new KEF KC62 dual 6.5" subwoofer

[DrStuhl]

1:change polarity of the power plug of the KC62
2: connect K62 and NAD preferably to same power socket.

Have you tried ground lift?

View attachment 151721

Thanks for your responses! I tried to both devices on one powerstrip and tried all combinations of polarity. Made no difference at all, like the GND Lift. No difference.

I've even disconnected everything to the AMP. No Input, no Preout. Only power, main in to KC62 and speakercables

Any other ideas?

 

[AdamG]

Thanks for your responses! I tried to both devices on one powerstrip and tried all combinations of polarity. Made no difference at all, like the GND Lift. No difference.

I've even disconnected everything to the AMP. No Input, no Preout. Only power, main in to KC62 and speakercables

Any other ideas?

Post a video recording that we can listen and possibly help diagnose.

 

[Laserjock]

Thanks for your responses! I tried to both devices on one powerstrip and tried all combinations of polarity. Made no difference at all, like the GND Lift. No difference.

I've even disconnected everything to the AMP. No Input, no Preout. Only power, main in to KC62 and speakercables

Any other ideas?

Cable TV or dimmer switch nearby?

 

[Hayabusa]

Only power, main in to KC62 and speakercables

main in to KC62?
You mean lineout of KC62 to Pre in of the AMP?
A more exact description of how all is connected would help...

 

[Matias]

As far as I know the analog input is digitized for the DSP to high pass the signal, and a DAC converts back to analog. Maybe that DAC has too high a noise floor compared to your DAC directly to the mains amplifier?

 

[DrStuhl]

Post a video recording that we can listen and possibly help diagnose.

Will do tomorrow! Even tough I don't know if the microphone of the phone can record that noise properly.

Cable TV or dimmer switch nearby?

Nope, only cable internet. But connected the socket about 2m away from it.

main in to KC62?
You mean lineout of KC62 to Pre in of the AMP?
A more exact description of how all is connected would help...

Sorry, meant "KC62 line out" -> "main in from the NAD".

It sounds like the KC62 raises the volume too much and dirty. But increasing the volume on the amp doesn't change the noise, it's always the same white noise. No matter if the volume on the amp is on minimum or increased.

 

[DrStuhl]

As far as I know the analog input is digitized for the DSP to high pass the signal, and a DAC converts back to analog. Maybe that DAC has too high a noise floor compared to your DAC directly to the mains amplifier?

Sounds exactly like this - but shouldn't everyone have that problem then? I mean LS50 is a common speaker. And even my girlfriend is annoyed by the constant noise. So it's not only me she noticed it also directly when connecting it the first time

 

[Laserjock]

@DrStuhl might try and isolate the coax from cable modem. TV or internet doesn’t matter, it’s the coax cable that’s been source for many people.

 

[AdamG]

@DrStuhl might try and isolate the coax from cable modem. TV or internet doesn’t matter, it’s the coax cable that’s been source for many people.

This ^^^ But this is the normal cause of Hum and not “white noise” as you initially posted. That is why it will be very helpful to post a recording of the noise you hear. It it is really Hum, it’s most likely being caused by the Cable and/or Internet Box.

 

[Hayabusa]

Will do tomorrow! Even tough I don't know if the microphone of the phone can record that noise properly.


Nope, only cable internet. But connected the socket about 2m away from it.



Sorry, meant "KC62 line out" -> "main in from the NAD".
But increasing the volume on the amp doesn't change the noise, it's always the same white noise. No matter if the volume on the amp is on minimum or increased.

I assume main in means pre amp in.. Then its logical your volume control does not work...

 

[DrStuhl]

This ^^^ But this is the normal cause of Hum and not “white noise” as you initially posted. That is why it will be very helpful to post a recording of the noise you hear. It it is really Hum, it’s most likely being caused by the Cable and/or Internet Box.

When I disconnect the internetbox, should that noise disappear? Just for testing?
And shouldn't it interfere other devices as well?
I would really describe it as white noise. I would guess that hum has a lower pitch?
I'll try to record it tomorrow

 

[DrStuhl]

I assume main in means pre amp in.. Then its logical your volume control does not work...

