Do all switching amps generate RFI?

warnerwh · « **on:** 27 Sep 2006, 03:32 am »

And does anybody use a switching amp that also listens to a FM tuner? I just read again that even the latest Nuforce 9SE generates RFI. After this many upgrades to this amp I'm surprised it still has this problem.

Maybe I'm the odd one as I listen to FM regularly and would never risk owning something that may cause problems. This RFI could also add noise to the system elsewhere I'd think.

If someone has technical knowledge and measurements that will show that some of these amps don't emit any RFI that could conceivably be significant I'd appreciate your input. Thanks

TheChairGuy · « **Reply #1 on:** 27 Sep 2006, 03:49 am »

Warner,

Just happened to me yesterday...

I had a switching power supply (wart type unit used to charge DC batteries) still plugged in to my BPT. I happned to have it on same outlet as my turntable. It wasn't connected to anything, but as they do not have on-off switches, it was powered on.

I happened to be listening to my TT at the time...and upon pulling the power wart from the BPT, I immediately noticed a layer of grunge removed. I couldn't believe it...the draw on this thing is only 0.5 amps, but it absolutely polluted the analog turntable output.

My computer is in my office, which is also my listening room. Despite all the power conditioning I have, things sound cleaner/better when I've turned off the computer completely (it is run thru a Brick Wall power filter and my audio system has a brick wall, the BPT and an effective Enacom mains filter in an unused outlet receptacle)

On the other hand, I used the JVC digi-receivers for quite some time...and noticed no such contamination with them plugged in or not. These receivers have small toroids, not switched supplies, btw. But, the FM in the last model I owned, the F10, was completely worthless. I assume due to RFI spewing out.

So it may be, all amps with switched power supplies generate garbage, but amps with linear supplies (transformers) do not. I'm not engineer, nor is my testing subjects vastly wide enough, it's just seems like it pointing to that, at least.

I owned a TEAC A-L700P with switched power supply, and don't remember if that contaminated the rest of the system. I was just so simply shocked how dang good that thing was for $99.00 with oodles of mains conditioing that I never bothered to check

Midnite Mick · « **Reply #2 on:** 27 Sep 2006, 03:56 am »

Intesting.

So are there even any solutions to this. Got me wondering as a Nuforce ref 9 owner maybe my sound could be cleaner.

Mike

Occam · « **Reply #3 on:** 27 Sep 2006, 04:19 am »

Resist.

I shall resist that lob that the devil tempts me with.

Edit - I don't want to imply that all (or even most) switching supplies or switching amps are guilty.... just those from manufacturers, no matter how highly reviewed, who can't even figure out to twist their output wires going to an output CMC, or install components as if they wish them to act like antennas.

Charles Calkins · « **Reply #4 on:** 27 Sep 2006, 04:42 am »

Warnerwh:
Like you I isten to a lot of FM(KKSF 103.7) I have the Ciaudo D-200's and do not have any RFI interference(I guess) Once in a while the comcast cable co. takes a big crap and has an effect on FM reception. Then I listen in mono for a few days and after that everything is back to normal. I have gotten an unbearable hum in my system and it always involves the cable FM. When I disconnect the coax lead to the tuner the hum goes away.

Cheers
Charlie

brj · « **Reply #5 on:** 27 Sep 2006, 05:01 am »

While the D200s do have switch mode amplifier modules (via Hypex), their power supplies are linear. They do not use switching mode power supplies (SMPS).

NuForce amps use switching mode power supplies as well as switching mode amplifier modules.

I have often seen switching mode power supplies (as a general class of components) criticized for high levels of RM or EM output, but I have not seen specific discussions comparing the RF or EM output of switching mode power supplies vs. switching mode amplifier modules.

warnerwh · « **Reply #6 on:** 27 Sep 2006, 05:04 am »

Thank you guys for the info so far. One thing that dawned on me a little while ago is that it appears I could be picking on Nuforce. That's not the case at all. A guy on another forum has been having an ongoing review of his new 9SE's and today he stated that it does emit RFI, that's the only reason I used the Nuforce amp as an example. A local Vmps owner has Nuforce amps and likes them, his ears for accuracy are no doubt better than mine being as he's a professional musician. My concern is where are we at when it comes to the switching amp evolution.

The reason I'm curious is even though I'm somewhat conservative I think a high powered switching amp for my bass section on my speakers may be a good option. I like the idea of little heat. Also I've heard a custom built and stock switching amp and liked what I heard. Both were quite different though. If I could find a well designed small efficient but high powered amp to drive my woofers I'd be inclined to try it. Otherwise I'll just get a linear amp. The one drawback though is I listen to fm radio alot as we have a great jazz station that also has a high quality(non compressed or only slightly) broadcast. Therefore no noise issues are acceptable.

I know a person in Washington with the CIA amps and he really likes them. As a matter of fact he compared them to the Van Alstine I have that I bought from him as being similar. I use the Van Alstine amp on the mid/tweeters. That's high praise imo. He singled out the quality of the bass on his large woofers as one of it's better attributes too. Unfortunately that's not enough power.

