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Earthing your amplifier/giving up on it?


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Since I've moved house a couple of years ago my amplifier has developed a hum in the right speaker which has gradually gotten worse. It has to be an earthing problem with the turntable as it isn't present when listening to cds. I have tried earthing the preamp from the earth point, switching from all the different inputs, changing the speakers and nothing works. The hum is a lot worse if you touch the tonearm. 

They are rega P2, Dynaudio dm 2/7, Cambridge audio 540P and 840A.  Any advice would be much appreciated as I'm very close to selling the lot and starting again, without a rega this time as I've heard they are notoriously difficult to earth?

Cheers. 

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I'm not into phono/vinyl (can't afford it) so I may be off the mark a little.

Switch the phono RCA's, ie, TT-Left plug into Right Phono RCA, likewise TT-Right plug into Left Phono RCA, expect hum to change channels.

 

Check the 4 wires that connect from the tone arm to the cartridge. 2 of the wires are for audio (L&R, white&red?) and the other 2 are earths(blue&green). Often they connect as a slide on "clamp", check connection of the green wire.

Edited by mbz
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MBZ, Thanks for your suggestion, however the turntable connections are hardwired into the unit. I have checked all the wiring along the tonearm and at the cartridge and all seem ok, I have just been listening through left channel which is really starting to get to me, I'm sure it's something simple but can't pin it down.  Because there's no hifi shops open I think I'll start replacing items, turntable goes first. 

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Hi koloss. I'm wondering if you could be having a ground loop issue, where two or more devices are connected to a common ground via different paths. You can Google and read up more about it and some potential solutions and see if it helps.

 

Rega P2's do not have a separate ground and the grounding is via RCA. Does the hum get worst if you touch the RCA connectors at the amp or phono side?

Edited by EasterlyDrake13
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Given that the problem is in one channel, I would wonder if a solder joint has become loose causing discontinuity in the earth circuit, or a component failing. 

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Posted (edited)

So that problem would more than likely be in the preamp? Since the amp has proven a'll channels and imputs are working fine with cd?

Edited by koloss
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I understand your frustration. Hum can be difficult to solve.

You say your "amplifier has developed a hum in the right speaker".

 

Making this statement means you have proven the amp to be the issue.

Correct or not?

That is to say you reversed the left/right inputs to the amp from phono pre-amp and the hum remained in the right speaker.
Plus then you have swapped the left/right speaker connections and the hum remained in the right speaker.

If you have proven this then the amp is the problem.

 

Being only in one channel means it is NOT a general earthing issue, but is an issue which is particular to one channel and may or may not be an earthing issue.

 

Just to clarify, you have Rega P2 turntable with RCA cable into a separate phono pre-amp Cambridge 540P and then RCA cable to the amp a Cambridge 840A and Dynaudio (passive) speakers?


Assuming that is correct (and I know this seems basic)...
Have you swapped the left and right RCAs from the TT into the phono pre-amp?

If so does the hum remain in the right speaker or does it change to the left?

If the hum remains in the right SP then the problem is NOT the turntable.
If the hum moves to the left SP then the problem is IN the turntable or attached RCA cable.
If that is the case then I'd suggest inspecting the connection of the cartridge wires. Perhaps use some small pliers and just rotate the press on connectors a little to ensure a clean contact on the cartridge pins.
If they prove OK, then unscrew the back shell of the TT RCA connector and visually check inside to ensure the connections in there are good and that there is no possibility of wires shorting.

 

In the right speaker is it hum only or is music coming out as well??
Does the hum volume change/follow when you turn the amp volume up and down or does the hum volume remain constant?

 

If you report your findings I will respond with more suggestions to try.

Doing this we will at least prove in which part of the system the issue is being caused by.

 

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I just swapped the connections into the preamp and the hum swaps from right to left. Also the hum does increase with the volume. There is music coming out too but it's very faint in comparison. I don't have the right 6 star screw driver bit to open it up but I'll get one soon. Thanks mate. 

