1
Welcome to the first batch of my
technical tips. These pages are not
just for hardware problems but also
software and programming difficulties.
Send your problems to,
Andy Nibbs
Tech-Tips
2 Seaview
Hoylake
Wirral
L47 2DD
These pages include:
Explaining how sound samplers work
Discussing MIDI interfaces
SOUND SAMPLING is performed by a small
and cheap hardware device called a
sampler and this simply converts the
Analogue audio data into Digital
data suitable for use by the computer.
ANALOGUE data can vary infinitely
and is so not defined in precise
steps but as a voltage.
DIGITAL data is represented by
either ON or OFF , HIGH and LOW in
digital electronics or 1 and 0 in
computing. When strings of these 1s
and 0s are strung together they can
form numbers.
...This conversion from Analogue to
digital is performed by an aptly named
Analogue to Digital Converter chip,
ADC for short. The BBC has a build in
ADC for analogue joysticks but this is
too slow for the frequencies in sound.
The computer using the sampler must be
driven by suitable software which takes
a sample and saves it to disk. Once the
sample is saved to disk, your own prog
can load it and use a little machine
code routine to play back the sample.
The BBC's sound system however leaves a
lot to be desired when playing back
samples and playback quality can be
disappointing.
COMMERCIAL SAMPLERS:
I personnally have not heard of any
commercial sound samplers and so
asked a friend to build me one. The
parts for this came to around £20 and
I am writing software for it for the
highest quality sounds possible! Sound
samples eat memory of course.
SOFTWARE:
I have written a program to collect
samples in a sequence and play them
back, this is for the MASTER128 only
and is on ISSUE 3 of my MasterDisk for
£1.50 and comes with some samples.
Q. Can DIMs be used in PROCedures
A. YES.
To connect a MIDI instrument to a BBC
you need a MIDI interface which plugs
into the 1MHZ bus. You can obtain an
interface for around £80 from EMR. Who
also provide plenty of software and
expertise to support the system. EMR
are on 0702 335747. Umusic also supply
MIDI hardware and software and are on
081 788 3729. Hybrid make a MIDI
interface to link in with their Music
5000 series, this is the MUSIC 2000
phone them on 0223 420360.