If someone knows of a good money back guarantee or used switching amp with alot of cajones I may like to try it. I'd need some convincing that it would work in my application well first. Christmas is coming and it's important I think of myself

Thanks brj for the info. That's something I'd not been aware of. I've not really delved into those type of amps as I'm an older guy and pretty conservative. However I like the idea of high efficiency. Someone needs to write an article to sort everything out for the average person. All these different models using Icepower, class T, Ucd etc. It's another language to me.

I just want an amp that will put out at least 250wpc and double that into 4 ohms or so minimum. Something that has stupendous bass and a wonderful midrange. Also perfect reliability. I think these cooler running amps should have lower failure rate, all else being equal, which it never is.

jules · « **Reply #7 on:** 27 Sep 2006, 05:43 am »

Warnewh,

I'm not an expert on Nuforce amps by any measure but as I understand it, the problem with RF is sort of inherent in the technology [at the moment?] and the "solution" applied to later models is still a compromise with other drawbacks. If they could eliminate the problem I'm sure they would have by now.

As far as switching power supplies go, I use one myself though it's a largish 1800W model [Xantrex Prosine inverter, 24V DC to 240V AC] and not a wall wort. I have absolutely no interference from the inverter.

I'm also looking at a similar issue to you at the moment in that I'm going to expand an MTM speaker system to add a bass.

Jules

John Casler · « **Reply #8 on:** 27 Sep 2006, 06:21 am »

Hi Warner,

I can't say if all switching amps cause the problem, but as a NuFORCE dealer I have had several pair.

My first two (early) pair not only interfered with my FM, but my TV reception too.

Now the last pair and the ones I'm using now, have absolutley NO effect on either.

I ran all pairs off a BPT Balanced Power Conditioner, so that had no bearing on the change, and I used the same balanced and single ended cables on all.

Kevin Haskins · « **Reply #9 on:** 27 Sep 2006, 07:26 am »

Yes.... all switching amplifiers have switching noise at some level. Properly engineered switching amplifiers control it so that it doesn't interfer with either tuner, television or any other external devices. To get something through normal FCC testing you have to pass standards. If you design and exceed those standards you won't cause problems.... period. If you have tuner problems the only reason is because the designer didn't meet FCC standards.

Also I'd like to point out that you don't hear this noise directly (don't laugh). Its only effect is in interference with other electronic equipment. That other electronic equipment can be your tuner, television or other electronic equipment in your audio chain. It is common practice to use RFI filters on the inputs of audio gear (PCB board level). The reason is because it can cause unexpected oscillation in a circuit which can manifest itself in very audible ways. Not positive ones either.

The bottom line is its just good engineering practice to control radiated and conducted noise. It is VERY doable with both SMPS power supplies and switching amplifiers but you need to know what your doing on the design side.

For those with their pocket protectors.

http://www.smps.us/standards.html

warnerwh · « **Reply #10 on:** 27 Sep 2006, 07:40 am »

Kevin: So does this mean these amps will have some sort of UL type rating? Something that will let you know for sure it will not contaminate the rest of your system? Any recommendations on a high powered amp that must be very well designed for me to buy it. Thank You

Dan Banquer · « **Reply #11 on:** 27 Sep 2006, 11:45 am »

Quote from: warnerwh on 27 Sep 2006, 07:40 am

Kevin: So does this mean these amps will have some sort of UL type rating? Something that will let you know for sure it will not contaminate the rest of your system? Any recommendations on a high powered amp that must be very well designed for me to buy it. Thank You

UL is concerned with safety only, for issues such as electrical shock or fire hazard. The present FCC rules appear not only to be rather lax, but not enforced.
d.b.

Scotty · « **Reply #12 on:** 27 Sep 2006, 04:49 pm »

Here is my suggestion for a rather simple way to test for RFI radiated from the speaker wires. Buy a small portable AM/FM radio and check for AM and FM bandwidth interference by holding the radio near the speaker wires while playing music through the amp.
Scotty

Kevin Haskins · « **Reply #13 on:** 27 Sep 2006, 08:07 pm »

Quote from: warnerwh on 27 Sep 2006, 07:40 am

Kevin: So does this mean these amps will have some sort of UL type rating? Something that will let you know for sure it will not contaminate the rest of your system? Any recommendations on a high powered amp that must be very well designed for me to buy it. Thank You

Dan is right...UL is safety related. Most high end audio companies are small. Very few of them go through UL & FCC testing for approval because its cost prohibitive. You can easily eat up $10,000 and several months trying to get the UL approval. Make one change to your design and you have to go through it again. It just doesn't work out for companies my size.

FCC isn't quite as bad but it is still cost prohibitive. It ISN'T cost prohibitive to design equipment to those standards though. In fact... it cost very little to meet the standards, it is the process and the stamp of approval that you pay for.

Dan is also right in that there are a lot of foreign companies that don't go through the process and put the stamp on their product anyway.

Fraud is the norm for many societies and some of them are puzzled by our desire to play by certain rules. There really isn't any enforcement of any of these programs outside of the obvious legal & liability issues. I'm not forced to get UL approval. If you design an RF communication device I'm fairly certain you DO need to seek FCC approval. An audio amplifier isn't supposed to be an RF transmitting device though so there isn't any necessity for seeking FCC approval.

