Re: Where to buy HQ pot meter and source selector switch



Serge Auckland wrote:

"Eeyore" wrote
jamesgangnc wrote:
"Eeyore" wrote
jamesgangnc wrote:
"Edmund" wrote

May be OT but I need an HQ pot meter for volume and
a source selector switch for my home build pre amplifier.
For the selector switch, the more selections the better!
Can anyone point me in a good direction?

Thanks

Edmund

You might take a look at chip switches. I have used them for a few
projects now. You can use as many as you want. They switch cleaner.

http://focus.ti.com/lit/ds/symlink/cd4066b.pdf

4066s are shockingly bad. At least consider something half reasomable
like a DG308 or 211. Or even discrete fets.

The spec sheet suggests they are ok. Did you test some?

4066s ? Sure. Look at the on resistance variation with applied signal
level. That means DISTORTION !

They are very inferior switches for audio. The Siliconix types I mentioned
are
vastly better put purists use jfets.

I speak as a pro-audio designer btw.


Yes, I missed the variation in on-resistance with voltage. My first design
job in Broadcast was to design audio routing switchers for OB vehicles. I
used a Siliconix jFET as a series element, and found that I didn't even need
a shunt element to provide more than acceptable isolation. However, with
professional levels, I couldn't get the switch to pass or stop +22dBu

Doubtless insufficient pinch-offf voltage.


and had to attenuate by 10dB going into the switch and restore by 10dB after.
Nevertheless, the router that resulted was considered at the time (1973)
pretty much state-of-the-art.

To this day I still use the J109-112 and J172-5 or whatever discrete jfet
series.

Graham

.

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