Meant main in, sorry

 

[KMO]

"Main in" is the input to the power amplifier section of the amp - it's got "pre out" and "main in" terminals that are normally bridged, and have been separated to insert the KC62.

(My conclusion from reading its manual in conjunction with DrStuhl's posts - if that's wrong, correct me...)

 

[DrStuhl]

"Main in" is the input to the power amplifier section of the amp - it's got "pre out" and "main in" terminals that are normally bridged, and have been separated to insert the KC62.

(My conclusion from reading its manual in conjunction with DrStuhl's posts - if that's wrong, correct me...)

Exactly - sorry for confusing

 

[AdamG]

When I disconnect the internetbox, should that noise disappear? Just for testing?
And shouldn't it interfere other devices as well?
I would really describe it as white noise. I would guess that hum has a lower pitch?
I'll try to record it tomorrow

Yes, when you disconnect the internet box the noise should stop completely. If not something else is happening.

 

[Hayabusa]

Hi, I also see your NAD has sub line outputs, have you tried that in stead of using the kef for xover?

 

[DrStuhl]

Hi, I also see your NAD has sub line outputs, have you tried that in stead of using the kef for xover?

Works flawlessly when not connected to the Line Output (KC62), yes! No noise then. But well, I've payed that much to also use the included HPF.

Yes, when you disconnect the internet box the noise should stop completely. If not something else is happening.

Thanks! I've disconnected everything around and unplugged the internetcable and all powered devices nearby in my test.

I've tried the most simple setup right here.

Only one Socket and one power strip. Only devices plugged in nearby: KC62 + NAD


NAD: only Main-Ins, Power and one Loudspeaker:


KC62: Power + Line Output (tried GND Lift)
(connected Line Input to get it out of standby, then disconnected it)


Recording-Setup: Via Laptop (not charging)


Got that noise recorded pretty good:
https://sndup.net/9cfr

 

[kyle_neuron]

How long is that RCA cable from the KC62 to the amp? Can you try routing it away from any mains cabling or power bricks?

Does the noise respond to the volume control on the KC62 at all?

Your amp’s manual takes quite a lot of care to separate the ‘Main In’ information from the other line inputs, and indicates that using it bypasses the NAD controls to go direct to the amplifier output. The line inputs are noted as 159 mV/Pa sensitivity but the MAIN IN is listed as 630 mV/Pa.

Does the noise disappear if you run the KC62 into the Aux In or any other line level inputs, and reconnect the NAD link cable from their PRE OUT to MAIN IN?

 

[DrStuhl]

How long is that RCA cable from the KC62 to the amp? Can you try routing it away from any mains cabling or power bricks?

Does the noise respond to the volume control on the KC62 at all?

Your amp’s manual takes quite a lot of care to separate the ‘Main In’ information from the other line inputs, and indicates that using it bypasses the NAD controls to go direct to the amplifier output. The line inputs are noted as 159 mV/Pa sensitivity but the MAIN IN is listed as 630 mV/Pa.

Does the noise disappear if you run the KC62 into the Aux In or any other line level inputs, and reconnect the NAD link cable from their PRE OUT to MAIN IN?

Wow, that sensitivity truly might be the problem? Even if I don't understand who's to blame or how to fix it.

I connected my Smartphone to the KC62 (Line Input) and Line Output to the AMP. I've put the original bridges in from pre to power amp.
In this case the noise is way lower! And in this case volume control does make a difference. It did not make a difference with the previous setup.



So the sensitivity differs too much? Is there any way I can align them?

I don't know if it's still relevant: The RCA-cable is 2m long and I tried another 1m cable.

 

[kyle_neuron]

The sensitivity difference is because the MAIN IN is expecting to be given the output of a preamp, but you’re plugging in a line level output - consumer, I presume, so -10 dBV nominal:
https://en.wikipedia.org/wiki/Line_level

As such you’re over-amplifying the noise floor of the KEF sub output. Since you have a line level output, you just need to plug it into a line level input. Nobody is to blame per se, it’s just simple gain structure

Is there a particular reason you wanted to use the MAIN IN of the NAD amp? From what I can tell, that negates the use of the remote control as well as the front volume dial, which seems like you’re giving away a lot of convenience!