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Old 26th April 2002, 03:44 AM   #1
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Question Mercury wetted relay contacts

Are there any audible signal benefits to using mercury wetted contact (MWC) relays that are in the direct signal path of the attenuator section of a preamplifier?

I did a search and found only one hit on mercury wetted relay contacts. It had no information concerning the audible differences between small signal, reed, or MWC relays.

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Old 26th April 2002, 08:35 AM   #2
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The mercury wetted contact are the only one (with low resistance) without contact bounces. Unfortunatly mercury is toxic and those kind of relays are forbibben to sell unless it's for replacement.

I think you should go for e.i. the NIAS DS-type (very good) and also read relays. The thing you must look for is the minimum current and power through the conatcts. Goldplated silver contacts is good. By accident I have DS-relays for sale....
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Old 3rd May 2002, 02:01 AM   #3
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You can get hold of them surplus pretty easily - try ebay. As to the sonic merits, I don't know. They were recommended in some tube book I once read, no chance of contact corrosion I think was the theory, but then having thought about that, something must make contact with the non-corroding mercury...

I'm going to use them, as I have them, but I'm not going to be any help in opining on relative sonic merits cause I've got 'em so I'm using in them, in fine scientific style!

I can let you have one or two if you want to play with 'em in your signal path, on condition that you report the results. Preferably, as I'm being so scientific, positively!

Jake
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Old 7th June 2002, 03:49 PM   #4
Alf is offline Alf
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I have used MWC extensivly in all of my preamp designs. I have found that "reed's" produce an audible 'ping' in the audio when closing. If not for that one problem, they would work great. Typical low signal relays corrode after a while. A thin "skin" tends to build up on the contacts, and being of a low level, current, the line signal can't break through it. I have tried every type of contact cleaner/conditioner there is on the market with not much success. As far as electronic switching, I have yet to find any worth while cct's that are bias free. Input and output decoupling always calls for the addition of more "caps" thus degrading the audio futher. The only problem I have found with MWC's, you can't tip them upside down. This poses a problem when working on your project. I have a pile of these beastys, if you'd like to try some, let me know.
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Old 7th June 2002, 04:43 PM   #5
tiroth is offline tiroth  United States
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Mercury typically oxidizes quite rapidly. Do these relays use some kind of alloy that is more resistant to this, or are they hermetically sealed? If the latter, I wonder whether there is a significant difference when compared to alternate hermetic relays in terms of corrosion resistance.

I try to stick to Au clad Ag for low level signals.
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Old 7th June 2002, 04:56 PM   #6
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Hiya, the ones that I use are sealed, much like the "reeds". The metal "can" also provides a shield when grounded. From my testing, these MWC relays are sonically invisable. I have replaced many mode switches and standard relays with the MWC's. I have also found, a lot of audio path wiring could be removed once these where installed, eliminating the potential for ground loops, inducted noise and capacitive loading.
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