LFE Noise problem

[boomtheroom]

Hey All,

I just purchased a Rel t9x subwoofer to replace my 20 year old Sony Sub. I hooked it up to the lfe channel on my Marantz 7013 amp (same outlet that the Sony has been plugged into)
and a nasty buzz transfers through all my HT speakers.
Now this happens regardless weather the Rel sub is on or not but as long as the rca lead is connected to the Marantz amp and the sub is plugged in to a power socket, the buzz/humm is there.
As soon as i remove the rca cable, the noise is gone.

I have tried different rca cables, but no avail...

Now more recently I have managed to reduce the Humm alot by plugging the sub into a power socket in the middle of the dining room.
I can plug the Marantz amp into any of the other 3 sockets, leaving the sub plugged into that middle socket in the dining room, including the middle one and the humm is
basically gone.
But if I plug the Sub power into any of the sockets other than the middle one, regardless of where the Marantz is plugged in the humm or buzzz comes back.

So confused.....

Any theories?

 

[Chrispy]

Rel subs are worthless is my first thought. Especially such a small one. Whether you have a ground loop not sure what you're doing with all the suggested connections Rel usually has. Not sure why your different power options do that but you doing the Rel suggested dual connections?

 

[sam_adams]

a nasty buzz transfers through all my HT speakers.
Now this happens regardless weather the Rel sub is on or not but as long as the rca lead is connected to the Marantz amp and the sub is plugged in to a power socket, the buzz/humm is there.
As soon as i remove the rca cable, the noise is gone.

The REL amp is grounded—three prong IEC connector on amp and three prong power cord.

The Marantz is double-insulated—no ground pin on the IEC connector on the back.

Circulating chassis currents are flowing in the shield of the subwoofer cable inducing a signal voltage into the the Marantz.

Since both devices use unbalanced connections (RCA), your best solution is to use an isolation transformer at the subwoofer end of the RCA cable.

The Jensen SUB-1RR is a good choice for this application.

 

[john61ct]

Cheaper - try disconnecting everything else

plugging both units into the same circuit

then ground the two chassis together and hence both to the same Earth grounding point

maybe confirm that circuit is properly grounded, ideally a big copper rod pounded deep enough to enter soil that is always wet.

Yes overkill but...

 

[tineared]

I suggest getting one of these adapters and un-ground your new sub and see if that fixes it

 

[wwenze]

I suggest getting one of these adapters and un-ground your new sub and see if that fixes it

View attachment 555288

On my first day in Japan I searched electrical shops for this (because laptop power cable...) and finally found one for like $5

Years later I saw people just simply removed the ground pin on their IEC cable

 

[boomtheroom]

Rel subs are worthless is my first thought. Especially such a small one. Whether you have a ground loop not sure what you're doing with all the suggested connections Rel usually has. Not sure why your different power options do that but you doing the Rel suggested dual connections?

yea tried all the solutions they suggested..in talks with their reps in my country atm.. yet to come back to me .

 

[boomtheroom]

On my first day in Japan I searched electrical shops for this (because laptop power cable...) and finally found one for like $5

Years later I saw people just simply removed the ground pin on their IEC cable

Is that even safe? BTW im in New Zealand if that makes any difference

 

[boomtheroom]

The REL amp is grounded—three prong IEC connector on amp and three prong power cord.

The Marantz is double-insulated—no ground pin on the IEC connector on the back.

Circulating chassis currents are flowing in the shield of the subwoofer cable inducing a signal voltage into the the Marantz.

Since both devices use unbalanced connections (RCA), your best solution is to use an isolation transformer at the subwoofer end of the RCA cable.

The Jensen SUB-1RR is a good choice for this application.

Yeah tried looking for the 1rr and even the 2rr as i will be using 2 subs but looks like they dont make them anymore.

 

[wwenze]

Is that even safe? BTW im in New Zealand if that makes any difference

Was responding to the totally not-New-Zealand socket adapter above.

It's not safe to remove the earth connector in New Zealand. Or in majority of countries. Japan is the only country I know where it is safe to do it in dry areas.

 

[boomtheroom]

Can anyone explain, why the noise goes away when the rel sub is connect to the middle socket in the room, regardless what ever
socket the marantz amp is plugged into?
But in reverse if the Marantz id plugged into that socket and the Rel is connected to any of the other sockets the noise comes back??

