Is this an Electrical problem or something else?

Andyman · Post by **Andyman** » Fri Jan 04, 2008 6:20 pm

Hey Guys,
I love this site and have been reading for the last few hours. I am newb audio guy and the reason I got into this stuff was for a love of manipulating sound. I have almost finished building my first home studio, and definately learned how not to do it the hard way, but now I truly feel like a man, as I have learned lots from the experience. Anyway although I have learned a lot I'm still not nearly as tech savvy as most of you pros so please bare with me.
I am getting some buzz in my mic pres, not sure if it is power related or something else. I was hoping to get away with not having to do any special circuit design, as I do not own the building and electricians are expensive but if I have to I will (and will probably have to tare apart the walls I worked so hard on

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Details of the Problem:

-There is buzz upon turning up the mic pres past 2:00 when the master is cranked.
-There is also some white noise when mic pres are turned up.
-Typically the buzz is insignificant until a mic is plugged in
-The white noise remains the same with or without anything plugged into the channel strip
-***When I hook up condenser mics the buzz dissappears when I turn on the phantom power, however the white noise remains apparent. (Very curious about this point)
-Additionally when phantom power is run down an empty cable (no mic) any present buzz dissapears.
-The exception to the above condition is I have a couple of cheap phantom powered dynamic mics made by BLUE, and they still buzz and produce some RFI even when I do run the phantom power.
-The mixer is a Mackie 1640 onyx
-All gear is plugged into a Furman M8 power conditioner which is plugged into a single wall socket
-Originally I thought that the problem was related to my wall panels, and having several connection points...I implemented the following grounding schemes for xlr connectors:
1. Connecting shield to pin 1 on both sides.
2. Terminating shield to pin 1 and the chassis on 1 and or both sides (terminating to shell on both sides yielded a slight improvement)
-After the above stage I got a little frustrated and went on several benders
-Next I tried hooking up a single mic cable to the Mixer plugged in Mic turned up pre and there was still BUzz following the same stated criteria above. Then I tried a shorter cable there was slightly less buzz...Then I tried a Long cable again with mic in the CR in close proximity to mixer instead of TR across the hall and there was also an improvement.
***THE SYSTEM IS COMPLETELY NOISE FREE UNTIL I TURN UP THE MIC PRES*****

What do you guys make of this? Is it electrical? or something else?
Would an electrician solve the problem?
Do I stand a chance?
What is the deal with the phantom power getting rid of the buzz with condensers?
Please help, and sorrry if this is a dumb question.

-Andy

Post by **Aaronw** » Sat Jan 05, 2008 12:42 pm

Hi Andy,

First off we'll need to do a process of elimination.

I guessing here...are you using outboard pre's? If so, what kind?

Does the onyx have built in pre's? If so do these do the same?

Can you give me your exact signal flow, from mic to the onyx?

If you haven't yet, plug a mic cable directly into the pre from you mic, bypassing your wall plates. See if this does any improvements.

What is you input into the onyx? 1/4" line? Is it balanced or unbalanced?

Andyman · Post by **Andyman** » Sat Jan 05, 2008 12:58 pm

I am not using outboard pres....The Mackie onyx has 16 built in pres, which are all balanced xlr inputs.
The signal flow is as follows: Mic -10' xlr cable to Tracking room wall panel through 35' balanced snake cable to control room wall panel - 10' xlr cable to mackie onyx xlr input.
The connectors used in the wall panel are Neutrik D series.
-When running a single 50' cable from mic to Mackie input there is roughly the same amount of noise.
-When using a 10' cable instead of the 50' cable the noise is reduced but not gone.
-Also when the mic pres are not engaged, there is no noise in the mixer or in the monitors.
I'm also curious to know why when I hook up a condenser mic and engage the phantom power the buzz dissapears?

Post by **Aaronw** » Sat Jan 05, 2008 1:19 pm

I'm also curious to know why when I hook up a condenser mic and engage the phantom power the buzz dissapears?

That's because "Condenser" mics require phantom (or power source). I'm having a brain fart at the moment for the exact technical reason on the power info.

What else do you have plugged into your mackie?

Try this...Unplug all connections to the console, except the monitors, and one mic. If the buzz goes away, start plugging things back in one at a time until the buzz reappears. That'll be your culprit.

Andyman · Post by **Andyman** » Sat Jan 05, 2008 1:41 pm

Normally the channel strip outputs of the mackie are plugged into an m-audio 1814 firewire interface unbalanced, only because I don't have trs cables yet. which is then hooked up to an intel mac computer....I am planning on purchasing the firewire upgrade for the mackie soon to avoid this step, especially cuz I am now better at using logic pro, than protools LE.

Anyway, I have already tried one mic one cable, and only headphones hooked up to the console, and the buzz remains, in that case what would the next step in this process be?

Post by **Aaronw** » Tue Jan 08, 2008 9:43 am

Does this problem happen with all your mics, or just the Blue?

Have you tried plugging into other outlets that might be on the other power leg?

Is the computer disconnected from you mackie as well?

Have you lifted the ground on the mackie?

Have you bypassed the Monster unit?

Just throwing some ideas out there...

Andyman · Post by **Andyman** » Tue Jan 08, 2008 12:36 pm

Yes the problem happens with all other dynamic mics such as my sm57s, as well as a the sure beta kick drum mic. The blue mic is moving coil, but for some reason it is phantom powered, and is the worst offender.

