Since releasing the Prophet ’08
(reviewed Nov. ’07), Dave Smith has been
on the roll of a lifetime. His follow-up, the
Mopho (reviewed Jan. ’09), brought massive
analog sound to earth at a price
almost anyone could afford, and still sells
like hotcakes. Now, Dave has taken the
monophonic Mopho, expanded it to fourvoice
polyphony, kept the book-like size,
and made the thing multitimbral.
Click here for audio example.
Big, fat, juicy analog sound. Direct USB
control from computer yields very tight
timing. Multitimbral mode means the
Tetra is four Mophos in one box. Twopart
splits/layers are savable per patch.
CONSFour-part multitimbral mode is a global
toggle, not per patch. Designing your
own sounds from the front panel is a
tad fiddly. No power switch.
$879 list/approx. $800 street,
Click image above for larger, numbered version.
1. Four dedicated knobs control cutoff, resonance, attack, and decay/release — usually the four most-tweaked settings in any patch.
2. These four knobs are freely assignable, and the factory patches do a great job of exploiting them.
3. What was a program/global switch on the Mopho now includes a third mode for the Tetra’s combo presets.
4. The “Push It!” button triggers sounds or sequences, and is flanked by a semi-circle of LEDs that indicate which voices are in use.
5. Tetra’s back panel ditches the Mopho’s audio input in favor of separate outs per voice, a Poly Chain connector for turning multiple units into one big polyphonic synth, and USB for connection to your PC or Mac.
6. An included universal AC adapter comes with plugs for every country — nice. Like the Mopho, there’s no power switch, so you unplug it to turn it off.
The Tetra is just a hair bigger than the
Mopho, and side-vented for cooling. On
the back are four discrete outputs for each
of the voices. Outputs 1 and 2 are a stereo
mix when nothing’s plugged into 3 and 4.
There’s also a nicely-amped headphone
jack and the wonderful Poly Chain connector
for adding more Tetras (or Prophet
’08s) to increase polyphony. Tetra is also
the first real analog polysynth to include
MIDI-over-USB, and the timing is slammin’ —
the improvement over using a regular MIDI
cable and interface was especially noticeable
when lining up Tetra sequences with
parts recorded on soft synths in my computer.
The USB port doesn’t stream audio,
so you’ll need an interface to record Tetra
audio into your computer.
As with the Prophet ’08 and Mopho, voices
consist of two oscillators, a fully resonant
lowpass filter, four LFOs, three envelopes,
four step sequencers, and an arpeggiator.
Oscillators. Each oscillator includes sawtooth,
triangle, and variable-width pulse
waveforms, along with a triangle-saw
hybrid that sounds like a muted saw with a
tad more beef. Like the Mopho (and unlike
the Prophet ’08), each oscillator sports its
own sub-oscillator, which gives it way more
bass than the Prophet. There’s also a noise
generator for whipping up whooshes and
You can hard-sync the oscillators for
those metallic squawks the Cars made
famous. Naturally, each oscillator includes
coarse and fine tuning, but with an extra
twist: oscillator “slop.” Turn this up, and the
tuning drifts in real time for a more vintage
analog sound. For more extreme pitch
experiments, there are individual glide
amounts for each oscillator as well. To
ratchet up the heat even more, a feedback
input in the oscillator section routes the
audio from the left channel of each voice
back into the filter section, and between
the feedback gain and feedback volume
settings, you can dial in everything from a
touch of grit to a wall of filth.
Filter. This really defines the modern
Prophet sound. Tetra’s filter is lowpass
only, but it has two- and four-pole modes.
In four-pole mode, it’s thick, warm, and
creamy. In two-pole mode, it’s a bit buzzier,
with more subtle resonance. There’s also
an audio mod parameter that delivers FM
based on the output of oscillator 1. This is
great for everything from grit to squelchy
ring-mod type effects.
Modulation. Three envelopes, four LFOs,
four step sequencers, and a truckload of
destinations make the Tetra extremely well
suited for creating complex sounds with
abundant rhythmic and tonal changes. Unlike some other analog synths, both vintage
and new, the envelopes have a lovely
snap to the decay segments, thanks to
Dave’s care in designing their curves.
