Switch Question

[schweigc]

Hello, I have recently ordered Crack with Speedball and fully expect to get high. I would like to add to the Crack base input and output selectors. I am new to DIY and an absolute electronics virgin (which I expect to change under the influence of Crack).

I potentially want to be able to switch 3 sources to 3 amplifiers (Crack, low impedance amp, and my HT system (no pre-outs)).
I am planning on using 2 3T4P switches so I am able to switch grounds as well. My questions are as follows:

1.   Do I need a “shorting” or “non-shorting” switch?
2.   Do switch voltage or amperage ratings matter?
3.   Do I need to put 1K Ohm resisters in the ground path?
4.   Is there anything else I need to consider?

Any advice would be greatly appreciated.

Thanks,
Chris

[Grainger49]

1) Shorting, is also called make before break.  It keeps down loud pops.  I would use these.
2) The voltage across and current through an input selector switch is very low.  Any rating is fine.
3) No.  I don't know why you are asking since no Bottlehead uses resistors in grounding.
4) Use stranded wire to and from the selector switch, the finer the strands the better.  Solid wire will break after you turn over the Crack in the first year.

Buy a good but not extremely expensive switch.  Silver contacts are nice since the tarnish is as conductive as the silver itself.  Gold tarnish isn't.

[schweigc]

Thanks Grainger, I truly appreciate your help!

[ramicio]

Does it even matter what a switch's contacts are plated with?  I would think any soft metal like silver or gold would wear off after a few dozen cycles.  Just look at ratings on gold-plated connectors and how many times they are rated to be inserted and removed.  It's not many.  And why would gold tarnish?  Are the switch makers not plating the contacts with 24K gold?  I'm not asking to insult, just asking to understand.

[Grainger49]

Absolutely ! ! !  Read post #2, Reply #1.  If the contacts do not arc (due to current) or slide giving mechanical wear, silver contacts last, as I said above, forever.

You can't see gold tarnish, you can't see aluminum oxide either.  But both are there and oxide and tarnish are not as conductive as the base metals themselves.

If you look through some catalogs you will find that more signal level contacts are silver than gold.  I don't remember seeing gold signal level contacts.  I may have never noticed them, but silver is the standard.

In addition, 24 carat gold is extremely soft, it would wear quickly.

[ramicio]

Except 24 karat gold does not tarnish in oxygen...  You need some pretty nasty chemicals for gold to react at all.  In my mind I was thinking of only sliding mechanics, instead of just a piece rocking back and forth.  Neither metal would wear away from just pressing contact.  Both are very soft metals and for use in jewelry often are taken down in purity.  For gold, this will allow it to tarnish.  I don't know why you would sacrifice the non-tarnishing nature of gold for just a slight bit of hardness for something that doesn't get abraded.  I see plenty of gold-plated contact switches in my electronics catalogs.  Now what conducts better, pure gold, or silver tarnish?

[Grainger49]

ramicio,

You shouldn't have asked the question if you didn't want to hear the answer.  I won't argue.

[ramicio]

Well explain to me how to the entire world it's common sense that gold does not tarnish, but you say it does.  That's the kind of misinformation being spread I take offense to.  But since you won't debate this, you've put yourself up on a plateau and can't be wrong.

[Laudanum]

My understanding is that 24 K gold does not tarnish.  But it is soft and can be worn through so the base metal that it is plated to may tarnish.  Also, if the plating wasnt done so that it was pore free, the base metal would be able to oxidize through.  If it's not 24K gold, then the impurities in the gold can tarnish. 
I dont remeber this for sure but I believe that silver is more conductive than gold.  And since silver tarnish is said to be just as conductive as silver itself, it would make sense that silver tarnish retains higher conductivity than gold.  But Im no expert.

[ramicio]

Pure silver is not much harder than pure gold.  Impure gold doesn't even start tarnishing in air in a normal human lifetime, or even centuries, until you start going below 14 karats.  Silver is the best conducting metal out there, but it tarnishes quite badly.  There is no way the tarnish is as conductive as the metal itself.  If that was the case, they would just coat it with the tarnish in the first place...  It's definitely harder than the metal, too, so you would have a win/win.

[Laudanum]

You seem to have answered your own question then.  So buy switches with gold plated contacts.

[Doc B.]

Guys I am forced to lock this thread. ramicio please read the forum rules.