Annoying Hum???

First Im kind of new to using more equipment than just an guitar,amp and FX processor.

I recently asked how to split my signal for recording so that I can record my amp and also at the same time a clean signal so I could use to reamp or play with VST plugins such as Amplitube and such.

I was told I would need a preamp mixer and was suggested that I get a Behringer Xenyx802.
I chose to get the 502 model since I didnt need more. Well I have it working but heres the issue.

I run guitar into 502 mic/preamp mixer then one out to my amp multi FX.
I then ruin another out to my M-Audio sound card.
Now as soon as I connect the cable from the M-Audio to the mixer output I get a very annoying humming from the amp I use.
If I unplug it,it goes away. It does not record this sound,its just audible through my amp.

Also I use a Boss GT-8 and Tech21 sound engine for my amp these days since I only play for myself.

This is the exact connections I use:

  1. guitar to Behringer 502 mic pre/mixer.
  2. Behringer 502 mic pre/mixer out #1 to GT8 input
    3.GT8 output to Tech21 Sound Engine
    4.Boss GT spdif out to M-Audio(PC)
  3. Behringer 502 mic pre/mixer out #2 to M-Audio(PC) This cable plugged in gives me the hum only into the amp,not the PC or in recordings.

Is there anything I can do to reduce this?
Like I said Im new to using anything more than guitar,amp and effects.

So by connecting your mixer to your audio interface, your amp starts humming?
Interesting :smiley:

Are your power sockets grounded?
Does the humming still occur when you take the Boss pedal out of the signal chain?

I think the problem is that your Boss Pedal and amp are expecting a guitar input, but you’re feeding them a line input from the mixer which is much higher level. You may be able to make this work if you keep the gain on the mixer input channel very low, or if the mixer allows to switch output level to mic level.

If I’m understanding your usecase correctly, I wouldn’t have bought a mixer to do this (I hope it wasn’t me who suggested that, I don’t remember it :astonished:). A simple DI with a through output would be sufficient. You could plug the guitar into the DI input, plug the DI output into your audio interface (to record the dry signal), and run the ‘DI through’ to your pedal/amp and use the SPDIF connection to record the wet signal.

I only get hum when I plug the mixer to the pc,if I unplug the cable going to pc it’s very quiet.
I do have a di box but my clean signal was to low to record in cubase 5 with and that’s why I was told I would need the mixer of which is working well except for the hum.

I do not have the di connected since it brings my signal low again. I’ll connect again but I think the di did drop the hum but like I said it dropped everything else.

Thank you for the reply.

Edit: I have checked and all’s grounded. I’m thinking it’s ground issue within the pc. Had this issue years back on another pc but I can’t remember what I did the ground the case to stop a similar issue.

You didn’t specify your audio interface so I don’t know what you use, but if it doesn’t have preamps then yes, a direct signal from the DI would be too low to record.
If the DI has a -30dB pad, make sure it’s not pressed.

New suggestion: Do what I described above, except you plug the DI output into the mixer first, and then the mixer output into the audio interface.

My interface was the M -Audio 2496. It does not have an amp.
I was just playing around with the DI box and I did get the hum to go away. If I remember right I did just as you said.
But doing really drops my clean unaffected signal even though I have the di dB set to 0. It’s a passive di box. Do I need an active di for this?
When I did a test record the clean signal was barely showing in the recorded peaks…I assume this isn’t normal?

I really wish I could just mic the amp but I play late at night mostly and the wife likes her sleep.

Active or passive shouldn’t affect the output level, so that will not help you.

The DI shouldn’t ‘drop’ your output signal, The output level of the DI is the same as what you’re putting in, the guitar signal. Did you try taking the output of the DI to the mixer (turn up the gain on the channel you’re plugging it in) and then the output of the mixer to the audio interface?
If you max out the gain on the mixer, and push your faders up all the way, you should be clipping the audio interface. If not, something is wrong.

Ok I’ll check it out.
But from what I remember earlier, the di box is dropping the signal lower. I have 0 dB selected and thought that it shouldn’t lower the signal.
But I was having to boost the gain on the mixer to nearly max or at max. Then that gave an audible static kind of sound.
Maybe I got a bad box. I think I can still return it.
As for the mixer it’s working great for me. I can now record my acoustic with the passive pickup it has.

Ok, I’m not sure what else to suggest then.
I hope you can get it resolved.

Thank you for all the help.
I’ll be returning the box for another, probably a better one at that.

Thank you again,been a lot of help.

Another thing to consider - where/how are all of your pieces of equipment plugged in? Consider star grounding. Much could be said to explain star grounding, but here is the simple version - have all of your studio gear going into ONE outlet (hence, ONE ground). That, and using decent shielded cables, such as Mogami, can go a long way in keeping hum out. If you can use an outlet without other stuff on it (like light dimmers, or other appliances), that will be even better.

In my studio, I ran a separate 20amp line that I plug everything into. All grounds of all electronics equipment all goes to the same ground.

Strophoid had some good comments about your signal chain.


Yeah its all on one outlet by itself.
I think my issue is the pc,just poor grounding inside the desktop case. I had this issue a few years back and had to connect a ground wire inside the case. Problem now is I can’t remember exactly what I did. When I feel better I’ll Google on it.
Also I’m pretty sure the di box I got is faulty. Above was said it shouldn’t drop my signal and definitely is and by a lot. It nearly cuts my signal out completely.