The four LFOs include triangle, positive
or negative sawtooth, square, and random
options, as expected. They can sync to
tempo for rhythmic effects, which sound
especially tight via USB. When the LFOs
aren’t synced, their rates cover an
extremely wide range, extending well into
the audio realm, which delivers even more
FM and ring-mod nastiness.
Step sequencers. These are a total
knockout. Sure, they can embed TB-303-
style note riffs in your patches, but that’s
barely scratching the surface. Each of the
four sequencers can drive almost any Tetra
parameter. All the usual pitch, cutoff, volume,
and pan options are present, but
things get really interesting when you
sequence changes to, say, pulse width,
filter FM amount, LFO rate, or envelope
segments. As if that weren’t enough, each
sequence can have a different number of
steps, so polyrhythmic madness awaits
more adventurous players. Unreal.
With my Prophet ’08 and Mopho at the
ready, I took the Tetra out for a spin to see
how it handled. Comparing sound quality
was easy, as all three units share quite a
few presets. As mentioned before, the
sound is identical to the Mopho, and when
feedback or sub-oscillators aren’t involved,
it’s the same as the Prophet.
Speaking of presets, the Tetra is packed
with sounds ranging from legendary vintage
patches like the ELP “Lucky Man”
square wave glide and Van Halen “I’ll Wait”
brass to modern, club-oriented sounds.
These are equally satisfying, with stylistic
emphasis on progressive, tech, and a smattering
of electro-friendly patches.
Unlike the Prophet and Mopho, the
Tetra also includes a bank of 128 combo
patches, many of which are layered multitimbral
sequences. Hit a key or the “Push
It!” button and stand back — this is where
the Tetra is in a league of its own. A sizable
chunk of these multis are one-finger
demonstrations of the versatility of this
beastie, whereas others are massive unison
leads. Click here for an audio example of this.
Each of the four voices can be its own
independent synth, responding to its own
MIDI channel, but only if the global multimode
parameter is set to on. While we’d
rather see this handled as part of each
combo preset, that you get multitimbral
mode at all in an analog synth at this price
is tremendous. Plus, the limitation only
applies to four-part mode; two-part splitting
or layering (just like on the Prophet ’08) is available per patch.
Tetra’s editor (Mac or PC) makes designing your own sounds (or sequences) much easier than flipping through parameters on the hardware’s LCD. The LE version is included; a Pro version adds librarian features and other amenities for $39.99. At press time, both were standalone apps only, but Dave Smith is working on a plug-in version that’ll let you automate the Tetra from within your DAW.
It’s no secret that I love my Prophet ’08
and Mopho. Their sound has been a key
component in almost every recent track I’ve
done. The Tetra’s sound is every bit as
deep, rich, and fat as the others. In fact,
had the Tetra been available in 2007, I
might have bought it instead of the
Prophet. That’s not a knock against my
baby, it’s just a testament to the Tetra’s
unprecedented value. Any two-oscillator,
polyphonic, true analog synth for around
$800 would be a game-changer. One this
good means that if you’ve been on the
fence about buying an analog synth, there
has never been a better time to jump. Dave
Smith has hit another one out of the park —
an obvious Key Buy winner.
Is it fully analog? Tetra’s audio signal
path — the DCOs, filter, and amp —
is fully analog. The LFOs, sequencers,
and envelopes are digital, which
allows for MIDI tempo sync.
NEED TO KNOW
Are DCOs really analog? Absolutely.
Both VCOs (voltage controlled oscillators),
and DCOs (digitally
controlled oscillators) have analog
guts, but voltage control is a tad less
consistent than digital, so the latter
provides better tuning stability.
What does the Prophet ’08 have
that the Tetra doesn’t? Four more
voices, lots more knobs, and (except
for the rack version), a keyboard.
What does the Tetra have that the
Prophet doesn’t? Sub-oscillators and
a feedback loop back into the filter, so
its sound has a bit more meat on its
bones. Also, the Prophet is only twopart
multitimbral; the Tetra is four-part.
How does it compare to the
Mopho? Since the Tetra is basically
four Mophos in a box, the sound is
identical but the flexibility is vastly
increased. On the downside, the Tetra
omits the Mopho’s external input, so
you can’t process external audio