6

                     September 8

      Z80/13 D7 July 7 C7


          \

      A2 11
Z80/32 / C


      __ \ 1

      WR E
Z80/22 /

                        October 1920

      ____ / 5

      IORQ
Z80/20 /


         KD512 2k



       Port address COVOX: FBh (251)



      Connecting to the Scorpion ZS-256:

      -----------------------------

  Signals C0 ... C7 are connected with contacts
CENTR0 ... CENTR7 at the system connector. In
Basically, this is possible and limited, so
only "play" only those programs
that allow you to choose a port that is connected to COVOX, 
such as adapted by COVOX editor of Digital Studio. 


  Address Skorpionovskogo port: DDh (221).


  In order to play ALL Mouzon, you need to
a little more work:


                Variant_1:


         cut

            \
D55/14 x D10/11


            1

               March 1 555LL1

            2
Z80/32



                Variant_2:


         cut

            \
D55/14 x D10/11


            /

                      2K

            \


            /
Z80/32

            \

         KD512



  The only difference between these two
options that the for 1 is required
melkoshema, and for the 2 nd - only two diodes
and a resistor ...


  (The numbering scheme corresponds to the chip
NGOs Graphics-M)


    COVOX'a connection to the amplifier:

    ---------------------------------

  Exit "sound" can be connected to a separate amplifier, and 
can and already connected to AY'shke the following scheme: 


            off o

                /

               /

              / O Left


 Covox o

                /

               /

              / O Right


              on


      Installing a toggle switch pursues

              a dual purpose:

 - No toggle switch for the printer

   will be distributed to "rattle"

 - The translation toggle switch to position "on"

   power switches to single-mode


  And give the signal from Covox'a directly to
power have, because the volume
sound Covox'e low ...


  That's it. Collect COVOX, and run
Application of music for him.


  Make the sound louder, turn off the 'slows down' and 'turbo 
mode' and enjoy the Super Digital Music! 

P.S. Here is the Mouzon, who in an application
cool so that the sound is not unlike the Sound Blaster'a! The 
sound is so clean that just can not believe that ZX is playing! 
Everyone who has ever listened to him, immediately gathered 
himself easy shemku and a few days (and some even

night) listening to him, phoned all his
friends and acquaintances invited pisishnikov
a visit and pisishniki dragged along with them, because even on 
a PC takoe meet infrequently! It is a pity that the guy who 
wrote it went on the Amiga, taking with him (for how long;) 
original algorithm for mixing and its unfinished music editor 
... 


        __________________________