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AM interference on sound card

L

Lazy J

OK Gents (and ladies?),

I am trying to eliminate AM interference on a production computer. The studio is co-located with the tower, so it's bad. The production computer is a Dell and it's using the on-board sound card. I tried an ART clean box and it sort of helped, but it added a 60hz hum. I added a Radio Shack ground loop isolator and the hum went away... along with all my bass. I removed the clean box and used only the ground loop isolators. That actually fixed all of the problems... for about a day, now the AM is back with a vengeance. I am trying to avoid putting .01 caps on EVERYTHING in the building.

So, I am considering installing pro-grade sound cards like my favorite Delta 44, but I don't want to spend the money if it won't help. I was also looking at USB sound cards, wondering if that might help.

Anybody have any experience with this? Any Suggestions?
 
You should try a Henry USB matchbox II. The unit has balanced inputs and outputs, and digital AES out! They are very rugged and have an internal power supply. Unbalanced audio around an AM site is a disaster! Henry is a great product, and if it does not work for you, they will take it back. I just started using them a while back instead of on-board balanced cards. Some of the major market clusters use them exclusively to get audio in and out of production computers. That is where I saw them. They will run on XP, Vista 32-64, and Windows 7, 32-64. http://www.henryeng.com/USBmatII.html
 
Interesting. But at that price I would hope to get the ability to do 96k at 24/32 bit sound for those special recordings and productions that get special love and care.
 
Looked into the E-MU 1212?
Balanced in/out, 24-bit/192kHz

Included mixer software is a bit complicated, but once it's set up you don't have to touch it anymore.
Very nice value for money
 
If you are feeding the computer from the balanced output of a typical broadcast quality mixing board, then any good quality brand sound card with balanced inputs should be OK. E.G. Digigram, Audio Science, Lynx, etc.

If you are using a sound board type mixer, like a Yamaha, Behringer, or Mackie, you may find the RF is getting into the board as well, once you change the sound card. Then the Match-Box may be useful, especially if your mixer output is unbalanced.

We have a similar problem, except it is an FM antenna 200' above the studio with 17 kw ERP. Chicken wire in the walls and ceiling when we built the building made a big difference. You could also use hardware cloth (which looks like window screen material except it is heavier, and made of metal). Ground either well.
 
Goat Rodeo Cowboy said:
Interesting. But at that price I would hope to get the ability to do 96k at 24/32 bit sound for those special recordings and productions that get special love and care.
Click to expand...

That is overkill, considering that the backbone sample rate of every single radio I work for is 48 kHz. Anything recorded at high sample rates is ultimately down-sampled and dithered back to lowered rates and word lengths. The thread was about interference from an adjacent AM transmitter. Consumer grade equipment usually has problems in those kinds of environments. The Henry was designed for rugged use in a radio environment where noise is usually a problem. Other sound cards usually suffer from grounding / shielding issues, pops and clicks, and the noise floor is never what is advertised.
 
fm-engineer said:
Goat Rodeo Cowboy said:
Interesting. But at that price I would hope to get the ability to do 96k at 24/32 bit sound for those special recordings and productions that get special love and care.
Click to expand...

That is overkill, considering that the backbone sample rate of every single radio I work for is 48 kHz. Anything recorded at high sample rates is ultimately down-sampled and dithered back to lowered rates and word lengths. The thread was about interference from an adjacent AM transmitter.
Click to expand...

I understand that. When you have experienced, profession announcers recording typical radio stuff, Even 48/16 is more than adequate.

If I am recording a client or news maker who is not "studio broken", some one with widely varying dynamic range, some one with strange breath noises between phrases and maybe contributing to the noise level with finger-thumps on the table while recording, and I have to do some very tedious editing, with a lot of opportunities for dithering, it gives me a sense of confidence that I can do all the manipulations I want with minimum damage before I down-sample to the final product.

Overkill? Yes! Guilty! But if you ever end up with a crummy tape of a city council meeting that suddenly goes ballistic and you need that distant voice that is almost unintelligible pulled out of the mud, send me the file. I'm your dude. And how often does that happen in the radio business? Maybe twice in a lifetime.

I edit recording for a religious organization. It's every week for me.

Yes, my earlier comment seems a bit stupid in the context of a radio station setting. But... the price is still HIGH for a device that can't do 96/32. The lesson is: If in a radio station within the ugly transmitter pattern, and you need to record a soft voiced subject and edit the tape, take them somewhere else for the recording session.
 
