1 (edited by Roomie 2021-04-26 17:57:15)

Topic: Ground loop problem

Hey guys,

Trying to solve a ground loop problem with my Babyface Pro, and am willing at throw whatever at it to just make it stop. I use a Babyface Pro (Original, not FS), and I'm getting fluctuating noise from the computer components in the mic inputs (it records to the tracks, so it's quite the issue).

I've tried:
The RME external power supply (no change)
Intona USB 2.0 Isolator (slightly attenuates the noise, but still there)

I haven't tried breaking my cables, they're mogami gold ones and it feels like a waste.

Are any of the other RME interfaces better with the ground loop issues? UFX+? I use it for work, I'm looking to solve it in any way possible, just ASAP since it interferes with daily recording work.

J

Re: Ground loop problem

Hello!

Is all your equipment connected to the same wall plug, using a good power strip? (computer, monitor(s), speakers, the BF Pro, anything else)

Did you try reversing the polarity of the BF Pro's external Power Supply? (connect the plug the other way, around)

RME Gear: Digiface USB, HDSP 9632

Re: Ground loop problem

MetalHeadKeys wrote:

Hello!

Is all your equipment connected to the same wall plug, using a good power strip? (computer, monitor(s), speakers, the BF Pro, anything else)

Did you try reversing the polarity of the BF Pro's external Power Supply? (connect the plug the other way, around)

Yeah, it's all connected to the same wall plug with a proper power strip with surge protection etc. Just tried connecting the power plug the other way around, problem is still there sadly. Any other ideas? Maybe it's time to break one of the microphone cables. I have been eyeing to upgrade the babyface to a rack based unit with a totalmix compressor for tracking, but unsure if that would actually help with anything.

I have two Razer Blade laptops I work from, when using the other one in the same room I had buzzing in the speaker outputs, but the microphone was clean. Now I have buzzing in the microphone input, but the speaker outputs are clean. Bizarre. Any other ideas on what could help?

Re: Ground loop problem

Weird update, I tried unplugging the USB with the power supply in and the interference was there without the USB cable as well. So it seems there's interference both via USB and via the power supply, or perhaps it has to do with something else. Will do another round of switching all audio cables

Re: Ground loop problem

Solved, kind of. It was the cloudlifter picking up interference, or potentially handling the phantom power from the babyface poorly. Never heard of that before.I'll try ordering another cloudlifter & a fethead and see if they have the same issue.

Re: Ground loop problem

Got an sE Electronics DM! "Dynamite" mic booster in today. It's less pronounced than the cloudlifter, but the interference is still there. Starting to feel like a madman here, I think it might have to do with the phantom power coming from the Babyface being dirty. I guess it's time to bit the bullet and try breaking the Mogami Gold cables.

Let me know if you have any other ideas!

Re: Ground loop problem

Hmm, I don't think breaking the cable and using phantom power is a good idea!

What sample rate are you using? Higher, than 44/48K, sample rates might pick more RFI because of broader frequency range.
If you 're using a sample rate above 44/48K, can you try decreasing it and check if the noise is still there?

Also, what happens if you operate the BF Pro bus-powered and the Laptop on battery?

RME Gear: Digiface USB, HDSP 9632

Re: Ground loop problem

Are you sure the noise is not just amplified by the cloud lifter and is coming from whatever is connected to it.

Vincent, Amsterdam
https://soundcloud.com/thesecretworld
Babyface pro fs, HDSP9652+ADI-8AE, HDSP9632

Re: Ground loop problem

vinark wrote:

Are you sure the noise is not just amplified by the cloud lifter and is coming from whatever is connected to it.

Hi, good question. Even if I gain up the source (an SM7b) without the cloudlifter, there's no interference like what I hear with the cloudlifter or sE DM1 engaged. Since both of them exhibit this issue in some capacity, it seems to be an issue with the phantom power supplied from the babyface to the cloudlifter/DM1, per above. I'm not entirely in need of that extra clean gain for now, but it's unfortunate and makes me feel like I need to replace the babyface soon.

Re: Ground loop problem

Have you tried your setup in another room?

I've got RF interference from a VFD that's outside, driving sewage pumps. It only shows up in one corner of the room. I imagine there must be an old piece of electrical wiring below the floor. It drove me mad, until I moved my gear. Now, it's my RFI test bench :-)

I don't think you need a cloudlifter. My FF400's preamps have enough gain, even for a very low output dynamic.

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

Re: Ground loop problem

cyrano wrote:

Have you tried your setup in another room?

I've got RF interference from a VFD that's outside, driving sewage pumps. It only shows up in one corner of the room. I imagine there must be an old piece of electrical wiring below the floor. It drove me mad, until I moved my gear. Now, it's my RFI test bench :-)

I don't think you need a cloudlifter. My FF400's preamps have enough gain, even for a very low output dynamic.

