Inspired by the ever-colorful Fletcher of Boston-based Mercenary Audio,
the Great River MP-2NV is a stereo mic preamp based on the Neve 1073 module.
Like a real Neve mic preamp, the MP-2NV has a rotary switch for coarse
gain and the equivalent of a fader to trim the gain. (The gain switch
actually dials in various combinations of amplifier stages, gain and input
Input Gain for the MP-2NV is in 5-dB steps, Output Gain is continuously
variable from –20-dB through unity to +10-dB plus metering
for both stages. As such, it is possible to purposely run the preamp
hotter than the output amp, or vice versa. I found this extremely helpful
when recording drums using a single pair of Marshall MXL-2003 large-diaphragm
condenser mics (in X-Y about 3-feet off the ground and about 3-feet in
front of the kit). With the "Fader" set to unity gain I allowed 4~6dB of
headroom, easily readable via HEDD’s metering, which is in 1dB steps all
the way down to –10dB FS.
THE ANIMAL RUMBLES
Drummers being the animals they can be, repeated "overs" during moments
of excitement can be tamed by turning down the output gain and cranking
up the input gain. Again allowing 4~6dB of headroom at the converter,
the new settings eliminated all "overs" and, with drums at least, there
was no sign of undesirable distortion. How cool is that? Of course
you also can be "nice" to the MP-2NV. On vocals and cello I found
it full-bodied — round on the bottom and crystal clear on top.
It is common to see Neve gear being abused — I always felt sorry for
the mechanical VU meters because people "buried" the needles. Maximum
output level is +27dBm, easliy 10-dB more headroom than any mass-produced
IC opamp-based preamp or mixer. At the other end of the spectrum,
the Great River MP-2NV has 15- to 20-dB less noise than its vintage ancestor.
By consolidating all the plug-in cards onto one circuit board, and using
low-noise components throughout and a very quiet power supply, the signal-to-noise
ratio is in excess of 105dB at the 30-dB gain setting and 96-dB at 60-dB
When driven hard, Class-A Neve circuits — and the transformers that
interface them — react to transients like peak limiters. There is even
a dynamic recovery time, although that's not easy to show in print. You
can see what happens to "static" sine waves in Figure-2a. Note that
each stage behaves similarly, clipping only half the wave first.
Assuming your signal "goes there" only momentarily, the effect is must
less obvious than with any IC opamp, where symmetrical clipping is "instant
nasty." In reality, the color starts before any obvious
clipping occurs. In Figure-2b, the third octave display of
the NTI MiniLyzer indicates
not only the second harmonic, but a cluster of harmonics starting with
Figure-2a: From left to right, a "clean" sine wave with distortion
below .01%. Next, 1% distortion of the Direct Input FET is barely visible
on the bottom of the wave. At 2%, the bottom edge of the Preamp Stage is
clearly flattened, while the top is just beginning to get leveled. Finally,
the output amp is taken to 5% distortion and still doesn’t show any signs
of clipping the positive excursion of the wave.
Figure-2b: A 3rd octave analyzer shows the spectral
content of the MP-2NV output amp driven to 2% distortion. This is not an
easy thing to do as the maximum output level is +27dBm!
Three other features make the MP-2NV an asset starting with the Direct
Input. A traditional mic pre / active DI connects the instrument directly
to the first amplifier, bypassing the input transformer. Fletcher insisted
on using the input transformer for additional color and, as unconventional
as that might be, Dan Kennedy’s clever and effective solution was to put
a FET impedance converter in front of it for Hi-Z happiness — the perfect
match for passive bass and guitar.
My Univox P-Bass copy sounded surprisingly round through the direct
input. It was neither clangy nor unnecessarily subsonic. While there is
no metering to indicate FET overload, doing so is pretty obvious. I simply
turned the level control down on the bass. Again, manipulating the input
and output gain controls can massage the tone range, which is enhanced
by good technique and a consistent touch. (I’m still working on that.)
To further trick out the MP-2NV, the input transformer has multiple
windings, just like the Neve modules, only now the input impedance switch
— which provides the correct impedance range for 50- to 200-ohm microphones
— is on the front panel. This is cool if you have ribbon mics plus
the "50-ohm" setting loads the FET for a different sound. (The input
impedance range is actually 300- and 1200-ohms.)
Output termination rounds out the options. Many people, accidentally
or not, run Neve modules un-terminated, the resulting sound can be brighter
due to transformer ringing. (See Figure-3.) By placing the
option on the front panel, users can run either way and not have to futz
with resistors or ever have to go to the rear panel for anything other
than Input, Output, Insert and Power connections. This also changes
the overload characteristic of the output amp.
Figure-3: The effect of termination (and lack of same) on a 1-kHz
square wave. The un-terminated "spike" indicates transformer ringing that
produces a 7dB boost at 50kHz.