[xenithon]

I came across this when researching the topic of grounding via interconnects:

"As long as interconnects remain in place and any of the components are grounded then there's not much risk"

This is false and taking this approach can create a false sense of safety. There are several things wrong with this notion. The most prominent are:

1. Signal grounds are not always tied to chassis ground.

In this scenario, if a ground-defeated component experiences a fault, the dangerous current will not flow through interconnects. Even worse, a ground-defeated component with signal ground tied to chassis ground could fault, and the current would flow via interconnects to another component that doesn't have signal ground tied to chassis. Now you have TWO components with dangerous current flowing through them.

2. Most interconnects cannot handle fault current.

The typical audio interconnect (the even really expensive examples) uses thin-gauge wiring designed for low voltage/low current, with connectors also designed for low voltage/low current. A ground fault involves high voltage/high current. Even if a fault is shunted through an interconnect, it may fail/melt/catch fire before a fault can travel to a grounded component and cause a circuit breaker to trip.

I am a little worried of using an anearthed PC with the DAC with IC's providing ground via the amp

. The above suggests that this is a band-aid fix to the ground loop problem.

 

[xenithon]

There is one additional thing that is confusing/bothering me - since disconnecting the earth got rid of the noise/hum it indicates it was a ground loop. However, I was under the impression that ground loops are at a constant level, and do not increase as the volume of the amps is turned up? Are there other possible problems I should investigate with similar symptoms but which are affected by the volume level?

 

[Andrew_WOT]

I've been using cheater plugs to fight ground loop problem for quite a while and recently tried HumX, to my surprise it worked with the same results as lifting the ground whilst keeping safe earth. I highly recommend to try it out.
And yes, hum gets louder with volume going up.

 

[Traddad]

Quote:

Originally Posted by Andrew_WOT /img/forum/go_quote.gif I've been using cheater plugs to fight ground loop problem for quite a while and recently tried HumX, to my surprise it worked with the same results as lifting the ground whilst keeping safe earth. I highly recommend to try it out. And yes, hum gets louder with volume going up.

I gotta ask....any change to the SQ?

 

[Andrew_WOT]

Quote:

Originally Posted by Traddad /img/forum/go_quote.gif I gotta ask....any change to the SQ?

It's not in a signal path, google for it.

 

[Traddad]

Quote:

Originally Posted by Andrew_WOT /img/forum/go_quote.gif It's not in a signal path, google for it.

THX. Now I have to make the decision whether to go that way or sell my alien and buy a DAC with an optical in.

 

[Andrew_WOT]

Quote:

Originally Posted by Traddad /img/forum/go_quote.gif THX. Now I have to make the decision whether to go that way or sell my alien and buy a DAC with an optical in.

Coaxial is always better, there is a lot of crap that gets introduced in electrical/optical conversion.

 

[xenithon]

I tried another thing last night - I connected just one IC at a time. With the right IC only, there is no noise; with the left IC only, the noise comes back. To eliminate an issue with the amp, I connected the left IC from the DAC to the right input of the amp, and the noise moved to the right side. Does this possibly indicate an issue with the grounding of the left RCA jack of the DAC? Or is it just that the ground is only connected via the left IC?

The fact that the left channel results in the hum matches up with the fact that the noise exhibits only in the left channel of the headphones; and when moving it to the right input of the amp, the noise moves to the right channel of the headphones etc.

 

[Herandu]

Quote:

Originally Posted by Andrew_WOT /img/forum/go_quote.gif Coaxial is always better, there is a lot of crap that gets introduced in electrical/optical conversion.

Nothing wrong with the optical connection between Europe and the US that runs along the bottom of the Atlantic ocean.
I am yet to find a single human who can tell the difference between coax and optical in a double blind test.

 

[Herandu]

Quote:

Originally Posted by xenithon /img/forum/go_quote.gif I tried another thing last night - I connected just one IC at a time. With the right IC only, there is no noise; with the left IC only, the noise comes back. To eliminate an issue with the amp, I connected the left IC from the DAC to the right input of the amp, and the noise moved to the right side. Does this possibly indicate an issue with the grounding of the left RCA jack of the DAC? Or is it just that the ground is only connected via the left IC? The fact that the left channel results in the hum matches up with the fact that the noise exhibits only in the left channel of the headphones; and when moving it to the right input of the amp, the noise moves to the right channel of the headphones etc.

I would borrow a multi meter and do some resistance and continuity testing to see if you got a broken track on the DAC PCB. You just have to measure between the ground side of the L & R RCA output and the DAC casing. The fault you got is quite complex. If you lived up the road I would have popped round and have a look at it for you in return for a beer or two.

 

[xenithon]

Herandu, I tried the following scenarios:

* both channels connected, hum/noise in left channel
* right channel connected only (to right input of amp), no hum/noise
* left channel connected only (to left input of amp), hum/noise in left channel
* left channel connected only (to right input of amp), hum/noise in right channel
* right channel connected only (to left input of amp), no hum/noise

I thought this would indicate something is amiss with the left RCA jack of the DAC, but the thing is, when I had the previous DAC in house a couple weeks ago the noise/hum was also in the left channel (and moved to the right with cables swapped). Was it a coincidence? I am starting to fear something with the grounding in the amp??

. Or could it be something with the how the system works when all connected, and not one particular component which has issues or is faulty?

I'm thoroughly perplexed by this problem. The observations thus far are:

#1 - earthed DAC causes hum/noise (left channel)
#2 - earthed DAC with cables swapped causes hum/noise (right channel)
#3 - unearthed DAC is silent
#4 - unearthed CD player is silent
#5 - earthed DAC no. 2 from a couple weeks ago causes hum/noise (left channel; moves to right when cables swapped)

 

[Herandu]

I had a word with one of my fellow audio engineers about this and after making a rough drawing on paper to try to 'simulate' the fault we both think that it could be a break in the earth track in the amp close by the RCA input socket. Crazy at it seems, you can check this out by shorting out the ground between left and right channel input on the amplifier at the RCA socket end and then listen out for the hum. If the hum vanishes, you have a broken track or a lose soldering point on the earth in the amp.

 

[xenithon]

Herandu - thanks, I will try that. So I would just touch the wire between the two RCA input jacks? Should I just touch the outside of the jack or the inside? Also, should I touch it on the input to which the IC's are attached from the DAC, or a different set (it is the WA2 which has multiple inputs).

 

[Herandu]

Just the outside. If you touch the inside you'll get no sound...

 

[xenithon]

Hi herandu. Tried that - no joy