 George
Shilling reviews:
SPL
Tube Vitalizer
The
Tube Vitalizer looks impressive, with a nod towards vintage valve
equipment. It is a 2U steel box, with a bare metal front panel.
There are plenty of black knobs, and three grilles revealing glowing
tubes. Actually, most of the glow comes from the lamps illuminating
the little VU meters.
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Below
these, two old-fashioned black knobs are labelled
"ATTENUATOR". Switches light up red when pressed in, apart
from a couple of metal toggles, and there are blue LEDs to show High
and Low frequency compression. When you switch on, your attention is
drawn to two LEDs, proudly labelled "TUBE STATUS", with
the "WARM UP" one glowing for 45 seconds before a relay
kicks into "ACTIVE" mode. During this 45 second period the
circuitry slowly builds up to 250 volts to increase the life of the
valves. This is sensible, but I am not sure that the LEDs are really
necessary. The back panel features XLR connectors and also plastic
balanced jack sockets for inputs and outputs. The unit runs at +6dB
instead of the more usual +4dB. Jack connectors are also set to +6dB
operation, unfortunately without a switch to enable -10dB operation.
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The
Process Level control works like the Loudness button on your hi-fi.
Above a frequency set with the High-Mid Frequency control (22kHz
down to 1kHz) it applies a shelving EQ boost. Simultaneously there
is a low frequency boost centred at approximately 50Hz, and a mid
cut centred at about 1.5kHz. The manual states that the Process
achieves mid damping by "amplitude-controlled phase
shifting", and claims that this improves the perception of
loudness, clarity and bass punch. It sounded little different from
conventional EQ in practice. |
There
is some explanation of Fletcher-Munson curves in the manual, which
then makes the astonishing claim that "The Tube Vitalizer
alters the frequency spectrum in such a way that the balance is
maintained between all frequency ranges even at varying monitor
volumes". This is hard to swallow, as most of you will know
that Fletcher-Munson curves show the ear perceiving less HF and LF
as volume decreases. There is a drive knob to control the intensity
of the processing which adds a warmth and subtle distortion when
increased. The Bass control is labelled Soft to the left and Tight
to the right. Turning the knob in either direction should intensify
the bass sound, but this is not what I perceived. Tight seemed to
boost the low end, but Soft seemed to decrease bass content of the
signal. Bass Comp. compresses only the low frequency content of the
signal. There is an LC Filter which adds a passive coil/condenser
filter to the resistor/condenser filter network. There is some
enrichment of the sound with this added, midrange as well as low
frequencies seemingly affected..
Unlike
some "exciters" the Tube Vitalizer's High EQ and harmonic
filters do not add distortions to the original signal. So what do
they do? Well, they do not say exactly, but it SPL claim that the
processor extracts all the information needed from the original
signal. "By influencing the phase relationship in an
intelligent fashion, the filtering emphasises the perception of high
and harmonical frequencies." The Intensity knob adds HF gain,
and the HF control apparently sets the shelving frequency. The
manual claims that this section picks out particular frequencies,
but the accompanying graph (tracing response with Intensity and
Frequency both set at 10) shows a plain 4dB shelf boost from about
4kHz upwards, or 2kHz when the adjacent LC filter switch is pressed.
The third knob in this section is labelled High Comp. which
compresses only the high frequencies. It is possible to brighten the
signal and then compensate with this knob, giving little audible
change except for some subtle compression. By pressing the Activate
Tubes switch the output stage is swapped over from solid state
circuitry. In this mode can you use the Attenuator knobs to
compensate for any gain during processing. The valves add a pleasant
warmth and depth to the signal. Each channel has a toggle switch
labelled Atten./Limit.
The
manual states that in Limit mode all signals above the 0dB mark will
be softly limited. Audibly, signals below this point are affected by
distortion, and the sound is not dissimilar to a guitar overdrive
pedal. Despite the switch labelling, the Attenuate knobs still
attenuate. With a piece of equipment such as this you need to hear
it yourself to evaluate whether you like it. I could imagine using
it on particular instruments in a mix, or when recording, to bring
them forward. It usefully adds a bit of sparkle to a part in need of
something special, but I am not sure I would want to use it across
an entire mix: amazingly the manual itself admits that the brain
soon acclimatises to changes of timbre, which surely defeats the
object.
The
manual is full of pseudo-scientific claims and techno-babble, and
there are a few typographical errors, but as the unit is of German
origin, perhaps it loses something in the translation. Not
essential, but for something a bit different, on occasion this might
be your box.
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Reproduced
with kind permission from www.George.Shilling.Com. Copyright ©1997
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