iMac 27 2010 + KRK Rokit8 = NOISE turning me insane

R

Ruffftec

New member
Yo hoo everyone.

Got me those nice bling bling KRK Rokit 8 monitors and am struggling as they keep playing a noise. It can't be the monitors or cable. Am running them raw via 3,5 mm to chinch even though that is not really the final setup but it must/should work. Tested MacBook and MP3 player...brilliant sound. iMac..? Bssssssssssssss! Gosh how that irritates me. Tested my Audio 8 DJ sound card which I usually just used in clubs for time code vinyl: Even this device give a noise. The Rokits were on lowest volume and the volume of the noise stayed constant even when I leveled up the volume of the iMac. I tried to just run the iMac and Rokits, no help. Tried all kind of switching plugs, run iMac and Rokits from different plugs (I think I tried all plugs on this level of this building), no help. I never used monitor on this iMac as I got it not soon long ago and before I used Audio Technica ATH-M50 headphones for monitoring. No noise, nothing. Same 3,5 mm plug. How come? I have noooo clue! Do those headphones have a special iMac-Noise filter? I doubt it. I am lost why they don't play the same noise though. Getting a new sound card at this point is no option and somehow it looks like this problem even would effect another sound card as it did appear on the NI Audio 8 DJ too. It irritates me and I wished to be able to not hear this noise whenever it should actually be silence.

Apart of that the KRK's sound nice hey. Ok low end is yaaah....it doesn't blow me from the chair but I guess it needs a sub for that - plus own house to not annoy neighbors so till then I will do the bass check on our soundsystem which is luckily located in a building that has no neighbors lol.

Ok. So. Anyone who shares my pain? Listen the noise sample and you will. The noise goes along the activity as scrolling up down or when the cpu works for other jobs. The start of the sample is the 'normal' noise. Sometimes it got a pulse somehow. I read about ground loop and isolators which can be plugged in between Comp and Speaker but I mean...really? I heard the sound card of the iMac is good so wtf?

TIPS and HELP very welcome. Thanks a lot.

Ruffftec
 

Attachments

  • iMac-Noice.mp3
    774.2 KB · Views: 31
Last edited:
How did you record the noise? Did you hold a microphone in front of your speakers?
Did you try the ground loop?
Find yourself a proper ground connection. You should have one somewhere in your house. Then loop any metal part of your laptop or speakers to that ground connections. I use to run one to an electric guitar from a copper gas line, through a 4mm speaker cable. The copper gas line transmits electricity well and is connected to the ground. I do this because ground connections through my electric wiring are scarce in my house , somehow. I have one freshly made to my washing machine and one in my kitchen, that's it.
Your AI has a ground connection as well, you could hook up the ground loop to your AI.
Another thing, do you have balanced cables? Like these: Klotz B3PP1-0200 6.3mm jack 3p naar 6.3mm jack 3p 2m kabel kopen? | Goedkope | Promo | Jack kabels (actually the cheapest I could find with proper connectors, they work like a charm) .
I used to have similar type of noise being picked up. Connecting my monitors through balanced cables and the balanced outputs of my AI solved that.
 
Last edited:
I would caution against any amateur electrical work to do with ground loops, as you cannot be certain that you will not make the problem worse or end up killing yourself or someone else

A ground loop occurs when two independent circuits do not share the same pathway to ground

Step one to eliminating a ground loop is to put all audio equipment, including the computer, onto the same circuit - guaranteeing that they share the same path to ground

Step 2 is to look at what your power sources are and why there may be problems

a lot of issues that are termed ground loop problems by folks are actually power problems where the power supply is not providing the expected current @ the expected voltage, normally an issue with USB buss powered devices (USB says 5v @ 2A or 10W per port but usually is implemented as 5V @ 2A per 8 ports, i.e. 250mA (1.25W) per port), but can also be experienced with anything using a wall-wart/power pack.

