                            EARS FOR YOUR CPC
                            =================

HOMMADE A/D-CONVERTER
Multimedia - everywhere you can hear that word. What always is meant with this
expession is digitalised speech, noise or sounds. But the CPC can do that,too.
Our circuit plans for a small soundsampler will help you to get a mini recor-
ding studio. And if you have the "Digiblaster" [*available on my Homepage*]
you can play your sounds with a for the CPC very good quality.


One of the wishes all computerfreaks have is to get hearable sounds out of
their computer. The CPC has to do that the 3 level soundchip, with that you
only can get good sounds with highlevel source-code. It is easier to catch
with a sampler real sounds, edit them, if you want, with your computer and to
play the sound at the right moment in your program. With that possibilty it
is easy to describe why the Amiga is known as a sound-wondermachine.
The quality, that you can get while sampling or playing, depents one a lot of
facts. A very important one is the used hardware. Also not to neglect is the
samplingrate. For the dynamic the bitsolution plays a big role - if you use
16bit for sampling you get 65536 values between no sound and maximum volume.
So 16bit are better then 8bit with only 256 values.
Sampling means that you read the values regularly. The used IC in our plan
outputs the value as a 8bit number. With that you can get 256 values. For
every sampled moment a byte is used in the memory of your CPC. With that you
can calculate what the maximum sample is:
If you want to sample music you have to get frequencies about 8000 Hz. They
have to be read three times a period, that is a samplingrate about 24000 Hz.
So you need 24000 bytes a second. With a free memory of 40000 byte that is
1.6 sec - very short.
But if you only want to sample speech you have a maximum frequency of 2000 Hz.
With a sampling rate of 6000 Hz you can record 6 sec speech.


The circuit is build very easy: The sampler consists of 24 cheap elements.
But this have also a black side: Because it is not adress decoded you should
not use other extensions. If you use known free I/O ports you can prevent any
crashs.
You can build it with the plan which is in the graphik-file.
Der NF-transmitter is a well known component. You can get it in all elektronik
shops. You can also get them in old transistor radios.
For power you need 5V which you can get from your monitor. The input port of
the circuit, directly at the transmitter, is connected to your mic.
If you've build the circuit you have to look if there are not wanted connections.
Then connect the circuit with the extension port of your CPC and provide it
with your power supply. After switching the computer on you should see the
normal message if not turn it off and controll your circuit again.
If everything is alright you can connect the "Digiblaster" to your printer port
Now load and run the program DIREKT.BAS, you have to hear all what you get
in of your sampling circuit out of the "Digiblaster". If you don't hear
anything try to raise the volume. If that doesn't take any effect you have
to search for errors on the circuit.
Now you can try to use these listings:

DIREKT.BAS: samples sounds and play them directly with the Digiblaster;
=========== you can use this to test your circuit and to choose the volume

DIREKT.ASM: sourcecode of DIREKT
===========

OSZI.BAS: shows the sampled sound graphically verarbeitet jeweils einen
=========

OSZI.ASM: sourcecode of OSZI
=========

RECPLAY.BAS: samples speech or music and outputs them later on the Digiblaster
============

RECPLAY.ASM: sourcecode for assembly part
============

                                                            Matthias Vogl/jg

List of used components:
========================
1 IC            ADC 0804
8 Diodes        1N4148 or other (D1-D8)
1 LED red                       (D1)
4 Resistors     10k             (R2,R3,R4,R6)
1 Resistor      1k              (R1)
1 Resistor      330             (R5)
1 Capacitator   150pF           (C1)
1 Contacter (release if you don't press it) (S1)
1 NF transmitter                (T)
1 Connect       6mm (5 Volt CPC)
1 Plug          6mm (5 Volt CPC)
1 Centronics plug 50-pol (CPC 6128) or mainboard plug 50-pol (CPC 464,664)
  for extension port
1 shaded cable (to your signal)
1 plug for your music signal

[*I hope that you understand my expressions. I don't know much about the
spelling of electronic components in english*]

----------------------------------------------------------------------------
original : Matthias Vogl and Jrg Gurowski
copyright: DMV-Verlag 1992
from     : CPC-AMSTRAD International 8/9'92
converted: 1996 Tim Riemann (TCS-Software@t-online.de)

Whether the author nor I are responsible for defects with your hardware.
