NHT PVC Passive Volume
Control
 When I reviewed the NHT M-00 powered compact monitors -- and again this month when I
began auditioning the xhi-fi Xducer 2.1 three-piece desktop system -- I discovered a huge
problem with computer-based listening. The volume control built into most computers really
affects the sound of the signal you feed your loudspeakers.
On the other hand, you must have some kind of loudness
control or you'll be a menace to the other folks in your office (or to your own hearing,
if you work alone or don't care about getting crushed by a booby-trapped lateral file).
What to do?
This is a situation that virtually begs for a passive
preamplifier. Most products marketed as passive audio preamps are a little expensive,
though -- not necessarily for what they are, but in the context of a desktop system,
certainly. That's why I was so glad that Adam Sohmer, who handles PR for NHT, casually
mentioned the NHT PVC.
A voice and nothing more
"When I send you the M-00 speakers, shall I include a
PVC?"
"Huh? Isn't that polyvinyl chloride?"
"No," Adam responded. "That's a passive
rotary volume control that allows precise two-channel level adjustments within 1dB from 0
to -40dB, with ± 0.5dB interchannel accuracy to -60 dB. It costs $99."
"Oh great," I said. "I really walked into
that one -- and now you're quoting ad copy at me. How's that fair?"
"Oh don't get your panties in a bunch. You knew what I
did when you called me," Adam replied. "Do you want to know this stuff or
not?"
"Please do proceed."
"In addition, the PVC features completely balanced
operation with its Neutrik combo XLR/TRS input jacks, and XLR outputs, and can be used in
unbalanced applications with the enclosed standard RCA-to-quarter-inch connector."
"Let me get this straight," I said. "It's
passive, it's balanced, it's extremely high-quality, it comes with the connectors I need
to attach it to my iPod docking unit, and it's all I need -- along with a pair of powered
speakers -- to have really good sound in my office?"
"Mmmm-hmmm."
"And it costs less than one hundred bucks and you're
telling me I can hear a difference between it and the attenuator on my computer?"
"Mmmm-hmmm."
"This I have definitely got to hear."
"As it were."
That Adam -- clever lad!
"But the Emperor has nothing on at all!" cried
a little child
Thing is, he was right. The NHT PVC is an impressive,
albeit tiny (5.5"W by 4.5"D by 1.75"H; 1.25 pounds) black box with a single
knob on the front panel and a pair of XLR inputs and a pair of XLR outputs on the rear
(actually, the input jacks are really slick Neutrik combo jacks, which take either
0.25" phono plugs or XLRs). No switching capabilities, no buffering (no need!), and
no active circuitry -- just a very high-quality metal case, a top-notch stereo
potentiometer, and industry-standard connectors. The unit comes with a pair of
male-phono-to-female-RCA adaptors, so you don't need a balanced input from your
computer or portable player.
And that's essentially it.
Since there's nothing active in the unit, its noise and THD
are reportedly unmeasurable. Does it sound better than the built-in attenuator on a
computer? Well, that depends on how yours is configured. On my iBook, there's a trace of
groundplane hum that is clearly revealed when I run the computer's loudness full out and
use the PVC for my volume control.
On the other hand, other than that steady-state noise, the
signal is clearer and more detailed, if extremely tiring (the buzz, you know?). However,
if I come straight out of the iPod's docking cradle, which bypasses the player's own
volume control, there's no hum or fizz, and the sound is superior in every way to that
coming out of the headphone jack. So, if I wanted to listen to anything off my Apple
system, I just downloaded it from my iBook's iTunes onto the iPod and listened through the
docking cradle/PVC/Xducer system.
This produced sound that was clearer, cleaner, and more
robust than when I went through the iBook's audio output. That output may be fine for
short trips and suchlike, but the PVC very quickly spoiled it for me as a permanent
option. Better is good.
My desktop PC-based system in my office has an RME Digi96/8
PAD computer soundcard feeding a Perpetual Technologies P-3A D/A processor, and this
system feeding the PVC/NHT M-00 combo produced sound that was about as clean and powerful
as anything I have ever heard in the near field.
You think you can't get high-rez sound out of a
computer-based system? You don't have a clue how good it can get. Of course, the trick --
as with everything in high-end audio -- is to pamper the signal every step of the way. The
NHT PVC is a crucial link in the chain.
Oh, I know what you're thinking, of course you're
getting great sound out of a high-tech soundcard and a separate DAC, how could you not?
A valid question -- but unlike less high-falutin' systems,
this one demands an outboard volume control and the one I ordinarily use is the Monolithic Sound PA-1 preamplifier ($499) and HC-1b
dual-mono power supply ($279),which also works extremely well, but costs about eight
times more. If I actually required source selection or needed to run long cables, the
Monolithic combo would actually offer features that the PVC simply doesn't have. On my
cluttered desktop, however, the smaller, simpler option is what I'm looking for.
But it would be wrong to imply that the PVC would only work
in a desktop or near-field environment. I have also used it to control remote amps in
other rooms in a crude multizone setup. Using a balanced preamplifier, you can run
extremely long cables to a remote amp -- say, in the kitchen. The PVC can then control
that remote amp's volume and you can enjoy what the folks are listening to in the main
system while you're toiling over a hot stove.
Resentful? Who me? Not when I can sooth my savage
breast with good-sounding music!
I have nothing to say and I am saying it
The NHT PVC cannot chop or dice or core an apple, but if
what you need is a high-quality, low-noise device to control audio volume, it's just what
the doctor ordered.
...Wes Phillips
wes@onhifi.com
NHT PVC Passive Volume Control
Price: $99 USD.
Warranty: Five years parts and labor.
NHT (Now Hear This)
6400 Goodyear Road
Benicia, CA 94510
Phone: (800) 648-9993
Fax: (707) 747-1252
Website: www.nhthifi.com
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