TomT said:
If you are feeding the computer from the balanced output of a typical broadcast quality mixing board, then any good quality brand sound card with balanced inputs should be OK. E.G. Digigram, Audio Science, Lynx, etc.

If you are using a sound board type mixer, like a Yamaha, Behringer, or Mackie, you may find the RF is getting into the board as well, once you change the sound card. Then the Match-Box may be useful, especially if your mixer output is unbalanced.

We have a similar problem, except it is an FM antenna 200' above the studio with 17 kw ERP. Chicken wire in the walls and ceiling when we built the building made a big difference. You could also use hardware cloth (which looks like window screen material except it is heavier, and made of metal). Ground either well.
Click to expand...

The console is an AudioArts R-5, so everything is balanced. I guess ultimately my question is if a USB or Balanced sound card will really solve my problem. They don't need anything fancy, and $500-$600 is heart-attack range for the owner, so I need to be 100% sure before I ask...
 
First - let's address this sample rate nonsense. I've installed thousands of digital audio systems and at radio stations 44.1 kHz is the standard. That's what music is recorded/released at. Any station using any other rate is simply asking for trouble.

Lazy J said:
The console is an AudioArts R-5, so everything is balanced. I guess ultimately my question is if a USB or Balanced sound card will really solve my problem. They don't need anything fancy, and $500-$600 is heart-attack range for the owner, so I need to be 100% sure before I ask...
Click to expand...

I'd definitely go the external card route.

You don't need to pop $500 for a balanced sound card. There's plenty of balanced I/O USB adapters in the $100-$150 range (Lexicon Alpha, Alesis I/O 2, Yamaha Audiogram 3, etc). But buy the card from a vendor with a liberal return policy and no restocking fee in case it doesn't solve your problem.
 
at radio stations 44.1 kHz is the standard
Click to expand...

Thank you, SRP... you read my mind. The music you're getting from the record labels is 44.1; upsampling is asking to add sampling errors, especially if you later down-sample again.

The only time you should be getting 48 Khz file is if the person sending it to you doesn't know what they're doing, or it's audio from a DVD.
 
A balanced-input sound card, mounted inside the computer case, has the added advantage of shielding from that case. On the other hand, an external USB sound card--if the audio inputs are balanced--will have the audio into the digital domain when it hits the computer, so should also be OK--IF that external device is properly shielded. (Then again, you might have other problems from RF getting into the USB connection but that would be more likely show up as stuttering, clicks or other artifacts in the recording). RF is a sneaky critter.

As been suggested, best work with a firm that will allow a return. I've installed an Echo Mia-Midi card, which is balanced in, at another small station. Seemed to work well for an inexpensive card. However, that station didn't have any RF problems. At $179 (BSW) it might be a place to start without risking too much money.
 
Try wrapping your unbalanced cord through a clip-on ferrite core... It makes your cord's length appear to be non-resonant and won't affect sound quality (at least not on a Dell on-board).

http://www.radioshack.com/product/index.jsp?productId=2103222

$6.00, It's worth a try. Works great on phones/phone cords too..

An Echo Mia-MIDI is about $179 from BSW. The Dell on-board sound cards have horrible DC offset problems (IE, center line being off on Adobe Audition/Cool Edit, etc.) A pro grade sound card of any brand is likely to improve the sound.

Mixing sample types and rates is usually not automation system friendly. Most automation systems choke on anything other than 44.1kHz, 16 bit audio, and if they do work, the software DSP is likely to make a mess of the mixing especially against music, which you probably rip from CD's (again 44.1kHz)...
 
Having worked many Am facilities at one point early in the game computers were just not an audio source.

If everything was fine one day then this can be fixed. Good one day and not the next is the typical AM rf nightmare. This happened years ago until we used literally hundreds of caps.

Then we found the torroidal cores. They work on AM and FM btw. They control overload. It essentially places a transformer in the line eliminating AM ingress.

The ferrite cores need to be able to eliminate the rf entering through the power. There are many types for many uses. A few bucks for the cores then the process of winding input and output audio, and the AC lines (an area that is where a lot of junk enters. (Are your power lines overhead sucking up signal from the tower, strung along the tower field?)

Radio Shack types are no good normally. I looked at the link and found these are identiacal to the clipons I have been using. No specs.
 
