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New Cartridge Humming - Help! Audio Technica VM750SH


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Hi There - wondering if anyone out there has experienced anything like this??
 

Since installing the new cartridge on my turntable I have had a ground loop type humming/buzzing noise.

I have tried everything to isolate the problem and it appears to be a problem with the cartridge itself.    

In summary:

- There were previously no noise issues with the HiFi system using the old cartridge (ortofon quintet)
- This not my first time installing a cartridge.
- The cartridge has been installed on the tonearm and correctly aligned.
- The tonearm cable, including the earth cable, has been connected to my phono stage
- Phono stage settings have been adjusted to suit the cartridge specifications
- the noise began immediately and is audible through both headphones and speakers
- the other channels on my amplifier remain silent - only a problem with the phono channel
- when I disconnect the turntable from the phono stage, the phono channel becomes silent again
 
The noise is constant. I have tried the following with no effect:
- Changing load capacitance settings
- Changing phono stage gain settings
- Disconnecting power to the turntable
- Removing the stylus from the cartridge
- Removing the cartridge from the tone arm AND headshell
- Turning off power amps
- Turning off all other nearby appliances 
- Moving the turntable around in the room (no issues previously with location)
- Removing and then reapplying connecting wires to cartridge
- ‘Jiggling’ wires connecting to cartridge
- Checking wires connected to correct terminals on cartridge
- Stripping back the earth wire to create a fresh contact with the phono stage
- Connecting to a different preamplifier
 

I have run out of ideas.

Does anyone have any suggestions?!

 

Thanks

Adrian

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The difference I am seeing in photos on the net, is that the AT has an earth tab on the back that goes around the green pin.  The Ortofon doesn't.   Maybe that's a clue.   Does your tonearm wiring, particularly the blue/green wires, connect to the metalwork of the turntable and/or tonearm - maybe where it terminates underneath?  Maybe this is forming an earth loop with the case of the cartridge grounded via this tab?   That combined with the phono preamp grounding etc.  just might give you some further things to try.

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24 minutes ago, aussievintage said:

 

The difference I am seeing in photos on the net, is that the AT has an earth tab on the back that goes around the green pin.  The Ortofon doesn't.   Maybe that's a clue.   Does your tonearm wiring, particularly the blue/green wires, connect to the metalwork of the turntable and/or tonearm - maybe where it terminates underneath?  Maybe this is forming an earth loop with the case of the cartridge grounded via this tab?   That combined with the phono preamp grounding etc.  just might give you some further things to try.

 

Hey thanks - I didn't notice the tab around the green terminal. Good spot. Ill try the connections again.

 

The trick is the hum is still there even when I disconnect the cartridge from the tone arm. Also I think its the same cable all the way from cartridge to phono stage without any connections - but maybe the next think I'm doing is pulling apart my tonearm to see if there is a terminal somewhere...

 

Oh well its 40 degrees and windy outside - I'm not going out anyway!

 

 

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28 minutes ago, B3lly said:

 

Hey thanks - I didn't notice the tab around the green terminal. Good spot. Ill try the connections again.

 

The trick is the hum is still there even when I disconnect the cartridge from the tone arm. Also I think its the same cable all the way from cartridge to phono stage without any connections - but maybe the next think I'm doing is pulling apart my tonearm to see if there is a terminal somewhere...

 

Oh well its 40 degrees and windy outside - I'm not going out anyway!

 

 

 

OK - so I was completely wrong about terminal connections in the base of the tonearm - seems to feature some of the flimsiest wire connections that I've ever seen. I can't actually see an issue but they make me nervous....

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17 minutes ago, Fenda said:

Maybe try disconnecting the earth wire coming from the turntable , my turntable owners manual says to try that if there's a hum

 

hey thanks - but removing the earth connection seems to make it waaaaay worse!

 

I'll keep trying.

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A curve ball to look at. When you remove the cartridge from the arm it’ll reveal the four pins in the collar housing. These are sprung to make a firm connection. It might pay to check that they are all indeed sprung. I had a tonearm with one pin that got stuck in the ‘in’ position...

