Stehno: Can you provide a link for info on the "Woodhead" products ?
Francisco and Dan: I would start with the basics. That is, try replacing the breakers in your breaker box. Breakers deteriorate with age, so start at the source.
Next up would be replace the outlets with something "decent". I think that the Hubbell hospital grade units will probably be about as good you can get without spending a lot more money. I am basing this on other recommendations and my past experience with Hubbell products. Obviously, others might have specific suggestions based on their experiences. I suggest this as the second step as all wires and connections corrode. Going to new outlets will assure you of fresh metal with tighter contacts for your power cords to plug into and a fresh clean connection from the wall wiring to the receptable. Less noise, reduced series resistance and improved conductivity can never be a bad thing when it comes to electricity and electronics.
At this point, i would fire up all of your equipment and measure the voltage at the wall outlets with the gear playing at normal volume. Pick a recording that has a lot of steady high output low frequency info, as this pulls the most power and will create the most voltage sag. Anything between about 117 volts and 123 would be considered normal. If your voltage is much above or below this level, it might need attention. Obviously the further it is away from 120 volts, the more serious the situation becomes. Keep in mind that voltage will vary depending on time of day, what your neighbors are pulling for power at that very moment, etc...
This testing will tell you if you need some type of voltage regulation. Since a voltage regulator will have filtering in it, investing in multiple PLC's and a voltage regulator(s) would be somewhat redundant and quite expensive although some might swear that there are benefits to such an installation. That is possible but i have never tried it myself.
If the voltage seems to be hanging within an acceptable range and you don't think you need regulation, i would suggest working with power cords and parallel line filters. This is not that i think regulation or regeneration aren't important or worthwhile, it's just that all of the devices on the market that i've seen are quite expensive. My goals in most systems are to build a solid platform to build upon with the least amount of initial cash outlay. Should one want to make changes or add further refinement, that can always be done later without having to backtrack to correct smaller things that should have been done first. Obviously, others may have a different point of view on the subject. Follow your heart and what your common sense tells you. 99% of the time, your gut reactions are typically correct. Just don't allow yourself to be fooled by what you "want" to hear.
Others might feel that a good PLC should be next. I have my reasons for taking the approach that i mentioned. First of all, a good power cord reduces the potential for RFI and eases the delivery of better quality power to the component. It does this by reducing the resistance within the circuit ( typically heavier gauges with better connectors ) and by taking advantage of proven geometries that are beneficial to power delivery. Personally, i am not a believer in "high dollar" PC's or "brand names". I think that this is an area that most people that are willing try can make noticeable improvements to their system. The REALLY great thing is that you can do this for pennies on the dollar compared to what one would have to pay for an equivalent commercially available product. Besides that, a good power cord will always benefit the system / individual component even if you were to add additional filtering / regulation at a later date.
As to the parallel line filters, these help reduce the amount of grunge floating throughout the entire AC system. They do this without placing any type of filtering or impedance altering devices in series with the equipment that could limit current flow under dynamic conditions. Some of the results of these might not be readily apparent right after installation, but the typical results are a lower noise floor, blacker background, reduction of hash in the upper frequencies and an overall more liquid presentation. The effects of parallel line filtering are additive. In effect, the more parallel line filters that you run, the more benefit you'll get. I would advise reading an article
written by David Magnan.
Once you've done all of this, and if you've paid careful attention to what most "audio tweakers" would consider the bare minimum set-up procedures, you should be enjoying your system to a great extent. As a further note, you might want to check out this thread about AC Polarity
. I found that it made a difference in my system and think that it is worthwhile to investigate such things. Disregard my "knuckleheadedness" near the end of the thread as i was clowning around at Bob's expense. Good thing he has a sense of humour : )
It is at this point in time that i would begin to experiment with various PLC's / electrical isolation devices and see if you like their effects. Don't think that all of these filters are created equal, as they surely aren't. Keep in mind that most PLC's shunt the "filtered" noise to ground. If the ground in the building is not up to snuff due to poor connections or a long run of resistive wire to get to Earth ground, they won't do much for you at all. The parallel line filters work no matter what as they are strictly connected between the hot and neutral.
I hope this helps and you can understand why i have recommended the path that i have. Obviously, it is nothing more than my opinion and worth just slightly less than what you paid for it : ) Sean