leok Posted July 17, 2004 Share Posted July 17, 2004 After hearing my problems with smeared sibilances on the Dylan "Highway 61 Revisited" SACD, a friend, who is a professional musician, with substantial studio experience suggested that the problem sounded like RFI, and did I have a strong RF source nearby? Well, I do. The WCRB AM towers are across the street and RF is everywhere in my house wiring. I installed common-mode rf beads in the SET input .. BIG difference. I then purchased a Belkin F5C980 "Isolator" which has surge protection and several stages of RF filtration. Substantial difference there also .. that finally cleaned up the SACD top end. The audio seemed overly un-dynamic at first, but after some careful experimentation I determined that the "dynamics" that was missing was, in fact, modulated trash that had been riding on all the audio which gave it an extra, but not particularly musical, dynamic boost. The Belkin is inexpensive .. under $70 I think. I purchased it at Staples. I know many believe many line filters to more damage than good, especially non audio designs. But I like the Belkin design, and perceive no ill affects, and plenty of sonic improvement. In the case of my tube amps, because they both operate all class A, there is no variation in current drawn by the amp due to audio output variations. Class A B+ power is constant current and voltage. When power goes to the speaker, the output tube is dissipating less. It could be the inductive Belkin circuits may have a negative impact on class B operation in which there are B+ power fluctuations. Anyway, for those having trouble with noise, especially with roughness in strong high frequencies, such as sibilances, here's another line filter succes story. Leo Quote Link to comment Share on other sites More sharing options...
Deang Posted July 17, 2004 Share Posted July 17, 2004 Important stuff Leo. Is there a simple way a commoner like myself can determine whether or not RFI is at a poblematic level in the home? Quote Link to comment Share on other sites More sharing options...
thebes Posted July 17, 2004 Share Posted July 17, 2004 Great report Leo. Couple of questons though. Is the Belkin you mention simply one of those surge protector gizmos I have my computer, tv etc. hooked up to. Or is it something a bit more esoteric like those expensive boxes I see in the hi-fi stores? Also are you saying this might degrade the performance of the standard a/b reciever? Quote Link to comment Share on other sites More sharing options...
Marvel Posted July 17, 2004 Share Posted July 17, 2004 http://catalog.belkin.com/IWCatProductPage.process?Merchant_Id=&Product_Id=100991 Quote Link to comment Share on other sites More sharing options...
leok Posted July 17, 2004 Author Share Posted July 17, 2004 Dean, Are there recordings (such as the Dylan) that you listen to in which sibilances are obviously distorted, such that you are inclined to think: well, the microphone was too close, or the recording is too bright? If so, you might give the Belkin a try. I mentioned this model because I think it is effective, reasonably priced, and doesn't do any damage. If you don't have the problems I mentioned, RFI may not be an issue in your location. thebes, I selected the Belkin because it has substantial rf filtering features. It is not a "gizmo." Its features are real. I work with similar devices in industrial products and the Belkin approach is sound. It looked like a good way for me to see if such a device would make a difference. Would I want a more expensive "audio" power line filter? Maybe, but some convincing would be in order. As far as the degradation of Class AB amps .. I can't figure out how this filter could have a negative impact (even if the amp's power requirements vary substantially with output). The Belkin F5C980 (F5C960, or F5C940 based on # 0f AC sockets) is an inexpensive way to see if RFI is an issue. In the end, it may be all the protection you need. Leo Quote Link to comment Share on other sites More sharing options...
thebes Posted July 17, 2004 Share Posted July 17, 2004 Leo thanks for the response. Please understand that I was not trying to belittle the Belkin by calling it a gizmo. Although I try, and thanks to this place, I am learning, I really don't know, or claim to know all of the terminology particularly when the subject gets into things like line conditioners. As far as my question on the a/b amps/receivers, I did not read your initial post carefully enough and thought you were talking about the B+ side of the a/b amp. Actually I've been thinking for a while now about starting a topic that hopefully straightens out some of the confusion I've experience when people start talking about class a, a/b b, and now I undertand class t amps. with your permission I'd like to PM you when I have put it together to make sure I'm phrasing the topic correctly. I know it would be of value to me, and hopefully others on this board. Thanks again. Quote Link to comment Share on other sites More sharing options...
