Setting correct Interface to Monitors gain

[alexejm]

My monitors are making a hissing noise (if the XLR is plugged into the monitor), I am using balanced cables (XLR to TRS). Reading that it might be due to a mismatch in gain, I started reading about that.

My PreSonus AudioBox 22VSL outputs +10 dBu signal, my monitors have a gain knob which is labeled "+4dBu" half way turned up and 75% turned up "-10dBV". When set to -10dBV, the noise/hiss disappears.

Did I set it correctly? Not wanting the speakers to blow up of course...

[BertKoor]

Usually you'd set the gain in the interface loud. Then trim down the input at the monitor side. That's what you notice, the noise comes from the amp in the mo itors

[annode]

I can`t support what Bert is seeing here.
Turning down the monitors will just lower the overall volume at the poweramp stage. The noise ratio is still the same.

To be honest, the manual I see, is 84 pages and I don`t have the time to go into all that.
I suggest you call company support for help. It could be many things...i`ll guess your peaking some pre-stage in your mic pre`s or your effects.

When set to -10dBV, the noise/hiss disappears.

Naturally, your turning your Presonus output way down.

[alexejm]

Turning the output way up doesn't increase the noise. Is the gain in the monitors interchangable without any possible damage? Can I set it to -10dBV and lower the output on any interface? Funny thing is, the noise changes with computer load: if my PC is doing something more intense, the noise changes shape. However, with gain on -10dBV it's a lot less noticable.

I don't really understand the relationship of dBV and dBu.

[thecontrolcentre]

Which monitors are you using?

[alexejm]

These are ESI nEar 05 Experience (they no longer make them).

[thecontrolcentre]

The "gain" control on those monitors is a volume control (not a gain) ... I would turn the volume right up on the monitors, and control the level using the main volume control on your soundcard.

[bmrzycki]

the noise changes with computer load: if my PC is doing something more intense, the noise changes shape.

This right here is raising warning flags for me. I've had this problem before and it was related to poor isolation of the power and audio paths in the audio interface. I think you're encountering ground loop problems.

I bet you have your monitors and PC all plugged into the same power strip which means they are sharing the exact same ground plane. And what further complicates this issue is most modern USB interfaces receive their power from the USB port and not from your house mains. This reduces the number of ground points and increases your chance of getting ground hum.

I bet if you disconnect the XLR/TRS cable from the back of your monitor the noise disappears even if the monitor is on. That will tell you right there the amps in the monitors aren't producing the hum on their own.

So what can you do? Well, unfortunately, ground loop problems can be a nightmare to troubleshoot and are annoying as hell. I've gone through this myself. I had two audio interfaces, a Saffire LE and a Komplete Audio 6 and both had problems with unwanted noise.

There's a few things you can try:

1. try moving the power source of your monitors to a different wall plug in your house/apartment. Even better would be to move them onto a different circuit (different breaker switch) if you can. This forces the audio interface + PC to be on a different ground than the monitors.

2. Try using a better quality USB cable for your audio interface. Don't go crazy here, something like this looks pretty good with thicker internal wires and double ferrite cores: Chroma Cables. Make sure this cable is plugged into its own USB port on your PC (no hub) and isn't zip-tied or bundled next to another large group of wires. Try to use one that is just long enough: the longer the wire, the more of a chance for interference. To be fair, I haven't used these guys but I do have an Amazon basics with single ferrite on my interface. Were I to have this problem again I'd give the Chroma guys a try.

3. If your Audio interface has a ground screw on the back, try connecting a small wire to it and the other end to something metal in your house like a water pipe. Likewise, if your audio interface has a Ground Lift switch, try enabling it. Both of these methods attempt to force your audio interface on a different ground domain.

4. Purchase a ground hum eliminator, here's an example of one ROLLS Buzz Off. The downside here is it's inserted in your audio path, isn't cheap, and might require you to buy more cables.

5. If none of this works you may want to consider purchasing a different audio interface. It's what I eventually did to eliminate problems. I purchased a Roland QUAD-CAPTURE because it's one of the few interfaces in the sub $500 market that completely isolates the power domain on a separate physical PCB (second pic). I have to say this is the least noisy audio interface I've ever owned. Interfaces that have ground lift switches are good too and ones that have the option to run off a wall adapter mean you can remove the dependency of the device from USB PC power, a traditionally noisy power source.

However, with gain on -10dBV it's a lot less noticable.

You're just hiding the problem by lowering your amp volume. It's still there.

