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Old 25th August 2013, 04:12 AM   #1
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Default HELP - Sound quality issues

Hello all. I run and own a DJ business in Columbus, OH. Its just me and I do it as a 2nd job.

I ran into a snag. I use my laptop to DJ weddings, HS dances and such.

Their is a humming noise coming out of my speakers when I play songs thru my laptop. I can't quite figure out what it is? When I play songs thru my CD players...no hum.

I have 2x B52 Matrix systems, that's I run with a Numark mixer, BBE sonic maximizer, Numark dual deck cd players, Furman power conditioner, monster cable everything.

Anyways I think I might have a grounding issue w my laptop as far as the hum is concerned. Not sure how to trouble shoot it? I've even tried hooking it up directly to my Furman power conditioner. Still same issue. Its also intermittent - meaning I only have the issue at some venues.

I know u can buy what are called "hum eliminators" but they are $50 per plug. Surely there has to be a better way.

BTW....I run the sounds from the laptop to the mixer via 1/8" (head phone jack from laptop) to RCA. haven't really found any other way to do it ?

Anybody who has more experience then I at this feel free to chime in!

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Old 25th August 2013, 08:55 PM   #2
djcgtr is offline djcgtr  United States
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Quote:
Originally Posted by silentcropduster View Post
Hello all. I run and own a DJ business in Columbus, OH. Its just me and I do it as a 2nd job.

I ran into a snag. I use my laptop to DJ weddings, HS dances and such.

Their is a humming noise coming out of my speakers when I play songs thru my laptop. I can't quite figure out what it is? When I play songs thru my CD players...no hum.

I have 2x B52 Matrix systems, that's I run with a Numark mixer, BBE sonic maximizer, Numark dual deck cd players, Furman power conditioner, monster cable everything.

Anyways I think I might have a grounding issue w my laptop as far as the hum is concerned. Not sure how to trouble shoot it? I've even tried hooking it up directly to my Furman power conditioner. Still same issue. Its also intermittent - meaning I only have the issue at some venues.

I know u can buy what are called "hum eliminators" but they are $50 per plug. Surely there has to be a better way.

BTW....I run the sounds from the laptop to the mixer via 1/8" (head phone jack from laptop) to RCA. haven't really found any other way to do it ?

Anybody who has more experience then I at this feel free to chime in!

sent from double thumbin' it


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Greetings

The hum/buzz/noise from a laptop to a sound system is very common. Basically you ought to seek a passive Direct Box (DI) to transformer isolate the audio signal from the laptop that is feeding your mixer.

I presume you are in "stereo" so either use 2 DI's or a stereo (dual channel) transformer isolation device(s) (DI). Pretty much guarantee that the noise will be eliminated. I make no particular brand or model recommendation, there are plenty out there to locate via a 'net search or a visit to local audio store in the Columbus area.

Every system install I participated in, provided this type of isolation for the exact issues you describe. The explanation for the noise can also be found by a 'net search, so I will let that be...

Just my personal feelings on the expense of Monster cable, you already possess the cables, but in your case you probably didn't have to spend the extra money for Monster...

Additionally, the use of the BBE (and the expenditure) is debatable. While a BBE does provide a quick and handy boost in the low and high ends of the audio spectrum, you probably already have wide band EQ adjustments on your mixer that do about the same effect.

Checking YouTube for the technical evaluation of the BBE explains the "processing", and you will see the benefit is not much more than an EQ adjustment.
There certainly is marginal music quality on older recorded material from back in the day - that has a noticeable reduced low frequency content compared to more recent source material...

I will say welcome to the forums here. There are many knowledgeable individuals, from around the world who participate in these forums and this is a very interesting place.
Columbus is about 2 hour drive from me, I periodically am in your home area.

Best wishes and carry on

Deric
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Old 25th August 2013, 09:24 PM   #3
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Quote:
Originally Posted by djcgtr View Post
Greetings

The hum/buzz/noise from a laptop to a sound system is very common. Basically you ought to seek a passive Direct Box (DI) to transformer isolate the audio signal from the laptop that is feeding your mixer.

I presume you are in "stereo" so either use 2 DI's or a stereo (dual channel) transformer isolation device(s) (DI). Pretty much guarantee that the noise will be eliminated. I make no particular brand or model recommendation, there are plenty out there to locate via a 'net search or a visit to local audio store in the Columbus area.

Every system install I participated in, provided this type of isolation for the exact issues you describe. The explanation for the noise can also be found by a 'net search, so I will let that be...

Just my personal feelings on the expense of Monster cable, you already possess the cables, but in your case you probably didn't have to spend the extra money for Monster...

Additionally, the use of the BBE (and the expenditure) is debatable. While a BBE does provide a quick and handy boost in the low and high ends of the audio spectrum, you probably already have wide band EQ adjustments on your mixer that do about the same effect.

