Advertisement
frequency characteristic, you may
notice it for the fir t
time when using
the Dolby System in the Model lOOA.
In
many instances, such
non-linearitie
go
unnoticed
without the Dolby
ystem.
One
reason
that the Dolby
System
makes
them
audible
has
to
do with the removal
of
the tape hiss:
if for example your
recorder had
a gradually
sloping-off
in the highs, the hiss on the tape would tend
to mask the rolloff, due to the psychoacoustic phenom-
enon we
discussed
in answering number 3, above.
By
removing the hiss
by
means of the Model lOOA, the
noise
no longer masks the
rolloff
which
may
be there.
The
obvious solution
to this problem is
quite clear-
the recorder
should
have
a
flat high-frequency
character-
istic.
It
is
highly
unlikely
that
any irregularities
which
might now
exist in your tape
recorder
are
due to the
quality
of
the recorder itself
(assuming its
heads
are
not
worn). More often than
not,
they
are
due to the recording
bias current
not being
optimum forthe
kind
of tape
you're
using.
The
amount of bias
required
changes significantly
with
the type
of
tape,
most
distinctly between
standard
formulations
and
the low-noise
type.
By the
way,
we
have
found audibly incorrect bias setting even on
those
recorders
which are supposed
to be
factory-adju
ted
for a particular
kind
of
tape.
The solution is
both
simple and inexpensive. If you
wish
to
assure yourself
that
you' re getting
the last
ounce
of performance of which your
recorder
and
the Model
lOOA
are capable,
then
take your
recorder,
and a
reel
of
the type of
tape you intend
to
stick
to
using,
to
a com-
petent
tape recorder
technician.
A
k him to
adju
t the
bia
of your
recorder
for the ft.attest
possible
high.-
frequency
response.
In
order
to
show you what effect incorrect
bias
can
have,
on
the next
page we've provided frequency
respon
e curves of a good home tape recorder at
3% ips.
Figures 1
and 2 show variations due to improper bias for
a given
kind
of
tape
which are
large
enough
to
be audible
when
comparing source
to tape. Figure 1
shows
the
effect
of too little bias
current
for the
tape
being used,
and
figure
2
shows what
happens
with
too much bias.
Figure 3
shows
the
results of
optimum bias,
and
indicates that
a
careful source-tape comparison would
reveal
no audible
change in frequency
respon
e
between
source and tape
when using the Dolby
System.
5. What kind of tape
should be
used?
In
order
to
get
the best possible
performance,
we
recommend
that
you
use the best
quality tape.
Along
these lines we have two
specific sugge
tions.
First,
we recommend
that
you avoid
the unbranded
"white
box"
tape available at
many
dealers.
Although
some of
this tape
can
be quite
good, you
take too big
a
risk
18
in
u ing it. The problems
of
the
poorer
type can be
both
mechanical,
such a
the
coating'
flaking
off and
causing
undue head wear,
and sonic,
such a audible
drop-outs.
Of the first quality tape
available,
we
uggest that
you
try
the
so-called "low-noise"
formulation .
This
kind
of
tape is
capable of a 3
db
improvement
in
ignal-to-
noise ratio, and every bit helps, particularly
at
low
peeds.
There
are
also
the very
newest
types
of
low-noise
tape which can be
even
better.
The slightly
higher cost
is
overwhelmingly offset
by the fact that if
you u
e 3%
ip for most of your
recording,
as
we
predict
you
will
with
the Model l OOA,
your
raw
tape costs
will be
cut in half.
Keep
in mind one
thing,
however: The high-
frequency characteristics
of
low-noise tape are
different
from
standard
formulations, and
so
require a
different
(higher)
bia
etting for
flat high-frequency re pon e.
More
and more tape
recorders now
come
through from
the
manufacturers
biased
for
low-noise tape, although
it'
a good
idea to
check for correct
bias
setting.
If
you
wi
h
to
change tape
formulations
,
we
suggest
that
you
have
the bias
checked as we discussed
previously.
You should
then tick to the
type of tape you've
decided on.
Remember
finally
that
if you change
formulation,
you should also
redo the
Record
Calibration of
your
recorder and
the Model lOOA.
6. What speed should be used?
ince we
don't know
what
recorder
you'll
b using
with
the Model
lOO
A, we
can't
tell
you what speed
you'll
find best
suited
to
your
purposes. We
can
warn
you
of
one
thing, however-
in evaluating
what happens
at
low
speeds with
the
Model lOOA,
don't let
your prejudice
against slower speeds influence your
listening. Listen
with an open mind.
If you
have
one of
the
better
home recorders
of fairly
recent manufacture, which
is
properly adjusted,
and
which is capable at
3%
ips of
record response up to 13
or
14
kHz,
a
mo tare-then
we would
predict the follow-
ing
based
on our own experience with
uch
machines:
At
3% ips,
the
tapes
that
you
make will
probably
be
indistinguishable from
the best
tape ,
records,
or "Ii e"
FM broadcasts that
you can
find to
copy.
With this kind
of
performance,
beli
ve us when
we
say
that there would
be
no
advantage
in
using a faster speed except for live
recording.
If you
have
such a
recorder,
very good microphone ,
and a
desire to
capture more of the
dynamic
range oflive
music
than
you ever dreamed po
ible
with home equip-
ment,
then
we suggest that you
try
using 71h
ip .
In
term
of frequency
respon
e
,
noi
e, distortion,
and
mo
t
im-
portantly
dynamic
range
, the tape made "live"
with
th
Advertisement
Need help?
Do you have a question about the 100A and is the answer not in the manual?