So... how do you know which companies use good design? I'd say it is rather obvious. Just do a quick search for the product name and if you see a couple hundred situations where there are obvious consumer RFI problems that might be a hint.

For me.... I wouldn't sell a product that didn't meet those standards. All of the Hypex UcD products have ZERO RFI noise issues, either conducted or radiated. Since I've been selling them I've not had even ONE instance of a customer having interference problems with another device..... not one. I've sold them to small OEMs, labs and many many diverse applications where the customers were putting them in enclosures with other electronic equipment and not once have we had a noise related issue. Why??? Bruno Putzeys spent years at Philips running their Class D program. Philips obviously had to design products that met and exceeded FCC standards. It is simple engineering skill and experience.... not voodoo BS.

In terms of safety.... I'm down right anal. I don't want to be responsible for hurting anyone. It is part of the reason that I design the enclosure to exceed UL standards. I double insulate everything possible and safety ground the chassis. Every amplifier we sell also has short circuit/overcurrent protection, DC protection and is fused to prevent the amplifier going into thermal overload from a failed MOSFET or external short. It is just responsible business ethics to make sure what you put out the door is bullet-proof as possible. It doesn't cost that much more to overbuild for safety and in high-end audio where a couple dollars in the final price is irrelevant, why not build to higher standards?

nathanm · « **Reply #14 on:** 27 Sep 2006, 10:36 pm »

Right on, Kevin! Why indeed spend money to have some bureaucrat flunkie generate paperwork when all you really need to do is please the CUSTOMER!

ACME Hi-Fi has to satisfy my needs and make me happy before they get my money, the FCC gets paid either way.

Kevin Haskins · « **Reply #15 on:** 28 Sep 2006, 12:01 am »

Quote from: nathanm on 27 Sep 2006, 10:36 pm

Right on, Kevin! Why indeed spend money to have some bureaucrat flunkie generate paperwork when all you really need to do is please the CUSTOMER! ACME Hi-Fi has to satisfy my needs and make me happy before they get my money, the FCC gets paid either way.

If your a big enough company your lawyer and insurance company will make you to get that UL approval. The consumer pays for it but small fish (most high end audio companies) go under the radar.

Midnite Mick · « **Reply #16 on:** 28 Sep 2006, 12:15 am »

Quote from: Scotty on 27 Sep 2006, 04:49 pm

Here is my suggestion for a rather simple way to test for RFI radiated from the speaker wires. Buy a small portable AM/FM radio and check for AM and FM bandwidth interference by holding the radio near the speaker wires while playing music through the amp.
Scotty

I am fairly new to the whole audio thing and don't really even know what all these abreviations stand for or what they are but I just tried this with some newer (bought in spring) Nuforce ref 9.02's and could not get an FM signal at all. I did not even have to play anything, all I had to do was power them up. If this is indeed being emitted from the speaker wires then does this imply that shielding of the wires is also a factor. I am just using 12 gauge magnet wire.

I don't remember names as I am typing this but I wonder why the Summit guy (apologies) is not experiencing this with his newer models.

Second poster, no need to hold back.

Lastly, Mr. Haskins I appreciate your regard for the consumers and professionalism in the way you do business. I wonder how your amp modules compare to the Nuforces as these type of amps appeal to me more than the SS monsters. I feel like I am tending to lean more to the DIY in audio like the rest of the other fields that I have always done myself (maybe I am just cheap

)I am looking forward to the completion of the Exodus 2641 kit as I am getting close (finally).

I hope this thread continues so I can try to put some of the pieces together and come away with a new understanding (wish I knew more about electronics - would read more but soooo many projects on the go and in mind)

Thanks,
Mike

John Casler · « **Reply #17 on:** 28 Sep 2006, 02:09 am »

Quote from: Midnite Mick on 28 Sep 2006, 12:15 am

I don't remember names as I am typing this but I wonder why the Summit guy (apologies) is not experiencing this with his newer models.

I hope this thread continues so I can try to put some of the pieces together and come away with a new understanding (wish I knew more about electronics - would read more but soooo many projects on the go and in mind)

Thanks,
Mike

Hi Mike,

I am that Summit Guy.

You know, now that I think about it, I did go back to using my AudioQuest Volcano Speaker cables, instead of the Gibraltars.

Both are AudioQuest, but I think the Volcano has more shielding.

When I get time, I'll have to switch back and see.

Midnite Mick · « **Reply #18 on:** 28 Sep 2006, 03:22 am »

Thanks John. I have some apature silvers that have alot of shielding I may have to try with these as well.

Mike

John Casler · « **Reply #19 on:** 28 Sep 2006, 03:30 am »

Quote from: Midnite Mick on 28 Sep 2006, 03:22 am

Thanks John. I have some apature silvers that have alot of shielding I may have to try with these as well.

Mike

Hi Mike,

If you're talking about the Accusound Silver, I'm not sure how sheilded it is unless John has beefed up the sheilding, since I got mine.

I have tried them on the Ref 9.02, and in their price range they have a wonderful sonic quality.

Very Natural

and Relaxed