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HI there!

Just received my DDRC-22A unit and made my first measurements and filters.
Greatly improved transients! It is amazing how I survived without it before!
One concern that I have is that once a filter set is downloaded to the unit, that filter configuration starts producing a high pitched noise. The noise is present even without any signal in the input, even without any cables plugged in to the input jacks. Also, the 4th filter set is still cleared (not loaded with any filter configuration yet) and its quiet without any high pitch noise at all (with or without the filter on/off switch). One the first three (loaded) slots, the noise doesn't go away when I turn off the filter switch.

Is this a known issue? Could it be a problem with the way I conducted the measurements? The weird thing is that even with the "bypass" on/off switch, the noise is still there.

I am attaching the filter export for the first slot, just in case you can do some troubleshooting on your end.

--Stefanos.

@ Stefanos,

We've indeed never heard of this issue before. I wonder what is different with your configuration. Did you try to remeasure the room again to see if you can reproduce the issue? a bit more info and a step by step on how you reached that setting (e.g modification of the house curve) would help.

Feel free to start a ticket with the Support - > Contact us. It's the easiest way for us to track an issue. Thanks.

DevTeam

Hi devteam,

I haven't really modified the house curve.
I followed the directions as described on the user's manual.
I've set the output gain within the 20% of max. The UMIK-1 gain was almost left untouched and I setup my amplifier for a reasonable to high level output.
I took the measurements using the "chair" configuration. Distance between the mic and the speakers was about 2 meters.
I made a recording of the noise. I realized that the noise is present even on the 4th slot (which currently doesn't have any filters loaded) but at a much lower level.
The recording (mono, 24bit, 44.1K) alternates between slot1 and slot4 configurations. You will notice the much louder noise on slot1. Also during the switching from slot1 to slot4 you will be able to hear some "digital" chatter noise as well.

I am wondering if my DAC / ADC unit is defective.
Sorry, I didn't open a ticket on the Support -> Contact us link, since there was no way for me to upload my reconding file there.

Thanks again for looking into this,

--Stefanos.

P.S. It turns out that I cannot attach my recoding to the forum post. What is the max file size allowed? I have send an email to This email address is being protected from spambots. You need JavaScript enabled to view it. instead!

hi
i have the same noise in my ddrc 22da.
have yo an solution?

cheers

I solved the problem by isolating the CPU and front panel boards from the case. It seems that digital noise was escaping through the mounting screws of these boards to the case and then to the analog board. I used plastic screws to remount the CPU and front panel boards and the noise is completely gone (lost in the noise floor).

etl17-good idea !my thoughts are seperate power supply für the DAC and the Sharc.
but ,yes i try your idea now---wait a moment

cheers

hi
ok
i have solve the problem!
now i use two 5 volt supplys ,one for Sharc and one for the DAC Plate.
the Sharc is completly isolate from the case!

thanks!

etl17 wrote:

I solved the problem by isolating the CPU and front panel boards from the case. It seems that digital noise was escaping through the mounting screws of these boards to the case and then to the analog board. I used plastic screws to remount the CPU and front panel boards and the noise is completely gone (lost in the noise floor).

Has this been implemented from the factory as of now? I've just ordered a 22DA and would appreciate if I didn't have to do the modifications myself.

Thanks!
andy

etl17 wrote:

I solved the problem by isolating the CPU and front panel boards from the case. It seems that digital noise was escaping through the mounting screws of these boards to the case and then to the analog board. I used plastic screws to remount the CPU and front panel boards and the noise is completely gone (lost in the noise floor).

griffith500 wrote:

Has this been implemented from the factory as of now? I've just ordered a 22DA and would appreciate if I didn't have to do the modifications myself.

Yes, I think it is being done now .
I purchased 3x OpenDRC-DA machines in Nov 2015, and they all have plastic screws between the MiniSHARC board and the metal case.
I remembered reading this post before, so I actually looked to check while I had the lid off. It's nice to see these improvements. Good idea!

Nice to hear about the measures taken. I will test the it asap.
Nonetheless this is just a workaround for the core problem: the CPU shouldn´t emit any HF and the design should be altered accordingly.
Otherwise interference can only be suppressed not eliminated.
Thanx
M