Lexicon Lambda - Behringer HA4700 --> Ground loop when Cubase 5 is opened.

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alin89c

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Hello everybody!
I'll say what my problem is and then i'm going to list my hardware.
The Behringer HA4700 is connected to my LEXICON Lambda's headphone output. The problem I have is that when I open Cubase 5 I get this ground loop in any of the 4 headphone output channels of my Behringer HA4700. This ground loop is not present if i connect directly the headphones in the LEXICON Lambda's headphone output.
I've read on a site this information about ground loop and i'd like to ask your opinion on it.
...make sure to connect the grounding cable on the back of your turntable with the grounding screw on the back of your audio interface...
So, should I connect the ground of the HA4700 to the ground of my LEXICON Lambda? How can it be done? I know the HA4700 is not a turntable, but the situation is similar (I guess...).

My PC:
Motherboard: ASRock P5B-DE
RAM: 8 GB
CPU: Intel Core2 quad q9450
HDD: 2x WD with 7200 RPM

P.S. The ground loop/buzz/hum doesn't get recorded. You can hear how it sounds downloading attached mp3 file.
 

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I had possibly a similar issue with my HA4700. I finally gave up and bought a Samson S-phone. No more noise...

It may just be a noisy piece of gear.
 
I'm not reffering to the noise, but to the ground loop. I don't know if you've played the mp3 audio file to hear what a ground loop sounds like...
 
alin89c said:
I'm not reffering to the noise, but to the ground loop. I don't know if you've played the mp3 audio file to hear what a ground loop sounds like...
Click to expand...

Well, I am using my phone to reply and cannot play the clip. The HA4700 I had also had a low level hum. And yes, I am well aware of what a ground loop sounds like.

I will have a listen later.
 
Wow! What the heck is that noise?

That sounds like no ground loop I have ever heard. Not sure what the mains type is where you live but in US a ground loops typically cause a 60hz hum.

I realize this was recorded from your phone, but with a spectrum analyzer I see spikes at each 1k, 2k, 3k, 4k, 5k, up to 10k.

Not something I have ever seen or heard. :eek:

I sent a PM to ecc83 (Dave) to see if he has more insight.

Best of luck! I look forward to hearing what this is.
 
I also have the HA4700. It is noticeable noisier than the headphone output of the Presonus. But its noisiness is not particularly off-putting.

What the OP has would be immensely distracting. I wonder if the HA4700 is picking up computer noise? For example, does it change if the mouse gets moved around?

Will the Lamba operate without being connected to the computer? If so, that's worth a try.
 
An easy one - digital noise, absolutely NOT ground loop - which is simply mains derived. I'd bet that this sound is digital feedback. The clue is that it starts when cubase starts. I have had that noise on cubase when used with a lexicon Omega interface, and somehow some of the feed too it was returning to cubase. It only happened when the record monitor was turned on. Using the blend control on the interface solved the problem. It wasn't in the cubase routing, but just seemed to always be there. The same interface works fine on my macbook - so maybe an anomaly in the driver?

The harmonic content is the giveaway - it's digital noise, not analogue noise locked to the mains power frequency. It also doesn't get recorded, which a ground loop certainly would - it's a monitoring issue. If you accidentally set routing to link out to in, you get this noise but a zillion times louder.
 
Have you tried connecting the HA4700 via the 'line outs' from the Lambda?

I assume you are using a TRS to TRS cable between the Lambda headphone output to the HA4700 front panel 'Direct In' jack?

I only ask to see if we can rule out some issue with the connection cables or fault of the Behri unit. Starting with the basic connections and troubleshooting what works or doesn't is the best way to find the problem.
 
rob aylestone said:
An easy one - digital noise, absolutely NOT ground loop - which is simply mains derived. I'd bet that this sound is digital feedback. The clue is that it starts when cubase starts. I have had that noise on cubase when used with a lexicon Omega interface, and somehow some of the feed too it was returning to cubase. It only happened when the record monitor was turned on. Using the blend control on the interface solved the problem. It wasn't in the cubase routing, but just seemed to always be there. The same interface works fine on my macbook - so maybe an anomaly in the driver?

The harmonic content is the giveaway - it's digital noise, not analogue noise locked to the mains power frequency. It also doesn't get recorded, which a ground loop certainly would - it's a monitoring issue. If you accidentally set routing to link out to in, you get this noise but a zillion times louder.
Click to expand...

