You are here

Log in or register to post comments
judicata
judicata's picture
Offline
Last seen: Never ago
Joined: Jun 26 2008 - 11:55am
Wherefore art thou, humming noise?

Every now and then I get a humming noise from my TT source. When I touch the headshell or wires attached to the cart, the noise changes. When I touch the preamp the noise changes. When I touch the contacts of the interconnects the noise changes. And then it eventually goes away when I've moved enough things around.

Grounding? As I have a Rega TT, there is no ground. There IS one on my phono pre, and on my amp. Would grounding the pre potentially help?

Elk
Elk's picture
Offline
Last seen: 2 months 4 weeks ago
Joined: Dec 26 2006 - 6:32am
Re: Wherefore art thou, humming noise?

This sure "sounds" like a grounding problem.

This may be heresy, but have you tried running a ground wire from the TT to phono pre? (Does the Rega have a three prong grounded plug?)

judicata
judicata's picture
Offline
Last seen: Never ago
Joined: Jun 26 2008 - 11:55am
Re: Wherefore art thou, humming noise?

I dont' know if it is three-pronged plug, but I don't think it does - I'll check when I get home. From where on the TT would i run the grounding wire?

Elk
Elk's picture
Offline
Last seen: 2 months 4 weeks ago
Joined: Dec 26 2006 - 6:32am
Re: Wherefore art thou, humming noise?

TT ground wires begin at the tonearm, attach to the frame and the extend out from the frame to be connected to the phono pre.

I wouldn't try to ground the tonearm as I would be concerned with messing up the way it pivots, etc. but I would try connecting a ground wire from a screw in the frame to the preamp.

I don't know Rega turntables well enough to know, but they probably provide the ground through the shield in the RCA interconnect. If so, the connection from the frame to the interconnect may be broken.

My question re three prong plug is more out of curiosity than anything. The TTs I have had all are two prong, but since yours does not have a ground wire it occurs to me that it may separately ground the frame through the power cord. This seems unlikely however as the hum we hear is caused by a minute voltage differential between the TT and phono pre. This would not be eliminated with a power cord ground.

linden518
linden518's picture
Offline
Last seen: Never ago
Joined: Dec 12 2007 - 5:34am
Re: Wherefore art thou, humming noise?

Dude. Totally sounds like a grounding issue. You can try using tonearm cables with grounding wire built in, that way, you get your grounding worked out with minimal fuss. See if you can audition first, so you don't get stuck with a new tonearm cable without having your problem fixed.

Jim Tavegia
Jim Tavegia's picture
Offline
Last seen: Never ago
Joined: Sep 1 2005 - 4:27pm
Re: Wherefore art thou, humming noise?

The Rega ground is the shield of the phono cables...I believe. I would try some of the Gray 69 cent ground lift adaptors on you amp/preamp setup. You may have a ground loop somewhere that is causing your issues. Often people with tube gear have an issue here as well. You could try and use a cheap volt meter and test the continuity from your phono leads from the headshell back. Detach them gently from the cart first.

I have not had any issues with my P3, but I am not surprised having to deal with grounding issues myself at times. Surprisingly, when my current 11 year old house was one year old I had some new wiring installed and had my electrician check out my breaker box. He found most of the connections, including the ground lugs, loose to very loose. Since he tightened them I have had no issues. Just because my builder's electrician is licensed doesn't mean his worker are.

Elk
Elk's picture
Offline
Last seen: 2 months 4 weeks ago
Joined: Dec 26 2006 - 6:32am
Re: Wherefore art thou, humming noise?

Good to point out the main service box connections. They often become loose over time.

Jan Vigne
Jan Vigne's picture
Offline
Last seen: Never ago
Joined: Mar 18 2006 - 12:57pm
Re: Wherefore art thou, humming noise?


Quote:
When I touch the headshell or wires attached to the cart, the noise changes. When I touch the preamp the noise changes. When I touch the contacts of the interconnects the noise changes. And then it eventually goes away when I've moved enough things around.

Clear some things up first.

* Why are you touching the wires attached to the cartridge? Any cartridge will hum when you touch the cartridge leads.

* Is this a noise that comes and goes without you doing anything?

* Is this a noise that appeared when you first plugged in the Rega table? Or did it show up after a period of time?

* Is everything plugged into the same AC source? Any surge protectors/line conditioners common to both turntable and pre amp?

* Where is the turntable located in proximity to your pre amp/power amp? Have you tried moving the table to a different location to get the cartridge away from any power transformers that exist in electronic devices?

* When you touch the pre amp how does the noise change? "The contacts" of the interconnects would be what? The ground sleeve of the RCA going into the pre amp?

As has been mentioned you cannot ground the Rega arm since it already has been grounded by the left channel shield. Either this grounding scheme works or it doesn't. It does not just fade away into nothingness.

