Recording - November 2014 - 42

B Y PA U L V N U K J R .

SBS Designs

SP-1PRO 2UBE Processor

This high-end bus processor uses vintage tubes in a truly new way

The SP-1PRO is a tube-based audio
processor ("Vacuum 2UBE") from a
brand-new company known as SBS
Designs. That's short for Systems By
Shorty. "Shorty" is the nickname of
designer Craig Bernabeu, who has
launched SBS Designs with a former
head engineer at Summit Audio. The SBS
website shows off a growing line of gear
that crisscrosses between the pro studio,
DJ, and home audiophile markets.
The product we are looking at here, the
SP-1PRO, tilts towards pro recording facilities and mastering houses. It's a 2-channel
audio processor that uses a pair of vacuum
tubes to, according to SBS, "sweeten up
and improve the dynamic range of any full
range source."
You might be thinking, "I've seen this
type of thing before." Yes, there have
been many audio processors on the market that run your signal through tubes to
give it warmth and grit. However, this is
nothing like a box that uses tube-based
overdrive to give the illusion of "tube
sound". Let's see what it does instead.
Layout and controls
The SP-1PRO is a 1U 19" rackmount
box, handmade in the USA with a 10year warranty, whose faceplate is done
up in gray with white and red script
nomenclature, a rather 1980s-utilitarian
style. Its seven vintage-style knobs are
painted blue, dark gray and red, with
LEDs for power, clipping and bypass. A
black bypass button and front-panel 1/4"
headphone jack complete the front panel.
The first two knobs are for Low and
High Threshold, each one with a red

RECORDING November 2014

overload light. These controls affect both
channels equally. The next four knobs
form the Tube Mode section. Here channels 1 and 2 each get a Low and a High
control of their own. Finally we have the
bypass button and blue LED, then the
headphone output section.
This headphone section lets you hear
what the unit is doing in great detail, and
can also act as an additional headphone
output for your setup. Probably owing to
Shorty's background in dance club system
design, this may be the single loudest
headphone output I have ever heard.
Moving the Volume knob over halfway
was enough to overdrive my beloved
AKG K271 Studio headphones... you've
been warned!
The rear panel is made of blue plexiglass and features the two inputs, balanced XLR-1/4" Neutrik Combo jacks, and
the two balanced male XLR outputs. The
last control on the rear is a recessed flathead screw pot, which adjusts the overall
input level-more on this in a second.
Inside look and some specs
Taking the top off shows off a beautiful
and impeccably laid out circuit board
design, complete with two large toroidal
transformers, a pair of 12AU7c tubes,
and no VCAs in the signal path. There
are also a few internal switches and pots
that you may need to initially adjust to set
the correct levels for your system.
A pair of toggle switches changes input
levels between +4 and -10, and near the
front are a pair of small board-mounted
trimpots which set the output level of the
effected signal.

From the website the SP-1 Pro's specs
include a frequency response of 12 Hz to
30 kHz (±0.1 dB, 2 dB down at 8 Hz
and 44 kHz), max line level in of +21
dBu depending on the rear-panel pot setting, max line level out of +19 dBu, Total
Harmonic Distortion of 0.03% through
the solid state circuits, and 0.3% secondharmonic distortion through the tubes.
But what does it do?
The SP-1PRO is essentially a pair of
dynamic low-frequency and high-frequency
expanders designed to add detail and
dynamics. From that description, it would
be easy to think of it as a tube version of an
Aphex Aural Exciter or Big Bottom
Harmonic Synthesizer, but it's neither.
The SP-1PRO enhances and even clarifies the signal, but unlike the abovementioned units, it does not add anything new
to your audio. It's almost like a classic
expander with EQ skills, one that only adds
content when a certain threshold is hit. It
reminds me of my experience with the Kush
Audio Clariphonic Parallel EQ (reviewed
March 2013) that takes an existing signal,
isolates certain tonal content, and then
blends it back in with the original signal.
The website states that "the low & high
frequencies are separated, expanded,
then mixed back together and then sent to
the tube output buffers." How the tube
reacts depends on how the threshold is set.
It starts with a pair of optoelectronicscontrolled low and high threshold controls. These thresholds determine when the
two expanders will trigger, just like a
threshold on a compressor would. The difference is that like a shelving EQ, the

Recording - November 2014

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