Im looking at panel mount push button switches and in the data sheets for many switches you can find minimum current/voltage rating specified. I believe this should be followed to prevent the formation of insulating oxides (wetting current). So for true bypass wiring for a guitar signal is this value critical when choosing switch? The push button switch I wanna use has 10mA 5VAC minimum current/voltage. I have never thought about this before and maybe I'm overthinking it but I'm interested to know if you guys has anything to say about it. Thanks
It would be negligible or irrelevant for guitar pedal uses I reckon.
Quote from: Buffalo Tom on July 18, 2017, 06:10:08 PM
The push button switch I wanna use has 10mA 5VAC minimum current/voltage.
?????
@B.T.: Unamplified guitar signals are a fraction of a volt and microamps. There are few switches that will talk about switching those levels. But you'll likely be fine with a 10ma/5VAC switch.
The specs for minimum signal on a switch don't really mean that they will not switch any smaller signals, just that the manufacturer will warrant the nominally specified lifetime at those signal levels. When new, metal contact switches will switch small signals well. The problem comes with aging and oxidation on the contacts. Oxide and crud layers form an insulating surface that can keep the contacts microscopically separated. The crud layer isn't a particularly durable insulator, so some amount of voltage can punch through it. The manufacturer tells you what minimum voltage is needed to punch through the typical crud layer on his metallurgy in the contacts. Current can burn away crud and remove oxides as well. The minimum current spec is a suggested minimum to help clearing the crud.
It used to be common for service techs to carry a relay contact burnishing tool - a small "file" type thing with a mildly abrasive/polishing surface. This was for inserting between contacts and rubbing back and forth to clean the contact surfaces.
There are switches designed explicitly for switching even microvolt levels, but they're the exception, not the rule.
Quote from: antonis on July 19, 2017, 05:52:10 AM
Quote from: Buffalo Tom on July 18, 2017, 06:10:08 PM
The push button switch I wanna use has 10mA 5VAC minimum current/voltage.
?????
(https://cdn.pbrd.co/images/GBFonce.png)
My bad, Tom - thought you made some kind of typo.. :icon_redface:
Some switch manufacturers including relay manufacturers have contacts rated for "dry" service down to zero current and voltage. This is a contact made of noble metals that will not oxidize and therefore will not require the arc you get when the switch is opened (and to a lesser extent, closed) to keep the contacts clean. Reed switches and relays with sealed contacts are often plated with ruthenium, a noble metal that is soft but resists arcing very well and these contacts are suitable for dry contact to higher current service. Some relay manufacturers had relays available with optional contacts for different current levels.
There doesn't seem to be a lot of trouble with stompbox switches getting intermittent or going to higher resistance. They tend to fail due to excessive soldering heat moving the contacts or mechanical trouble with the alternate-action switching mechanism. The switches are the most unreliable part of the design which is why Boss and other commercial manufacturers have gone to purely electronic switching actuated by a single normally-open contact. If you are using a panel-mount pushbutton switch, your burst box will probably be fine.