New Power Cord Creates Hum Noise

[photonman]

So I purchased a Wireworld Electra power cord for my class D amplifier to replace my Isotek Premier one.  I was looking for a larger gauge wire which was my only reason for changing.  With the Isotek everything was black and dead silent with no music playing.  I swapped in the Wireworld and there is a horrible hum.  I am not sure if it is the 60 Hz or 120 Hz type but I am leaning toward 120 Hz.   I swap the Isotek back in and everything is better.  Why would the WW one cause that hum?

 

Things I noticed:

• turning up volume had no effect on the hum level
• disconnecting the source had no effect on the hum
• swapping out different interconnects had no effect (DAC direct connected to amp)

[The Computer Audiophile]

Is one cable not grounded and on the inside?

[sandyk]

14 minutes ago, photonman said:

So I purchased a Wireworld Electra power cord for my class D amplifier to replace my Isotek Premier one.  I was looking for a larger gauge wire which was my only reason for changing.  With the Isotek everything was black and dead silent with no music playing.  I swapped in the Wireworld and there is a horrible hum.  I am not sure if it is the 60 Hz or 120 Hz type but I am leaning toward 120 Hz.   I swap the Isotek back in and everything is better.  Why would the WW one cause that hum?

 

Things I noticed:

• turning up volume had no effect on the hum level
• disconnecting the source had no effect on the hum
• swapping out different interconnects had no effect (DAC direct connected to amp)

QUOTE : Isotek EVO3 Premier Power Cable(C7)

The Perfect Audio Upgrade, Lets Your Audio Or Visual Component Perform Much Better Than It Can With The Standard Basic Lead Supplied With It
Good RFI & EMI Rejection, Silver Plated 99.9999% Oxygen Free Copper Conductor, 24ct Gold Plated Terminations, Designed & Made In England C7 Figure Of Eight Plug

 

 Perhaps RF/EMI from your Class D amplifier is getting back into other components ?

It seems unlikely that RF/EMI is getting into the Class D amplifier via the new power cable from other lower powered devices, whether Linear or SMPS.

[photonman]

Both cables have ground pin intact.  That is interesting how the Isotek specifically mentions RFI/EMI rejection which I did not even think about when I got the Wireworld.  I am going to see if I can swap it out for another Isotek.  Darn as the Wireworld is really nicely made.  My interconnects are double shielded.  Thanks for the replies.

[The Computer Audiophile]

I’d try a generic cable just to see if there is hum on that one. Could be something wrong with the WW. 

[plissken]

If you have a multi-meter with tone close circuit each pin and make sure you get tone.

 

Then also check the other pins in regards to your ground pin. You shouldn't hear anything.

[sandyk]

58 minutes ago, The Computer Audiophile said:

I’d try a generic cable just to see if there is hum on that one. Could be something wrong with the WW. 

 

  Quite possibly, however well designed equipment shouldn't need expensive aftermarket mains cables to prevent this kind of problem.

[The Computer Audiophile]

Just now, sandyk said:

 

  Quite possibly, however well designed equipment shouldn't need expensive aftermarket mains cables to prevent this kind of problem.

Using a third cable will give us an idea what’s going on. 

[tmtomh]

The new power cable could simply be defective - the sound line could have a small internal break, in the middle of the cable or perhaps at the internal connection to one of the two plug ends.

[One and a half]

47 minutes ago, tmtomh said:

The new power cable could simply be defective - the sound line could have a small internal break, in the middle of the cable or perhaps at the internal connection to one of the two plug ends.

I'm thinking the same lines here.

 

The Elektra is a dual 'coaxial' type construction, with each conductor wrapped in a separate shield. If one of the shields is not connected to a ground, there would be hum induced. 

 

You could bell out each conductor and it would show a healthy state and trick the readings. @photonman, I would return the Electra cable for another one.

 

The Isotek EVO3 Premier Power Cable(C7) is a non shielded design, so fields can escape, but depends on how the symmetry of the conductors is built that can reduce these impacts.

 

 

[photonman]

Okay so I plugged in a generic Baohing shielded 3 x 16 awg I had from some other computer or whatever and it is dead quiet too, just like the Isotek.  So the problem is with the Wireworld.  Wow, I would never had suspected that result but I will be contacting the dealer to see about getting a replacement.  Either that or getting a refund and just running with the Baohing!

[tmtomh]

12 hours ago, photonman said:

Okay so I plugged in a generic Baohing shielded 3 x 16 awg I had from some other computer or whatever and it is dead quiet too, just like the Isotek.  So the problem is with the Wireworld.  Wow, I would never had suspected that result but I will be contacting the dealer to see about getting a replacement.  Either that or getting a refund and just running with the Baohing!

 

Honestly if your previous cable - not to mention a generic one - is producing a dead-quiet background, my suggestion (with respect) would be to rethink the need for any replacement cable at all.

[bluesman]

16 hours ago, photonman said:

 With the Isotek everything was black and dead silent with no music playing.

I'm with tmtomh. Why are you looking for another power cable?

[sandyk]

4 hours ago, tmtomh said:

 

Honestly if your previous cable - not to mention a generic one - is producing a dead-quiet background, my suggestion (with respect) would be to rethink the need for any replacement cable at all.

 In this case, the replacement cable was not a simple generic type, it was also shielded.(?)

