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Topic: Getting rid of hum |
Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 8 Jun 2002 10:29 pm |
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Recently I have picked up a small Mackie mixer and changed my soundcard to a Soundblaster Audigy Platinum Ex which has an external box that sits on top of or near the computer. It has a headphone out, SPDIF in and out, as well as a mic and aux in (RCA). It is real convenient for patching in and out of and my goal is to record myself. The problem is when I attach the mixer to the soundcard I get a hum - not unlike a ground loop hum. I have tried lots of different approaches to solve it but cannot find the answer. As well as putting the computer and mixer on the same circuit, I have also put them on different circuits and electrically isolated them from each other (as well as possible)- they are physically located about 6 feet apart, used a battery backup unit as a power conditioner (don't really know if that has much of a conditioner in it tho), checked all the cables which seem fine, measured voltages from each end (seems negligible), etc. I have also lifted the ground from the mackie and that has helped but I'm not comfortable with this option long term as I recently fried an amp this way. I also just isolated the ground from the guitar amp and mixer circuit and installed a ground rod (8 feet long into the ground and fed the circuit ground to that to no avail- as soon as I hook up the computer to the circuit the computer hums like crazy. Any ideas would be appreciated.
Also on this same topic- the guitar gets real noisy but primarily after 7 PM. I have gone thru the house and shut off all lights/appliances/computers, etc and cannot seem to change the noise which is fairly high pitched (not unlike alternator noise in the car radios awhile back)- during the day the magnitude of the noise is about 1/3 of what it is at night- and I have no idea what to do about it. I have tried different pickups but the problem remains and it is present in multiple guitars located in multiple areas around the house separated from the amp. I have also verified that the recepticles are wired correctly. There is no noise to speak of in the amp until I plug in the guitar. I did just get a Furman PL Plus power conditioner from ebay today and have some hope for help in this manner but not much. Thanks anyone in advance for the favor of a reply- Jim Palenscar [This message was edited by Jim Palenscar on 09 June 2002 at 09:36 PM.] [This message was edited by Jim Palenscar on 10 June 2002 at 07:23 PM.] |
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chas smith R.I.P.
From:
Encino, CA, USA
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Posted 9 Jun 2002 11:01 pm
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Jim, I'm probably not the best qualified to answer questions about grounding etc since I think it truly involves VooDoo. If you've lifted the grounds from the plugs and the computer and the Mackie aren't sharing any metal and it hums more when the guitar is plugged in, then it's probably the guitar pickups and/or the cable and/or the volume pedal. If you have single coil pick ups, then that's it or if you have buckers they could be picking up the RF from the computer and/or the monitor.
I have a HUGE problem with this in my studio and with my racks which all have digital equipment in them. In my main rack I have at least 7 digital "engines", depending on the set up. I had to put EMG pickups in the guitar that goes with it, and it still hums and has a constant noise level at -60db. If the guitar gets noisier after 7pm then it might be a radio transmission of somesort. I think that radio stations get to boost their power at night. I once played a night with KNX coming out of my amp. You could put a positive spin on it and think it was space aliens trying to contact you. |
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 10 Jun 2002 5:41 am
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| Thanks for the feedback Chas. It is really beginning to get on my nerves. Both problems. After about 7 at night there is a decidedly louder high pitched hiss/hum- comes on b4 the street lights and nothing else is on in my house- I dunno but it is frustrating. |
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Gary Peaslee
From:
Hideaway, TX USA
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Posted 10 Jun 2002 7:52 am
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Hi Jim,
I have the same problem with hum here in Texas, so at least you know it's not unique to your area. I have a small, 6-channel Berhringer mixer which is very quiet until I plug in the cable from my computer's sound card. Even if I unplug everything going into the computer including the power cord, it still hums! I also tried most of the things you tried but to no avail. The only thing that helped a little was to make sure that external power supplies (i.e. from the mixer, wall warts, etc.) were away from the audio cables. This reduced the hum but did not eliminate it. For now, I simply unplug the sound card cable when I'm not using it. |
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Steve Feldman
From:
Central MA USA
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Posted 10 Jun 2002 3:37 pm
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| Why don't you try one/some of those ferrite cores (beads) on the power cabling to reduce RF noise. |
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 10 Jun 2002 6:21 pm
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I've not heard of the Ferrite application Steve- can you elaborate please? I've got the power company comin out tonite to see if the 2nd part of my problem is being generated within my house or is it comin in on their line. Will keep you all posted. a soon to be forum member contacted me via e-mail and recommended a couple of things paraphrased below which I intend to follow up on:
"1. The physical location of the sound card in the computer-get it as far away from the IDE controllers and especially the video card as you can. Try to plug it in to a slot that is away from all other cards.