All my condenser mics fall into 2 categories when concerning this problem:
Category 1: No buzz at any time. All my Audio Technicas fall into this category.
Category 2: there is buzz until phantom power is engaged, at which point the buzz dissapears. My Rode Nt2a and Nt5s fall into this category.

The Mackie is not hooked up to the computer...and I have tested it with nothing hooked up to it except 1 mic 1 cable, and AKG headphones. Have also tested with different cables...smaller length yields slight improvement.

I have tried other power outlets however i'm not sure if they are on a different leg...the way this house is wired is very very strange...1 breaker works certain thing in the basement and upstairs...and other breakers work just 1 room....its kind of a mess.....is there any way of telling the legs apart?

I have not ground lifted the mackie yet...how would I go about doing that...would I purchase something that goes on the plug for it?

What do you mean by the monster unit?

Thanks again for your continuing input

Post by **Aaronw** » Tue Jan 08, 2008 1:16 pm

I meant Furman unit, not Monster power. Oops.

Yes, just a cheap $0.39 (or however much they cost) ground lift plug to put on the end of the power cable. But then again, you've got nothing else connected to the system to have multiple paths to ground. Hmmm...

How old is the mackie? Have you contacted them yet? maybe there's an issue with the board? A bad internal connection? Have you taken the mic(s) to another studio or rig to see if the problem happens there too?

gibong · Post by **gibong** » Tue Jan 08, 2008 2:37 pm

Is there a source of high-freq interference at your studio like a noisy fluorescent light or dimmer, etc?

(conjecture ahead...)

BTW...I notice (looking at your mic locker list) that the mics that seem to pick up the noise are moving coil or have internal audio transformers (NTs, etc.). The AT4040 is transformerless....so may be less susceptible to picking up this RFI. As far as turning on phantom power eliminating the buzz...I have also experienced this with some condensers - I think it may be the way a standard phantom power circuit is wired up so that the noise is somehow shunted or canceled.

Andyman · Post by **Andyman** » Tue Jan 08, 2008 3:36 pm

Yes I tried bypassing the Furman....no improvement. I even have another conditioner that I use made by belkin with a backup battery and tried plugging the mackie into that without plugging into the belkin into the wall using only the backup supply....interestingly enough that made it worse, w a quiet but constant buzz with nothing plugged to it...then I tried plugging back into the wall and the buzz did not go away in that case until I moved the belkin about 15 feet away from the mackie....

The mackie is about a year old, and was purchased new.....I also have an M-audio project mix I/o which I got so that I could do certain things with protools LE and I hooked the mics up to that unit and got similer results...However I will contact mackie anyway....just in case.

Yes....there are dimmer switches on the upper floors of my house as well as flourescent lights in the basement laundry area which is adjacent to the studio....Can they emit Electrical inerference throughout the air like radiowaves or is it confined to electrical circuits?
Also this may be a stupid question but if they are switched off can they still cause interference?

gibong · Post by **gibong** » Tue Jan 08, 2008 6:19 pm

Andyman wrote:
Yes....there are dimmer switches on the upper floors of my house as well as flourescent lights in the basement laundry area which is adjacent to the studio....Can they emit Electrical inerference throughout the air like radiowaves or is it confined to electrical circuits?
Also this may be a stupid question but if they are switched off can they still cause interference?

They can travel down your wires (most likely) and by air depending on the offending device. Turn them off or take them right out the the circuit (ie at the fusebox) to see if they are the source of the problem.

Post by **Aaronw** » Wed Jan 09, 2008 7:25 am

Most definately. Yes, balasts can be a nightmare in those lights, as well as wall or lamp dimmers. Heavy motors such as refridgerator, HVAC, and the like can also have an affect on your power too.

Andyman · Post by **Andyman** » Wed Jan 09, 2008 10:33 am

Ok I'm going to experiment with this....and I will let you guys know the results either today or tommorrow...I have tried turning them off in the past...but this time I will do it at the fusebox(wherever possible)....see the furnace is in the basement too...so that wil probably be a challenge as well.

Andyman · Post by **Andyman** » Fri Jan 18, 2008 6:25 am

Hey guys,

Sorry it took so long to get back to you on this one....I've been very busy with my job, and also had to coordinate with the people living upstairs a good time to cut all the power.

So first I cut all the power except for the breaker that the control room is on...there are no dimmer switches motors flourescent lights or energy saving bulbs on this circuit.....I also unplugged everything except the studio on this circuit. I found that there was no improvement or reduction of the buzz sound.

Next I tried it on a different circuit upstairs with the same results.

I have another question which may be another dumb question but I have to ask it to clarify things....If electrical interference is coming in through the power outlet is it sometimes only heard when you turn up the mic pres because it needs amplification to be heard? or would I be hearing it without the mics pres turned up?
Because it I just turn up the faders on the board it is buzz free.

jbaptista · Post by **jbaptista** » Mon Jan 21, 2008 11:56 pm

I think that you problem is far more simple than that. Please ask an electrician to measure you earth connection. All houses must have an equipotential connection to earth. If the values are wrong, then you should ask him to do onther earth connection just for your studio.

Best regards - Buy earth i mean GROUND