Im confused....

 

[boomtheroom]

The REL amp is grounded—three prong IEC connector on amp and three prong power cord.

The Marantz is double-insulated—no ground pin on the IEC connector on the back.

Circulating chassis currents are flowing in the shield of the subwoofer cable inducing a signal voltage into the the Marantz.

Since both devices use unbalanced connections (RCA), your best solution is to use an isolation transformer at the subwoofer end of the RCA cable.

The Jensen SUB-1RR is a good choice for this application.

Will this do the same job?

https://www.amazon.com.au/Earthquake-Sound-GLI-200-Kleaner-Isolator/dp/B07Z5SKRMR?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&shipTo=NZ&language=en_AU&smid=A4XRJ8S0WXSO0&th=1

 

[wwenze]

Can anyone explain, why the noise goes away when the rel sub is connect to the middle socket in the room, regardless what ever
socket the marantz amp is plugged into?
But in reverse if the Marantz id plugged into that socket and the Rel is connected to any of the other sockets the noise comes back??

Im confused....

Probably because the middle socket earth is broken, better get it checked.

 

[Redacted]

Probably because the middle socket earth is broken, better get it checked.

Assuming the Marantz has no "ground lift" switch or that it does but makes no difference, then there could be a mains wiring fault.

The level of noise can depend whether the mains in the house is the "ring main" type (common in the UK, dunno about elsewhere) or the radial type, and whether your neutral is tied to ground at the fuse panel or not. So, if the the two (distant) sockets you tried each had a separate wire back to the fuse box, you may well get less hum than on a ring circuit (as live, neutral and earth can be directly connected between each socket, creating a short path local "sub loop" via two pieces of kit).

I'd start with one of those test plugs with LEDs on the front that do the most basic tests for faults (commonly used by motorhomers and caravanners). After that, you may need an electrician.

Never mess with earths that are integrated into plugs - that's just dumb.

 

[john61ct]

Never mess with earths that are integrated into plugs - that's just dumb.

Amen.

Getting the house wiring looked at for proper Earthing

should not be a lower priority than other solutions.

It's a human lives safety issue, much more important than audio SQ.

Finding an electrician who is au fait with the latter is pretty rare though, so that may not get the whole situation fixed.

A solid starting point though, is once the former has been corrected, get both components plugged into the SAME circuit, and both chassis grounded to each other.

 

[DonH56]

Will this do the same job?

https://www.amazon.com.au/Earthquake-Sound-GLI-200-Kleaner-Isolator/dp/B07Z5SKRMR?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&shipTo=NZ&language=en_AU&smid=A4XRJ8S0WXSO0&th=1

I would try that first.

 

[Curvature]

I would switch to gear with XLR connections and never think about ground loops again.

 

[kyuu]

I was not aware that XLR is immune to ground loops. I wonder why ground lift switches are a thing?

Spending up for XLR-equipped equipment in a home environment is not the most cost-effective way to avoid ground loops, in any case.

 

[john61ct]

^ This

Just "going XLR" by itself isn't any kind of silver bullet.

 Long distances and / or RF/EMO noise are more likely what makes spending more on differential interconnects worthwhile.

Grounding issues are distinct, but at least component chassis' CAN share earthing (or be floated) via balanced wiring to help when troubleshooting these too.

 

[Curvature]

I was not aware that XLR is immune to ground loops. I wonder why ground lift switches are a thing?

Spending up for XLR-equipped equipment in a home environment is not the most cost-effective way to avoid ground loops, in any case.

I don't know that a cost increase is necessarily true. I guess with certain devices, like AVPs, yes, but for most other things competently designed professional gear is cheaper for its level of performance.

Differential circuits work by sending a pair of the same signal out in two different legs, one 180 degrees out of phase from the other. If a ground loop is introduced, it affects both legs, which are recombined and phase shifted back to the same polarity. This effectively cancels common noise and parasitic currents while doubling voltage. The implementation is not perfect, and is measured in terms of a common mode rejection ratio (CMRR). The system can also be unbalanced by introducing single-ended (RCA, etc.) connections, although if competently designed this won't be an issue. There were also wiring differences in older gear that caused issues (the pin 1 problem). But in every practical sense these are a superior method of interconnection.