2. Most of the semi-pro audio cards have a ground loop problem when connecting to external devices. A relatively cheap
way to test this is to pick up a "hum eliminator" for auto stereos. It is an isolation device sold at most auto parts stores for less than $20.00. It has two sets of RCA jacks on it. If it is a ground loop problem, this will take care of it.
3. If you are running any kind of florescent or especially halogen lights that use the dimmer-these will definitely make noise"
--thanks to all of you responding- hopefully I'll get it solved with all the suggestions I've been getting~~ |
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Steve Feldman
From:
Central MA USA
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Posted 11 Jun 2002 4:29 pm
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Well, I don't know xactly, but they're these wart things that are on the ends of video monitor cables, power supply cables, etc. that supposedly reduce or eliminate radio frequency interference. They're largely comprised of iron oxides of one form or another and are magnetic. Beyond that, I don't know, but they're widely used and fairly widely available. Radio Slop has them and you can buy a couple and clamp it down on your power supplies of other cabling to try to reduce interference.
Hope this helps.
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Donny Hinson
From:
Glen Burnie, Md. U.S.A.
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Posted 11 Jun 2002 5:35 pm
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| Does the noise go away if you turn the monitor off? Those ferrite filters (torroids) usually work best at suppressing high RF frequencies, I'm not sure they would do much at attenuating 60 cycle hum. If the hum's getting in through the guitar line, then a "notch filter" would eliminate most of it. Increased power line noise at night is usually caused by lighting sources such as neon lamps (signs) and vapor-type (sodium/mercury) streetlights. An easy way to track down the source of the noise is to us an AM portable radio (tuned off-station) as a "sniffer"...just walk or ride around 'til you find it! Nearby substations and stepdown transformers used by utilities also radiate hum, while the big (33kv) high-tension towers can make most nearby audio gear (except FM) totally useless. |
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 11 Jun 2002 7:36 pm
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| Thanks for the ideas!!! The power company came out last night at 9:30 and checked everything hooked up to the house and said all was well. They are going to put a recorder on the line for 24 hours and check it. The tech. also said to contact the head engineer which I did this morning. He seemed interested and said that he was going to monitor nearby transformers for me to try to see who was doing what and when. Pretty cool that they seem to respond to a small time guy with his own schtick of a problem. Will keep posting with findings as they occur. Thanks again everyone for the favor of replies. |
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David Wright
From:
Pilot Point ,Tx USA.
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Jim Palenscar
From:
Oceanside, Calif, USA
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Posted 16 Jun 2002 4:31 am
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| Just a quick update. One of the the recomendations by soon-to-be forum member Jay Fagerlie included a "ground loop isolator" from Radio Shack which I have purchased (14.95)and that took care of the 1st part of my problem- the ever-present hum when the mixer and recorder were hooked up to the computer- even tho they were all hooked up to the same circuit. Now if I can just solve the 2nd part of the equation- the onset of the 7 PM noise. Thanks for the help - especially you David- I'm moving next door to you (with my 5 ex-wives, their families, 13 dogs 17 cats). |
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