[ddots-l] Wave Arts - Tube Saturator Plug-in Review

  • From: Chris Smart <csmart8@xxxxxxxxx>
  • To: ddots-l@xxxxxxxxxxxxx
  • Date: Tue, 13 Sep 2011 01:11:58 -0400

This review is taken from TapeOP Magazine. The plug-in being discussed is a proof of concept, meaning that it's a trial run of new circuit modelling technology. I'ts new, and it really uses up precious CPU resources. But, as the article suggests, it's very promising for the future, as CPU power increases.

Review follows,


Wave Arts
Tube Saturator plug-in
Wave Arts claim that Tube Saturator, "a basic circuit
consisting of a Baxandall-type three-band EQ feeding two
12AX7 triode preamp stages... is the world's most accurate
real-time tube-amp plug-in." Let's examine how they can make
this outrageous claim?and why I agree. Before we start, I'll
say the manual is worth reading. It even publishes the circuits
with component values. (You could build them!) It also goes
into more detail about the SPICE-like modeling method and
explains the theoretical inferiority of other methods for making
two-stage digital tube amps. I will try to cover topics that are
not in the manual. Let's talk theory first, then listen.
This is the only plug-in I know of that does true
component-level modeling; that is, each component has its
own equation. This is very similar to SPICE modeling, a
regular fixture in computer-aided physical circuit design for
many years now. SPICE does not run in real-time though, and
it will also utilize the equivalent of very high sampling-rates
(GHz or more) to solve a circuit equation at any given point
in time, so the Tube Saturator designer created his own realtime,
bandwidth-limited (limited by the sampling rate)
SPICE-like audio-processing system. This is amazing in itself
and worth a pause, because within the limits of CPU power,
Wave Arts can now make any analog model relatively quickly.
Also, they claim it's the only way you're really going to get
a two-stage digital tube amp. Unfortunately, this method is
extremely CPU intensive. For example, I can barely run a
mono instance on my Macintosh Dual 2.3 GHz G5 with
Nuendo, on a single audio track at 96 kHz. [On a 3 GHz Core
2 Duo, a single, 96 kHz mono instance takes up roughly 33%
of a single core.] If your DAW supports it, you can take
advantage of non-real-time bouncing to disk, to use the
plug-in up to 192 kHz. For reference, I asked Wave Arts when
CPUs are expected to have enough power to run a Fender
Bassman head model using the Wave Arts engine ? about
five years.
It's important to consider parasitic effects of components
in analog design (see "Behind the Gear" in Tape Op #75). In
Tube Saturator, tube microphonics and noise, for instance, are
ignored. The only parasitic effect that was seriously
considered for inclusion was having the tubes warm up! They
passed on that. Where non-linear components, such as the
tubes, are concerned, measurements of actual components
were used to derive the equation data, rather than pure
theoretical models. The designer claims this sounded way
better, and that's not hard to believe. On top of that, the
tubes are digitally "matched" (measurements copied from
one tube to the other), so if you subscribe to Groove Tubes'
theory about tube matching, this is tube paradise. Linear
components like resistors and caps are simplified to pure
equations and are "perfect." Things like the power supply and
I/O impedance are not modeled and are therefore also
idealized. In theory, it's a perfect tube amp without noise,
microphonics, power-supply problems, etc.
A Baxandall EQ, named for the original designer, uses low
and high shelf filters so wide that the flat part of the shelf is
out of the audible band, and similarly, the mid band has superwide
Q. Tube Saturator models a Wave Arts?modified version of
a published circuit. I'd never heard of a Baxandall EQ, so I had
to look it up. The only folks that talk about them online are
Hi-Fi DIY'ers and Dangerous Music, who released one recently
for mastering. I asked, "Why the Baxandall EQ?" and it was
simply because they wanted EQ, and wanted "something
different." I think they stumbled onto something very special,
and this plug-in is easily worth more than $99 just for the EQ.
More on that later.
This plug-in is not anti-aliased, which in my mind is sort of
like operating a circular saw without the safety guard. Digital
processing is capable of generating frequencies above the
upper bandwidth limit ("Nyquist frequency") of the system it's
on. If allowed to pass into the D/A converter, it is called
"aliasing." Aliasing is digital garbage; I've only ever heard
aliasing sound good on Tom Yorke's The Eraser, where I am
pretty sure he did it on purpose. Anti-aliasing filters remove
the offending frequencies before the D/A. I asked, "Why no
anti-aliasing?" Simple, it increases CPU load even more, and
they couldn't hear the difference. Plus, the claim is that no
anti-aliasing is needed at 88.2 kHz and above, so the manual
suggests that if you can hear aliasing, up-sample before
processing. The manual also suggests up-sampling if you want
to increase the resolution of the distortion modeling, and that