Checking YouTube for the technical evaluation of the BBE explains the "processing", and you will see the benefit is not much more than an EQ adjustment.
There certainly is marginal music quality on older recorded material from back in the day - that has a noticeable reduced low frequency content compared to more recent source material...

I will say welcome to the forums here. There are many knowledgeable individuals, from around the world who participate in these forums and this is a very interesting place.
Columbus is about 2 hour drive from me, I periodically am in your home area.

Best wishes and carry on

Deric
My apologies, I believe I jumped the gun too soon. I did search the interwebs lol...but I wasnt getting any results. Mainly because I wasnt searching for the right thing. I ordered a $50 hum eliminator. Which should work. And is cheaper than a DI box, but not by much.

As for the Monster Cable...75% of it I got free by having big orders from professional audio/lighting companies in the past. My cabling is about 5 years old and if I knew what I did now, I know I dont need them. Seeing how I do have them, you're correct - no point in getting rid of them. Same with the BEE SM - I bought it for $50 off a friend a long time ago & had to re-soldier the RCA female plugs on the back. It does make a small difference in the sound, but nothing to write home about.

Thank you for your input though.
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Old 25th August 2013, 11:33 PM   #4
wg_ski is offline wg_ski  United States
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Quote:
Originally Posted by silentcropduster View Post
I know u can buy what are called "hum eliminators" but they are $50 per plug. Surely there has to be a better way.
A direct box with transformers inside should cost less than $50 for stereo. An acive version with amplification goes for about $65. I use one of those because my DJ console's output is too low without it.

And I found that I needed another transformer between the light system controller and the sound system. If they were on separate phases it put a LOT of hum into the light controller and that's all it responded to.
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Old 25th August 2013, 11:37 PM   #5
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A direct box with transformers inside should cost less than $50 for stereo. An acive version with amplification goes for about $65. I use one of those because my DJ console's output is too low without it.

And I found that I needed another transformer between the light system controller and the sound system. If they were on separate phases it put a LOT of hum into the light controller and that's all it responded to.
I'll see how the him eliminator works. If I dont like it, I'll try this route. What r u running for audio out of curiosity?

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Old 26th August 2013, 01:10 AM   #6
wg_ski is offline wg_ski  United States
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Hercules RMX console, into a Clean Box Pro. From there into either a DCX2496 or Driverack 260, depending on which PA I'm using. I had no hum problems going from the console to the dBx, but not only hum but also a lot of digital squeal going into the Behringer. The system was unworkable without the box. Passive transformers are cheaper if you don't need gain and will work just as well at breaking ground loops.
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Old 26th August 2013, 01:24 AM   #7
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What does the cleanbox pro do? Clean up ur audio signal?

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Old 26th August 2013, 01:01 PM   #8
wg_ski is offline wg_ski  United States
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Converts an unbalanced signal to balanced. It has internal amplifiers and a wall-wart power supply. It effectively breaks ground loops if you drive a proper balanced input with it.

Unbalanced interconnects are prone to ground loops, which pick up a lot of hum. This especially happens when mixing pro audio and consumer gear. Computers of any kind are usually the worst offenders - because they have a safety ground on the power supply which is electrically connected to the audio ground. With balanced interocnnect, the audio "ground" contains no return current and any signal developed on it does not contribute to the signal going into the amp (or equalizer, or ....). If you feed one side of a balanced input with an unbalanced signal, that does not count - because you've made an unbalanced input and the return current flows through the audio ground, which is connected to the safety ground at the AC mains. If you trace out these "ground loops" they can be VERY large - hundreds of feet long even. Imagine all of that being a big antenna. You may only pick up a few hundred microvolts but if that's -30dB continuous it's very annoying at 120dB peak.

A transformer may also be used to break a ground loop because the two sides need not be connected at all. A transformer's output is also inherently balanced, unless one side is intentionally connected to "ground". If you are driving an unbalanced input a passive box with a transformer is actually more appropriate.
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Old 26th August 2013, 02:08 PM   #9
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You sold me, I bought one for $55 on Amazon just now. As far as the connect goes. Currently I uae a 1/8" to RCA into mixer. I assume the same set up applies only I'm going from laptop to cleanbox then RCA's from clean box to RCA's in mixer?

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Old 27th August 2013, 03:57 AM   #10
dangus is offline dangus  Canada
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Another way to solve it would be to use a USB sound device that has S/PDIF output, and feed that to a DAC at the mixer (if the mixer doesn't have a digital input). Even a $20 eBay DAC is likely to be better than the laptop's onboard sound.

Onboard sound tends to be polluted with digital noises from hard drive activity, and even mouse movements... is it possible that you've mistaken internal noises for a ground loop? I normally avoid every using onboard sound, but when I do, I keep the output from the computer at maximum, then reduce the gain at the mixer or preamp (or a passive volume control inline with headphones), which minimizes the background digital noise.

Still, I would have expected that simply using a 2-wire AC power cord for the laptop's power adapter would be enough isolation.
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