To begin repairing this noise, you need to stop "moving enough things around". There is a high likelyhood you will do more damage than good by constantly moving connectors.

If the noise goes away after a short period of time, without anything being moved, the problem is very likely a bad solder joint or a broken circuit trace on a phono board. As the pre amp warms up the heat causes expansion and the circuit is completed.

You can test the table by plugging it into any other system with a phono section. That would rule out the table as a possible cause. I doubt the table is at fault as there just isn't much to go wrong with a table as simple as the Rega. The possibility exists you have damaged the Rega in some way by fiddling with connectors and headshell leads so it would be a good idea to eliminate the table as a possible source of noise.

* Most importantly, does the noise go away on its own accord if you do nothing but simply wait for the pre amp to warm up?

judicata
judicata's picture
Offline
Last seen: Never ago
Joined: Jun 26 2008 - 11:55am
Re: Wherefore art thou, humming noise?

Thanks Jan:

First, by "moving things around" I'm just takling about shifting the interconnect cables(gently), and picking up my small phono pre and setting it back down (again gently), and the like. I'm not being aggressive or anything. But still, I can see how it is always a risk moving a bunch of stuff around.

* Everything is plugged into the same power strip/surge protector. I should note that the wiring in my prewar apartment (updated last I think in the 70s, judging by the avocado bathroom) sucks. Not much I can do about it unless I can make a good argument that it is dangerous.

* I didn't touch the leads to the cart until I heard the hum - I was just making sure there wasn't a short or the leads didn't come loose (that had happened before).

* I've noticed the hum more frequently after I have left the phono pre on all day, and I *think* the integrated amp, but I can't remember.

* I don't know if it goes away on its own eventually. I have a complusive need to fiddle with things when there's a noise. I'll restrain myself next time.

* I have a (cheap) three shelf audio rack. My Power amp is on the bottom shelf, my phono pre and digital source is on the second, and the TT is on top. There is about 3 inches of clearance above the power/pre amp, and about 5 inches of clearance above the phono preamp.

* On the RCA plugs, I actually just removed them one by one to see if the noise would stop, or if I could identify where it was coming from.

One more thing, I didn't mention it because I'm not sure how to explain it. But the hum is not smooth and constant, there is a rapid "beat" to it. Sort of like what happens when certain cell phones get around equipemnt (I've ruled that out). I haven't heard it in the past few days.

Jan Vigne
Jan Vigne's picture
Offline
Last seen: Never ago
Joined: Mar 18 2006 - 12:57pm
Re: Wherefore art thou, humming noise?


Quote:
One more thing, I didn't mention it because I'm not sure how to explain it. But the hum is not smooth and constant, there is a rapid "beat" to it. Sort of like what happens when certain cell phones get around equipemnt (I've ruled that out). I haven't heard it in the past few days.

Well, that kinda throws a spanner in the tranny! That would at first glance appear to be power supply noise and likely coming from a switching type ps. A power amp with a switch mode power supply? A wall wart ps for a digital source perhaps?

But it went away?!

Then I would assume something changed between the time you heard it last and now. Can you think of anything?

The pulsing went away but the noise remains? If so and the noise remains unchanged in all other ways, then the pulsing was very likely coincidental to the problem and not the cause of the problem. So how does the noise change when you touch various points in the system?


Quote:
First, by "moving things around" I'm just talking about shifting the interconnect cables(gently), and picking up my small phono pre and setting it back down (again gently), and the like. I'm not being aggressive or anything. But still, I can see how it is always a risk moving a bunch of stuff around.

OK, so there's a separate phono pre amp involved. That could very well be where the problem exists. Two things here, first, have you run a grounding cable from the phono pre amp to your line stage? Second, the polarity of one of the components could be reversed at the AC plug. Try reversing the orientation of one plug at a time to find out if they are out of phase with each other in regards to the incoming AC line. Reverse the phono section first, and if no change, plug it back to its former configuration and reverse the line stage's AC plug. Also, what happens when the phono pre amp is plugged into the line stage but the table is not plugged into the phono pre amp? Or only one RCA from the table is plugged in at a time? Are you positive you have the cartridge leads properly wired for polarity? Does the catridge have a metal ground tag attached to one of the "ground" pins and running to the cartridge body?


Quote:
I didn't touch the leads to the cart until I heard the hum - I was just making sure there wasn't a short or the leads didn't come loose (that had happened before).

A short?!!!

Cartridge leads must be snug and tight. If they are loose enough to "fall off", they are not snug and tight. If you have not done anything to alleviate this problem, then you need to address the situation ASAP. Be careful when squeezing headshell leads, if you crimp them too hard, they will collapse and you'll never get them open enough to fit back on the cartridge pins. Then you'll have a much more difficult problem to deal with.


Quote:
Everything is plugged into the same power strip/surge protector. I should note that the wiring in my prewar apartment (updated last I think in the 70s, judging by the avocado bathroom) sucks. Not much I can do about it unless I can make a good argument that it is dangerous.

I don't remember if we've dealt with this in your system yet but you need to buy a AC outlet tester - a few bucks at Home Depot. You need to make certain the outlets are wired properly and hot/neutral/ground aren't reversed. Do you know with certainty whether the outlets are two or three wire conductors? I assume your power strip is a three pin plug but the fact there are three pin receptacles on the wall plate doesn't mean there are three conductor cables behind the wall plate.

Have you tried removing everything related to the phono and line stage from the power strip and testing for problems originating in the strip? Just plug the table, phono pre amp and line stage into a wall outlet (the same wall outlet not two distinct outlets that might be wired differently or on a different circuit) or a short extension cord with three receptacles to make certain there isn't a problem that is being caused by the power strip.

If there is noise when you have the three pieces running from a common outlet, you should try running a ground wire from the phono pre amp and the line stage. With the wire attached at the component end touch each wire to the center screw of the AC receptacle. If the outlet is wired properly, this should be a reliable earth ground location.


Quote:
I've noticed the hum more frequently after I have left the phono pre on all day, and I *think* the integrated amp, but I can't remember.

To solve the problem we'll have to be certain about what is happening and not work from guesses. Take notes if need be but accurate details are important.

If the problem is a cold solder joint or broken circuit board, then about 30 minutes to one hour warm up should be sufficient time for the problem to either occur or cease. So there's no need to wait through an entire day to make the determination. Allow the units to cool to room temperature about the same amount of time for retesting if necessary.


Quote:
I don't know if it goes away on its own eventually. I have a complusive need to fiddle with things when there's a noise. I'll restrain myself next time.

Yep!
M-u-s-t
r-e-s-t-r-a-i-n
s-e-l-f!


Quote:
I have a (cheap) three shelf audio rack. My Power amp is on the bottom shelf, my phono pre and digital source is on the second, and the TT is on top. There is about 3 inches of clearance above the power/pre amp, and about 5 inches of clearance above the phono preamp.

Are you powering down the digital source when you are playing LP's? Have you tried moving the phono pre amp and turntable away from the other components to at least the extent the cables allow?


Quote:
On the RCA plugs, I actually just removed them one by one to see if the noise would stop, or if I could identify where it was coming from.

And you deduced what from this procedure?

Do you have the ability to listen to the system through headphones with the power amp powered down?

Finally, has this problem existed from the moment you inserted the table and phono pre amp into the system or did it develop over time?

(I would suggest you print out this post and take it with you when you try each question or suggestion. Your answers to each question will determine where to go next.)

judicata
judicata's picture
Offline
Last seen: Never ago
Joined: Jun 26 2008 - 11:55am
Re: Wherefore art thou, humming noise?

Wow, thanks for this time and effort. I'm at the office. When I get home, I'll work on all of this.

Jan Vigne
Jan Vigne's picture
Offline
Last seen: Never ago
Joined: Mar 18 2006 - 12:57pm
Re: Wherefore art thou, humming noise?

In case you haven't figured it out yet, the AC plugs on modern equipment are polarized - one blade of the plug is larger than the other. This means you cannot simply reverse the orientation of the plug in a polarized receptacle. You will need to buy a few ground lift "cheater" adapters, the type used to go from a three conductor grounded plug to a two conductor plug. These should be easy to find in any of numerous locations, drugstores sell them in the aisle next to the tires and snow skis.

This adapter will still be polarized so you'll have to shave/grind/cut off the ears on the larger blade to get it to a size that allows a reversal of the plug in the receptacle.

judicata
judicata's picture
Offline
Last seen: Never ago
Joined: Jun 26 2008 - 11:55am
Re: Wherefore art thou, humming noise?

Sounds like fun.

I WILL do all the testing and give you the rundown - I didn't get off work until midnight, so it may be this weekend.

mturkel99
mturkel99's picture
Offline
Last seen: Never ago
Joined: Sep 19 2008 - 6:37pm
Re: Wherefore art thou, humming noise?

Not sure if you still having the problem. If you are, however, I had a similar one (Rega TT, Preamp...) and I simply ran a wire from the preamp's ground to the third prong - ground - in an outlet and... goodbye hum.

Hope this helps!

judicata
judicata's picture
Offline
Last seen: Never ago
Joined: Jun 26 2008 - 11:55am
Re: Wherefore art thou, humming noise?

Thanks. The problem simply hasn't come back yet.

  • X
    Enter your Stereophile.com username.
    Enter the password that accompanies your username.
    Loading