Manual

109
Microphone Preamplifiers
& Line Inputs
ASP880 features eight impeccably
optimised class-a micprohone preamplifiers.
Featuring a discrete 8-transistor front end,
the mic pre is optimised for 0 to 60dB gain
with an EIN (equivalent input noise) of -127.5
dB. The frontend has high-input headroom
and will be happy to accept any level from
your microphone collection, however for
situations where you reach very hot signal
levels such as drum recording, a switchable
-10dB pad is included on channels 1 & 2 to
provide a -10 to +50dB padded gain range.
Microphone inputs are provided on the rear
panel using Combi XLR connectors - here
the 1/4” Combi Jack connector provides a
padded balanced line input (input impedance
>6kΩ)directlyintothemicprestage.
These Combi Jack line inputs run through
the mic preamp, providing a slightly sweeter
tone (due to the 2nd and 3rd harmonic
distortion in the mic pre) and have access
to all input conditioning functions apart from
phantom power.
Please be aware that the input impedance
switch functions as a variable pad for any
line input signal (a secondary benefit!).
Discrete JFET D.I
(Instrument) Inputs
ASP880 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 tha 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 ASP880 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 plenty of 2nd and 3rd
harmonic distortion (minimum 0.03% to
lots!) ensuring that your instrument has a
rich sound and some c o l o u r!
Hardware Features
CAPTURE GREAT TONE JUST BY
PLUGGING IN DIRECT!