I don't really understand the relationship of dBV and dBu.

dB is simply a ratio between a golden reference value and your measured difference. That little suffix on the end V,v,m,u just specifies what your golden reference value is. Because we've used this ratio for electrical audio signals for over 100 years humans have found it convenient to use different golden values for different problem domains. This page on Wikipedia will make your brain hurt with details about the suffixes.

But none of this has to do with your undesirable noise problem.

[annode]

- Do you get a 'zippering' sound when you drag something across the screen? A sort of digital buzzing. Does the noise get louder when you do that?
- Can you plug all of your power cords into a single wall outlet/socket? Do you still get the noise?

[alexejm]

About the dragging: even though it's not doing it now, I remember it did something along those lines before. The noise gets a lot quieter when setting the monitors to -10dBV (and interestingly going higher than that introduces the noise again).

bmrzycki: Yes, the noise goes away when I disconnect the TRS from the interface.

But if the monitor gain is not a gain but a volume attenuator, there shouldn't be any harm in turning it up to -10dBV, it's just that I read the manual for the monitors and they state I should set them to whatever my audio interface outputs. It outputs +10dBu. So I don't know where that is on my monitors - it just has 2 labels on the knob: +4 dBu and -10dBV when turned up more.

[annode]

- No noise associated with video graphics and dragging, good...that eliminated graphics card and so on.
- As I guessed, and may have been defined earlier in the thread;

You'll want to run them at +4dBu. -10dBV is typically referred to as "Prosumer" or "Consumer Line Level" and is common on consumer-level equipment; RCA connectors are usually involved.

-10dBV= (approx.) -8dBu (a 12dB difference from "Professional Line Level"!) A difference of 6dB equates to a halving of the voltage; -12dB would give you one-quarter of the original voltage (from 1.23V down to about 0.316V).

(this came from another audio site user)

- I asked you above about power outlets. How many outlets are you using?
This includes all wires where the ground of the wire comes in contact with any other part of your system.

BTW, is the noise primarily hiss, (as in pink or white noise), or is it more of a buzz? If it`s a buzz, read below.

- You can try unplugging everything from your system except your audio interface, your computer(no peripherals), and your monitors. If the noise at +4dbu goes away...start plugging one thing in at a time until the noise returns. If the noise doesn`t go away after removing everything try unplugging only one monitor audio cable...then do the reverse (to see if one cable is the cause.)

[thecontrolcentre]

Desktop or laptop computer? if its a laptop, try unplugging the mains and run it on the battery. If the noise disappears you have a ground loop ... a DI box between Audio Interface and monitors should sort it out.

[alexejm]

annode: I will try to check the steps you described. It's all connected to the same wall socket. By the way, now it's doing the low pitched buzz when dragging a window around.

thecontrolcentre: It's a desktop computer.

[annode]

annode: I will try to check the steps you described. It's all connected to the same wall socket. By the way, now it's doing the low pitched buzz when dragging a window around.

thecontrolcentre: It's a desktop computer.

My pc will make this buzz as well when I have objects open on my screen...and it really will buzz when I drag.
My pc has PCI audio card. I feel there is a bleed from PCI vid card to PCI audio card. My buzzing is NOT being recorded, only playback audio and it will totally stop if I 'minimize' all open screen objects.

One cause for this problem is not seen anymore this days, I think. Used to be when the windows mixer and audio driver were active in the background as well as the ASIO driver and the Windows mixer`s mic input would be 'unmuted', this would cause a severe drag/buzz.
These days, ASIO drivers turn off Microsoft driver/mixers during install.


I suspect your drag buzz is very minimal...but is more noticeable because something in your PC audio is turned up causing a high input gain, creating a high sensitivity to any pc background noise...which it will amplify.
I believe this is also the origin of the hiss you hear when monitors are at +4dbu....the proper input level. (more below)
EDIT - the buzz origin could be a bad internal audio circuit ground/connection or external cable.

Ground loops will never produce hiss, so I don`t believe that`s any part of your prob...being in one outlet pretty much proves that....but not always.
Assuming this outlet did not have a ground wire, and the neutral and hot were reversed, (USA), that could create some serious problems. Always check your outlet configuration with an inexpensive plug-in outlet checker to be sure.


Have you checked the audio device mix software? (driver software)
Make sure there are no faders turned up, especially mic faders..if there are any. If you can mute all the inputs in that mixer as well, try that.

You also may have a fault causing one mic preamp circuit to be full up.
A hiss symptom is always from an active circuit...meaning an amplifier circuit.

I`m an old audio tech, so i`m not just blowing my horn.