I recently started working with Equitech, and Ive learned a ton about all the different types of "power conditioners" available. It is very confusing world with many different types of units all called power conditioners.
Surge protection: not power conditioning, although some people call it that. This is surge protection and is designed for exactly that, surges in power lines like lightening or? Mostly uses MOV's to deliberately blow if a big surge happens to protect the gear downstream but there are other methods. Many pieces of gear have MOVs built in to the power supply. But for spike protection, this is the only way.
Regulation: also not power conditioning, these can raise level of AC lines that are sagging due to poor power transmission or very high demand. So this is to correct power dropping down to well below 120V. "Brown outs" do create a significant problem for audio gear, computers etc. Many pieces of gear do not work right on 100V, 90V or even 80Volts. There are places in the country that have this problem and you can measure this with a meter.
Power Conditioning via regeneration: These type actually redraw the AC line sine wave and recreate the AC power via a unique design (PS audio is well known for this). Sounds attractive and can work to separate inside from outside. Can help some noise or very dirty power conditions or clipped power but is also risky to some types of power supplies. There is a major console company on the pro side called SSL that has seen a lot of damage to power supplies from power regeneration, recently sending a letter to dealers telling them not to use power regeneration on their products. Not much regeneration in use in pro.
Power Conditioners using fitering: These don't seperate inside from outside, but they attempt to filter out noise riding on the AC line. Think of it like EQ on the AC , reducing certain frequencies of noise on the AC sine wave. This is about the only way to get rid of certain types of EMI and other noise BUT doesn't recondition the line, doesn't prevent noise- it attempts to reduce it after it's already present.
Power conditioners using transformers: These are about the best system for separating inside from outside and can significantly reduce noise by preventing it. They don't regulate, protect from surges or filter. They are sized as to total amperage draw of everything plugged into it, so they can be bought in different sizes for different demands. For home audio a 15A transformer conditioner would be the right size unless you have a lot of high draw amplifiers. They actually use a massive transformer to isolate things on the incoming side vs the outgoing side of the transformer. You can often tell a transformer conditioner from specs: the weight and various choices in maximum draw- transformers are big and very heavy and limited to draw. [Little power strips don't use big transformers- they are often only filters or surge with no statement as to maximum draw, only surge limit (in joules). Surge protection doesn't use a transformer and power regeneration doesn't use a transformer. ]
Balanced Power conditioners: These are a high end version of the transformer type of conditioner and the type to use for audio. It uses the same technique as a balanced audio to cancel noise. Few 120V transformer power conditioners are balanced, Equitech is the inventor of this and dominates recording/mastering studios to lower AC line noise and improve dynamics. They are the major player with a 120V balanced transformer, buy there are others in larger applications based on 240V incoming and 30A to 100A + draw).
Some difficult noise problems in major markets for industrial customers use ALL the above: transformer balanced conditioning, regulation and surge protection all via different units on the same incoming power feed.
I work primarily in pro audio as TransAudio Group calling on major commercial studios and these balanced conditioners are the ones they buy and install (sometimes larger units in the wall at the incoming power box, or sometimes smaller rack units in the room itself in the gear rack).
The #1 preventative thing is to have circuits that do not any non audio gear plugged in to them, so no refrigerators or lights or computers etc plugged into the same circuit. Studios almost always get a dedicated line that isolates their power feed from anyone else in the building, down the street or next door. They also try to operate rooms from each other, using individual transformer type balanced power conditioning. Noise is commonly transferred around among gear on the same AC system, especially lighting, motors, digital gear, air conditioners, etc. Your neighbors stuff can affect your power, and balanced conditioners can prevent 90% of this. Large computer users and manufacturers (plus medical device users/manufacturers) need this type of low noise power feed as well.
An isolated incoming power line costs a small fortune from the local power company but is crucial in low noise applications like commercial recording where low noise is a feature. Blackbird in Nashville has its own power line and multiple equitechs in house to isolate rooms. My office has a massive refrigerator sized transformer on our power as it used to be a computer manufacturer.
There is validity to using better connectors, wire etc in your power lines. Audio demos do happen in Equitech world, where a better version with significantly upgraded parts does indeed improve the audio performance of gear plugged into it. Equitech makes a 2R using an imported balanced transformer and basic switches and outlets, and a 2RQ version with a better transformer and better connectors, wire and switches. Mastering guys all comment on the sonic differences when they demo both, the 2RQ is the one they typically buy. Normal small studios buy the lesser cost 2R.
Not sure what regulation is used commonly.
Anyway, hope this helps someone. Its taken a while to understand all this but still a lot I don't know.
Brad