On/Off Switch

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.

I would be more concerned with the IEC connection made between the power cord female connector and the male inlet connector on the back of the equipment, than the power switch.

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.

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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.  

The on/off function in our Olympia power Amplifiers are made with a 40A Triac in series with 4 Inrush Current limiters in series parallel - once the initial inrush current is over  (which is VERY large when using a 4KVA transformer / 1 Farad  power supply)  2 each 20A relays with 2 contacts on each (theoretically capable of switching 80 Ampere) bypass the Triac/inrush limiter circuit.   To turn off the amplifier the low level signal to the relays coils are switched off.

This have proven a very reliable way to handle the on/off function. 

http://pbnaudio.com/audio-components/audio-amplifiers/olympia-ebsa-3

Good Listening

Peter 

"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