G&W TW-03D POWER LINE NOISE FILTER FOR TUBE
AMPLIFIERS
This AC power line noise filter is sold on eBay. When I ordered this unit in
April 2005, there were two auctions offering it. The auction out of Britain
asked $85 for the unit with $30 shipping; out of Hong Kong it was $80 but
the shipping was $40. I opted for the British version. Two weeks later it
arrived from Hong Kong.
Basically this is a passive device. AC current goes in one end, gets filtered,
and comes out the outlets—potentially scrubbed clean. The unit includes an
AC cord--16 gauge and about 6 feet long. There is a voltage meter on the
front. On top are four universal outlets for various 220V systems and two
American duplex AC receptacles. One US receptacle is grouped with the 220
outlets; I am assuming that this marking indicates that these are the outlets
being filtered. In any case, this was the outlet that I used. There are red
and green leds on the top of the unit to indicate, it appears, power (green)
and that polarity is reversed (red). The unit measures approximately 15 X 5
X3.5 inches (lwh).
I plugged the unit into the wall using the supplied cord and checked the
polarity of the 110 receptacles with my neon polarity tester. It showed
correct polarity. I then tried a heavier 14 gauge homemade cord and got an
indication of reversed polarity. Subsequent checks with various homemade
and factory IEC cords indicated that this unit reverses polarity. Use the
supplied cord or make one that reverses the positive/neutral connections at
one end (and mark it so you don’t use it for anything else). I am using a
homemade 12-gauge cord with a Marinco 320IEC15 female socket at the filter
end and a Pass & Seymour male AC plug at the wall. An instruction sheet,
entirely in Chinese, is also included. It has a very nice picture of Tsinghua
University where this unit was developed.
I kept the TW-03D plugged in for about two weeks before inserting it into
my system. In theory, it should need no break-in but I saw no drawbacks to
plugging it in. It made no noises and generated no heat.
I hate to admit to what I have been using as an AC filter with the VTL tube
amp. It’s a gray, metal-boxed Xerox unit that I found at a garage sale. It’s
obviously some sort of filter/surge protector and that’s about all I know
about it except, according to the nameplate, it actually belongs to Xerox. I
have used the VTL both plugged into this unit and plugged into the wall and
have heard no discernible difference. Assuming that it might prove beneficial
in the event of a voltage spike, though, I have used the Xerox box pretty
much all the time.
My motive in buying the TW-03D was to feed the VTL with a quality AC line
filter made specifically for a tube amp and audio use.
I did a couple of tests prior to listening to this unit. The first was to make a
series of in-room measurements using the test tones on the Stereophile
Test CD 1 and my Radio Shack meter. There was no difference in output
from the VTL, at any of the test frequencies, between the Xerox box and the
TW-03D. Frankly, based on my AC cord experience with the Hafler amp, I
had expected some increase in output simply by going from the 16-gauge
power cord on the Xerox box to the 12-gauge cord on the TW-03D but
there was none measurable. The VTL itself has a captive 16-gauge cord,
which is totally stock.
The second test was to put my ear to the Magneplanar MG 10 tweeters and
assess the noise level. It sounded exactly the same with either unit—a just
audible hum at six inches away.
I inserted the TW-03D in a warmed up system and listened for any
immediate differences, good or bad. I heard no change. I have spent
considerable time listening since then and have still heard nothing in the way
of an improvement attributable to this unit. (In fairness, the seller does not
make any outrageous claims for its performance. The eBay auction mentions
“reduced background noise”, “more details” in the music, and that it’s “price
is cheap” for the performance it offers.)
There is no discernible change in the sound staging, low-level detail, clarity,
or any other parameter that I can think of. This makes the TW-03D utterly
consistent with all of my other experience with AC devices whether filters or
cords, with the exception of the Hafler amp’s output (see Tweaks)--no
audible changes, that I can hear.