 It would have been interesting to see what happened with a  normal 3 core mains cable.

If special mains cables are needed, I then wonder about the amount of crap going back into the A.C. mains sewer, which may, or may not, affect other sensitive devices such as a DAC.

[photonman]

Only reason I wanted to change the power cord was for "something better" to get the most out of my amp.  I lost control of my audiophilia I guess.  I will find a normal generic plug and try that too.

 

I did a lot of testing this morning with various configurations.

• With only amp plugged into power, all interconnects disconnected, all other devices unplugged from wall, the amp is fine.
• Plug in the dac (wall wart or the LPS made no difference) to power, connect dac to amp with IC's (shielded vs. non-shielded made no difference) the hum was back.
• Plugged amp with Wireworld into a ground cheater, still had hum.  Plugged Qutest with wall wart to remove ground, still had hum.
• Powered the dac with a USB from my Mac, Mac running on battery, made no difference, it hummed.

Wish I could of tested a balanced DAC with the balanced amp inputs.  I am back to using the Isotek for the amp and the Wireworld for the LPS to the Qutest and this is fine.  There really is nothing special about the Isotek whereas the WW touted shielding and being a "power conditioning" cord.

[Allan F]

20 minutes ago, photonman said:

Wish I could of tested a balanced DAC with the balanced amp inputs.  I am back to using the Isotek for the amp and the Wireworld for the LPS to the Qutest and this is fine.  There really is nothing special about the Isotek whereas the WW touted shielding and being a "power conditioning" cord.

 

Have you considered contacting Wireworld or the dealer who sold you the cable to see if it may be defective? That's what I would do if I were in your shoes.

[MOONCRIKIT]

With a V.O.M. perform a continuity check on both the ground pin of the male wall plug end and the center top internal ground slot of the IEC female end...

[One and a half]

3 hours ago, MOONCRIKIT said:

With a V.O.M. perform a continuity check on both the ground pin of the male wall plug end and the center top internal ground slot of the IEC female end...

The ground wire on the cable is split in two. You  don’t know if the other ground wire fell off, the meter won’t tell you.

[photonman]

MYSTERY SOLVED!

 

Apparently my Mapleshade speaker wires were sucking in noise, possibly from my Class D amp switching power supplies.  I swapped them out for Blue Jean Canare cables and my system is dead quiet again.  I have the Wireworld PC plugged back into my amp and it really does make a difference from the 5 other homemade cables I tried.

[sandyk]

52 minutes ago, photonman said:

MYSTERY SOLVED!

 

Apparently my Mapleshade speaker wires were sucking in noise, possibly from my Class D amp switching power supplies.  I swapped them out for Blue Jean Canare cables and my system is dead quiet again.  I have the Wireworld PC plugged back into my amp and it really does make a difference from the 5 other homemade cables I tried.

 This is a distinct possibiltiy, as even living several KM from a nearby high powered Analogue TV transmitter (200MHZ) caused Frame pulses of the video to get into my amplifier via it's speaker leads, then into the Negative Feedback ( gain setting)) area of the Gain Clone type SS amplifiers in use at the time. The cure was to feed a couple of turns of the speaker cables through large Toroids  Even clip on ferrites such as found on some USB cables and Mains cables may have helped too. 

[One and a half]

Interesting.  By changing the power cord or the speaker wiring causes the hum, points to grounding of the amplifiers or a severe instability.

 

@sandyk, if the transmitter was interacting with the amp,  there would be more of a buzz/squeal. 

[R1200CL]

I suppose the OP is has a 110 VAC ?

 

Someone of you may find this Norwegian article interesting. 
 

https://translate.google.no/translate?hl=no&sl=no&tl=en&u=https%3A%2F%2Fsenorc.no%2F%3Fp%3D226

 

A nice tool:

https://www.ebay.com/itm/Supra-Cables-AC-Sensor-110-230V-Contactless-Voltage-Test-Phase-New-Boxed-/383242572063
 

Supra has some nice and cheap boxes and speaker cables as well. 

 

[sandyk]

2 hours ago, One and a half said:

Interesting.  By changing the power cord or the speaker wiring causes the hum, points to grounding of the amplifiers or a severe instability.

 

@sandyk, if the transmitter was interacting with the amp,  there would be more of a buzz/squeal. 

Gary

In my case, it was frame buzz (Vertical Sync) from one of the nearby transmitters at Gore Hill in Sydney. It wasn't a continuous loud buzz and it's level could be seen to vary with large brightness changes on the TV screen. I only quoted this as an example of how RF can get into an amplifier via the speaker leads and NFB area.

 

Alex

[Speedskater]

5 hours ago, One and a half said:

Interesting.  By changing the power cord or the speaker wiring causes the hum, points to grounding of the amplifiers or a severe instability.

Power cord and hum : maybe.

Speaker cable and amp instability : maybe.

* * * * * * * * * * * *

Twisted pair or Quad speaker cables are always a good thing.

Twisted power cords are always a good thing.

[photonman]

What do you guys mean by instability?

[One and a half]

1 hour ago, photonman said:

What do you guys mean by instability?

Its not necessarily a real problem, circuit elements can resonate, oscillate at a given frequency and the device, usually a cap can behave odd and play up.

The designer had not considered this event from happening.