SPHINX
Phono Equaliser
11
6. OPERATION
After you have properly adjusted all settings you
may start using the Phono equaliser.
Connect the mains cable to a mains outlet
Switching on
Once you have finished connecting all components,
you can power on the
Phono equaliser
with the
mains switch
O / I
(9).
The LED (1) will blink
red
for some time after which
it changes to
green
(when the Myth setting is
selected it will go
off
).
The
Phono equaliser
is always switched on.
This way the electronic circuits will be kept at
optimum working temperature so you can enjoy
maximum audio quality immediately after switching
on. Additionally it significantly increases the life span
of the component.
Standby
The Phono equaliser may be remotely switched to
Standby by another Sphinx component if it is
connected to the CONTROL IN (3) optical input.
The LED will switch to red.
Switching off
The only way to switch the Phono equaliser off
completely is with the
0 / I
mains switch.
7. THE 78 RPM MODES
When ‘cutting’ a record master for vinyl records the
audio signal is sent (for technical reasons) through a
special correction equaliser: this
in
creases the highs
and
de
creases the lows. During replay of the record
this correction curve is ‘reversed’ by the replay filter
in a phono pre-amp.
The
RIAA
curve is an international standard curve
for 33 and 45 rpm records. This attenuates the
frequencies above 2120 Hz and amplifies those
below 500 Hz (these points are also known as the
‘corner frequencies’ or f
c
).
For 78 rpm records there have been a number of –
incompatible – standards. Research by the Sphinx’
designers showed however that the most commonly
used standards were the
RCA
(2120 and 500 Hz)
and
AES
(2500 and 500 Hz). These actually use the
same curve as the RIAA, so
most
78 rpm records
can properly be played with the normal phono input.
An important (and differing) group was formed by
EMI, Decca and Columbia with f
c
-‘s of 250, 200 and
300 Hz respectively.
That is why the
Phono equaliser
offers the special
78RPM
mode of 250 Hz (as described in
5e
). So
you may also play all these specific 78 rpm records
properly.
In the 78rpm era quality of the audio systems was
much worse than today, especially lacking response
above 4000 Hz. Due to this ‘natural low-pass filter’,
record surface noise, etc. was undetectable.
When you replay these records via a modern audio
system however, you will hear an annoying amount
of surface noise and maybe even a ‘thin’ or
‘scratchy’ sound quality.
That is why the
Phono equaliser
offers the
78RPM
FILTER
mode (as described in
5f
). This special filter
is designed with the help of many listening tests. It
ensures a usable high frequency replay quality with
modern audio systems.
Note
: A special problem are recordings using the
following different standards: ‘old’ RCA, EMI or
Decca. These did not incorporate any HF record
correction!
Playback via a normal system will thus result in
extremely attenuated highs. This is inherent to these
recordings and not caused by the modern replay
systems!
