On/Off Switch

LED indicator lights have also been found to slightly pollute the sound as well.

All this shows nothing more than the futility of cheap power switches. In gear that can be left on all time, you might consider removing the switch, and its associated wiring leads, altogether and use slightly better wiring in the bypass. Many DIY'ers and modders have recommended this. 

If you need the switch in place, consider something like the higher-quality, silver-contact, 2-way toggle switches. Online electrical supply houses often have them. Parts Express might have one or two, I don't know. Also try Goldpoint.

The cheap-@ss sliding, pushbutton or rocker switches in almost everything are indeed a bottleneck for sound, but most audiophiles are not aware of it and as a result, so far, neither are the manufacturers. I'm sure they'll figure it out someday.

nenon,

Reading from your subsequent posts, I think maybe I've been going about this all wrong. Since you're building your own amp And you need the switch installed at the rear panel before the fuse and power supply, then that may change our game entirely. It will be easy IF you have room enough in your chassis to swing it, but here we can likely dispense with considering the usual small, or "miniaturized", switches and focus on the "large" switches instead. These (heavy duty) switches have a form factor that allows them to be a drop-in replacement into a standard residential light switch...I know this is a rather large size to think about putting in an amp build, but I think this likely the way to go and I'll tell you why.

With the form factor this large, all your wire gauge and soldering concerns are eliminated. Just one I happened to look at from Hubble (HBL 1201IL) has a solid copper contact arm with both large contact, surface patches being silver (not some silver alloy) (necessary in these larger, heavy-duty switches to prevent welding). The contact arm and internal wiring are generously beefy and you just connect your large gauge wires to the screw terminals, same as with any other light switch - no soldering at all, and the contacts can be cleaned out as often as you ever need. This switch comes in single-pole, 15A, 20A and 30A. Online prices for these types of switches appear to be roughly anywhere between $20 to $50 each, depending.

But, like I say, maybe the only real concern with this type switch is whether or not your chassis can be made to accommodate the larger size and how difficult it will be to drill for the switch cutout. Exact dimensions are always available online with these large switches, along with all the specs.

But, in short: heavy duty, correct amperage rating for your app, best materials, easy to connect/disconnect. 

Even if it's a challenge to install something like this in your rear panel from a practical standpoint, I think that I would much rather try this than a circuit breaker since (you guessed it) they too degrade the sound (as virtually Any switch or connector can be expected to do, really)...even the ones in our circuit breaker box, but there's not all that much that can be done about that, of course.

Hope this helps.

Congrats to Astros fans. Finally a world series win!!

I did neglect to address your other Q’s in your OP, but I’d say that your original instincts are correct about that if all the other AC ancillaries (power cords, fuses, power supplies, IEC inlets, duplexes, etc) are fair game for ’getting it right’, then why not on/off switches? I concur. Might throw in fuse holders too, really. In fact I’d say that ALL switches, connectors, fuses, breakers, et al, are The Spawn of Satan in the audio world. The best sounding connector or switch, ideally, is none at all...hardwired bypass will always sound better. But, what can we say, there’s no practical way to live with a "hardwired bypass" condition on everything - totally impractical, impracticable, and definitely downright dangerous! So they are evil - but, a necessary evil, so we accept them and what they can do for us in the real world.

As for an amp power switch, most of the time, from a purely operational standpoint anyway, we might consider for a moment that a power switch for the usual hifi amp may not even be necessary. We could, if the amp is not in a rack or cabinet, just plug and unplug the power cord, presumably, for amps that are not to be left on anyway. 

But, in practice, this can be a little dicey sometimes. Unplugging or plugging in too slowly or awkwardly can exaggerate the arcing at the contact points and the arcing may be enough in some circumstances to blow that expensive designer fuse, or perhaps do some kind of damage to the amp, even whether it has some measure of protection or not. Even if no damage to the gear ever occurs, the carbon buildup inside the female AC receptacle will be frequently occurring and impossibly difficult to clean.

And suppose that very rare instance occurs to you one day and your amp suddenly is making a very LOUD and nasty noise and in a second you realize that the power has to be cut immediately or the worst may happen. If the power cord were momentarily inaccessible (as in the rack or cabinet scenario), then the front-panel switch could be a gear saver. An available switch would be the fastest and most reliable way to avoid imminent meltdown. Rare maybe, but in the life of many an audiophile, that day has already come...or is probably going to.

So, for those practical concerns alone, I’d argue that the switch is necessary...and that as long as that’s true, then it might as well be audibly the best kind for the job that is still affordable overall.

"Note. The power switch is a snap switch and should always be manually closed and opened in quick follow through movement. Especially on power amps. This will help in preventing of arcing when the switch is being opened. Arcing can/will cause pitting of the contact surfaces. Sufficient pitting will result in lower conductivity through the closed contacts. Enough pitting will cause a VD, voltage drop, to be created across the contacts of the switch. With VD, heat, followed by carbon, followed by more VD, more heat, arcing, and eventually the switch will fail."

Absofreakin'loutely. Great point about reliability.

"When you make Power amplifiers with extremely large power supplies the on/off function becomes an important issue, not only for being able to start the Amplifier but also for making the switching function last for a very long time."   

Agreed again, another great point: the more power, the more the concern about the power switch.

The power switch under normal circumstances is not necessarily the biggest concern in the power path, true, but if you're building and looking to upgrade the whole chain, then perhaps it should not be forgotten.

Regards to all, John