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my sympathies - earth loops/hum are such a pain to pin down - try @markielinhart' suggestion...I ran out of good ideas after you'd tried disconnecting the earth lead to the pre-amp....but I find them so annoying, I'd go back to your old cartridge, and hopefully the hum goes....

...best wishes

 

Mike

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1 hour ago, markielinhart said:

A curve ball to look at. When you remove the cartridge from the arm it’ll reveal the four pins in the collar housing. These are sprung to make a firm connection. It might pay to check that they are all indeed sprung. I had a tonearm with one pin that got stuck in the ‘in’ position...

 

Apologies for my ignorance - when you say collar housing what do you mean? I have the standard 4 wires connecting to the cartridge then running down the length of the tonearm to connect up to the rca cable and earth wire that go to the phono stage.

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20 minutes ago, almikel said:

my sympathies - earth loops/hum are such a pain to pin down - try @markielinhart' suggestion...I ran out of good ideas after you'd tried disconnecting the earth lead to the pre-amp....but I find them so annoying, I'd go back to your old cartridge, and hopefully the hum goes....

...best wishes

 

Mike

 

 

I know the hum is killing me - listening to digital is keeping me going for now but I'll need to get back to analogue soon!

 

 

 

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1 hour ago, markielinhart said:

A curve ball to look at. When you remove the cartridge from the arm it’ll reveal the four pins in the collar housing. These are sprung to make a firm connection. It might pay to check that they are all indeed sprung. I had a tonearm with one pin that got stuck in the ‘in’ position...

 

6 minutes ago, B3lly said:

Apologies for my ignorance - when you say collar housing what do you mean? I have the standard 4 wires connecting to the cartridge then running down the length of the tonearm to connect up to the rca cable and earth wire that go to the phono stage.

 

I think Mark is referring to an arm which has a removable headshell.

 

If your arm doesn't - ignore his post. :)

 

Andy

 

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1 hour ago, B3lly said:

then running down the length of the tonearm to connect up to the rca cable and earth wire that go to the phono stage.

 

I think you should experiment with how they connect to the RCA cables.  In some systems the green/blue and the RCA shields all connect together are connected to the chassis as well.  If yours is like that, try isolating them from the chassis.  Just one example of the possible combinations.

 

Edited by aussievintage
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2 minutes ago, aussievintage said:

 

I think you should experiment with how they connect tom the RCA.  In some systems the green/blue and the RCA shields all connect together are connect to the chassis as well.  If yours is like that, try isolating them from the chassis.  Just one example of the possible combinations.

 

 

This is an interesting theory - after having pulled apart the base of the tone arm I can see that the green and blue wires connect up to their respective red and white RCA cables. There is a 5th wire (dark blue) which alone connects to the earth cable. That disappears into the tone arm and I don't know what that connects to. I'll have to summon some more bravery to pull things apart further to check that connection - possibly reaching the limits of my comfort zone here!

 

 

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6 minutes ago, B3lly said:

That disappears into the tone arm and I don't know what that connects to.

 

Most probably the metal of the tonearm wand.  Try it with that disconnected - relying on the green wire earthing the tonearm via the little metal tab on the cartridge.  This is all pure guesswork, but you just have to try stuff to see what works sometimes.   

 

Is the tonearm electrically connected to the metal work of the rest of the turntable?  Where does the dedicated ground wire from the phono preamp connect?  Try connecting it to the tonearm only or the table only if they are separate.  Try connecting them...  etc

10 minutes ago, B3lly said:

I can see that the green and blue wires connect up to their respective red and white RCA cables.

 

Do they make  this connection on a tagstrip or circuit board?  Does that have any connection to the metalwork.  The centre connection on a tag strip (or the ends of a big one) often screws onto the metal somewhere to hold it firm.

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26 minutes ago, pwstereo said:

You've got to admire its enthusiasm 🤣

you try everything to get rid of hum...and sometimes you don't actually know "why" it stopped, just very glad it did...my background/education is in electronics engineering...earth loops/hum suck big time and are hard to track down/isolate/fix...

