I would try a Humbuster on the turntable.
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.)
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Follow-up to this problem. So in looking at other grounding/hum issues with my system ( and after listening to some advice from Bill at Fred's Sound of Music om Portland, OR), I purchased a bag of these little devils Brass noise caps for RCA connectors. IMMEDIATE IMPROVEMENT! The hum on the phono selector is gone, and things are pristine again. I still have another intermittent hum issue I am working on, but I am pretty close to getting that solved. Thanks for the suggestions/advice. Should these caps no work, then I have some good ideas of where to go. |
If those caps work to reduce the noise you’re hearing, then the source is most likely not “hum” in the strict sense of the term, which is a 60hz or 120hz (in countries with 60hz AC) noise due to a ground fault. As I understand those caps, their noise reduction effect is due to blocking RFI. I’m still wondering what you use for phono amplification and RIAA filtering. |
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