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Re: Turntable hum [message #12625 is a reply to message #12622] Sat, 19 November 2005 22:50 Go to previous messageGo to next message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
My set up is really simple. Turntable --> preamp --> speakers/headphones. The preamp itself is grounded; it has a 3-pin power plug and it has never been altered in any way.

The phono stage, if I understand you correctly (I may not be very familiar with terminology), consists of two RCA-type input jacks (one is for the left channel, and another is for the right channel) and two RCA-type output jacks. No other jacks, just these four.

The preamp does have a grounding post, but I am not sure if it is "dedicated to the phono", although it should be, because turntables is what this preamp is made for. I tried grounding my turntable to this post, but it did not help.

Re: Turntable hum [message #12626 is a reply to message #12625] Sun, 20 November 2005 07:23 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Well; let me ask; you must have the pre-amp connected to a amp in there somewhere. Can you tell us what that is and how it is connected. See; if you have isolated the pre-amp and that is not the cause; you've isolated the turntable and you say that is not the cause then we know this; the pre-amp has no problem internally since it works independent of your existing system. The turntable motor is not affecting the cartridge causing hum. The turntable you say worked with another system so that is good internally. This leaves only the possibility of an external connection problem. Either in the wiring between components or in the grounding scheme coming off the wall.
If the pre-amp has a three pronged plug and the turntable has a three pronged plug and the amp also; all going into the house outlet; thats your problem, then you need to float one of the components with a three to two prong adapter because you are creating a ground loop.

Re: Turntable hum [message #12627 is a reply to message #12626] Sun, 20 November 2005 17:21 Go to previous messageGo to next message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
My amplifier is inside my speakers. They are computer speakers and, like most, have an amplifier built in. Speakers work fine with my computer and all other devices, so they are not the cause of this problem.

I tried connecting the grounding wire to the grounding post of my outlet, but the problem is still there. Literally, I grounded my turntable like I would ground any other device that needs to be grounded.

Having this, I begin to think that the problem is really "Either in the wiring between components or in the grounding scheme coming off the wall." as you said.

Tomorrow, I am going to check the inside of my turntable and if everything appears to be fine, then I will have talk to my building's superintendent about the faulty outlets...

Thanks for keeping in touch!

Re: Turntable hum [message #12628 is a reply to message #12627] Sun, 20 November 2005 19:48 Go to previous messageGo to next message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
By the way, do you have any suggestions on what and how I should check inside the turntable?

Re: Turntable hum [message #12629 is a reply to message #12628] Mon, 21 November 2005 06:38 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Just let me ask; did you say you tried the table with another amplifier?

Re: Turntable hum [message #12630 is a reply to message #12629] Mon, 21 November 2005 10:43 Go to previous messageGo to next message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
Setup 1: the preamp (RCA AH500) and the amplifier built into my speakers.

Setup 2: the preamp and the amplifier built into my TV.

These are the only two ways that I tried to set up my turntable.

Re: Turntable hum [message #12631 is a reply to message #12630] Mon, 21 November 2005 12:36 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
And you got hum both ways?

Re: Turntable hum [message #12632 is a reply to message #12631] Mon, 21 November 2005 12:43 Go to previous messageGo to next message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
That is right.

Re: Turntable hum [message #12633 is a reply to message #12609] Mon, 21 November 2005 12:55 Go to previous messageGo to next message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
A series of interesting experiments I did:

1. I tried powering my preamp from one circuit and my turntable from another (had to use an extension cord), not from the same as I did before. No difference. I kept it connected separately until the end of this series of experiments.

2. I tried disconnecting the cartridge. No difference. Then I connected it back.

3. In addition to the hum, I noticed some quiet irregular sounds, short buzzes in particular.

4. Before grounding the turntable, I would get a slight decrease in hum intensity when I touch the platform or the tonearm. Now, having it grounded, it makes no difference whether I touch them or not.

5. Having everything connected I tried touching the RCA plugs with my hands. This did make a difference: the hum intensity decreased slightly.

6. I tried unplugging the turntable out of the power outlet. This did make a difference: the hum intensity decreased a little more than in # 5 and those sounds (see # 3) disappeared.

7. I tried unplugging the turntable's RCA cables out of the preamp. This did make a difference: the hum disappeared completely. (Wow! Now I can really enjoy the music!)

8. The most interesting one! I unplugged the turntable out of the power outlet and began touching the RCA connectors (without disconnection them) with the turntable's power plug prongs. The hum disappeared ALMOST completely. Then I touched the RCA connectors with the grounding prong and the hum disappeared completely.

Sad and funny. Now I am trying to come up with a more precise idea of what might be wrong...

Re: Turntable hum [message #12634 is a reply to message #12631] Mon, 21 November 2005 12:55 Go to previous messageGo to previous message
Anonymous is currently offline  Anonymous
Messages: 38
Registered: December 1969
Baron
See this: http://audioroundtable.com/Turntable/messages/1211.html

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