Hum and Directstream grounding


#1

I’m getting a little more hum at the speakers with the Directstream than usual, and I suspect its just a grounding issue. It’s the same for high or low output.

So I was just curious whether the analog ground is connected to the chassis, or it is floating in some manner?

Thanks.


#2

The grounds of all of the input and output connectors are firmly connected together and to the chassis ground.

If you are using USB, your computer may be floating (if, say, it’s a laptop) or connected to a different outlet circuit than the rest of your audio system (and hence could have a big groundloop.)


#3

Note: this is not a commentary on Uptone’s gear (which is great). It’s just that my only ground loop situation (ever, I think) happened at the same time. Uptone isn’t responsible for the physics involved here. smile

After I installed Uptone’s kit:

http://uptoneaudio.com/products/mac-mini-dc-conversion-linear-fan-controller-kit-mmk

…my system developed a nice big ground loop through the HDMI connection from the Mini to the receiver, through the receiver’s RCA connection to the DirectStream, out the DS’s ground, and back to the ground pin on the new external power supply attached to the Mini. It was internal digital noise (only present when the CPU or GPU were busy) from the Mini getting fed back through that new 12V external power supply because that’s apparently just how it is when converting AC to DC like that in a non-linear supply.

I’m not entirely comfortable with it, but the only solution anyone I talked to has been able to offer is using a “cheater” plug (no ground pin) on the Mini’s external power supply.

This cheater plug may unfortunately be the solution for your situation as well, assuming you can figure out everything participating in the ground loop (if that’s actually what it is) and can live without one of them having connection to ground.


#4
Minimalist said I'm getting a little more hum at the speakers with the Directstream than usual . . .
What's "usual?"

That is, what did you change that led to the hum?


#5

Oh, the “usual” is with my old DAC or phono stage. And its not terrible now, just noticeably louder. I’m running the Directstream directly into my amp at the moment, but it is plugged into a different branch of the house wiring. I’ll plug it into the dedicated circuit for the amps and see what happens.


#6

@Jim: The cheater plug is a reasonable way to go in this situation. It will confirm where the problem lies if it works or eliminate the Mini ps ground as the problem if it doesn’t (it’s cheap, too). The amount of current involved here will not create a dangerous situation. Running audio and video on the same system increases the chances for ground potential differences since there are more connections. Something’s gotta give and I’ll bet you don’t want to stare at a blank screen.shaking-head-no-smiley-emoticon_gif

Welcome to the forum!


#7
Ted Smith said The grounds of all of the input and output connectors are firmly connected together and to the chassis ground.

If you are using USB, your computer may be floating (if, say, it’s a laptop) or connected to a different outlet circuit than the rest of your audio system (and hence could have a big groundloop.)

Creating a new system over the past year, starting with the DS DAC at the centre, has been exciting and fun. I now enjoy a sound well beyond initial expectations, and it confirms just how good the DS DAC (Yale) really is. The better I treat it, the more it keeps delivering.

Starting to think my way through feeds, earths, grounds, shielding etc. - though what I’ve got is quiet as the grave. Thinking more about SQ than hum.

Questions:

How are the input/output signal grounds connected to each other - series or star - does it matter?

Where does signal ground connect to chassis ground?

I’ve seen an earth connection to chassis at the power inlet - is this chassis ground?

If the DS DAC signal/chassis/earth grounds are all connected, and the same is true for a connected power amplifier, a ground loop will be created. Do you have a recommendation for breaking this?

Thanks

Lonan

[edited to fix formatting]


#8

All input and output signal grounds are firmly tied to each other. The signal ground is connected to the chassis ground at one point on the digital card near the I/O connectors. The chassis connection at the power inlet is the chassis ground.

The best way to combat ground loops is with balanced interconnects. FWIW some preamps are noticeably quieter if no unbalanced connections are used, even if those inputs or outputs aren’t being used. If one must use unbalanced connections a wideband audio transformer may isolate the two grounds. Jensen Transformer’s site has good papers talking about noise and ground loops.