Focusrite ISA 430 MKII User Manual page 22

14. What is 'split mode'?
Split mode allows the ISA 430 MKII to act as separate
processors at the same time, handling totally separate audio
signals. So one channel of audio can be routed through the
EQ sections, with a second, discrete audio channel being
routed through the dynamics sections. Furthermore, if the
mic pre-amp is also being utilised to output direct to a
recording format as well as the ADC dealing with 2 further
signals, the unit is acting as four separate processors at
once!
15. Can I route any EQ sections to the
dynamics?
Yes: the hi- and lo- pass filters, the low-mid and hi-mid
parametric EQ, and the hi- and lo- shelving EQ can all be
routed independently to the sidechain of the compressor,
or to the sidechain of the gate. This means that you can
control the action of the compressor the gate from any
individual section of EQ ('frequency selective compression').
Also, you have a 'listen' button in the compressor, gate and
de-esser sections, which allows you to monitor whatever is
feeding the sidechain of each section so that you can easily
hear and tune the frequency you want to trigger each
dynamics processor. There's even a separate 'listen' LED by
the main meter to warn you that you are listening to
something other than the main output – like a 'PFL' warning
light on a mixing console. The VU meter can also be
selected to view the sidechain for additional control.
16. Can I use the ISA 430 MKII as a 24-
bit/192kHz stereo A/D converter?
Yes – the external input, plus the line input (bypass on) or
the ADC inputs can be used as a stereo feed to the optional
A/D converter. They also pass through the soft limiter
before reaching the A/D, preventing digital clipping.
17. What if I want to use the mic pre-amp in
isolation?
There's a Post-Mic Pre-output which allows you to take
signal out of the ISA 430 MKII from a point immediately
after the mic pre. Using the ISA 430 MKII in this way
provides a very short signal path to tape, for ultra-clean
recordings. Also, connecting the Post-Mic Pre-output does
not interrupt the signal flow from mic pre-to EQ, dynamics
etc, so a direct feed to tape can be achieved whilst
simultaneously allowing processing of the same source
signal.
18. The Air switch sounds great but what's
actually happening to my signal?
This feature increases the impedance effect of the
transformer on high frequencies, adding further "air" to its
sonic quality. It does this by including an inductor circuit
into the secondary of the transformer, giving the pre-amp
an input impedance that varies with the frequency, having a
smaller voltage drop at the top-end. So, additional clarity is
introduced by the interaction between the mic and pre-amp
alone, without EQ.
19. What if I experience problems with the gate
'chattering'?
The ISA 430 MKII is equipped to deal with this – simply
pressing the Hyst button, which introduces hysteresis,
solves the problem. Gates sometimes 'chatter' when the
source audio is just above or just below the threshold level,
as the gate is constantly trying to open/close/open/close etc.
Hysteresis reduces the dB level at which the gate closes
from (e.g.) -55dB to -65dB. Thus even if a signal is
modulating whilst fading out, the gate is prevented from
'chattering.' Since hysteresis is non-destructive in terms of
having no other effect on audio, the Hyst button should be
left on most of the time when using the gate.
20. The limiter is described as 'soft limiting'
What does that mean?
Derived from the groundbreaking soft limiter featured in
the ISA 428 Pre-Pack, the opto-circuit has different ratios as
it approaches peak 'full scale' level (0dBFS), whereby the
ratio becomes infinity:1. This creates a softer limiting effect
but still ensures that the maximum level isn't exceeded.
21. How does the de-esser work?
The de-esser uses Focusrite's proprietary phase invert
technology. Once the user has selected the frequency at
which the de-ess is to occur, the ISA 430 MKII generates a
180º out-of-phase signal at that frequency which cancels the
specific frequency selected at the moment it occurs,
without having a negative effect on other related
frequencies.
22. When I travel internationally can I take my
ISA 430 MKII with me?
No problem. The power supply is a multi-tap design, so all
you need to do is turn the fuse holder around to change the
voltage to match whichever country you are in.
23. Why is a Superclock/x256 input important?
If a customer has a Pro Tools TDM system and wants to
lock it to an external analogue multi-track (s)he needs a
USD (Universal Slave Driver, Digi's premier sync box). This
box looks at the speed of incoming timecode and then
varies the Superclock frequency up and down to match.
Therefore, because the Superclock is basically 256 times the
speed of word clock, the playback or record speed of Pro
Tools is matched (very accurately) to the machine's speed
and any attached Digi. Audio interfaces will also be adjusted.
If the customer now wants to record off the multitrack into
Pro Tools via an ISA box, they have a problem if they don't
have a Superclock input because the ISA would be running
off its own internal crystal and not looking at the speed
information being calculated by the USD. It would be
running at precisely 44.1 or 48k with a very high stability,
however the analogue deck would be 'wowing and
fluttering' all over the show.
Therefore by providing a Superclock input, you can use the
USD to clock the ISA module, and therefore lock the ISA
up to anything you are locking Pro Tools up to.
Also any TDM Pro Tools equipped with a USD can be
switched into varispeed mode. Using Pro Tools' Session
Setup window, a slider allows the overall speed of Pro
Tools to be moved up or down. This is achieved by telling
the USD to adjust its internal clock and therefore its
Superclock output. This varied Superclock output then
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