Which leads me to wonder if he has the correct Lambda driver installed for his OS? Which is what?
 
I've had issues on some Behringer gear with TRS inputs labeled Bal/Unbal. They are actually not that good at dealing with unbalanced connection so I always connect them balanced when possible. When not possible I use Rane's Sound System Interconnection page as my guide and connect the Behringer end with TRS wired according to that page's info. This may not have anything to do with the OP's problem but it's still useful for anyone with certain Behringer gear.
 
I've normalized the sound a bit. That's why it's this loud.
The sound (digital noise or whatever) doesn't change when I move the mouse around.
I'm pretty sure that i didn't set the routing to link out to in.
I have installed the correct driver.
I use a 1/8'' stereo cable at an end and two 1/4'' mono plugs which go to the back of the HA4700 (main in).

I'll try to connect the HA4700 via the 'line outs' from the Lambda. I don't have a proper cable now.

Thanks a lot for all of your answers!
 
I have been summoned by Jim!

No, I don't think it is a ground loop either. If you varder the spectrum you will see spikes at 1,2 3,....kHz but nothing in the LF area.

I suspect the recording level is slammed at 100% in Windows sounds. I don't know if ASIO drivers are available but if so, use them and then level control is out of Msods hands AFAIK.

Dave.
 

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  • spectrum grnd loopnot.webp
    spectrum grnd loopnot.webp
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Thanks again for all of your replies! I've solved the problem. I've connected the HA4700 via the 'line out' of the lambda using 2 mono 1/4' mono plugs on both ends of the cable. So now i have 5 headphone outputs :D (four on the HA4700 and one on the lambda)

P.S. One more thing, I've noticed that if I connect a headphone with a lower impedance (lower ohms, e.g. 32ohms) the noise/hissing becomes more present than with a higher impedance headphone (e.g. 55 ohms). Did I observe this right? What could be the explanation for the phenomenon?

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HA4700_P0184_Rear_XL.webp
 
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"P.S. One more thing, I've noticed that if I connect a headphone with a lower impedance (lower ohms, e.g. 32ohms) the noise/hissing becomes more present than with a higher impedance headphone (e.g. 55 ohms). Did I observe this right? What could be the explanation for the phenomenon?"

Not an explanation merely the laws of physics/electrikery! The lower the impedance the cans, the more power they will absorb from the source, everything else being equal. Note, this process has a lower limit since most headphone amplifiers have an output resistance of at least 30 Ohms and connecting phones lower Z than that will result in a lower level. Headphone vary in sensitivity quite a bit tho' so the effect is not cast in stone.

N.B. Some "audiophool" headphone amps boast a very low output Z (and high drive capability). There is no evidence that this is needed and IMHO is bloody dangerous to people's hearing.

Dave.
 
So, what you're saying is that, e.g. an 8 ohm headphone will just sound louder than a 55 ohm (or whatever) headphone? Assuming the output level of the amplifier is the same on both headphones, obviously.

Alin.
 
alin89c said:
So, what you're saying is that, e.g. an 8 ohm headphone will just sound louder than a 55 ohm (or whatever) headphone? Assuming the output level of the amplifier is the same on both headphones, obviously.

Alin.
Click to expand...

Not quite! The H/P amplifier normally has a significant output resistance (often an actual, physical component). Let us say it is 32 Ohms? If you connect cans or greater impedance* than 32R to that amplifier, more voltage will be developed across the phones than the 32R so more power goes into the cans.

32 Ohm headphones wiil have exactly the same voltage across them as the OP R so there will be equal power dissipated in both. This is the (well known to us geeks!) Power Matching condition.

I expect you are ahead of me in seeing that phones LOWER than 32R will have LESS volts on them and thus take less power. MORE power being dissipated in the amplifiers OP R.....All this of course assumes that headphones with different impedances have nonetheless the same sensitivity, i.e. sound pressure level (SPL) for a given input power, this is often around 100dB SPL for 1mW (1/1000 watts) but of course this varies between models and brands.

A headphone amplifier with a near zero OP R would just put ever greater power into ever lower Z cans with nasty consequences to ears and possibly the phones themselves. This is why you should NEVER connect headphones directly to the speaker output of any amplifier.

*Headphone are quoted with an "impedance" (aka Z) but in almost all cases this is pretty much just the DC resistance.

Dave.
 
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