From: paul j guy <paul@gaitlab1.Uwaterloo.ca>
Subject: power line tweaks
Mailer: Elm [revision: 64.9]
Originator: tjk@csd4.csd.uwm.edu
Organization: University of Wisconsin - Milwaukee
Date: Mon, 31 Aug 1992 13:12:40 GMT


In article  rchau@news.atitech.ca (Ray Chau) writes:
>SJKlyne@exua.ex.ac.uk (S.J.Klyne) writes:
>
>
>>When I bought my Naim Nait about 5 years ago a tweak i was recommended
>>Wto try was to replace the internal 1A fuse with a 10A, which after
>>Winstallation and listening for a few days I did and yes it was
>>Wbetter...
>
>Simon,
>       Some of the better high-end electronics actually bypass the 
>       fuse with a high quality film capacitors.             
>

        You guys make my hair stand on end, thinking about what some
of your tweaks might cost you, your house and your family.....
        If you ever get around to putting capacitors on the
primary circuit (the 110V side of the power transformer) MAKE SURE
that they are U/L (or CSA, for Canada) approved for such service.
I have worked in the TV manufacturing industry, a number of years ago,
and a number of houses were burnt down and, I believe, lives lost
because of improper bypass capacitors installed across the line.
Unfortunately, looking at my WIMA capacitor flyer, the only types
approved for power line use, are the MP3- series, and they
are resin impregnated paper. No polypropylenes ! Mallory makes
a metallized polyester type (158 series) that is rated for line use.
The polypropylene types used for motor run capacitors and snubber
applications depend on their series load to limit current, and so
aren't appoved for direct connection across the 110v circuit.
        If you do fool around with unapproved types, stick 'em
on the secondary side of your power transformer. The power is limited
on this side, you can sleep a little easier knowing the chance of
fire is much reduced. A capacitor across the secondary is more
likely to allow the power supply to see a lower impedance at high
frequencies since it doesn't include the quite significant leakage
inductances of the power transformer. (This is the residual series
inductance of the transformer, amd has nothing to do with leakage
currents).
        If you start messing around with the fuse values, and putting
10 amp ones in place of 1 amp, update your insurance, write your will.
        Better yet, get a decent amp with a regulated supply. Amplifiers
that show improvements with line tweaks either have dismal regulation,
or live in a really hostile noisy environment. If line noise is your 
problem, get commercial APPROVED line filters, and/or line
regulation/isolation transformers. 
        Don't start pulling off ground lines as a former article says.
        You might be better off with a bonding wire going from
chassis to chassis. Chances are, the bonding wire doesn't
have to be grounded, since most uptodate electronics grounds the cases.
The bonding wire should reduce the small chassis - chassis potentials
that might affect the audio. If you do this, you will probably be 
loosening the screws on the various audio units, make sure you don't
inadvertently loosen up the grounding screws for the internal wiring.
A safe bet is to use the screws that are normally removed to gain access
to the unit. The paint may require being scraped off to get a decent
contact.
        Pay attention to your local electrical safety codes !
Some tweaks may not be worth the risk of fire, electrocution, or
injury to others.

        -Paul



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