Given the fact that huge numbers of people evidently hear big differences
when they add after-market AC conditioners and cords to their systems, this
kind of bothers me. The Monster HTS 1000, for example, replaced one of
those computer surge protectors/switching boxes that were made to sit
under your computer monitor and let you turn on the system. Remember?
The computer box was actually very well made, well shielded, and had good
quality filtering parts inside it. Despite the audiophile credentials of the HTS
1000, adding it made no audible difference in the sound of my preamp,
crossover, or CD transport.
I will continue to listen through the TW-03D, as I feel certain that it is at
least doing no harm and will update the web site if I hear anything worth
noting. At some point, I will unplug the VTL from it and plug it directly into
the wall and see if I hear any change then. Getting used to the sound of a
new configuration and then reverting to a prior configuration has often
proven more useful, in my experience, in hearing differences than trying to
ascertain them immediately upon inserting a new component.
Overall, this is a nicely made unit and inexpensive even allowing for the
shipping costs. I had really hoped its virtues would prove more obvious at
the outset. But then I have hoped that for all the other AC stuff I have
tried, too.
Kent Johnson
May 2005
FOLLOW UP
August 30, 2005
I spent about four hours today comparing the sound of the VTL plugged into
the TW-03D to the VTL plugged into the wall. There were a few times where
I thought I heard a subtle difference in some low-level information such as
the clarity of the background singers or drum kit. Each of these times it was
with the VTL plugged into the wall. Not good.
I decided then to do what anyone would under the circumstances: I took the
TW-03D apart.
Given its cost, I can’t complain about the parts used in this unit. The case
alone probably couldn’t be manufactured in this country for $85.
AC power enters at the unit at the rear. The red (hot) lead goes through a
circuit breaker. The three lines then split into two branches. One branch
powers the unfiltered 110V duplex receptacle. The other branch heads for
the printed circuit board at the front of the unit. After passing through the
coils, caps, and resistors there it comes out of the circuit board and is
connected to the outlets themselves. Its path is 220 outlet, 220 outlet, 110
duplex outlet, 220 outlet and 220 outlet. The connections are made via
push-in connections, not ideal in my opinion. What was obvious, though,
was that it would be easy to simply disconnect all of the 220 outlets, so I did.
Rewired, the output of the circuit board now goes straight to the filtered 110
duplex outlet. I made the connection from the circuit board output wires
using wire nuts so that I can undo the changes should I want to. It would
be possible to replace the filtered 110 receptacle with a better quality unit but
I did not have one around so I just left the original in for now. I don’t like
the push-in connections but the outlet itself grips the VTL power cord very
well.
In making this modification, I corrected the reversed polarity for both 110
outlets. I also corrected the polarity of the AC cord I am using. Everyone is
happy now except the little red led that indicates reversed polarity; it’s on all
the time.
It was time to put the TW-03D back in the system.
August 31, 2005
Once the system was thoroughly warmed up with the VTL directly plugged
into the wall, I switched back to the TW-03D. Again, I heard no obvious
change in the sound with this unit inserted. I used two CDs for evaluation—
Diana Krall Live in Paris (Verve 440 065 109-2) and the soundtrack to the
movie De-Lovely (Columbia CK 90640). Both albums are very well recorded
and provide a variety of songs from which to listen. This was really helpful
since I was listening to the same tracks over and over.
This time, I could not detect any differences at all between the two setups. I
have to conclude that there is no clearly audible improvement resulting from
using this line conditioner nor is there any clearly audible detriment. Perhaps
I’m deaf. Perhaps I really don’t need what the TW-03D does. Maybe my AC
lines are reasonably clean. I usually listen during the day and I make a point
of having everything turned off in the house that does not need to be on. I
can not control the heating/air conditioning, refrigerator, or freezer but
otherwise everything is off.
The TW-03D will stay in the system as it does not hurt the sound, seems
well made, might be doing something I am unaware of, and I own it.
Evaluating it has given me some ideas for some future experiments that may
prove interesting as well. In the meantime I will still continue to wonder,
“When it comes to AC, what is everyone hearing?”
Kent Johnson
August 2005
