[sdiy] Relays or reed switches for routing?

[Mike Bryant]

Go to Mouser and sort by highest price first and work down.   Good relays aren't cheap.  

If you want to see "as good as it gets no matter what the price" have a look at https://uk.rs-online.com/web/p/high-frequency-rf-relays/7582455/
10 million cycles, DC to UHF, almost zero resistance .... and now almost $100 each :-)    We used to use them by the handful at HP, but they used to be a lot cheaper.





-----Original Message-----
From: cheater cheater [mailto:cheater00social at gmail.com] 
Sent: 31 May 2021 21:56
To: Mike Bryant
Cc: Gordonjcp; synth-diy at synth-diy.org
Subject: Re: [sdiy] Relays or reed switches for routing?

On Mon, May 31, 2021 at 9:56 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> > The fine layer of oxide on the contact that never gets wiped away and never gets "burnt through" because the current is too low.
>
> The highest quality relays can't have a layer of oxide as gold plating on silver nickel simply cannot oxidise - it's chemically impossible.   The thickness of the gold plating determines the lifetime of the relay, with ones available for over a million operations if you want.  But a typical 100,000 operation one will be more than good enough for any audio application I can think of.
>
> Or if you want something a little cheaper the hermetically sealed but unplated or rhodium plated silver nickel contact ones likewise won't oxidise as there is no oxygen in the sealed contact area.
>
> It's only the vented ones with pure silver contacts that do what you suggest as those have the lowest resistance and are designed for switching power lines or high current signals, not low level audio signals.
>
> Cheater just referred me to a product I designed over 40 years ago 
> that is still running and the audio path on that is absolutely stuffed 
> full of relays.  http://www.museum-nt.de/objekte/hp_3779c.html

That's really interesting. I knew all that stuff about relays ages ago, so thanks for reminding me about all of it. I'll have a gander at what's available on Mouser - sounds like a fun evening.

Cheers