Motu 896mk3 Hybrid hum when something is connected

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Hi,

I have just purchased a Motu 896mk3 Hybrid and I am experiencing the same issue as this post (which I've also added to)...

http://www.motunation.com/forum/viewtop ... =2&t=47944

...only mine is occurring at more like 1670Hz. The poster there has tried 2x Motu's now.

Basically no matter which mic or cable is used, whenever something is connected the hum is there and can be seen with the CueMix FX FFT tool - and of course heard (depending on trim). There also appears to be harmonics of the tone repeated going up the frequencies, but at a lower level. If the mic is disconnected the tone goes away - it is not the mic or cables.

I have raised a support issue with Motu (and my supplier). Has anyone else had this issue/know what the problem could be?

Thanks in advance.

PS. I'm worried it might be some internal ground hum design issue in the Motu hardware.

[torrentg]

I would test the unit in a complete other room or even possibly another location altogether.

Too many variables to consider...poor house wiring, florescent lighting nearby, old skool CRT glass computer monitor(s) nearby, poor grounding near setup, other devices in the house which could potentially interfere...

worth a shot as a test so you know exactly what you're dealing with - a room problem or a unit problem.

If it exhibits the same results elsewhere, then you know it is something inherent to the unit.

I would also test the unit off firewire power and then also with standalone AC power. Just be careful never to plug in the firewire cable upside down to the unit or pc. It will damage the MOTU if you do.

[Spencil_Splodge]

Thanks for the reply...

I have already tried different AC outlets and different rooms. I now have it connected to my filtered PDU. None of these changes made the issue go away...

Also, this unit requires AC power and cannot run from Firewire/USB.

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Still note received anything back from Motu - guess it's Christmas afterall.

Also note, without anything connected, not even a cable, switching on the PAD causes the tone to occur...

[Spencil_Splodge]

Please refer to...

http://www.motunation.com/forum/viewtop ... =2&t=47944

...for more information - this issue appears to be related to the unit as others are also experiencing it. It's not specific to Windows/Mac.