1 Topic by Bubba (edited by Bubba 2020-02-19 21:43:41)

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Topic: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Just got my ADI-2 Pro FS which unfortunately is affected by occasional hum problems while using asymmetric cables (TS to RCA). Elsewhere in this forum it is stated that earthing the ADI-2 Pro via XLR is mandatory for avoiding hum. But what to do in a private listening setup where XLR is not available? Is there some kind of standard workaround recommended by RME?

How about building a custom XLR->RCA cable where the earth lead coming from the XLR plug gets individually connected to ground while the other two leads go in the RCA plug?

2 Reply by Curt962 (edited by Curt962 2020-02-20 01:26:59)

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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Bubba,

Pg. 53 of the ADI-2DAC user manual details the Correct Wiring for XLR > RCA.   I don't have a Pro User Manual at hand, but both devices share the same/similar output circuitry, so the Rules are the same.

Understand however that this Cabling Adaptation results in a Simple, Unbalanced Cable.  XLR Connectors themselves have no "Special" abilities, and it will have NONE of the noise cancelling properties of a True, Balanced Termination, which is becoming increasingly more Common in the Home Environment.   To that end, try to verify that your existing Cabling arrangement is in good order.   Keep unbalanced Cables AWAY from AC Cords, etc.    It's the little things that cause the Biggest Headaches.

Good Luck,

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes
  • Bubba
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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Curt, thanks for your comment. Of course did I check the manual. For non XLR environments it recommends TS->RCA cabling. This is what I did.

BTW I am not exactly a techie so I asked a friend who suspects the problem is not grounding related but a defective or at least poorly shielded power supply. Below a more detailed description. It would be great to hear what others think.

  • The noise is best described as sizzling („knistern“ as we say in German)

  • It is clearly audible but not very loud. The main signal is always significantly louder.

  • Moving the power supply or its cables usually fixes the problem immediately but up to now it reappeared some hours or a day later.

The most obvious solution might be to place the ADi-2 power supply as far as possible from all other stuff and take care for its cables to be shielded from any potential harm. However for now I think such a trial and error approach is ok for a 100 Euro China DAC but a pro grade DAC should avoid such problems by design.

  • Registered: 2018-11-19
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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Bubba,

I had a similar issue with the ADI-2 Dac and an amplifier I used to own.  My issue did, indeed, turn out to be a grounding problem which was solved using this (admittedly a bit inelegant) solution:

https://audiophilestyle.com/forums/topi … /#comments

5 Reply by Curt962 (edited by Curt962 2020-02-21 00:20:59)

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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Hallo Bubba,

The "Trial and Error" bit is part, and parcel of using a Single Ended Cable of unknown shield integrity in close proximity to a SMPS.  That's just BEGGING for trouble.   In the future, I will caution against not only keeping such Vulnerable Cables away from AC Cords, but also SMPSs...Aquarium Heaters, Light Dimmers, etc.   In summary, you have just demonstrated the reason WHY Balanced Cabling (and associated circuits) have become the De-Facto Standard in an ever increasing number of Audio Set-Ups.   Our Modern World is full of Electromagnetic Chaos that largely didn't exist 60-70yrs ago when Single Ended connections (and their Antennae-Like behavior) were de-rigeur.  We need to adapt to the Modern Standards.  wink

Tschuß!!

Curt

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes

6 Reply by MC

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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Knistern bedeutet andauernder Wackelkontakt oder elektronischer Defekt. Ich frage mich ob der Netzteilstecker vollständig im ADI steckt, oder rumwackelt.

Selbstverständlich ist ein solches Geräusch selbst bei unsysmmetrischer Verkabelung nicht normal. Unsymmetrisch erzeugt entweder tieffrequentes Brummen, oder ein ähnliches, aber mit Oberwellen angereichertes Signal (Leckstrom des Schaltnetzteils, welches man durch Erdung des ADI beseitigen kann. Sehr niedriger Pegel). Beides ist konstant, und ändert sich nicht mit der Position des beigelegten Schaltnetzteils.

Regards
Matthias Carstens
RME

MC's Website

7 Reply by Bubba (edited by Bubba 2020-02-23 16:47:47)

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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Thanks a lot for your comments. It seems the problem is fixed. I placed the power supply cables of the ADI-2 Pro far away from all other power cords and speaker cables and fixated them that way. Up to now this works like a charm.

I only wonder whether this behaviour should be considered normal or if it is better to have the power supply exchanged/ checked by RME.

8 Reply by Curt962 (edited by Curt962 2020-02-23 17:54:30)

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Re: Hum problem with TS -> RCA cables - ADI-2 Pro FS

Hallo Bubba! 

Gehts Dir gut?

It seems your PSU/Cable Separation technique works just fine!   To me, that's just "Smart" Cable Routing.  And...when we don't hear noise, that is proven to me to be a leading indicator that there ISN'T any noise.  smile    Just my opinion however...and we all know how "opinions" are.   They're like another part of the Human Anatomy. We all have one. smile

Best for us to allow MC to make the final technical judgement.   Me?  I think you're just fine.

Enjoy your New RME!!

Tschüß!

Vintage 2018 ADI-2 DAC. "Classic AKM4490 Edition"
Cables:  Red, and White Ones.
Speakers:  Yes