weird hum from turntable

[leeroy]

I just bought a Project RPM-1 carbon with the Ortofon 2M red on it, I get an odd hum at all times and as I add volume it gets worse but the only time it goes away is when I put the needle cover on it. I changed the ground a couple times and it is still there. Moving the turntable from the speakers makes no difference on the hum.
 the TT sits on a wooden legged stand with 2 metal bars across the top and a glass shelf sitting on the bars. the UMC-200 is below it and below that is the Amp.

[mdenari]

So is your TT sitting on a glass shelf?

[leeroy]

yes

[mdenari]

Glass is well known for being very efficient in transferring all sorts of vibration. Try a cheap trick, get one of those plastic food chopping boards that come with 4 rubber little legs and put the TV on top of it. Believe it or not, they are great for isolation. See What happens...

[leeroy]

k thanx will try this tomorrow. what about wood? tv is hung on wall and is always off when TT is on

[mdenari]

Could also work, I used the plastic one and removed 100÷ of the hum. I have a rep 1.3 génie.

The idea is at least see if it changes, for good or worse, then you know your line of work...

[leeroy]

true gotta start somewhere

[plm]

It is mains hum? I would start with physically moving the turntable off its current shelf temporarily to see if the noise level changes. Plus I'd also drop the needle on a record and disconnect the turntable mains power completely, so you can see if it's proximity of the cartridge to the motor. Some cartridges are prone to this.

Essentially you want to figure out what the source of the hum is, and then you can look at ways of mitigating it.

Also, with it in its current position, pull the mains to the UMC, unless you're actually using that as your 2-channel preamp as well.

[dougport]

What kind of phono pre-amp are you using?

[deltadube]

Feb 22, 2015 15:05:32 GMT -5 leeroy said:

k thanx will try this tomorrow. what about wood? tv is hung on wall and is always off when TT is on


mdf!

[leeroy]

I am using a Nad PPe4
 Um Dah on my part but what is "mains"

[dougport]

Feb 23, 2015 3:03:34 GMT -5 leeroy said:

I am using a Nad PPe4
 Um Dah on my part but what is "mains"

Double check to make sure you have the NAD PPe4 set to MM on the back since you have a moving magnet catridge and also it looks like it has separate inputs for MC & MM cartridges so need to check this as well.

[Priapulus]

You say the hum gets louder if you turn up the volume, so it's coming thru the speakers. It's not mechanical so changing the tt stand won't help.

Turntables require extremely high amplification; the slightest hum (ac noise; ground loop kind) get amplified to annoying amounts. When I first setup my turntable I was bothered with a hum. By connecting a ground wire to the metal sub-chassis of the turntable, the metal parts of the tonearm and to the ground side of the signal interconnect (or the chassis of your preamp); I got rid of it. Don't connect it to the power cable (motor) ground!

The metal parts of the turntable are acting like an antenna and picking up stray AC radiation (e.g. from your lights, amplifiers or house wiring).  Be sure to use good, well shielded interconnects; the $25 brands, not the $5 brands. Googling turntable grounding will probably help you. [edit: no don't google! I just tried it and most of the suggestions were idiotic.]

Sincerely
/b

[leeroy]

ok tried a couple of things - I moved the speakers forward and as far as I could from the TT and I placed felt under the little leg bases and now it is a lot better but still not 100% I won't be able to do much else now until I move.