After running around with a laptop and babyface in my house, I found that this is exactly it. There seems to be RF interference all across my top floor. I also have had acoustic panels installed all across the walls in one of the upstairs rooms, dang. If I take my kit downstairs, everything sounds fine but I only have living room and ki t chen down there, so I'm not crazy about that idea.

How do I find what is causing this? Is there a way to counteract it?

Re: Ground loop problem

Set the Babyface to it's highest sample rate. Open Digicheck and check the pattern (frequency, harmonics, level).

That will tell us a bit more about the signal.

Any cell towers, police stations, emergency services, taxi... in the direct vicinity?

Another test is putting laptop and BF into a metal enclosure (Faraday cage) and see if that kills the RFI.

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

Re: Ground loop problem

Thanks for the helpful suggestions and info!

Here's a recording of the interference: https://www.dropbox.com/s/v69lttex86cag … e.wav?dl=0

There seems to be some variation in severity, when I booted it up today I had no audible interference without a mic activator. However, with the mic activator enabled (today I used an sE DM1 "Dynamite") it was back again. If touch the activator, the interference reduces in level somewhat.

I used my UFX+ today, set to 192,000hz. I'm unsure about what you mean with frequency/harmonics/level but hopefully everything is in this: https://www.dropbox.com/s/2emfajhztsrnh … 2.png?dl=0

I've reached out to a few local electricians who do work in studios, hoping to get someone over and have them do an investigation. Maybe they can build a faraday cage.

There's an AM radio station about a mile away, nothing else closer than that.

Re: Ground loop problem

Sounds and looks like the AM transmitter and some PSU noise, combined with excessive gain are your problem.

The sE DM1 offers +28 dB gain. That's a lot. But why do you need it? The UFX+ already has plenty of gain (75 dB). Together, that's a whopping 103 dB...

More than 100,000 times amplification. 1 mV would turn  into a 100 V!

These pre-preamp thingies nearly all contain FET transistors. High impedance, wide bandwidth. Ideal for radio pickup. An accident waiting to happen, if you ask me.

I'll bet that AM station is a few hundreds of KWs, if not more. At just a mile away, it's a major interference source.

You're in the US, I presume?

Your gear is FTC certified, so the AM station shouldn't interfere. You could try calling the FTC and see if they take this serious enough to look into it.

The simplest solution, of course, would be not to use the DM1.

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

Re: Ground loop problem

I see! I realize now I had the misguided idea that a mic activator would add less noise than driving the pre. You're right then, I can just drive the UFX+. I always thought of mic activators as "free gain" without any extra noise added but now that I think of it, the UFX+ gain should be enough.

Interesting about FET transistors, thanks for sharing! I've had project studio setups all over the world in the last 10 years and this is the first time I've run into any issues whatsoever, your input is very appreciated.

Yeah this setup is in the US.

I'm afraid that even without using any of my 'activators' I still pick up the interference, to higher or lower extent depending on the day and time. In more intimate recording scenarios or when stacking tracks, the interference gets quite noticeable.

Is there any type of company that deals with this type of thing? If it ends up being AM interference I wonder if the electricians can help.

cyrano wrote:

Sounds and looks like the AM transmitter and some PSU noise, combined with excessive gain are your problem.

The sE DM1 offers +28 dB gain. That's a lot. But why do you need it? The UFX+ already has plenty of gain (75 dB). Together, that's a whopping 103 dB...

More than 100,000 times amplification. 1 mV would turn  into a 100 V!

These pre-preamp thingies nearly all contain FET transistors. High impedance, wide bandwidth. Ideal for radio pickup. An accident waiting to happen, if you ask me.

I'll bet that AM station is a few hundreds of KWs, if not more. At just a mile away, it's a major interference source.

You're in the US, I presume?

Your gear is FTC certified, so the AM station shouldn't interfere. You could try calling the FTC and see if they take this serious enough to look into it.

The simplest solution, of course, would be not to use the DM1.

16 (edited by cyrano 2021-06-15 16:22:51)

Re: Ground loop problem

Start with your electrical system.

Has the ground connection been tested? And I do mean tested with a real ground measurement device.

Put the equipment inside a sturdy metal rack en connect the rack to mains ground.

Make sure your mic cables are OK, including pin 1.

RFI filters for mains aren't frightfully expensive. This is a case where one of those could be appropriate.

Have you tried inserting a DI into the chain?

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

Re: Ground loop problem

Thanks for your continued help. I booked an electrician for Monday to have a look at the ground connection.

I've also ordered a Gotham dual shielded cable (Up until now I've been interchanging 3 different Mogami Gold cables with pin 1 intact, as well as a no-name brand cable).

Would something like this suffice as an RFI filter?

https://www.sweetwater.com/store/detail … ion-system

or

https://www.sweetwater.com/store/detail … lsrc=aw.ds

Depending on what the electrician says I'll try a DI early next week.