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Subject: FAQ: rec.audio.* Misc 7/07 (part 13 of 13)
This article was archived around: 15 Jan 2009 06:01:57 GMT
20.1 What do I need to know about warranties?
Warranties have a few basic components. The first is the term
of the warranty. The second is what is covered. The third is
who supports the warranty. The fourth is what restrictions.
Term is fairly self evident. What is covered is more detailed.
In audio electronics, typically everything is covered with a
"parts and labor" warranty. Often mechanical components such as
tape heads are covered by different terms, such as shorter terms
on labor and longer terms on parts. Likewise, speaker
warranties vary widely, from unconditional with no term limit to
a basic 30 days parts and labor.
Some warranties come from the manufacturer. Others come from
the dealer. Still other warranty support is available with
certain premium charge cards.
A common restriction on some warranties is that the equipment is
not covered unless it is sold by an authorized dealer. A few
dealers have lied about being authorized dealers. Equipment
sold by an unauthorized dealer is almost always sold completely
legally. This unauthorized dealer may, in fact, be fully
authorized to sell, but not authorized to sell manufacturer's
warranties. In buying gear this way, dealers can get it
cheaper, and provide the service themselves. This kind of gear,
with a full warranty from the dealer is referred to as gray
market equipment. Manufacturers discourage buying from these
gray market dealers, but the risks are fairly low. If the
dealer is local and well established, the risks are minimal.
If you buy equipment mail-order, a dealer warranty may be a pain
in the neck, especially if you have to ship the gear to the
dealer more than once to get it fixed correctly. Then again,
some factory service requires shipping gear far away at your
Frequently, home audio equipment is sold with a warranty
restriction that if the gear is used commercially or in any
profit-making enterprise, then the warranty is void. This is to
protect the manufacturer from having to frequently repair
equipment meant for light service. Professional audio equipment
often comes with very liberal warranty terms, such as lifetime
parts and labor. Professional gear takes heavy use and severe
wear from constant transportation. It is expected to be able to
take this abuse.
All gear, electronic and mechanical, is known to have three
principal failure modes: abuse, infant failure, and end-of-life
failure. In addition, a few of the failures occur at random.
Infant failure (also called juvenile failure) occurs in the
first fifty hours of use, and is the principal responsibility
of warranties. Infant failure is frequently caused by defective
parts or a design defect.
Abuse failure is that caused by a person who pulls a cable too
hard, bangs the equipment on the table, pushes the controls too
firmly or too fast, or does anything else which the manufacturer
did not expect. These are the gray areas of warranties. They
do not represent a manufacturing defect in the manufacturer's
eyes, but they do leave you with a broken device. To get
the best chance of coverage against this kind of failure, select
a brand or a dealer with a very liberal warranty policy.
End-of-life failures are rarely covered by warranty. Tape heads
have a finite, calculable life, as do rubber rollers, speakers,
cables, batteries, bearings, and motors. The life of some of
these components can be extended by intelligent care. For
example, the life of common rechargeable batteries can be
extended by good recharging practice. Likewise, some cleaners
can dry out rubber, and will lead to premature failure. Don't
expect warranty support for any of these problems, and if you
get it, feel lucky.
20.2 What is blind testing? Non-blind? Double-blind?
If you want to compare pieces of equipment, recordings, or
people, you could run an experiment. You could select an
experimenter to initiate various trials, select some subjects
to listen to the sounds, and then ask the subjects questions
about what they hear. However, if you want meaningful
results, it is necessary to set up the experiment correctly,
and ask the right questions.
One of the major problems with any experiment is that the
subjects may become aware of the experimenter's hypothesis
and allow this awareness to influence their behavior. One
technique for preventing such bias is to keep the person
who conducts the experiment unaware of the hypothesis of the
research. Unfortunately, experimenters invariably form SOME
hypothesis of what's going on, and these hypotheses affect
how they deal with subjects.
A more reasonable solution involves allowing the experimenters
to know the true hypothesis but somehow keeping them ignorant
of the specific experimental condition of each subject. This
is known as a Partial Blind Experimenter technique. An example
of this is that the person running an experiment knows that the
main experimenter wants to determine which connecting cables
are best at signal carrying, but would not know which cables
are being used at any given time during the experiment.
It is also important for subjects not to become aware of
the experimenter's specific hypothesis. Subjects often
become highly responsive to any cues, intended or unintended,
in the research situation that suggest what they are supposed
to do to appear normal or "to make the study come out right."
This problem can be present in judgment experiments,
particularly those in which each subject is exposed to more
than one variation of the stimulus. Such a procedure, by its
very nature, increases the probability that the subject will
begin to guess which aspects of the experiment are being
systematically varied by the experimenter.
