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In need of a GOOD 3:1/4:1 passive input selector

I have two turntables and will be adding a 3rd to my main system. It will be used to screen records purchased from less than ideal locales (goodwill, garage sale, etc). I have a 4:1 passive ’preamp’ (sic) that I use with my primary turntables on my Bryston 1B-MC. The problem I hear is a audible low-frequency hum over the speakers at around 70 hz regardless of the input I select. Both tables are grounded. If I select one table over the other and connect directly to the back of the preamp, the hum goes away. This tells me that the selector i have is, well, a cheap POS.

Is there a solid 2:1 or 4:1 passive selector that filters out the hum?

(NOTE: worst case, I could create a filter that filters out the hum. but seeing as it is the 70hz and below region, I will cut-off some low frequency information.)

jcipale
jcipale's avatar
jcipale OP
71 posts
 

More good news on this front.

I started looking "behind the curtain" if you will. While the last vestige of noise was rattling my brain, I shifted one of my power cables and the hum went away. Hmmmm...

After contemplating things a moment, a slash of inspiration like a bolt of lightning from Zeus hit me! Basic electrical wiring knowledge! So I remounted my power strips,  rerouted and secured the cables along a horizontal shelf, oriented the cabling to be at 90 degrees to the power cables and wrapped them in rfi shielding. Everything is crystal clear!

I knew keeping those old circuits books would pay off.

dogberry
827 posts
 

Well done!

jcipale's avatar
jcipale OP
71 posts
 

Another thing I did (which I failed to elaborate), I utilized the Bryston's two switched outlets (and soon 3rd once I fix the BIC). I think that was the biggest fix that was, in all actuality, the simplest fix. Common ground between the turntables referenced a single reference.

 

You gotta love electricity. 

😁

Thanks for all the words of wisdom to everybody!

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