Rather
than trying to recreate vintage tube gear, Pendulum Audio designs
tube processors that incorporate modern, extended-bandwidth,
Class-A circuit designs. Both the MDP-1 tube preamp ($2,495)
and the ES-8 variable Mu tube limiter ($3,495) are 2U, dual-channel
units that feature transformerless outputs, low noise and a frequency
response from below 20 Hz out to 65 kHz (75 kHz for the ES-8).
Classy aesthetics, impeccable front panel screening, positive-action
knobs and switches, gold-plated I/O connectors, and large, illuminated
ANSI VU meters suggest the rigorous attention to quality that
lurks below the hood. There you'll find gold-plated switch/relay
contacts and tube sockets, polypropylene caps, metal film resistors
and custom toroidal power transformers with hum-blocking shields.
On both units, the chassis is ventilated through the top and
side panels.
MDP-1 Tube Mic/DI Preamp
The MDP-1 can be ordered with either Jensen 13K7 transformers
or custom transformers for the balanced audio inputs. (My review
unit had the Jensen transformers installed.) Each channel's audio
path passes through one 12AX7A and one 6922 tube. On the rear
panel, an XLR connector for each channel
accommodates mic inputs and unbalanced 1/4-inch phone jacks service
mic/line DI inputs. These DI jacks have a 1-megaohm input impedance
when a DI input switch on the unit's front panel is set for instrument
input. When this same switch is set for line input, the rear
panel DI input jack's impedance becomes 100 kilohm, and a 20dB
pad is inserted into the audio path. The circuit path is transformerless
for all DI inputs.
Conveniently, the unit's front panel also features DI inputs
on unbalanced phone jacks. When you insert a plug into a front
panel jack, the rear panel DI jack for the same channel becomes
disabled. The front panel DI jacks each have an input impedance
of 10 megaohms for instrument inputs and, like the rear DI jacks,
100-kilohm impedance for line inputs. Depending on how much you
want to load down your electric guitar or bass pickups, you can
plug into a front or rear panel DI input and get a different
sound (due to the differing impedances). I found that electric
bass tended to have a slightly tighter bottom but less top end
"air" when plugged into a rear DI input, as compared
to plugging in through a front panel jack. It's great to have
such flexibility to get sounds.
The MDP-1's rear panel outputs are unbalanced XLR and 1/4-inch
phone jacks, wired in parallel. The transformerless, tube output
stage can handle blazing output levels as hot as +35 dBu. A rear
panel power switch feeds a soft-start circuit that mutes the
audio output and preserves tube life. The three-prong AC cord
is detachable. The MDP-1's front panel is replete with useful
knobs and switches, yet remains very user-friendly. Separate
toggle switches are provided for each channel to enable 48V phantom
power, switch in a 20dB mic input pad, flip the mic signal's
polarity, and switch between mic and DI inputs. An
additional DI input switch, mentioned earlier, optimizes the
DI input for instrument or line sources.
Each channel sports a switched, rotary gain knob-fixed in 3dB
steps-that controls the tube gain stage. The gain range spans
30 dB but varies for each type of input: +33 to +63 dB for mic
input, +20 to +50 dB for DI instrument input, and 0 to +30 dB
for DI line input. Additionally, continuously variable rotary
knobs allow you to passively attenuate each channel's output
level. Besides allowing you to smoothly bring levels down, these
output knobs also serve a creative function. By cranking the
gain knob that serves the tube stage and lowering the output
gain level, you can overdrive the tubes and introduce subtle
distortion. This feature makes the MDP-1
a very versatile beast, allowing you to dial in a variety of
sounds from ultra-clean to slightly funky. I've heard cheaper
units that offer tube overdrive topologies and many make your
tracks sound like bumblebees trapped inside tin foil. The MDP-1,
however, gives you that sweet splatter of harmonics you lust
for.
Yet another rotary switch for each channel allows you to roll
off the low end for mic signals at 10 different corner frequencies
from 20 to 180 Hz, with an 11th setting for flat response. Finally,
a three-way switch for each channel allows you to source the
VU meters to show tube gain (pre-attenuator) or output level
(post-attenuator) or to turn the meters off when you're pinning
the meters. Sourcing tube gain allows you to gauge whether or
not you're overdriving the tubes and by how much.
My first test of the MDP-1 was on male lead vocals. This singer
had a very woolly voice, for which my AKG TL-II was the perfect
mic. But I've never heard my TL-II sound as good as this. In short, the MDP-1 made my solid-state TL-II
sound like an awesome tube mic. The vocals were beautifully articulate,
sweetly scintillating, tonally balanced and clear as a bell,
yet eminently warm. The overall sound was lush, brimming with
nuance and possessing great depth. I got similarly great
results using a Lawson L47MP tube condenser mic on another vocalist.
On acoustic guitar, recorded with a spaced
pair of B&K 4011 mics, I was, again, completely blown away.
The stereo imaging was hands-down the widest I've ever heard
with any mic pre. Transient response was outstanding, offering
copious detail but without a hint of stridency. For comparison
purposes, the MDP-1 was more understated in the upper bass/low
mids than a Millennia HV-3 mic preamp, but, nevertheless, was
much warmer sounding (love that glowin' glass!).
Next, I A/B'd the MDP-1's DI path against that of my super-pristine
Aguilar DB 900 tube direct box - a tough opponent. On electric
bass, the DB 900 sounded cleaner and clearer, with a sweeter
tone. The MDP-1 sounded slightly honky and veiled in comparison,
but also bigger, lusher and more aggressive. Overdriving the
MDP-1's tube stage and daisy chaining into an Empirical Labs
Distressor yielded a bawdy, burpy bass, gushing with overtones.
Next, I DI'd my '62 Strat. Again comparing to the DB 900, the
MDP-1 at its cleanest settings produced a tone that had less
air and nuance but fuller and creamier low mids, making for a
beautifully mellow sound. Overdriving the MDP-1's tube stage
to various degrees, I could get ultra-clean or subtly gritty
tones. Interestingly, overdriving prerecorded ADAT tracks via
the MDP-1's DI inputs (set to 'line') yielded far more subtle
results. And, without overdriving the tubes, the line inputs
sounded basically neutral - nothing added, nothing taken away.
The MDP-1 is an awesome tube mic pre that
also does a great job on instrument DI duties. For the creative
engineer, the topology of its tube gain stage and output level
control bestow tones ranging from ultra-clean to slightly funky.
Outstanding transient response, superior depth, superb spectral
balance, unbelievably wide stereo imaging, extended frequency
response, low noise and a lusciously warm sound make this fully
featured and classy-looking mic preamp a great value at $2,495.
Pendulum Audio, PO Box 339, Gillette, NJ 07933; 908/665-9333;
info@pendulumaudio.com; www.pendulumaudio.com.
Michael Cooper is a Mix contributing editor and owner of Michael
Cooper
Recording in beautiful Sisters, Ore.
