1 Topic by Maddcow (edited by Maddcow 2020-10-28 03:10:43)

  • Registered: 2019-11-06
  • Posts: 140

Topic: [SOLVED] Why am I getting this hum through my UFX+?

Hi all
A long story but to cut it short: I need to use my gig rig with a 12V battery setup (using a pure sine wave inverter) but when I run the audio out from my 12.9” iPad Pro into the UFX+, I get a loud hum/buzz through the UFX+ channels with the iPad audio. This hum/buzz is not present when the rig is running on mains power. Also, an ART DTI 2-Channel Transformer / Isolator Box box placed between the iPad and UFX+ removes the hum/buzz when the system is running on 12V power.

Does anyone know why I’m getting this buzz/hum from the iPad audio when the UFX+ is using 12V power? I’ve got other devices running audio into the UFX+ (e.g. Sennheiser wireless mic system) but there’s no noise with that.

Cheers
Gary

  • Registered: 2019-11-06
  • Posts: 140

Re: [SOLVED] Why am I getting this hum through my UFX+?

Hmmm, interesting. The thing is that my iPad isn’t connected to any other power source or ground, which has me a bit confused. Or maybe that’s the issue? i.e. the other units in my rig are connected to power and therefore grounded, but the iPad isn’t?

  • From: Gothenburg, Sweden
  • Registered: 2007-05-01
  • Posts: 441

Re: [SOLVED] Why am I getting this hum through my UFX+?

Hi!

So, please do yourself the favour and look for professional advise from actual experts.Not sure you'll find them here (or in general on the internets with all the self-proclaimed experts).

The people from RME know what they are doing and saying!

but read from good source is one way :-)

https://en.wikipedia.org/wiki/Ground_loop_(electricity)

Better be safe than sorry wink

I agree ;-)

regards S-EH

4 Reply by cyrano (edited by cyrano 2020-10-26 11:44:04)

  • cyrano
  • DAW Mastermind
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  • From: Belgium
  • Registered: 2015-04-28
  • Posts: 695

Re: [SOLVED] Why am I getting this hum through my UFX+?

You can run both iPad and UFX+ from external batteries. Probably the Sennheiser too. Macs and other laptops too. Hec, even a desktop can be run from a 12V battery supply. And I suppose the inverter is fed by 12V lead-acid batteries.

So my simple mind immediately wanted to know why you're making it hard on yourself by inserting a known-to-be-a-pita device like an inverter?

It's a ground-loop of some sort. These are hard to fix when complicated inverters are involved.

MB Pro - 2 X FireFace 400, FF800 & DigiFace USB
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  • Registered: 2019-11-06
  • Posts: 140

Re: [SOLVED] Why am I getting this hum through my UFX+?

cyrano wrote:

You can run both iPad and UFX+ from external batteries. Probably the Sennheiser too. Macs and other laptops too. Hec, even a desktop can be run from a 12V battery supply. And I suppose the inverter is fed by 12V lead-acid batteries.

So my simple mind immediately wanted to know why you're making it hard on yourself by inserting a known-to-be-a-pita device like an inverter?

It's a ground-loop of some sort. These are hard to fix when complicated inverters are involved.

It's a long story but my gig and power requirements can only be met by using a 12V battery.....I've looked at literally every other option and 12V is the only way I can go, so I need an inverter.  I've been using a lead-acid battery for testing but plan to get a 120AH Lithium Iron Phosphate battery so it's nice and light, in addition to having some serious gig time.

However, I discovered today that the inverter I've been borrowing to test my proof-of-concept doesn't appear to be pure sine wave (even though it's SUPPOSED to be) and that is almost certainly the problem.  I only realised this morning that it's not the iPad at all because every 1/4" output on the UFX+ has hum, even if no audio inputs are connected.  I get no hum when the rig is connected to mains power and so it must be the inverter.  I'm looking at getting a Victron Phoenix inverter and these are supposed to have cleaner power than mains, so hopefully this will solve the problem.

  • Registered: 2019-11-06
  • Posts: 140

Re: [SOLVED] Why am I getting this hum through my UFX+?

Solved: I bought another pure sine inverter and the hum has disappeared. The first inverter was also pure sine wave but I guess it wasn’t actually pure at all.

7 Reply by cyrano (edited by cyrano 2020-10-28 17:15:09)

  • cyrano
  • DAW Mastermind
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  • From: Belgium
  • Registered: 2015-04-28
  • Posts: 695

Re: [SOLVED] Why am I getting this hum through my UFX+?

Now you know why I don't trust the specs for inverters. Too many imaginary data out there...

These also usually don't age too well. Your sine could turn into a triangle wave in a few years.

MB Pro - 2 X FireFace 400, FF800 & DigiFace USB
ADAT gear: Korg, Behri, Fostex, Alesis...

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