it will be preserved when you down-sample. I did listening
tests to confirm both of these assertions.
While this plug-in is not specifically for guitar, guitar is
as good of source as any for this test. I tuned my guitar
carefully and played around until I got the most glorious
sounding open E-major I could play and sampled it at
192 kHz. I used BarbaBatch to make 96 and 44.1 kHz
versions. I ran them through Tube Saturator. EQ is
switchable; I left it enabled but knobs at 0. There is a signal
Drive knob which controls a ratio between the input and
output volume to keep the level constant as distortion
increases. I cranked that to 10. There is a gain-boosting Fat
switch, which I left off. There is also an output volume knob
that does not affect tone ? nice for feeding into other
plug-ins. I created versions at each sampling rate, then used
BarbaBatch to convert them all to 44.1 kHz. As usual, I
thought I could detect small differences, but when I listened
without knowing which was which, I could not hear any
difference at all. I then compared the files by differencetesting
? that is, mixing two files together while flipping
the polarity of one. The result is the difference between the
two files. There were definite differences.
Comparing the file that was processed at 44.1 kHz to the
one at 192 kHz yielded a difference file full of aliasy, raspy,
sparkly crap. The file peaked at about ?25 dBfs, with the
original files at just below 0 dBfs. The difference file between
the 192 kHz and 96 kHz had no digital garbage. It peaked at
about ?40 dBfs. It sounded pretty good, like a thinner version
of the original. These tests suggest that there is aliasing at
44.1 kHz, and none at 96 kHz as promised. Three, there is good
sounding stuff being generated between 96 and 192 kHz that
stays in the signal when you convert to 44.1 kHz. Woah!
Again, Tube Saturator is not a guitar amp, but for
reference, I compared it to Native Instruments Guitar Rig 3
anyway. I used the amp model that sounded the closest to
Tube Saturator with gain at 10 and compared using the
aforementioned 96 kHz E-major sample. GR3 cleaned up my
guitar signal before it went to the amp, so I imitated this
with some pre-EQ using another plug-in. I could get them
pretty close sounding, but Tube Saturator seemed slightly
more 3D, lively, and real-life than GR3. I liked it, but I don't
think I'd put up with the CPU load to use Tube Saturator on
guitar in a mix, because GR3 still sounded good and is much
less of a CPU hit.
60/Tape Op#77/Gear Reviews/(continued on page 62)
My trials with the EQ were a revelation. I was confused at
first, "Is it supposed to sound this good?" It can't be used for
surgery, but if you're asking for (more or less) lows, highs, or
mids, this Baxandall thing has a beautiful answer. I think there
will be a Baxandall revival if enough people check this out. The
EQ is before the tubes in the circuit, so you can also use it to
color the way the tubes are driven. In conjunction with the
drive knob, you can get pretty creative. It's just viscerally great
sounding; check it out.
A cool trick for digital recording is to add inaudible amounts
of distortion to each track in a mix. Even though you can't hear
it on the solo'ed tracks, it can, for instance, produce a mix with
more apparent loudness. Some mixing consoles do this
naturally. I tried this with Tube Saturator on a 96 kHz session,
for a "real" tube version of this trick, without adding noise.
Since I can only run one, I bounced one track at a time. It took
an hour for 11 tracks, but it was worth it. With the settings
used, the mix didn't get louder but without changing the overall
tone, all of the little ear-piercing moments that I had been
struggling with were gone. Overhearing, my fiancé asked me
what was going on; she said, "Well, you can tell Tape Op I could
hear it; it sounds great."
Mastering engineers could also add a bit of tube distortion
to stereo masters and to use the Baxandall EQ as a tone
balancer between songs. For high-end mastering folks, I think
it would be worth buying a dedicated computer just to run this
plug-in, and the whole setup would likely be price competitive
with a similar analog unit, if it existed. Plus, Tube Saturator
doesn't have the noise of analog tube circuitry.
Wave Arts dropped the price from $149.95 to $99.95 while I
was writing this review. I think they are valuating Tube
Saturator too low, because it's relatively impractical to use due
to the CPU load, unless you are limiting its use to just a track
or two on a high-powered rig. But it sounds spectacular, and
this is the only way you're going to get this sound. If I was
doing the marketing, this would be called the "Baxandall
Mastering EQ with Tube Saturation" and would sell it for at least
$495. Be glad I don't work for Wave Arts. In fact, my only wish
is that you could disable the tubes and just use the EQ for a
much lower CPU hit. Highly recommended. Download the 30-
day unrestricted demo, and try for yourself! ($99.95 direct;

?Joseph Lemmer <jlemmer@xxxxxxxxxxxxxxx>
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