Why whole house surge protectors are not enough

Erik - 

If the spike your equipment encounters is coming from the same branch circuit feeding it (say a wonky vacuum cleaner in the next room), the spike will probably get to your components before it is snubbed by the WHSP back at the service entrance panel. It can be tough to explain that to the cleaning service.  BTW, my WHSP was a Square-D that I installed when putting an addition on my house back in 1997.  A big, clunky 7" cube I mounted next to the SE panel, but I never lost equipment to a surge, and that is a lot of service years.  

On the topic of MOV's - they absorb surges until they can't, then they pop. If the surge is a long one or a big one, there may be enough of it left to still do some damage beyond where the MOV USED TO BE, and if it is a tree branch shorting between phases or worse - to a higher voltage circuit, the MOV may now be just a couple of leads with an air-gap between them.  

The VR feature you mention can be quite valuable, although it may not be a big deal with all solid state equipment because SS runs at low voltages internally, and a swing of 20-30V on the line may end up being quite low once it gets past the step-down circuitry in the device. Even so, the dielectric stress, across the tiny dimensions within the semiconductor chips can still be impressive.  OTOH, with tube equipment, especially older units that lack VR in the device, when the line voltage is stepped up for the tubes themselves, that swing is magnified and is more likely to impact the sonics and life of the tube.  When the unit was designed and tubes cost $5 from your corner TV shop, that was not the concern it can be today.  Probably most people have had a "brown-out" at one time or another caused by a tree branch shorting a power line to ground in a storm.  Worse is when a higher voltage distribution line gets in contact with the low voltage feed to your home and raises the voltage to your place by a couple orders of magnitude. I had that happen to a customer and the utility company got to replace a bunch of stuff for them. Hardware can be replaced, but not so easy to rebuild what is on your media server. 

It is an uncommon step to take, but having a device (or simply a single connection to unplug and air-gap your sensitive stuff from the outside world) can go a long way to protecting you.  Keep in mind that you should also disconnect the cable feed to your cable modem and protect the power feed to EVERY point on your network.  A surge or non-standard voltage can come in through ANY point that is not protected and will continue until it is snubbed or it literally burns out the circuitry  --  be it a semiconductor, capacitor, or even a trace on a circuit board - an effect that is usually terminal for the device.   Unfortunately, a good spike can often turn the diodes in your power supply rectifier bridge into fuses, and they seldom just clip in.

Surge protection and isolation are intended to protect you from something from somewhere else getting to the stuff you want to protect.  I designed in Whole House protection at the main panel of my home and that protects two ways - between the two 110V phases that add together to provide 220V to HVAC, stoves, and other large loads like big swimming pool pumps, etc. 

That does NOTHING to protect you from the start-up spike put on the line on a single 110V phase when you turn on a vacuum cleaner, table saw, refrigerator or other significant motor load anywhere inside the perimeter protection of a WHSP unit. Your HVAC Air Conditioner will often put a spike on BOTH poles because those units usually run on 220 V. the worst culprit is not the fans inside or out, but the compressor motor in the outdoor part of your system.  If you look in your circuit breaker box, you will usually find several double-wide breakers with a handle that links both sides together.  That will be something that uses 220V and is probably a big load that can noticeably affect your whole house. 

Although some of your devices may have their own universal power adapters that will output the desired voltage to the attached equipment despite the incoming voltage, a large but purely resistive load like electric heat kicking on will drop your line voltage enough so your other equipment may still notice the effect and not be running at optimum unless you have a buck/boost AVR (automatic voltage regulation) unit like a good UPS between that big load and your sensitive devices.  Just don't get an inexpensive unit that puts out anything other than pure sine wave power or you will be creating more pollution on the power line than you are isolating your stuff from.  Some units even run you on batteries full time and just use the house power to charge the batteries. 

Just make sure you do not run different parts of your system on multiple sources or you may have serious grounding issues. This also means that you want to avoid running some devices from the "surge only" outlets on a UPS and other devices on the "battery backup" outlets of the same UPS, or worse, from another UPS' battery supported outlets.  Having a variety of ground potentials across your system can have some weird and undesired effects.  This is where you want someone who can design and put together a good system isolation and protection scheme for you, not just someone who can meet local codes for safety. 

Any decent sized motor load (or a poorly designed one) can also put a sharp spike on the power line when it turns on or off that can cause even more havoc. Transients are NOT your friend and are more likely to be regularly attacking you from within your home than the less likely but occasionally more devastating external hits.  You want to get the best possible sound from your investment, AND protect the devices that give it to you.

I happen to use a combination of Monster Power and PanaMax line conditioner / surge suppressor devices that isolate each outlet optimally for the type of interference the connected devices are most susceptible to.  There are better and newer devices out there now, but these have worked well for me.  

Something I did not expect, was a hit one of my customers took recently when lightning came in on the shield wire of his fiber internet connection and took out about a dozen devices across his network.  The UPS isolated the power, but routers, modems, network switches and even network cards in workstations got fried.  The ISP had decided they did not want their ethernet cable grounded through the UPS, and they had not put a ground tie on the fiber cable before it went to their fiber-to-ethernet conversion box, so they replaced just about everything they had on site.  Not grounding their cable at the point of entry to the building was as egregious an error as not installing a whole house surge suppression box at your main power panel.   Electricity is like water - it will flow wherever it is easy to get to.  Just because the fiber isolates the data signal from EMI does not mean that the cable shield, which is there for mechanical protection as well as tensile strength, cannot carry a surge onto your premises.  

Mfinch - 

You may be right that it is hard to get the utility to pay for a new WHSP box, but my goal is to protect my audio equipment investment, and if I can just replace a couple of hundred bucks worth of surge protection and still have my sound system, I call that a win! 

Trouble is, not many folks rig up their WHSP box with full temporary isolation so they can take it out of circuit and test it to see if it still works after you think it has taken a hit.  I'm "old school" and although in-circuit testing can be done, I feel more comfortable when testing just the device, unaffected by anything else. 

In general, the components that provide the surge protection DO degrade over time from the many small hits they will inevitably receive, and so should be tested or replaced once or twice a decade, or more often if your area might indicate it is needed (Florida or similar?).

Erik - 

I totally agree.  I speak from the hard experience where the contractor originally building my home ran out of positions in the SE panel and rather than put in breakers with two circuits per box position or add a secondary panel, they just put the last 4 rooms on the same circuit.  Running the toaster and the garage door opener at the same time always popped the breaker. 

When I redesigned the home, I put in a new main SE panel that was the max allowed by the local utility and then added several subpanels throughout the house.  With well-marked and dedicated circuits available, it becomes very easy to isolate my gear when desirable. 

If the stud walls are still open, it is trivial to run separate circuits for your power amp and your lower-power devices.  I also got a deal on some cable so I ran 1/0 aluminum from the main panel to the subs, so there was minimal drop to each of the 60A panels. By running some #8 cable for the power amp back to the subpanel, that gives a fairly stiff source for the amp to draw from, and compared to the cost of the designer cables used between the wall socket and the devices, the extra in-wall cable cost was almost trivial. 

 #8 has twice the max allowable ampacity of the #12 that is almost universally used for residential outlet circuits, so when the amps ask for power, the in-wall wiring can provide it, potentially adding some punch to your music.  You just have to be careful to get #8 copper, not aluminum to get the full benefit because aluminum is used for the larger wire sizes because it becomes much cheaper, but the conductivity is somewhat less.  When you get up to sizes like the 1/0, those are almost always aluminum, and at that ampacity, the droop caused by the draw of your amp is minimal.