White noise coming from DAC or so it seems

[merrillaudio]

Problem:
When the DAC is plugged in and the Amplifier turned on, there is a significant amount of white noise being heard. Removing this specific DAC removes the white noise.

Set up:
Speakersipedreams
Amplifier: Merrill Audio VERITAS Monoblocks
Pre-Amp: None
Dac: Memory Player
Interconnects are balanced.
No Power conditioners.

Items tried:
1. Floating the ground even though there is no ground loop hum.
2. Changing the outlets so they are totally independent from the DAC
3. Changing power cords
4. Did not change XLR cables - wish we had.
5. Did not try another Source, also wish we had however anywhere else this has not been a problem.

This had a very low, acceptable level of white noise when using the Audio Research VTM2200.
This was tried on one other Memory player with no problem so it is specific to the memory player (or the amps).

What could cause white noise like this? It almost seemed like a connection in the balanced configuration was missing?

I would like to see if anyone else has had any experience with this types of issue and how it was solved, if at all?

Is the VTM200 balanced inputs not truly balanced, i.e. has an active ground as part of the signal?

 

[flez007]

looks to me it is either an interconnect or an impedance mismatch, I would try borrowing a preamp and see what happens or switch interconnects.

 

[treitz3]

Good morning, merrillaudio. I'm sad to hear that your system has an issue. There is nothing more frustrating than building something like this and having an unwanted artifact. It's gonna be hard to diagnose something like this over the net but I do hope for a quick solution so you can get back to enjoying the music. My first thought was a bad capacitor within the DAC itself. It's not that old so I do not think age would be a factor but I thought I'd throw it out there as a possibility. Best of luck for a speedy resolution.

Tom

 

[merrillaudio]

looks to me it is either an interconnect or an impedance mismatch, I would try borrowing a preamp and see what happens or switch interconnects.

We tried it with other Memory Players with no problem. It is only this particular setup, and if I understand the Memory player correctly, each one is a little different custom built for the owner.

You may be right that this Memory player would have a impedance mismatch however wouldn't that lead to frequency problems instead of noise?

Has anyone had direct experience with this kind of a problem and discovered a solution?

 

[mep]

What happens when you disconnect your memory player from your amp and just turn your system on with the inputs of your amp shorted? Noise or no noise?

 

[merrillaudio]

What happens when you disconnect your memory player from your amp and just turn your system on with the inputs of your amp shorted? Noise or no noise?

The white noise issue is limited to only with this particular memory player. With the memory play off or disconnected, the system is dead quiet.
The white noise is there only when the memory play is connected and on.

With another memory player, there is no white noise. I am talking about the Nova Physics Group Memory Player which has a DAC and volume built in to the music server.

With a noisy cap, the Tube Audio Research VTM 200 would have the noise also. However with the AR VTM200, there is noise but much, much lower. Perhaps the difference gain may also be an issue. I am hoping that is that magician who has tried it all and come across this situation and said, "Ahh, elementary my dear watson".

Your humble student.

BTW, the VERITAS monoblocks work on everything else and everywhere else without issue - so far. From Horns (104db) to electrostatics 2 ohms at 20khz to MBL 101 MkII E (84db). I have not tried it on the iHome iHM60GT 3.5mm Aux Portable Speaker (translucent colors) yet.
Also with many different sources without issue, balanced and unbalanced. The Quest Dragonfly DAC was something else - Cables, Cables, Cables!

 

[Steve williams]

Welcome to WBF Merrill

Time to ask for an undisputed return for a new Memory Player

 

[JackD201]

Welcome to WBF Merrill

Time to ask for an undisputed return for a new Memory Player

+1

That or send it in for diagnostics. White noise means something is broken likely from shipping and handling.

 

[merrillaudio]

Ok. Got resolution from Memory Player designer Mark.

The cause is parasitic capacitance, a known problem for the memory player that has shown up only twice so far. The solution is to have 1k resistors in series with all the outputs - balanced, so 4 but not the ground.

Independently the causes of parasitic capacitance is conductors/traces etc being very close to each other with high difference in voltage potentials.

Technical mumbo jumbo.
The capacitance causes oscillations. The oscillations are dependent on the equipment and the capacitance. Since the Memory player has a very low output impedance and the VERITAS Monoblocks (and some other solid state amps) high input impedance, the scenario is right for the Memory player to have the oscillations with the Amp. This is due to high transfer function translating to higher gain in the Memory player which translates to oscillations around the op-amps/circuits in the memory player. Typically the outputs have a small/medium resistor to remove the problem however in this case the Memory player did not have this, also the reason the output impedance is only 10 ohms.