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55 minutes ago, koloss said:

I just swapped the connections into the preamp and the hum swaps from right to left. Also the hum does increase with the volume. There is music coming out too but it's very faint in comparison. I don't have the right 6 star screw driver bit to open it up but I'll get one soon. Thanks mate. 

Indicating it is the cable, most likely which has the problem. Carefully inspect the RCA plugs, by undoing the shield cover, and repair broken wiring, or replace the cables with new ones.  

Edited by stereo coffee
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I had a Rega P2 that also had an earthing problem    i.e.    if you touched the tonearm, it hummed.   I solved it by wrapping some very thin thread tape around the finger lift bit of the tonearm, and painted it the same colour as the arm.   Yours 'sounds' like a cable issue

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I'm not going to try and get the hardwired cable out, I've had it with this turntable. Thanks everyone for your help. 

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18 hours ago, koloss said:

I just swapped the connections into the preamp and the hum swaps from right to left. Also the hum does increase with the volume. There is music coming out too but it's very faint in comparison. I don't have the right 6 star screw driver bit to open it up but I'll get one soon. Thanks mate. 

 

OK, so this proves the problem is within the turntable.
Anywhere from RCA connector of the TT cable to the actual cartridge.

 

The thing to note is that the channel with the hum the music is very faint compared to the other channel.
So either the cartridge is faulty or any connection point between the cart and the RCAs is compromised.

Cart-wires-reversed.jpg.a1b1b2f8af9ebea5afebaa486db9b861.jpg

If you can I would suggest you carefully swap the left right connections on the back of the cartridge.

Take note of the positions and colours before proceeding and take a photo for future reference.

In the sample image above you would need to swap red with white and swap blue with green.

Use fine pliers to pull the push connectors off the pins.

ENSURE you brace the pliers movement and pull carefully.

If you pull too hard and slip there is the risk that you will rip the metal push connector off the fine tone arm wire.

If this reversal swaps the hum to the other channel this proves the cartridge is faulty.

If the hum remains on the same channel then the wiring/RCA is the problem.

 

Why do you need a 6 star driver? What are you undoing?
Photo please.

Edited by rockpig
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15 hours ago, koloss said:

I'm not going to try and get the hardwired cable out, I've had it with this turntable. Thanks everyone for your help. 

I don't think you need to remove the hardwired cable to solve this.

See my other post.

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This power cover, I'm not going to mess with anything. I'll just sell it cheap. Just really glad it's not a problem with the amp Cheers

15972754314772345936294410350588.jpg

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Sorry for coming in late 

90% of the time it’s cable or bad contact related 

Sometimes the easiest thing like using wet dry sand paper on surfaces to remove tarnish can result in fixing all the issues 

 

 

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The "6 star screw driver bit" is called a "Torx", screwdriver/key sets can be bought at Bunnings at a reasonable cost (when we are allowed to shop there!).  I feel it's a good loong-term investment to make, like having an Allen key set.  You are not likely to use them often, but good to have on hand for when you do. 

 

I would encourage you to reconsider your thoughts on selling the turntable cheaply as-is.  The Rega P2 is a reasonable turntable.  Troubleshooting audio problems is always tedious, with lots of things to check to slowly narrow down where the problem is.  Especially if you haven't done this before! From a brief glance through the above posts, it appears that we are slowly working towards the cause, and the likely culprit could be a relatively easy and cheap fix.  A little more persistence will get to the end, and build your confidence for future maintenance work. 

 

If part of your thought process is that you would like to upgrade your turntable, fixing it and selling it in good working order will bring more money to subsidise the upgrade.  Or you might decide to keep the turntable, and do some upgrades on the turntable components (eg. new cart, etc.  You will be able to get advice here on what would be good to consider on this path). 

 

 

Edited by audiofeline
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Thanks mate, I would consider getting a new better cart installed and the problem fixed by a professional, would also like to get my amp serviced but not being able to leave a 5km radius of home makes repairs impossible for the next 5 weeks, unless there's someone in Rosebud who does repairs. Suppose I should just keep listening through 1 channel until I can travel. Patience has never been one of my things..

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