Audient ASP800, Руководство пользователя

Страница: 7 / 16

10 9
HARDWARE fEATuREs
Discrete JFET D.I.
(Instrument Inputs)
ASP800 features two discrete Class-A JFET
D.I inputs (Channels 1 & 2). Plugging into
these jacks will automatically select the D.I
signal over the signals present at the rear.
Why JFET?
Junction Field Effect Transistors are known
for their sweet tone and tube-like properties
when overdriven. You will often find JFETs
used in guitar pedals and such for this very
reason. They sound good and “can” provide
just a touch of sweetness and larger than
life tone. JFETs also have a very high input
impedance (often approx. 10
12 Ω) and
this makes them ideal for buffer circuits
that do not load down the source device.
In the case of electric guitars or basses with
vintage style passive pickups, the output
impedance of the instrument can often be
6,000 to 40,000Ω, depending upon volume
and tone pot positions. Typically we should
provide a load that is 10 times the source
to create a true bridging system. Therefore
we need at least a 400kΩ load to get the
most signal and tone from our instruments.
It should then come as no surprise that
most classic valve guitar amplifiers have a
very high input impedance - 1MegΩ!
We designed the JFET input on ASP800 to
have a 1MegΩ input impedance and thus
match the loading effect found on classic
guitar amplifiers.
This ensures you get the most tone from
your instrument and when pushed the
JFET
circuit will provide a touch of 2nd and 3rd
harmonic distortion
, and with the option of
adding HMX and IRON to your D.I. channels,
ASP800 is not short of features that can
provide your instrument with some
c o l o u r !
CAPTuRE GREA
T TONE J
usT BY
PLuGGING IN DIREC
T!
Input Conditioning
In order to correctly condition input signals,
ASP800 pr48V Phantom Power
and -15dB PADS on all inputs, as well as
polarity reversal on the first two inputs.
1. Phantom Power
Phantom power can be supplied on a per
channel basis by pressing the +48V switch.
This supplies power to your microphones at
48V ±4v @ 10mA per channel and is suitable
for any phantom powered condenser mics,
or ribbons with on-board active head amps
etc.
2.
ø
Polarity Reverse
Polarity reverse (180 degrees) can be
applied on the RETRO channels to ensure
that multi-mic setups sound as full as
possible.
ALWAYS REMEMBER TO CHECK PHASE.
3. -15dB PAD
Each channel on ASP800 features a
-15dB attenuator, designed to maintain
source and load impedances and offer an
inaudible attenuator from a tonal point of
view. Reducing the signal level from very hot
microphones by 15dB will provide immense
headroom when tracking loud sources.
Checking Phase
To check phase coherency on multi-mic
setups, first always use careful microphone
placement and then press the
ø
switch on
the channels to find the fullest, most solid
low frequency representation of the source.
On drum kit recordings typically you may find
either the kick drum out of phase with the
overheads, or the underneath snare mic out
of phase with the top snare mic etc, so move
mics first and then use the polarity reverse
switch to find the best compromise.
180 degrees out of phase = cancellation
1.
2.
3.