1 Topic by bejoro (edited by bejoro 2024-06-24 11:03:00)

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Topic: ADI 2 PRO FS R: Spike at 33 kHz

I performed some frequency response measurements of a DAC (digital filters) and noticed a spike at arround 33 kHz (sometimes 34 kHz, sometimes 35 kHz).

I disconnected the inputs and it was still there.
I tried it on another PC.
I exchanged the power supply.

Also my second ADI-2 PRO FS R BE shows the same behavior.
With analog input 1 it is about 30 dB above noise.
With analog input 2 it is only a few dB above noise, but visible.

Both ADI-2 PRO FS R BE show identical results.

Is this a defect in both ADI-2 PRO?

Image of REW RTA output at 96 kHz:
https://iili.io/d2bvq9p.png

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2 Reply by KaiS (edited by KaiS 2024-06-24 11:13:17)

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Re: ADI 2 PRO FS R: Spike at 33 kHz

You need proper termination and shield of the analog inputs for valid results.
Open-connection can catch whatever is “flying around“.

Use XLRm plugs with pins 2+3 shorted for termination.
If the spike still shows up, short XLRm 1+2+3, but not the XLRm case pin.


If the effect shows identically on two units, a defect can largely excluded.

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  • bejoro
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Re: ADI 2 PRO FS R: Spike at 33 kHz

Thank you Kai.

If the DAC to be measured is connected to the inputs of the ADI-2 PRO via XLR, the identical effect is seen. That's the configuration how I noticed this problem. Connected or disconnected makes no difference.

The DAC has a 3-prong power input, hence it's grounded.

Is this a proper termination?

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4 Reply by KaiS (edited by KaiS 2024-06-24 12:23:12)

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Re: ADI 2 PRO FS R: Spike at 33 kHz

bejoro wrote:

The DAC has a 3-prong power input, hence it's grounded.

Is this a proper termination?

The audio input needs to be terminated, this is independent and different from mains connection ground.


Are you using a non-RME PSU?
If so, try the original one.

SMPSs can deliver high amounts of their switching frequency, in various forms like via DC ripple, electromagnetic- or electrostatic coupling.

RME’s original PSUs are not known for this.

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5 Reply by bejoro (edited by bejoro 2024-06-24 13:00:09)

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Re: ADI 2 PRO FS R: Spike at 33 kHz

The PSU was my first idea.

I am using only the original RME PSUs which came with the device.

I tried a 12V/5A Leicke SMPS PSU just for testing purposes but the spike did not change.

But a connected device such as the DAC should be a proper termination?

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6 Reply by bejoro (edited by bejoro 2024-06-24 14:33:32)

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Re: ADI 2 PRO FS R: Spike at 33 kHz

I do not have a XLR termination plug at the moment.

I connected the DAC XLR outputs to the ADI-2 PRO inputs - no change.
I connected the ADI-2 PRO outputs to the ADI-2 PRO inputs - no change.

Attached the REW RTA images for the left and right channel of the ADI-2 PRO.

Please, any idea what the problem could be?

Left channel after 13k RTA averages:
https://iili.io/d2ykNgs.png

Right channel after 13k RTA averages:
https://iili.io/d2y8hSs.png

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7 Reply by KaiS (edited by KaiS 2024-06-24 15:07:16)

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Re: ADI 2 PRO FS R: Spike at 33 kHz

I don‘t have the exact same ADI-2 Pro FS R model at hand, so any test on my side would be meaningless.


Things to test:

• Does the level of the spike change with analog input’s reference level?

• What if you connect ADI-2’s own XLR output at Ref Level +4 dBu, volume full down, with it’s analog in at Ref Level +24 dBu?
This comes close to a shorting plug termination.

• What happens if you change display brightness?

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Thank you! Very good ideas. I will test these suggestions and report back.

Display seems not to be an issue because on one ADI-2 PRO was Auto Dark enabled and on the other one always on at 50%. But I will check this again.

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9 Reply by MC

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Don't waste your time - this can be fixed at our service center. It's a known issue.

Regards
Matthias Carstens
RME

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Matthias, thank you. I will contact the service center.

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Hallo Matthias,

beide Geräte sind bereits außerhalb der Garantie.

Das Service-Center (Audio AG) hat mir die Reparaturkostenpauschale je Gerät mitgeteilt. Das ist sicherlich gerechtfertigt aber für mich schon ein knackiger Betrag.

Gibt es denn keine Möglichkeit einer Kulanzreparatur nachdem es sich offenbar um einen Serienfehler der frühen Generation handelt?

Das würde mich natürlich sehr freuen.

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12 Reply by MC

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Das ist ein Mißverständnis - die Geräte werden kostenfrei modifziert, Sie müssen nur die Versandkosten tragen.

Regards
Matthias Carstens
RME

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Vielen herzlichen Dank.

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Bitte eine kleine Hilfe:
Wie sollte ich das Problem beschreiben (RMA-Formular), so dass die Kollegen das eindeutig identifizieren können? Lieben Dank.

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Re: ADI 2 PRO FS R: Spike at 33 kHz

Stichwort reicht, ist dort schon zur Kenntnis genommen....

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Daniel Fuchs
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Re: ADI 2 PRO FS R: Spike at 33 kHz

MC wrote:

Don't waste your time - this can be fixed at our service center. It's a known issue.

Is there a correlation with a certain production batch and can affected units be identified based on the serial number?