You might want to try a power filter. A very good option would be Isobar. http://www.amazon.com/exec/obidos/ASIN/B00006B81D/ref=nosim/9927774-rg2087-00-20

A lesser option might be a radio shack part # 61-188 61-189. I'd get into the sound card and put some .01uf capacitors across the hots and ground on the audio ins and outs. http://www.radioshack.com/product/i...Name=Type&filterValue=Ceramic+disc+capacitors

Sometimes grounds can be your friend. Sometimes they can just create more issues. Try it both ways. I've had many years under a big am blowtorch. Unbalanced anything gets tricky as it cannot get rid of the interference by cancellation as balanced inherently can (immunity). The USB sound device might also be the answer for you. I've had good luck normally with the Alpha, but I don't know if the input is truely balanced or not. You need to insure that it's balanced within it's design and not just unbalanced with some resistors, etc. to make it work with a balanced source as that will probably not really reject the interference.
 
A combination of ferrite cores and capacitors work better, but usually, the wire, especially unbalanced patch cords have some inherent built in capacitance. A 0.01uf is actually a pretty large value in the wake of any high impedance audio, if it is being driven by an 150 ohm output, it probably isn't a big deal, but it may muddy the high end a bit - depending of how good you can hear. (I used to, up until a few years ago, be able to hear the flyback frequencies of a TV, even a flat screen... oh well old age has caught up with me... hehe)

Keep in mind, the reason why you HEAR the RF is because a solid state component somewhere is rectifying it and turning it into audio. With this in mind, put the chokes as close to the sound card input as possible to minimize the amount of exposed cable. Most pre-made cables, unless you spend buku bucks on a Monster cable aren't 100% shielded. There are voids in the sheilding usually, if the shield wires aren't braided... the Radio Shack or Guitar Center Chinese cables aren't going to be braided. Belden wire with a foil shield is the best for this, again emphasizing the need to break out ye old soldering iron and make your own. Then you have room in the headshell of the connector to put the capacitors without playing with the surface mount stuff on the sound card!

A good pro grade sound card, like an Audio Science (several hundred dollars) have built in ferrite cores, capacitors, etc... balanced out to maintain good RF immunity and sound quality.
 
You mentioned the Delta 44. One thing to keep in mind is that the Delta 44 is not a true balanced card. Instead, it's a pseudo-balanced card (uses a resistor in the breakout box). If you wish to have a true balanced card and stick with the Delta series, you might wish to look at the Audiophile 192. Just remember that you need to use the proper driver. Currently, the most stable driver for XP is 5.10.5057V3.

I have a few Delta 44s running at different sites with the above driver and all is perfect. However, these sites don't have the RF issue discussed here.

Other nice, true balanced card are the E-MU 1212 or, better yet, the CardDeluxe.
 
My .02.... I am pro Delta 44 (they run all of my streams). I never have trouble.

I am against the Echo cards with a passion. I bought 4 of them over time and they have always done crazy sample rate related things.

If this output is important to you, you can get a new VX222 for ~350 from BSW or find one on ebay for around $200.
 
ChiefOperator said:
If you wish to have a true balanced card and stick with the Delta series, you might wish to look at the Audiophile 192. Just remember that you need to use the proper driver. Currently, the most stable driver for XP is 5.10.5057V3.
Click to expand...

I've gone through some grief recently with my Audiophile 24/96. I found that on those rare occasions where I wanted to record with a bit-rate higher than 44.1 or 48, all kinds of static and other failures occured. I read somewhere a post similar to yours. I had downloaded the driver m-audio shows as the "current" driver. So I rummaged around my hard drive and found the driver I had downloaded 4 years ago. It had 5057 in is ver number but some of the other numbers were different than what you listed. INSTANT FIX!

I have an m-audio TRANSIT for use with a laptop. (The Transit is an external device that connects via USB) It, too, had become hard to deal with and flaky. I haven't gone back and worked with driver changes on it yet.

The m-audio website is not user-friendly in helping to understand these driver options. If you are working 44.1/16 bit which would be typical in a broadcast or broadcast style set-up, the drivers may be for forgiving. If I go out and do an on-site recording of some musical student, or even a day long seminar or conference, I like the original at 96/24 so when I go to pull out a very low volume part of the music or try to salvage a question from the audience during a seminar, I want minimum recording system noise and all the possible data I can get. Not a traditional requirement for anyone doing streaming or typical broadcasting.
 
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