[sdiy] Relays or reed switches for routing?

cheater cheater cheater00social at gmail.com
Tue Jun 1 00:02:33 CEST 2021


On Mon, May 31, 2021 at 11:05 PM David G Dixon <dixon at mail.ubc.ca> wrote:
>
> For audio switching, why would anyone today use anything other than a CMOS
> switch?

Correct me if I'm wrong, but CMOS doesn't switch 50Vpp. That's the
line, unamplified signal, which needs to be switched.

> -----Original Message-----
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Tom
> Wiltshire
> Sent: Monday, May 31, 2021 1:48 PM
> To: cheater cheater
> Cc: synth-diy
> Subject: Re: [sdiy] Relays or reed switches for routing?
>
> [CAUTION: Non-UBC Email]
>
> It's not that they cause distortion. If there is a problem with relays, it
> would be contact bounce. The acoustic noise they make is not the issue so
> much as the electrical noise. They switch fast, so any non-zero signal
> causes a click. Obviously some are much worse than others. Some may be good
> enough. Silent switching generally means "slow switching" - it's a crossfade
> in a few tens of msecs, not a hard jump from one to another.
>
> In stompbox-world, a lot of people are currently hung up on "true bypass
> switching" which is (mostly) taken to mean a solid path of metal from input
> to output when the effect is out of circuit. This is the current holy grail
> because having extra buffers in your signal path is taken to be clearly
> wrong (despite highly-thought-of mixing desks having dozens between the
> signal coming in and going out). In an attempt to meet this demand whilst
> providing silent switching (and also to avoid expensive and failure-prone
> 3PDT footswitches), some manufacturers have moved to relays, but these are
> often (mostly) accompanied by some type of short-to-ground element to
> silence the output while the relay switches. This makes up for the
> instantaneous switching and contact bounce of the metal-on-metal relay
> switching. The previous pedal generation used FETs to provide this switching
> action, and they could be ramped on softly, unlike relays. But for
> pedalworld, switching FETs in the signal path and the buffers that go with
> them are now often regarded as not the right answer, so other solutions have
> been found that hit the current marketing buzzword.
>
> HTH,
> Tom
>
> ==================
>        Electric Druid
> Synth & Stompbox DIY
> ==================
>
>
>
> > On 31 May 2021, at 13:57, cheater cheater via Synth-diy
> <synth-diy at synth-diy.org> wrote:
> >
> > Why would relays introduce distortion? Aren't they just a conductor
> > that gets mechanically moved back and forth. What's the nonlinearity?
> >
> > On Mon, May 31, 2021 at 2:10 PM Gordonjcp <gordonjcp at gjcp.net> wrote:
> >>
> >> On Sun, May 30, 2021 at 11:22:38AM +0200, cheater cheater wrote:
> >>> Why can I not use relays to switch audio? What's wrong with relays?
> >>>
> >>> BTW, I was thinking of acoustically dampening relays. EG use sound
> >>> proofing foam.
> >>
> >> They're electrically noisy as well as mechanically noisy.  They're
> unreliable when you use them for switching tiny currents.  They introduce a
> lot of distortion.
> >>
> >> Literally nothing sane uses relays in the audio path.
> >>
> >> --
> >> Gordonjcp
> >>
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