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
...
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