Topic: Plug in noise

If I plug in my Sennheiser HD 800s into the big jack of the ADI 2 DAC, i get some distortion/buzz.

Could this damage my Headphone?

Why do I have this kind of noise? My good old Sony amplifier is not a dedicated headphone amp, but it produces not that kind of noise/buzz, if i plug in.

Re: Plug in noise

T.man,

I'm not a dedicated Headphone Guy, but nastiness is not fun for any Audio Transducer, so let's investigate!

Are You CERTAIN the Phone Plug is fully inserted into the ADI-2?

It's a very Small unit, and absent the Physical Size/Weight of your Trusted Ol' Sony...  You may need to ENSURE things are fully connected.

Let's make sure the Basics have been looked at!    Failing that, I'm certain MC (RME Technik) will stop in, and give us some guidance.

Good Luck!

Curt

3

Re: Plug in noise

> i get some distortion/buzz

That's an insufficient description. Without music? With music? At any volume? Both channels? Any source?

Regards
Matthias Carstens
RME

Re: Plug in noise

MC wrote:

> i get some distortion/buzz

That's an insufficient description. Without music? With music? At any volume? Both channels? Any source?

If I plug in, in a fast or in a carefully way, I get dsitortion/buzz. After the headphone is fully connected the distortion/buzz vanishes.

Conditions: Without music; Volume mute; even in stand by, unit is off.

5

Re: Plug in noise

With the unit off I have no clue how that could be possible.

Regards
Matthias Carstens
RME

Re: Plug in noise

I just reproduced it, but I also reproduced it with two other headphone amps too - not only when they're switched off but even when they're all unplugged from the wall. I figured out the common link - they're all fed from the ADI-2 DAC, but it's also feeding an Arcam receiver (that also feeds the ADI-2 via coaxial spdif). If I turn the Arcam off then any noise as I plug in headphones disappears from all of my headphone amps, whether the ADI-2 is on, off, or in standby. So my guess is that the noise is coming from something you have plugged into the ADI-2 DAC and it's leaking through.

Re: Plug in noise

This hum/buzz in the short moment you plug in the phones is completely normal and easily explained by the mains leakage currents of the stock supply.


A very simple experiment proves that right away:

- Connect the power-brick to the mains and to the ADI (on or off, doesn't matter), don't connect anything else (no source).
- Grab your phones plug at the shield portion of the plug and just touch the tip of the plug to the metal chassis of the interface, for example at the ring of the phones socket. A slight hum/buzz will be heard on the left cup.

- Now take a cable with alligator clips and connect that to the shield sleeve of phones plug and to PE Mains Earth (or earth-grounded water pipe etc). Again make contact to the RME's ground, this time holding the plug at the cable, not making any skin contact. The buzzing will be there again, and it will be louder (there is a more direct leakage path now).

- Finally, disconnect the RME from the supply and repeat the experiment, this time touching the DC-plug's outer contact with the tip of the phones plug. The results will be the same: buzz when your body skin is the return path, and louder buzz when a more direct return path is present.

In my case, using HD700 cans, this hum/buzz is very prominent.

With a source connected, things can change significantly. When the source has its GND connect to PE (3-prong mains plug), the hum will be (mostly) gone (the leakage current will take this path and won't flow through the phones), but when it is also powered from a high-leakage SMPS power-brick (the typical Laptop/Netbook supply) the effect can be softer or louder, depending on the actual electrical circumstances.


Fortunately, there is nothing to worry about because that is not a regular operating condition.

Re: Plug in noise

MC wrote:

Seriously, you should get a certified electrician to check your house electric net and wiring. Something is terribly wrong here. The ADI-2 DAC has a relais at its output phones, means the connection is as interrupted as can be. The 'leak through' therefore must be ground level versus your own body's electric level, so to say. If that causes noise in a high impedance, very insensitive headphone, then there is something really wrong.

In Stand by, plugging the headphone to the ground of the jack reproduces a noise with the frequency analog to 50 Hz. Very specific - I think.

Before I check the house electric  - there is no such effect with the sony device - same house power line. This device has also no ground at its power socket, a solid metal housing, but otherwise no buzz/distortion (50Hz?).

So how can that be?

9

Re: Plug in noise

I deleted my former comment. KSTR gives a very simple example that everybody can reproduce. I did not expect the leakage current to be powerful enough to become audible in the headphones, but that is indeed the case when using the body as return path. I tried several phones and unexpectedly the high impedance ones, that are usually the least sensitive ones (lowest volume) make the loudest noise (HD800, DT-880 250 Ohms).

It seems the initial description was not only insufficient, but also misleading, as the buzz only occurs during the plug-in process, for the fraction of a second. And then only if the used connector is not insulated. When not touching the phones ground contact, or having an insulated one, there will be no noise. If the audio system is grounded, to the same level as the body, there will also be no noise.

In the end this is all interesting but a non-issue.

The Sony device uses battery or a linear power supply. The latter causes hum in other areas.

Regards
Matthias Carstens
RME

Re: Plug in noise

It seems the initial description was not only insufficient, but also misleading, as the buzz only occurs during the plug-in process, for the fraction of a second.

If I plug in my HD800s only half way, I get a permanent buzz, entering fast - only for a second.

So your answer would be?:

  • The sony device has not this problem - but you've got more noise eg. by playing music. ADI 2 DAC Compromise: plug in - noise, playing music - very low noise?

  • The buzz/distortion doesn't damage my HD800s?

11

Re: Plug in noise

> The buzz/distortion doesn't damage my HD800s?

Definitely not.

Regards
Matthias Carstens
RME