Many studies avoid this problem with what is called a Blind
Subject technique. Using this approach, subjects are not told
specifically what the hypotheses are. Additionally, subjects
are not told what specific experimental conditions they are in.
For example, a subject might be told that he/she is supposed to
determine which stereo system sounds better, when in fact the
experimenter wishes to examine which color or appearance of the
same components looks better to subjects.
When both a Partial Blind Experimenter technique and a Blind
Subject technique are used at the same time, this is called a
Double Blind experiment. Double Blind experiments have higher
probability of producing statistically valid results than
Partial Blind Experimenter alone, Blind Subject alone, or other
techniques. Double Blind experiments are highly recommended.
20.3 Where can I get a service manual or parts for brand XXX?
The most reliable source of supply is the manufacturer's sales
office in your country. Here is a list of company contacts that
may be helpful in the US. (Please send additions & corrections
etc. to email@example.com.
Akai Service Center 818-794-8196
AR (now part of NHT; see NHT)
(AB Tech Services 800-225-9847
Ex AR Employee; Repairs old AR products)
Emerson Radio 800-388-8333
General Electric 800-447-1700
Alternately, contact one of the repair parts dealers listed
in section 10.15 above. MCM and Parts Express offer free
catalogs which can be very helpful for locating parts.
20.4 Where can I get good repairs on brand XXX?
20.5 How can I take 115V gear over to a 230V country or vice versa?
Some equipment is available with an international power supply,
which can be rewired by any serviceman to either power line
voltage. If you expect to be moving abroad, look for this kind
of equipment. Often, the same model is available both as US
only and as International. Some equipment will be rewirable and
won't say it. Adcom amps are known to be rewirable.
If you rewire equipment from one voltage to another, be sure to
also change the fuse(s). The correct value is often printed on
the case or chassis of the equipment. If an amplifier, for
example, is rewired from 115V to 230V, the fuse current rating
needs to be reduced by 50%.
If you know that your gear is limited to one power line voltage,
you can order a new power transformer for that receiver, CD
player, amplifier, or tuner which will be wound differently.
Contact the manufacturer's local service center. This can be
very expensive. A new transformer for a 40 watt receiver would
wholesale for under $25 but cost $75 from a service center.
Another alternative is to buy a power transformer that will
convert 115V to 230V and vice versa. This is only practical
for smaller gear. Larger power amps require prohibitively
massive and expensive transformers. Also, the addition of a
transformer may hurt the sound quality.
Here are some common transformer models and 1992 list prices.
Power ratings are total line current multiplied by line voltage
(2A at 115V is 230 watts). Larger transformers cost more. Some
of the costlier transformers are constructed with plugs and
jacks for immediate use. Those marked * have wire leads and
need safe connections to be used.
Before spending money, check into other things about audio in
the new country. Broadcast frequencies are slightly different
in some countries than in others, so a receiver or tuner bought
in one country may not be able to receive some or all of the
stations in another country. The US separates the AM broadcast
band frequencies by 10kHz while the UK uses 9kHz. Similarly,
the US separates FM stations by 200kHz, where the UK has
stations on a 50kHz spacing pattern. It MAY be very simple to
modify a receiver from US to UK spacings, but may not. Last,
but not least, some equipment will NOT work well on 50Hz power.
Also, FM Radio preemphasis is different in North America and
Europe. One uses 50us while the other uses 75us. To change
receiver deemphasis may require a modification by a technician
with special factory information.
Also, power line frequency is 50Hz in some countries and 60Hz
in others. Some equipment will overheat if it was engineered
for 60Hz operation and run on 50Hz power lines. Some equipment
uses the power line frequency as a reference for motor speed,
such as turntables and tape decks. Check the label first.
Step Down (230V in, 115V Out)
MagneTek/Triad N1X* 50 Watts $11.83
Stancor P-8620* 50 Watts $14.16
MagneTek/Triad N3M 85 Watts $29.95
Stancor P-8630 85 Watts $43.65
MagneTek/Triad N6U* 200 Watts $25.72
Stancor P-8632 200 Watts $51.80
MagneTek/Triad N5M 250 Watts $42.60
Step Up (115V In, 230V Out)
Stancor P-8637 85 Watts $43.10
MagneTek/Triad N150MG 150 Watts $49.46
MagneTek/Triad N250MG 250 Watts $54.69
Stancor P-8639 300 Watts $55.51
The Stancor and MagneTek Triad lines are carried by
large electronic distributors.
20.6 Are there really good deals in country XXX?
20.7 How do I find out how much an XXX is worth?
There is a "Blue Book" for used audio equipment called
"Orion Blue Book-Audio". This guide lists both a
wholesale and a retail value for most audio gear.
Orion Research Corporation
1315 Main Avenue Suite 230
Durango CO 81301 USA
Last I knew a guide costs $169. Each Nov, a new book is printed.
After June, the old book is discounted. If you need a single
quote from the Orion Blue Book, send a polite request to:
and you may get a quote back by e-mail.
20.8 Do people really hear those differences?
Who knows? They sure think that they do.
20.9 Why do people disagree on what is the best sound?
There are at least three different measures of what is "Perfect
Sound". All three have advocates, and all three are right, in
their own way. In general, whether they admit it or not, most
listeners fit into one of these three preference groups:
1. It must sound like live music. These people know what
voices sound like in person, they know what instruments
sound like without any amplification, and they have
heard orchestras perform unaided by sound systems. They
want to accurately reproduce that sound.
2. It must sound like the recording engineer wanted it to
sound. The recording engineer listened with extremely
good equipment to the sound coming out of the
microphones, and mixed them together for what he, at
that time, felt was artistically correct. It may not
have been the same as live, but it was exactly what he
wanted. In the extreme, people like John Fogerty used
to audition his final recording mix in his truck to see
how it would sound through a common, lousy stereo.
3. It must give me the most pleasure. No matter how good
or bad live sounds, no matter what the recording
engineer intended, if buy some equipment will give me
more listening pleasure then it must be the best.
With these three perspectives, it is clear that no one system
will satisfy everyone. Add to that confusion the variable that
everyone likes a different kind of sound, has heard live music
under different conditions, and has a different idea of what the
engineer intended. There is an enormous range of possibilities.
Another set of reasons is that people look for different things
to be right. Some want strong bass; others want male voices to
sound like male voices; others want violins to sound like
violins. Systems rarely do everything equally well. Speakers (in
particular) are compromises. Look for the speaker where the
designer had your priority first. You are perfectly right to
select speakers based on YOUR personal taste.
Confounding the situation further, we all say the greatest
things about the stuff we already bought. To do otherwise would
be to admit that we are either stupid or deaf.
Still another reason is that most people haven't heard enough
variations. Until you hear a system that can truly reconstruct
the three-dimensional accuracy of a stereo image accurately, you
may never realize that it is possible. Some excellent
recordings contain enough information that with a good enough
system, you can hear up-down, in-out, and left-right
distinctions very clearly. However, we will never experience
this until we are fortunate enough to hear such a fine recording
on a very good system.
Finally, some of us really can't hear much difference. We
aren't deaf, but we don't have a well trained ear, don't know
exactly what to listen for, and may even have slight hearing
deficiencies, such as bad sensitivity to high frequencies which
comes with older age, or hearing damage from listening to loud
sounds (machinery, rock concerts, etc).
20.10 How do I contact the manufacturer of XXXXX? How do I get repair
service on XXXXX? How do I get replacement parts?
Some magazines publish lists of contact phone numbers for the
manufacturers of equipment. In the US, Consumer Reports has a
small listing in each issue and a more comprehensive listing
in their March issue. Also, Audio Magazine has an exhaustive
listing in their October "Equipment Directory". In Europe, look
in "What HiFi?".
You can find many addresses by reading ads in hifi magazines.
You can also find out by asking at your friendly local hifi
shop, especially if you've built up a relationship with them.
There is a book called the "Electronics Industry Telephone
Directory". It comes out yearly and is available in some
libraries. Many reps from parts distributors pass them out for
free. If you want a copy and are willing to pay for it, call
Harris Publishing, 800-888-5900 or 216-425-9000.
The directory of the Electronic Industries Association is
similarly useful. You can reach the EIA at 202-457-4900.
A good source for parts and service is often the manufacturer's
repair center. The best way to locate one near you is to look
at the literature which came with your equipment when it was
new. Failing that, see the ideas mentioned above in 19.10.
The information contained here is collectively copyrighted by the
authors. The right to reproduce this is hereby given, provided it is
copied intact, with the text of sections 1 through 8, inclusive.
However, the authors explicitly prohibit selling this document, any
of its parts, or any document which contains parts of this document.
Bob Neidorff; Texas Instruments | Internet: firstname.lastname@example.org
50 Phillippe Cote St. | Voice : (US) 603-222-8541
Manchester, NH 03101 USA
Note: Texas Instruments has openings for Analog and Mixed
Signal Design Engineers in Manchester, New Hampshire. If
interested, please send resume in confidence to address above.