Ground Loop Or Bad Cable?

Jer.War

A bit of a curiousity here, looking for a little insight...

Recently I have upgraded my ICs in my 2 channel setup. First I changed out the PNF ICs to a set of Morrow audio MA-3 ICs that I had running from my CDP to my pre-amp. Noticed an amazing nice change in detail, tone, and sound stage.

I enjoyed these cables so much that i decided to buy a set of MA-5s with Eichmann Copper Bullet RCA connectors. I placed these in between the CDP and pre and slid the MA-3s between the pre and power amp.

After a long listening session I stopped the CD player and noticed a hum from both speakers that I have never experienced before. There is also an occasional louder buzz also. If I remove the MA-3s and replace them with the cables I had previously (Shielded) the hum disappears and the noise floor returns to what I am used to (very slight hiss, no hum at all). The noise is present no matter what input is selected on the pre and whether it is on or off. However, when I first turn on the pre, the buzz disappears but returns after a few minutes.

With the MA-3s back in place if I ground the chassis of either the power amp or the pre the hum/buzz disappears; however I have only done this temporarily and am not sure if the buzz will return.

Is it possible this noise is due to a bad cable, or ground loop issue? Is it possible a shielded cable would mask the/solve the ground loop (The Morrow's are not shielded)? Any thoughts on further trouble shooting to isolate the issue, or recommendations would be greatly appreciated.

Speedskater

When I read about someone using unshielded RCA interconnects, I am reminded of my 6 year old grandson. When I tell him not to do something because someone might get hurt or things might get broken, he will reply "I did it yesterday and nothing happened".

Analog RCA interconnects should always use a shielded cable with a heavy braided shield.

Just because some get away with using poor cables, doesn't make it a good idea.

Jer.War

As i understand it, a shield will protect against induced noise... However, if it WAS a case of induced noise on the unshielded cables causing this noise I just couldnt wrap my head around why the noise disappears when the chassis is grounded...

Msabot1

This is a case of picking up ambient signals from another source.....power supply ect...line noise from AC . Use the shielded cables...you will be happier!

zane77

I think the shielded cable is providing the ground between both pieces of equipment, the same as adding the external ground cable.

CoolJazz

The fact that you mention the buzz getting louder at times, sounds to me like a ground loop. Are your amps plugged into a seperate power feed from the front end?

If a heavy shield lowers the noise floor, then that sounds like it could be a situation where there is current flowing on the audio cable. Just because you lower it with greater conductor, it's still not good if that's what's happening.

An unshielded audio interconnect does not mean NO ground connection. It simply means not wrapped in a shielding mechanism. Several times through the years, I've seen reports including in careful magazine reviews, where they put under the microscope cables that were the same except shielding. And in every case I ever noted, they reported better audio quality, in there opinion, with the version that was not shielded. Expecially if you have a bit of impedance load at the input, with common sense on routing you can use unshielded cable and might well have better audio than a shielded version.

So I'd check some basics. Look for any routing issues that might be gaining noise. Check where power is derived and if you come up empty, then call Morrow and find out what they have for experience on that version.

Good luck with working it out and don't be too quick to get down on the interconnects.

CJ

Speedskater

The heavy shield co-ax does two things:

a] it acts as a shield from airborne interference (including magnetic because both the shield and the center conductor are in the exact same field).

b] the heavy braid reduces the end to end resistance of the cable between the two components. Because leakage and noise currents will always flow between the components, the less serial resistance the less noise voltage.

This is one of Bill Whitlock's favorite subjects.

F1nut

You've got a bad cable, plain and simple.