Re: ruthenium condemns ABX

"Robert Morein" <nowhere@xxxxxxxxxxx> said:

>I have found entire papers on the physics of the contacts that show the
>problem is far more complex.


I am aware of some aspects of those physics.
Generally, in at least line level audio signals, driven from a low
output impedance, those problems are negligible, providing the right
relay or switch is chosen for the application.

For line levels, for me, nothing else comes into consideration but
thoroughly gold-plated, gas filled relays.
For speaker-level signals, a combination of both silver-plated and
gold-plated heavy duty contacts with strong spring action (meaning
contact pressure) are a good choice (if one has to switch
speaker-level signals at all, something I don't like to do at all).

Switching an audio signal at microphone- or phono cartridge levels is
almost not possible without suffering from signal degradation.


>To give an example of something easier to grasp, consider lubrication oil.
>It turns out that lube oil in bearings oxidizes. In bearings with large
>clearances, the effect is negligible. In bearings with small clearances,
>this accelerates death of the bearing.


I'm not sure if this is comparable to relay switch action.


>There seems to be an assumption that because audio is low frequency, and
>because it's been around for a long time, and because it can be realized
>without microelectronics, that audio is far removed from quantum effects.
>But you, as a tube user, know this to be false, because when you turn up the
>gain, you hear shot noise, which is a quantum effect.


Correct, but what's the correlation between shot noise and relay
contacts, else than possibly involved quantum mech effects?


>Likewise, it turns out that the physics of contacts involves both quantum
>effects and something else. The contact pairs have the characteristics of an
>unintentional nanomachine. At this scale, mechanical and electrical
>characteristics become intertwined. Remember that line level audio, at the
>zero crossing, involves nanoamps and microvolts.


Also correct, that's why selecting the right relay for the job is so
important.
I've measured signal drops of >3 dB with badly chosen relays (IMHO),
in a circuit with impedances involved of about 50 kohms.
That was in a highly touted high end product (a preamp), the type of
which I won't reveal as to not disappoint readers in posession of said
preamp :-)


>In order to introduce the subject, I asked the question, "For two hard,
>imperfectly flat surfaces, what are the maximum number of contact points?"
>The purpose was to invite some discovery on the part of the readers of this
>newsgroup.


I said 3 contact points, 3 points being the most stable way to put two
surfaces together (think about a table with 3 legs).
Applying more contact pressure won't change that :-)

--

"Audio as a serious hobby is going down the tubes."
- Howard Ferstler, 25/4/2005
.

Relevant Pages

  • Re: ruthenium condemns ABX
    ... > Generally, in at least line level audio signals, driven from a low ... > Switching an audio signal at microphone- or phono cartridge levels is ... > I'm not sure if this is comparable to relay switch action. ... that audio is far removed from quantum effects. ...
    (rec.audio.opinion)
  • Re: Scottie Terrierborgs ongoing dread of DBTs
    ... :I did not 'invoke' Arny, ... I was talking about his audio ... his assertions about specs and audibility ... If two items produce identical signals, ...
    (rec.audio.opinion)
  • Re: Artifact Audibility Comparisons
    ... In the case that your original audio signal is a sine ... jitter and other kinds of distortion, ... single tone by itself wouldn't be at that level. ... probably isn't a file of naturally-occuring audio signals. ...
    (rec.audio.pro)
  • Re: BBC2 on UHF38?
    ... If you can see a picture, you can hear the FM sound. ... This used to be generally true when the audio was 6dB below the video. ... Of course reception of IF images of VSB broadcast signals will have no ... twisted together the incoming and outgoing cables and the flylead. ...
    (uk.tech.broadcast)
  • Re: Better than ABX?
    ... signals. ... Then, using Bill Waslo's "Audio ... A consumer player is certainly not good enough. ... I don' t know anything about the short term stability of consumer ...
    (rec.audio.opinion)
Loading