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240z4u 9th October 2007 05:08 PM

Will these work as input selectors?

I have been reading the archives, and I am looking for something to use as a selector switch for an input on 12b4 line stage.

Will these work okay?

Thanks - Evan

jackinnj 9th October 2007 05:18 PM

We used those all the time in ham radio for bandswitching -- the only problem may be some oxidation on the contacts. They are sure to be lower leakage than any phenolic switch you can purchase.

Note that you can often adjust the number of stops on the switch -- they come apart completely.

240z4u 9th October 2007 05:57 PM

Wicked, I read about these in the archives and they seemed like a good candidate.

Thanks alot! - Evan

AndrewT 10th October 2007 07:59 AM

standard wafer switch with a good substrate.
They have a wiping action on the contacts, helping to reduce the effect of corrosion.
No mention of contact material or coating/plating.

You may need to clean these annually. Switch cleaner and lots of twiddling usually works. Make sure power is completely off and allow time for volatiles to evaporate.

They often have a high torque requirement and need a flat ground on the shaft with a strong knob locking screw.

Have a look at the aikido attenuator. A cascaded pair of low db step change (also doubles up as balance control) and a high db step change to cover a range of 0 to -60db in 1db steps.
But change the resistor values from the standard supplied (all the values in the tables ignore the usual rule of attenuator <<< than Zin that follows).

240z4u 10th October 2007 12:35 PM

Thanks for the suggestion Andrew.

I actually have a stereo noble pot lying around for volume control.

Interesting observation on the torque required to turn that particular knob.

My dad is older, but not elderly. I would like to think he could be using this preamp for the rest of his life. A very stiff selector would be a bad choice I think.

I am going to go ahead and order something audiophile-ish for dad since I already had the volume pot.

Thanks guys - Evan

AndrewT 12th October 2007 10:13 AM

a big chunky knob or one of the pointer type knobs would be operable by the less able.

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