leok Posted July 18, 2004 Author Share Posted July 18, 2004 thebes, No issue at all with the "gizmo" terminology. Audio is complex, and among the solutions are plenty of devices that do no more than make one think there has been an improvement. I suspect that there are plenty of "power conditioners" that fall into this category. So, I found your question relevent in that context. If I can be helpful in sorting out amp classes or terminology I'll try to help. There are plenty of contributors to this forum who have a lot of knowledge in the field, so starting a few threads is a fast way to get a lot of information, as well as a wisecrack or two. Leo Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted July 19, 2004 Share Posted July 19, 2004 Leo: My brother also did some work for cleaning up the sound for an amateur radio club he belongs to. He said he was amazed at what he described as 'good old ferrite' beads on cables could do to filter out RF hash. I believe he has used this same technique with his music system. I think I've seen audio cables at Radio Shack with ferrite clamps, but they are probably much more expensive than a DIY installation would be. Quote Link to comment Share on other sites More sharing options...
hwatkins Posted July 19, 2004 Share Posted July 19, 2004 Thanks Leo - very useful information. As one who has lost hair over this same type of problem it does look like you have implemented a good solution. Thanks for the info - You win the 'practical solution implemented and tested' award for the month of July. Quote Link to comment Share on other sites More sharing options...
ben. Posted July 19, 2004 Share Posted July 19, 2004 ---------------- On 7/19/2004 7:22:42 AM Erik Mandaville wrote: Leo: My brother also did some work for cleaning up the sound for an amateur radio club he belongs to. He said he was amazed at what he described as 'good old ferrite' beads on cables could do to filter out RF hash. I believe he has used this same technique with his music system. I think I've seen audio cables at Radio Shack with ferrite clamps, but they are probably much more expensive than a DIY installation would be. ---------------- Those ferrite beads are cheap as heck as an appliance part. If anyone wants to try some, email me. They're under $5, I'm pretty sure. I don't know what they sell for elsewhere, though. Quote Link to comment Share on other sites More sharing options...
leok Posted July 19, 2004 Author Share Posted July 19, 2004 bclarke421, The input common mode chokes (ferrite beads) are very inexpensive, and effective, but only part of the solution. the ones I used are: Mouser: 434-6H-102 434-6H-102 Fastron Wide Band Chokes 4LD 1.5 TRN 490 OHM. The rest of the solution, filtration of AC power, was not so simple. I wanted power line filtration to clean up the digital source, which had already proven itself to be noisy. The Belkin proved effective. I'm sure there are more surgical solutions, but power line trash is ubiquitous and general noise reduction can be very effective. The Belkin addresses that. The finer filtration is still up to the application. Leo Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted July 19, 2004 Share Posted July 19, 2004 Leo: The other thing I wanted to mention as something I think would be extremely effective is an isolated, balanced AC supply. There are a number of companies that sell these, most of which are far too expensive for my taste and budget. This must be a tremendous help with line noise reduction, and doing a search on this, I found that Transcendent Sound sells just such a device in a nice looking chassis for a much more reasonable cost. I have a DIY friend in Germancy who builds his own amps and speakers (he went from his own SE 2A3 amps to the SE OTL), and also recently bought the toroidal transformer based balanced line supply, as well. I have also found a couple of companies that sell these transformers, and have seriously contemplated building my own version of this in an inexpensive Hammond chassis. Can you be a little more specific about what is going on inside the Belkin? does it provide transformer derived isolation from the house supply? If so, the cost you quoted is really good. Erik Quote Link to comment Share on other sites More sharing options...
leok Posted July 20, 2004 Author Share Posted July 20, 2004 Erik, There are inline and common mode ferrite inductors and caps before each pair of AC outlets (4 pairs in this case). That's 4 instances of filter sets. They are in series so the last pair is the most filtered from the line itself and the pairs are all isolated from each other. There are also MOVs for spike protection. I've thought of isolation xfmrs. They are expensive. Leo Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted July 20, 2004 Share Posted July 20, 2004 I agree, those transformers are expensive! Thanks for the description, Leo. I installed an MOV across the primaries of both power transformers, but they only provide spike relief. I think I will look into one of those Belkin devices when I can. Quote Link to comment Share on other sites More sharing options...
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