Turntable selector hum

[edgarryan]

Tried to build a turntable selector recently. Parts were sourced from Raon, mostly cheap. When I plugged in three turntables, I noticed a hum. All three are properly grounded. One TT is connected first to an SUT, while the other two are directly connected to the selector, then all three to a phonostage. What could the problem be? Should I use higher quality parts to avoid the problem?

[plasticman]

Hi sir!

You'll need to "hunt" for the source of the hum now. It can be quick, kung matyambahan, or a complete PITA.

i would suggest that you try to connect one turntable at a time and check if it is a specific turntable that produces the hum. You might have to also try to connect a single TT to the different inputs to check if it is a specific input connection that's the culprit.

Another thing is to get a length of wire and check if grounding the selector to the phonostage will eliminate or lessen the hum. Pwde din selector to preamp, TT's directly to the phonostge, etc. Or combination of groundings.

Like I said, it can be a real PITA!!!

Good luck!

[Jon Agner]

the more components along the line, expect that there'll be a hum

To find the hum, simply use a few alligator clips to gound all the components together (switch, phonostage, SUT, turntable, tonearm, amps,) then unclip each component at a time. If there is still a hum even if all components are already grounded together, then you'll need to have your equipment earth grounded. If you have a landline, or your cable company provided a ground rod for your cable/phone line, then simply run a gauge 12 or 10 wire to connect your equipment ground to the earth ground.

HTH.

[edgarryan]

I didn't think of grounding the selector itself. I thought grouding the components would be enough. WIll try your suggestions later. Thanks!

[ambel]

Did you use shielded wires and interconnects ? If not then the hum is induced.

[edgarryan]

Yup, I used shielded wire and interconnects. Even the RCA plugs are shielded with shrinkable tubes.

How do I ground the switch? The chassis is made of plastic.

[edgarryan]

Really going out of my mind here. Tried to do all suggestions, but the hum persists. The problem is not with the turntables since individually connected to the phonostage, they do not make noise. The selector really is the culprit, though I do not know how to remedy it.

[n_dot]

Really going out of my mind here. Tried to do all suggestions, but the hum persists. The problem is not with the turntables since individually connected to the phonostage, they do not make noise. The selector really is the culprit, though I do not know how to remedy it.

Sir I presume your selector has no ground connection? How did you connect ground leads of the 3 tables going to the phono stage? You can try to directly connect ground lead of your 3 tables to the phono stage ground.

[edgarryan]

Yup, that's what I did. The ground leads were connected directly to the phonostage. Might discard the project altogether and just buy a ready-made unit.

[Jon Agner]

did you do a common ground on your selector switch? also, check your connections, there may be a loose somewhere

[hypertriode]

You have a ground loop edgarryan. You have to switch all four phono terminals (R+, R-, L+ & L-) independently. No common ground with the R- & L-. Common ground is chassis ground. I can help with your problem if it can wait after the Hi-Fi show bro

[soundpurist]

You have a ground loop edgarryan. You have to switch all four phono terminals (R+, R-, L+ & L-) independently. No common ground with the R- & L-. Common ground is chassis ground. I can help with your problem if it can wait after the Hi-Fi show bro

Rene did a switcher for 3 tts several years ago for me, no hum whatsoever.Until now am still using it

[edgarryan]

You have a ground loop edgarryan. You have to switch all four phono terminals (R+, R-, L+ & L-) independently. No common ground with the R- & L-. Common ground is chassis ground. I can help with your problem if it can wait after the Hi-Fi show bro

Rene did a switcher for 3 tts several years ago for me, no hum whatsoever.Until now am still using it

That's exactly what I'm trying to copy. I looked at the pictures Rene posted, and it seems that I did the same. Iba talaga pag master ang gumawa.

Would it make any difference if I connected lugs for the ground in the chassis of the switcher? I only connected the ground wire to the SUT and phonostage. I have not provided any ground for the switcher.

[edgarryan]

You have a ground loop edgarryan. You have to switch all four phono terminals (R+, R-, L+ & L-) independently. No common ground with the R- & L-. Common ground is chassis ground. I can help with your problem if it can wait after the Hi-Fi show bro

Thanks for the offer. I will bring it to your shop after the Hi-Fi Show, if I still can't fix the problem. Condolences nga pala.

[hypertriode]

You have a ground loop edgarryan. You have to switch all four phono terminals (R+, R-, L+ & L-) independently. No common ground with the R- & L-. Common ground is chassis ground. I can help with your problem if it can wait after the Hi-Fi show bro

Thanks for the offer. I will bring it to your shop after the Hi-Fi Show, if I still can't fix the problem. Condolences nga pala.

Thanks bro!