Grounded turntable humming

[burton]

Hi, I'm new here

I've read a number of topics on this, but none seemed to be of any help.

I recently bought a second-hand amplifier and a set of speakers, and now I get a loud humming sound when I switch to the phono channel my turntable is connected to.

This is my setup:
A Pioneer SX-828 amp with a CD player on top of it, a cassette player (in/out both plugged in) on top of that, and finally a Technics SL-BD20 on top of that. I also have my computer in/out connected to the amp.
I have two sets of speakers, but the humming is still there when I disconnect the second pair.

I have an improvised wire connected to the ground plug of the turntable and the ground screw on the amp, which worked fine with my previous amp (Pioneer SA-610).
When I touch the ground screw on the amp, it improves slightly, but it's still there.

The amp and the turntable are plugged in to the same power socket, and the CD and cassette player aren't plugged into any socket, because I don't have enough available at the moment.

The humming is there regardless of whether or not the turntable is turning, but not when I disconnect it from the amp.

One thing I think might be causing this is that the amp appears to be an American model. I switched it from 210V to 220V though.

I don't know much about this stuff, so keep it simple if you can
Let me know if you need any more info

Thanks ^^

 

[DJTommyK]

There are other folks on here that will probably have better suggestions than I can offer, but I can give you some *very* basic things to check.

Verify that the ground wire has a good solid connection at both ends.
Verify that the ground wire doesn't have any breaks in it.
Verify that the ground wire doesn't have any exposed wire (except for the ends obviously).
Make sure that the ground wire isn't laying across any electrical outlets, exposed wiring, etc.
If you have a 2nd turntable, plug it in and see if you get the hum. If you don't, then there's something up with the first turntable. If you still get the hum however, it may be something with the receiver and/or phono stage.

That's about the best I have to offer, but again, there are some true turntable gurus on here, that will be able to give you great advice.

Good luck, and enjoy your vinyl!

 

[burton]

All of that seems to be alright.

Don't have a second turntable though. I'm thinking the problem might be a ground loop, but I don't know how to test for it, or how to fix it.

Thanks for the reply! I hope some of those gurus drop by ^^

 

[dnpainting]

Just a thought, I don't know if this would even effect anything, ground your turntable to a case screw on the amp, might be something wrong with the amp ground post.

 

[boreas]

Just a thought, I don't know if this would even effect anything, ground your turntable to a case screw on the amp, might be something wrong with the amp ground post.

Yes, I was thinking the same thing. The fact that the hum is diminished by your touching the grounding post could mean that you're improving the ground with your own body.

John

 

[boreas]

Also, are you using a 3-prong UK mains plug or a Euro 2-prong plug? If 2 prong you might try reversing it.

John

 

[elcoholic]

It's not always the ground causing the hum. A bad (cracked) RCA connector was the culprit on one of my TT's. Check the signal wiring from stem to stern as well. I have one TT that hums when I connect the ground lead and is dead quiet when it's not grounded.

 

[empirelvr]

I'm almost positive that the problem is your audio connection to your computer.

Computers have a 3 wire (grounded) connection and it is very common for ground loops to occur (humming) when the sound card is connected to a stereo, especially if the computer is plugged into a different electrical outlet than the rest of the stereo. The computer doesen't even have to be on for this to happen.

You mention that the turntable and the reciever are connected to the same electrical socket. What about the computer?

I'll bet you dollars to donuts if you were to unplug the computer from the wall electrical socket, the hum will disappear immediately.

If it does (like I'm betting it will) you then have two choices. Either get ground lift adapters for the computer's electrical cord, or use isolation transformers on the computer audio leads coming and going to the stereo.

The use of ground lifts is iffy, as it compromises the ground of the computer, but being connected to the stereo establishes a ground for it so it may not be bad.

Islolation transformers can be pricey and color the sound. It's a judgement call. FWIW I use ground lifts and have for over six years on my computer with no problems.

 

[Grainger49]

Adding to what everybody else has said, build a pair of shorting plugs. That is a pair of RCA plugs with the hot shorted to the shield. Put them in the TT input on your SX-828 and see if it hums. There should be no hum.

Unplug everything else from the 828 and plug the two phono leads to it while the TT is unplugged from the mains. If there is hum check that the cartridge has a grounding strap. Then plug in the mains. If this causes hum try a new wire from the arm to the chassis of the 828.

And, of course, post your results.

 

[burton]

I tried unplugging the computer. The loud buzzing hum goes away, but a low hum still remains. Does this mean that it's definitely the cause, or should I give the other suggestions a try too?
If it is the cause, there's still something else causing it too.

I'm beginning to think I should just have stuck to my previous amp.

Thanks for the replies.

To the post above, I don't know what you mean with "hot shorted to the shield." Cut off one end of the plugs and connect them to a screw on the amp?

Anyway, I'm going to do the rest of the testing some other time, as it's getting pretty late and I don't want to wake anyone up with all this noise. I might not have time to do anything else until Sunday
In any case, I think I'm going to buy new wires for everything, just to be sure. The ones I'm using are pretty old.

By the way, reversing the prong (I'm from Belgium) doesn't do anything.

Oh yeah, for the cassette deck I'm using RCA plugs with an extra yellow video plug (like the ones used for a TV), could this be causing anything?

 

[Grainger49]

I tried unplugging the computer. The loud buzzing hum goes away, but a low hum still remains. Does this mean that it's definitely the cause, or should I give the other suggestions a try too?
If it is the cause, there's still something else causing it too.

I'm beginning to think I should just have stuck to my previous amp.

Thanks for the replies.

Computers are very, very noisy. They should be feet away from audio gear or they cause noise without being plugged in.

I would guess you posted before seeing my post. Those steps are still suggested to help you find where the noise is coming from.

The reason I said unplug everything was to take the computer connection out of the mix. Getting it physically away from your amp is also a step. Or turning it off.

 

[burton]

Yeah, I edited my post to answer yours.

My computer is less than 10 inches away from the amp, but with the size of my room and the way everything is set up I don't have all that much choice in this, but I guess I'll have to think of something if it turns out it's necessary.

I'll let you know as soon as I have time to do some testing.

I just got myself two new LPs as well

 

[Grainger49]

I had thought if you were in 220V land you were up late.

I don't know what is available to you. An RCA plug is what is on the end of the cables. I can buy cheap ones at Radio Shack. There are two conductors in every audio cable (either left or right, not both). The center conductor, the hole in your amp, is the "hot." The outer conductor on your amp is the ground. Shorting them gives you the lowest noise possible from the amp.

If you are using old cables new ones are a good idea for many reasons. If you have another video cable with an extra cable, like the cassette, use that. The extra cable shouldn't cause the noise if it is not plugged into anything on both ends.

Do try turning off the computer as well as unplugging it. It could be the source of all the noise since it reduced so much when you unplugged it.

I didn't catch if you tried a new grounding wire from the arm (this assumes the arm is metal) to the chassis of your amp.

Also looking for the results of everything unplugged from your amp except the TT and your TT unplugged from the wall.

 

[burton]

Okay, turns out I have some time this afternoon.

Let's recap:
-Reverse mains plug: no effect
-Check wiring: everything seems alright, but I'm going to buy new wires just to be sure
-Unplug computer from mains and from amp: loud hum disappears, but quiet, low hum remains
-Unplug everything from amp, then plug in TT while unplugged from mains: quiet, low hum remains; then plug in mains: no change; as soon as I turn on my computer, the loud hum returns, but not when it's unplugged from amp

Still to try:
-Ground TT to screw on amp
-Build shorting plugs


In summary, I probably need to move my computer further away from the amp, but that doesn't completely solve everything.

I've noticed that the output on my TT is a bit loose, I can jiggle it around. Maybe there's some damage on my TT.


Okay, I tried connecting my TT to my previous amp. Even on that one it hums now, so it must be the amp. Also, when I touch the TT power cable on either end, so it moves just a tiny little bit, it makes all kinds of weird noises.
Am I right in thinking my TT must definitely be damaged?

 

[boreas]

Okay, I tried connecting my TT to my previous amp. Even on that one it hums now, so it must be the amp.

Must NOT be the amp. Is that what you meant?

Also, when I touch the TT power cable on either end, so it moves just a tiny little bit, it makes all kinds of weird noises.
Am I right in thinking my TT must definitely be damaged?

Yes, it sounds like you have damaged connections inside the TT, either the power cord or something else that is being moved when you wiggle the power cord. It could be the RCA cables.

John

 

[Maxray]

In a slightly different direction - my hum-chasing went through a lot of the steps outlined here, but ultimately it turned out to be a dimmer light switch that was on the same electrical circuit. Turning off the dimmer cured it for me. Just wanted to throw that out there. Good luck!

 

[elcoholic]

Computers are very, very noisy. They should be feet away from audio gear or they cause noise without being plugged in.

Huge over-generalization, should say "can be very noisy". We don't want the OP chasing phantoms. I have had 2 receivers (both Onyko SS) and 2 TT's/Carts inches away from 2 different computers for several years. A Sony Vaio and an iMac. Haven't done this with a CRT monitor though.

 

[Grainger49]

I'm happy the OP found his problem. Phono stages with the very small signal levels and the high gain are more succeptible to noise from all sources.

To elcoholic:

Yes, I should have said could be.... (Because they can)

I suggested first . . .

Computers are very, very noisy. They should be feet away from audio gear or they cause noise without being plugged in.

. . . The reason I said unplug everything was to take the computer connection out of the mix. Getting it physically away from your amp is also a step. Or turning it off.

Both easy things to do and test. Then I said . . .

. . . Do try turning off the computer as well as unplugging it. It could be the source of all the noise since it reduced so much when you unplugged it. . . .

Huge over-generalization, should say "can be very noisy". We don't want the OP chasing phantoms. I have had 2 receivers (both Onyko SS) and 2 TT's/Carts inches away from 2 different computers for several years. A Sony Vaio and an iMac. Haven't done this with a CRT monitor though.

Your personal experience may be different than others. What I offered was quick and simple. The clocks within a computer can inject noise into systems. Often the connection has to be isolated from the system ground. But I didn't suggest anything that would have been more than 2 minutes of troubleshooting. Hardly chasing phantoms as you say. It was a good suggestion never the less.

 

[elcoholic]

Grainger49,

I don't read where the OP has solved his puzzle. Hope he does. Your suggestion was a good one, I just question absolutes. Although when this subject comes up it seems dimmers are often the problem.

 

[burton]

Well, thanks for the help everyone. Guess I'll have to get my TT fixed, or replace it.