What happens as result of not getting the expected current/voltage is that the device still tries to suck that power but ends up surging up and down as it struggles to get the current or the voltage to reach expected levels: we hear it as noise on the audio lines (for those that doubt this I was given this particular piece of information by a 50 year veteran electrician/electronics repair man)

A second source of problems could well be that you have issues with lighting in terms of fluorescent starter ballasts - these used to generate all sots or spurious rfi and audio hash and could play havoc in live situations, modern ones are less prone to doing this but always worth a look

listening to what you have it is certainly a not a ground loop which would be dominated by 60Hz or 50Hz hum - this is power hash and more likely an indicator that you do not have properly shielded cables going from your iMac to your monitors, though it could be a sign of shielding issues inside the iMac

pics of your cable and your imac socket with cable in place, and cable attached to your monitors as well would be handy top provide further advice
 
Thanks for the helpful responses.

I recorded the noise via internal iMac mic. It has low, mid and top frequencies.

Well I think that this house (built 94, Germany) has proper electrics when ich comes to grounding. Plugs, monitors, iMac...they all are plugged in via 3 pole, usually into a multiple socket. So they all should be properly grounded. I ordered a ground-loop isolator (chinch to chinch) already so I will be able to check that next week but I doubt that this is the reason. I remember ground issues also as a straight bsssssssss. No ups and downs. I plugged all devices onto the same and different circuits to check it without making a difference. Usually I got them connected to one as it is practical.

After reanalyzing what you said I honestly am thinking more and more about this balanced-unbalanced cable issue. The headphones are highend but still unbalanced stereo what doesn't explain why they don't display the same noise except if they have some shielding and the iMac has some

The monitors have unbalanced RCA chinch and balanced TRS or XLR input.
My iMac probably got normal stereo 3,5 mm output, the NI sound card - which is made for DJing and not meant to be a studio sound card - has normal RCA Cinch outputs, probably all also unbalanced.
So no way to get it solved without getting a new external sound card supporting balanced outputs if I see it right. Mh....
 
balanced cables would normally fix this but as the output from either source is unbalanced it won't do a thing

pics please
 
Ah, i see there's a few mix ups. The audio 8 idd only has RCA, those are unbalanced yeah.
You could try and shield your cables somehow.
Your headphones are different in picking up radiation. The woofers/tweeters/cones in your headphones are different, and your cable is different, so , it wouldn't be strange that your monitors are picking up noise but your headphones not.
 
So here some picks. The golden one are the headphones cables. I use the 3,5 mm to connect to iMac. I know the 3,5mm>RCA are no pro-cables oh and there is a second RCA one so that is no mono cable. They worked for my needs till this point still. ;) Apart of that I used normal RCA>RCA cable for trying out the NI Audio8DJ sound card and I don't have a lot of devices. Just a USB hub, Alesis midi keyboard, a halogen lamp...that is it. So no devices madness. It clearly is a signal coming from the desktop computer whyever.

Yah I guess something like a small affordable sound card as the 'focus rite safari pro 14' or so would help (well I hope this one has at least balanced outputs but still looking up the specs). If there is a solution without getting the external card that would be cool for now though. I mean it very strange to listen music via iPhone just because even for listening some proper music I can't use my desctop computer ;)
Foto 1.JPGFoto 2.JPGFoto 3.JPGFoto 4.JPGFoto 5.JPG
 
As I said, you could try and shield the cables, but that's hard. Some cables are already pretty shielded.
As tips for AIs, there's a lot of posts on the forum about it.
Check this topic, there's a few good names in there, expensive and budget. Also a good link to some overviews. Link to a commercial review list and a link to a post of mine that has a list constructed from some reviews on FP and GS. Do check if it has balanced outputs just to make sure.
https://www.futureproducers.com/for...priced-audio-interface-446468/2/#post49874559
 
Last edited:
hmmm hard to say for sure the cause but those unbalanced cables will not be helping minimise hash pickup on the audio lines

adding shielding won't fix the problem as they are already shielded - mono means single core for the audio and a ground/earth return that is wrapped around the single core - doesn't stop the picking up of extraneous electrical noise, because balanced cables work on the premise that the hot and cold lines are 180[sup]o[/sup] out of phase and then recombined at the receiver end providing a 6db boost and cancelling any induced noise due to phase inversion

do you have a friend with an audio interface that you could borrow to determine if the problem is the computer or the cabling first?
 
You must log in or register to reply here.
Back
Top