From: gbb@watson.ibm.com (Gary Bronner)
Newsgroups: rec.audio.high-end
Subject: Power Line Conditioners
Date: 27 Aug 92 13:05:05 GMT
Organization: University of Wisconsin - Milwaukee
Originator: tjk@csd4.csd.uwm.edu

I am posting this for another employee, Bob Blase, who
does not have access to the net.  He has additional observations
on building your own power line filters.

---Gary Bronner


Subject: Power conditioners

I saw your posting to the hi-audio digest. I've been tinkering
with power filters for the past year or so, and I've found the
same effects that you did. Here are a few more ideas to tinker
with that I've found helpful.

Outdoor ground rods help quite a bit. The power line ground is
too noisy. I use a separate ground rod to the ground post of
each EMI filter (I know, that's a lot of them, but it sounds
better than connecting them together). And another one (two in
parallel, actually) that's connected only to the equipment
chassis (not to any power filters or the power ground).

I also disconnect any grounding plugs on the equipment so the
gear isn't connected to the power line ground (the filters
aren't either). The power line ground is noisy, and with all
the external grounding it isn't needed.

Filter design is similar to yours, except that I use more stages
of filtering: filter->transformer->filter->transformer etc. The
first pair is common to more than one piece of equipment, and
there's a second stage for each piece.

Some equipment doesn't like to see an EMI filter box at the
input of its power cord. (Don't ask me why, I just design them by
ear). My power amplifier (a Conrad-Johnson MF200) is especially
picky. Filter->transformer->amplifier sounds better than
filter->transformer->filter->amplifier. But,
filter->transformer->filter->transformer->amplifier is even
better. Strange but true. Maybe it just doesn't like seeing any
capacitance right across the input. You might want to try a few
combinations to see if any of your equipment is like that.

I've also found that turning off sources of electrical interference
while listening is very helpful. My electric fence is by far the
worst offender. A pool circulator and air conditioners have a
noticable effect too, and flourescent lights are bad. I can't seem
to get all the effects of that stuff filtered out, so best just to
turn it off.

A 20 microfarad 330VAC capacitor directly across the input
terminals of the first corcom filter is helpful too. (Two of them
connected from each side to ground didn't work as well, but it may
differ from system to system so you might try it). Big capacitors
later in the filter chain don't seem to work well.

Shielding on all power cords is helpful, at least until they're a few
feet away from the speaker wires and interconnects. For my CD player I
built a power cord from 18/2 double-shielded cable, gounded at the
power filter end only. The amplifier cord isn't detachable, so I cut
the plug off and made double shielded cable using shield braid with
electrical tape over it, then put on a new plug. Keep the speaker wires
and interconnects well away from unshielded power wires that are inside
the walls or under the floor, too. The better the filtering on the
equipment's power gets, the more such other sources of noise matter.

A good source for power filter parts is P & D Surplus in Kingston,
NY. They have corcom and other filters for anywhere from a buck
up to about 10 for the 30 or 40 amp jobs. Isolation transformers are
a little rarer, but last I was there they had some 7500 VA ones
(that's not a typo - they're BIG) for $75. That's what I use on
my power amplifier. They have lots of capacitors, wire, boxes, shielding,
and equipment to cannibalize for parts. A trip up there will more than
pay for itself if you need a bunch more parts. Plan on spending a while,
it's only partly organized and you just have to hunt around.

I don't have access to the net to post this, so if you think it
would be interesting to anyone else you're welcome to post it.

                                                     Bob Blase