I have to apologize, it seems I was wrong about that.
Reading your post I started doubting myself. According to WikiPedia, a DI accepts a line level input and outputs Mic level, which IS significantly lower than line level.
But your audio interface doesn’t have mic level inputs which is why your input signal is so low.
In theory the mixer preamp should still be able to give you enough level to record the guitar properly though.

Ok I have tinkered with different setups on this issue.
Using a passive DI box I get a very low signal on the clean signal to PC. It does remove all unwanted noise an is really quiet.
Also yes,my interface does not have mic level,only line/spdif levels.

I am starting to think I have all this setup wrong. Again I am new to using these things for anything more complicated than just putting my guitar signal straight into the 2496 and recording with Cubase or Audition before Cubase.My only recording expierence before that was using the Tascam 4 Track Tape recorder/mixer for years.

So I guess I need a good opinion for the best/cost effective method to do what I want.

What I want to do is record my amp signal and a clean signal at the same time so I can later reamp or toy with the clean signal.The reason Im using the mixer is to boost the clean signal to a good recording level. The DI box worked but when I ran the clean signal to pc it was weak.

Here is what I am doing now and think I may have the wrong idea for hooking it up.
Behringer 802 Mic Preamp/Mixer
Boss GT8 MutliFX using Tech21 Power Engine(use amp sims these days)
M-Audio 2496 Card- has 2 analog In/Out,2 Spdif in/out,no mic inputs
Also have a Passive DI Box
Extra I have the Behringer502 Mixer

-Guitar in > mixer input 1.
-Mixer Monitor out Left > Boss GT8 MultiFX Input > Boss GT8 Spdif out > Spdif In M-Audio 2496 interface
-Mixer Monitor Out Right(Clean signal) > Right input on M-Audio 2496 interface
-Boss GT8 Analog Left out to Tech21 Power Engine(amplifier)

I usually just record my amped signal direct from GT8 amp Sim into the PC by the way of SPDIF. But I may start recording mic’d providing I dont need really high volumes. I do have a Shure SM57 on the way.

So what Im asking is,
What is the best way to connect all this for what I am wanting to do?
Or do I need to get some other equipment to achieve this?

What I have done does work with the exception of the hum,but the passive DI does eliminate this but then drops my signal level for the clean signal.
Show I keep the same basic setup and get an Active DI box to eliminate hum and keep my signal level high enough on the clean side?

I think I have just been looking at this all wrong maybe plus I am just kinda new to all this digital stuff these days.Played guitar since the 80’s but never messed with anything other than playing and using the old school or simplified methods to record.
Thx for any help.

Just a thing to consider… is the hum coming only from your speakers only? Check if the speaker cables are balanced and if your audio card has balanced ins and outs… that fixed distortion in my signal path a while ago… I can now even plug my PC at the same outlet as my speakers.

If the hum is persistent throughout the signal path (headphones too)… then it is probably not an issue of balancing your outputs…

hope this helps

Active DI boxes have the same output level as passive DI’s, so that’s not a solution.
Additionally, Active DI’s need phantom power which your audio interface doesn’t offer.
Your mixer ‘might’, but it’s a bit unclear reading this topic:

Anyway, I don’t think you need a different DI.
The simplest solution would be an audio interface with SPDIF and a couple of analog inputs with preamps (2 would be sufficient for your current setup). That way you don’t need the mixer at all, and you can record anything you want, at any input level you want. (well ok, not any level, don’t plug in the output of a power amp :p)

Your current setup also works, so if you don’t want to spend any more money you should be fine. To add the mic, just connect it to an input on your mixer and route it to an output that you can send to your audio interface.
However: be careful to make sure you don’t also route the mic channel to the monitor outputs of the mixer, because that will create a feedback loop! I don’t know exactly how the behringer mixers work (and I’m too lazy to look it up, sorry :wink:), so check if there’s a way to route the mic signal to an output of the mixer and NOT to the monitor output.

Sorry I got the behringer 802 mixer. It does have phantom power on it. Friend gave it to me yesterday.
Yeah I was thinking about just getting a new interface since mine is older than dirt but I do like that it has midi in/out on it.

So an active still drops the signal? From reading I thought the active was to keep the signal? Not trying to be difficult here, just want a decent understanding how this works. Plus being on tramadol doesn’t help…lol.

Any recommendations on a new interface. Not too expensive and decent quality.

RME is the best, but is likely out of your budget. I’m a big fan of Roland after that. They support their devices/drivers for a looooooooooong time.


Thx for the suggestions.

I have made some headway. I did get an active in exchange for the passive. No signal lose now.
Guitar into active di,XLR out into mic pre,then link/Para out to amp. My clean has much more than enough signal now.

Hum is not as bad but more than I want. I will toy with some different things today and see what happens. I know it is the pc causing it.

As for reamping or using something like amplitube works great now.

I will follow up if I get this hum taken care of.

Thanks for that link Tommy-boy, I learned a thing or 2. :slight_smile:
It appears a good, very high impedance passive DI shouldn’t drop your signal level noticeably, but with a low output source in a relatively low impedance DI the output level will be low, which I suppose is what happened here.

I hope you can find a solution to your hum!

Finally…Hum is gone.
The issue was a faulty surge protector.

Hum free and good signal levels now.

So new surge protector,active di, and a new XLR cable.