Ground loop


#1

I have dac/cd player, pre-amp and power-amp all powered from Powerplant 5.

Interlinks are unbalanced.

I have a audible noise in my (passive) loudspeakers, even with the dac section not connected to my laptop.

The speakers are dead silent when the dac/cd player is disconnected from the P5. So the problem obviously lies with the dac/cd player.

The question I have: can I rule out groundloop as possible cause, assuming that the P5 provides a single ground for all components connected to it (as in my set-up) ?


#2

I am not quite clear on this setup. Please bear with me. With the amplifier connected to the speakers, but with nothing connected to its input, there is no hum?

When does the hum come? When you plug your DAC/CD player into the Power Plant?

If the answer is yes, does that mean the DAC’s outputs are connected to the power amp?

If that is true, then it does not necessarily mean it isn’t a ground loop.

Start with this tutorial and let us know. http://www.psaudio.com/ps_how/how-to-find-and-fix-hum/

Follow its directions EXACTLY.


#3

Hi Paul,

I’ll try to be more specific:

  • all components are powered via PS audio P5 (when powered)

  • when only power amp is connected to speakers (pre-amp and cd/dac disconnected from P5 and poweramp) : no hum/noise

  • when pre & power amp connected (cd/dac disconnected from P5 and pre-amp): no hum/noise

  • cd/dac & pre & power amp connected: hum/noise

My question is: can this be caused by a ground loop?

I have read somewhere that if there is a common ground, that there should not be a ground loop. With all components connected to the P5 is there a common ground? Maybe I misinterpreted (I am a newbee in this area)…


#4

That could easily be a ground loop. This has nothing to do with the P5 other than the P5 puts all the grounds together.

Is the CD DAC connected to anything else? Any chance there’s a cable TV connected to the DAC?

Try a cheater AC plug on the CD/DAC.


#5

Paul, it’s getting complicated for me…

The hum/noise is also there with nothing else connected to the cd/dac.

My cable TV is connected to a different AC outlet, albeit in the same electrical circuit.

As for the cheater plug: is this meant for diagnostic purposes only or as a permanent solution? And is the latter not hazardous?


#6

The cable tv isn’t the problem, then, if it has no connection to the DAC/CD.

For whatever reason, it sounds like there’s a ground loop between the CD/DAC and preamp. There aren’t a lot of options other than to break the loop - caused by the electrical ground of the two products being tied together.

Let me ask another question. Is the noise low frequency hum, or higher frequency buzz? I know that’s hard to sort out, but the buzz sounds “sharp” like an angry insect and the hum is “mellow” and low in frequency.

If it’s hum then it’s likely not a ground loop - if it’s a buzz, then it’s a loop.

You can try the cheater to see if it goes away. If it is a ground loop that’s fix it - if it’s a hum, it won’t.

Figure out what’s going on first, then we’ll see if there’s something we can do to solve it. Cheater plugs aren’t safe, though I’ve never had a problem.


#7

To be clear, the issue with the cable TV is not whether the box is plugged into the same outlet as the stereo but whether anything that is connected to the cable itself (e.g., the TV or a Blu-ray player or other device that is connected to the TV) is connected to the stereo. It’s the cable itself that can cause the loop as it is grounded where it comes into the house and that ground may be at a different level from your stereo. If id doubt, disconnect the cable from the box and see if the hum goes away.


#8

I’ve been chasing ground loops for awhile now (seems like forever) and the cable box was the biggest, tho’ not the only, culprit in my system.

I won’t go into all of it, but I found that using an optical digital audio out cable from the cable box (instead of a metal wire, like SPDIF) to my HT pre/pro dramatically reduces the ground loop hum. Makes sense as there is no wire connection and so, no audible ground differential.

After discovering this, I said to myself, “well, duh.” embarassed

Also, plugging the cable box into a dedicated 20amp line where it is the only piece of requirement plugged into that line helped a lot as well…basically, this plus the TOS cable electrically decouples the box from every other piece of equipment I have.

Again, well duh.

I’m posting this here as I hope that it will help others tone down the maddening ground loops.


#9

Thanks!