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1 hour ago, aussievintage said:

 

Most probably the metal of the tonearm wand.  Try it with that disconnected - relying on the green wire earthing the tonearm via the little metal tab on the cartridge.  This is all pure guesswork, but you just have to try stuff to see what works sometimes.   

 

Is the tonearm electrically connected to the metal work of the rest of the turntable?  Where does the dedicated ground wire from the phono preamp connect?  Try connecting it to the tonearm only or the table only if they are separate.  Try connecting them...  etc

 

Do they make  this connection on a tagstrip or circuit board?  Does that have any connection to the metalwork.  The centre connection on a tag strip (or the ends of a big one) often screws onto the metal somewhere to hold it firm.

 

It's got me defeated for this weekend - I'll have to try again when I get time next weekend. I might also try out the cartridge on another turntable just to rule out something weird going on with that.

 

Thanks for your suggestions.

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5 hours ago, B3lly said:

 

Apologies for my ignorance - when you say collar housing what do you mean? I have the standard 4 wires connecting to the cartridge then running down the length of the tonearm to connect up to the rca cable and earth wire that go to the phono stage.

Silly of me, I made an assumption based on my tt. I can remove my cart/headshell by turning a knurled collar forgetting that a lot of turntables now have a fixed headshell. I’ll go back to spinning into the night...

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I feel your pain, there is nothing that does your head in more than earth (presumably) problems.

I second the extra earth lead and just make it a long one so you it can reach from the connection of your phono amp to everything on your turntable and proceed to contact it with the arm and then the pillar as well as both at the same time.

Also unplug your digital setup from power and also from your pre amp to eliminate any interaction. I know it sounds weird but speaking from experience I was ready for a straight jacket before working that one out.

Good luck.

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19 hours ago, McCvinyl said:

I feel your pain, there is nothing that does your head in more than earth (presumably) problems.

I second the extra earth lead and just make it a long one so you it can reach from the connection of your phono amp to everything on your turntable and proceed to contact it with the arm and then the pillar as well as both at the same time.

Also unplug your digital setup from power and also from your pre amp to eliminate any interaction. I know it sounds weird but speaking from experience I was ready for a straight jacket before working that one out.

Good luck.

The straight jacket isn’t too far away! I had the turntable, phono stage and a different preamp set up on the kitchen table last night just to get it away from everything in the study. No improvement. I’ll play some more with earthing cables. After that I’ll try wearing a hat made from tinfoil. 

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Try to swap earth of both wire green and blue on your cartridge . I’ve the same problem before then friends told me to do this and the hum disappeared . Red and white are hot of right - left . 
green and blue are earth , swap the green and blue connect to your cartridge . 

Edited by palexsia
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Right so the saga continues. Turntable buzz/hum currently occupies 97% of my headspace with work, family, beer, sport etc relegated to the remaining 3% of my consciousness. (that's an estimate not an empirical measurement)

 

As far as solutions go swapping green and blue earth's always felt a long shot but I gave it a go anyway. Unfortunately no improvement.

 

Playing with an additional earth cable was however illuminating. Amazingly I discovered the spare earth cable in the box of 'cables that might be useful one day'. That never happens.

 

So after connecting the 2nd earth cable to the phono stage I proceeded to experiment by touching everything metallic on the turntable with the free end.  I discovered that touching the blue earth post on the cartridge eliminates the hum completely. But not the buzz.

 

So, this evening's revelation is actually that I don't actually have a buzzing/humming noise. I have a buzzing noise AND a humming noise. 2 separate noises.

 

So current theory on hum (not buzz) is that either I damaged the blue earth wire while installing the new cart or it was already crap and the old cart was somehow not affected. And given that the tonearm to rca cabling look very sketchy to me I need to consider rewiring the tone arm. Hopefully this would resolve the buzzing issue at the same time as the hum.

 

Thanks to those of you contributing ideas above - I'll post further developments here.

 

 

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  • 4 weeks later...

So... to close this out - I caved in and gave it to a turntable tech who replaced the wiring for me. Problem solved. And the answer was that I must have damaged the earth wiring in changing the cartridge.

 

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