1 (edited by Siemak 2020-01-09 21:13:19)

Topic: Humming with power amp

Hi all.
I'm happy owner of RME ADI-2 DAC smile

I accidently discovered humming noise audible ~0.5 mtr from speakers when the DAC is turned ON and no music plays.
The humming is static and independent from VOL level. 
The DAC is connected RCA to Plinius power amplifier and works as preamp.
Humming is audible even if all sources are disconnected from DAC. I've also tried using another pair of RCA interconnects to make sure the humming is not caused by faulty cables.
-That doesn't make any difference.

The humming stops few seconds after turning OFF the DAC.
My Plinius power amp has "ground lift switch" chassis/open - but it only decreases the noise in "chassis mode" a bit. 

Any idea why is that noise audible? Is that normal behaviour?
What else can I try to eliminate the noise?

It's not a loud noise but annoying since I know it's there sad

2 (edited by Curt962 2020-01-09 23:13:09)

Re: Humming with power amp

Siemak,

Sorry that you're experiencing this difficulty.   It seems though that you've done a good job with the basic troubleshooting.   

I'm neither an Electrician, nor an Engineer but would it be possible for you to have your ADI-2 DAC, and Amplifier plugged into the SAME outlet?  For testing?  If the Amp is plugged "here", and the DAC plugged "over there" It seems entirely possible that one wall outlet could possibly be at a slightly different Ground Potential than the other, and these things tend to lead to odd noises, which are NOT Characteristic of the RME unit n any way.

Lastly,  Let's just be sure that your RCA interconnects aren't getting TOO Cozy with AC Mains Cables.   No Bueno!  If they must cross paths...do so at Right Angles to minimize the possibility of noise introduction.

It's Late in Germany at the moment, so we don't have the Luxury of their (RME) Expert guidance,  but be confident that your problem WILL be resolved promptly!

Best Regards

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

3

Re: Humming with power amp

What does 'all sources' mean - only RCA and power supply left? Then you have a leakage current problem from the included SMPS, where its current runs over ground into your power amp, and is there translated into audible noise (the sound is NOT generated within the DAC).

What helps is to ground the ADI directly to either any available ground, or the same ground that your amp uses.

Regards
Matthias Carstens
RME

4 (edited by Siemak 2020-01-11 22:14:49)

Re: Humming with power amp

Curt, Matthias

Thanks for your support.
I don't blame the DAC itself  for generating humming noise. I'm not Electrician and can't guarantee quality of my house electrical installation nor its grounding quality.


Matthias, forgive me my incompetence but how do I ground the ADI? Both units - the DAC and amp are powered from the same wall socket.  What else can I do?
Does it make snense to give it a try  connecting ADI and amp XLR instead of RCA? I haven't got any XLR cables currently and the question is if it's worth to buy one.

Guys, please don't get me wrong, the humming noise is audible only very close to speakers and doesn't affect listenning to  music.   
I can live with it. It is just tempting me to fix it since I know "it's there".

Regards, Siemak

5 (edited by Curt962 2020-01-12 01:05:02)

Re: Humming with power amp

Siemak!  Nobody is keeping Score, nor giving you Demerits. smile   Hang in there Friend!   Problems such as this arise from time, to time.   

Let me suggest that as the noise is very low level, and unobtrusive that perhaps it's best to allow MC a bit of time to provide the engineering guidance to bring the matter to a proper resolution.    Too many Chefs  "spoil the soup"    smile  You understand.

Best to You!   

Curt

PS:  You don't have a Light Dimmer switch in the room do you?  Those Rotten B@!?#@'s!   Noise Generators....

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

6 (edited by Siemak 2020-01-12 01:07:17)

Re: Humming with power amp

No, no light dimmer around.

I'm gonna try XLR connection soon.  Just not sure about XLR pins compatibility between ADI and my power amp.

If my Plinius amp XLR inputs are:
PIN 1 to GND
PIN 2 to + sig
PIN 3 to - sig

-are they compatible with ADI?

Re: Humming with power amp

Look in your Users Manual.  The ADI-2 DAC's pin-out is industry standard. 

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

8

Re: Humming with power amp

XLR should fix that.

For grounding you connect a wire from any part of the DAC housing directly to the earth contact in your power outlet. The ground of the SPDIF input can also be used in case SPDIF coaxial is not in use. Note that in some cases this will not help but produce an even bigger ground loop.

Regards
Matthias Carstens
RME

Re: Humming with power amp

Siemak...See?

You won't need to spend HUGE $$ on a set of XLRs.   We'd be happy to help you choose a suitable product.

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

Re: Humming with power amp

Thanks again for your help guys smile

I'll buy XLRs and then comeback to this thread to let you know that humming gone.

I'm not "magic cable voodoo" fan so I'll get some reasonable priced, well built XLRs.

Regards, Siemak

Re: Humming with power amp

Siemak,

While you wait on your XLRs, here's a bit of light reading to help you better understand the principles of Balanced Circuits, and the advantage they offer the user.

https://en.m.wikipedia.org/wiki/Balanced_audio

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

Re: Humming with power amp

Hello again.

I've just connected my new XLRs and........ no humming at all!!!

I'm more than happy, enjoying my toys and pure music again smile 

Thanks for your support guys. Humming problem resolved.

Of course I love my ADI from here to the Moon and back!!!

Best Regards, Siemak

Re: Humming with power amp

That's FANTASTIC NEWS Siemak!   I'm happy your matter was quickly resolved.

Happy Listening!! 

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

14 (edited by Curt962 2020-01-14 20:56:39)

Re: Humming with power amp

Update!

With your New Cables Siemak, you must SURELY need these!  smile smile smile

https://shunyata.com/products/accessori … -elevator/

We would all be delighted for MC's asessment of this Quack Science!     Careful Though!   This is "Dark Field" Man!
Heady stuff,  and in some alternate Universe, it might make sense!  smile

Here? On Earth?   Maybe notsomuch.  Have a good laugh on me.  smile

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

Re: Humming with power amp

Curt

You made me laugh indeed. Hey LoL mate smile
"Dark Field" is the level I still haven't achieved in this game.

Siemak

16 (edited by Curt962 2020-01-14 21:20:38)

Re: Humming with power amp

You're in the UK I sense?

It's all good fun Mate.  Your new ADI-2 DAC is a Gem.  You'll Love it!!

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes