Ferrite Cores for Power cords

I am new to DIY and just made two power cords based on the Oyaide Tunami cable and Furutech connectors I purchased from vhaudio. My understanding is that I can possibly enhance the performance of these power cords by fixing ferrite core cylinders/boxes onto these cords. I will highly appreciate your advice/comments on the following regarding ferrite cores :

- Where can I buy them and which are the good ones/brands ? Any online source for buying these will be great.
- Should I attach them to both ends of power cords or only one end is enough ?
- Is there anything else I should know when I use them to derive maximum performance from the power cords ?
- Is it normal to attach the ferrite cores on interconnects and speaker cables as well

Please share your experiences.

Thanks in advance.
Wilfredt - I did not do extensive a/b testing with various types or brands. I read a couple of articles on line. Parts Express had a factory close out sale on Ferrites. 79 cent each for >10. I put them on everything. It seemed like a potential inexpensive, low risk tweak. In general, I put them at the end of the cord or cable closest to the device being powered or driven. (if the length of wire acts as an antenna - it seems to make sense to block the interference just before the "corrupted signal" enters a device; placement upstream did not seem like an effective way to block RF picked up downstream). I thought I heard an improvement in sound quality. Quieter and slightly more detail. It is subtle and I can't swear I'd detect a difference in a "blind test". Eventually, I might remove them and see if things sound worse. Might be worth an experiment for you as well. I will be very interested to follow any other responses you receive.
Ferrite rings filter very high frequency RFI/EMI. Most electronics stores carry them or just google and pick the right size. Ultimate Cables uses ferrite rings on both their power and speaker cords, in both cases, on the upstream side. They seem to work very well.
My experience, works well on a pc for digital, not so good on pcs for preamp or amp. I found when I tried them on the preamp or amp it caused the sound-stage to collapse somewhat. Just seemed to take the life from the music. Just a note here, my preamp and amp are tubes.

For the CDP it helped in two ways. It helped stop RFI from entering the unit through the pc and stopped the RFI generated by the CDP from going back out on the pc. I also found they worked best when installed on the pc where it entered the equipment.
Jea48, I have tried ferrite clamps extensively everywhere and you are indeed correct. Too many and it sucks the life out of a system. I think the best place to use them is on the power cord on the cdp. One on each end. Someone sent me a Analysis Plus Power Oval 2 with a ferrite clamp on each end and WOW this cord is extremely musical this way. Take the clamps off for a few minutes and more grain is added. It was very noticeable. This cord was not good on the amps but great on the cdp. My recommendation is to start at the cdp and work your way down. My system has changed recently so I may go and throw a couple of clamps on the ic's from cdp to pre. If the sound darkens or closes in they will come right off. I have not played around with these for a while except when I received the power cord I am using now.
Find a real good price on a used Power Oval 2 and put two of the box type ferrites clamps on it. I don't think enough can be said about rfi entering and exiting the cdp.
Digi-key has all kinds of ferrite clamps too.
These devices act as a choke (filter out higher frequencies that may be picked up as a cable acts like an antenna).

Generally these should not be required on a power cord or speaker cable as impedances are very low (unless you have a radio operator next door with a big antenna radiating you). The most useful application will be on video monitors or data cables that operate at high frequency with low signal levels and high impedances.
wilfredt, after reading this last night I played around with some of the ferrites I own. I tried 3 in the basement on my 20 amp circuit that powers my system. This was a nice improvement. More natural and smoother.

I also tried 3 on my virtual dynamics cable for cdp. One clamped on all 3 cables of the virtual power cord. This was another nice improvement. same as noted above.

I actually orded 60 of these on ebay and they seem to have the nicest prices. I bought some larger 11mm openings and larger ferrite to get more of the larger cables.

nice and worth the little expense considering how much these places sell their tweaks for.
Dear all, thanks a lot for sharing your experiences. I conclude it is definitely worth a try placing at different places mainly close to the CD player, especially considering the low prices involved. I shall buy some from the online sources you mentioned to play around with them.

Freemand, I could only locate one Hong Kong based source in ebay - did you buy from the same source or was there another one too.

I bought mine from Rogerdeane on ebay. I bought a ton. Actually all he had, but I am sure he will put more up. He was great...bought wednesday and recieved friday.

I have 60 of these things and will put them on everything in my house thats plugged in including every circuit that leads into my breaker box. Putting then on my systems 20 amp circuit proved to lower the noise.

the ones I bought have a nice 11 mm opening.
There are a lot of things I would like to do with the incoming power but that will have to wait. Two very young kids will put a stop to most anything that requires a lot of time on a project. I would like to try better sheilded romex on my dedicated lines eventually and I know some who have done this with good results.
Two days ago I put some ferrite clamps on my Reality cable ic's from the cdp to pre. Two clamps coming out and one clamp going in. They are not coming off of these ic's and I did not think to try them again until reading this post. These ic's are fairly new in my system and they do not have a lot of insulation/shielding around them. The high frequency did not roll off and the mid range became more coherent. Less noise less grain. One thing I did notice is that the ferrite has to fit fairly tight over the cable. These probably won't work on all ic's but the ones that do not have a lot of insulation or shielding may benefit with ferrite clamps. It Would have been interesting to put these around the Anti Cable ic's I was using at one time. Audio Metallurgy GA-0's use a magnet all the way down the middle of this ic and that seemed to roll the highs off for me too much. They are real good for a bright system. Still acts as a ferrite however.
There use to be Red Rollers, but I think the company is out of business. Appart from those used in the expensive Siltech line of cables, the Red Rollers are the only ferrites I could stand. They are quieter but at a high price in terms of the pace of the music. I retained a few Red Rollers for use in a dedicated ground but have heard they are useless on a ground.
Versalab "Red Rollers" are missed by Me, I got 6 in the '90's...lost one somehow. Adioquest made "Big Blockers", but not offered anymore.
Versalab also made "Split-rollers". I wanna find a couple, no inconvenience(struggle) to get past the bigger plug moldings on PCs.
In addition to my 5 Red Rollers, I am using the largest ones from Parts Express here and there. Under $4. bucks ea.
I consider them essential for Line Level connects.
Anyone got any Versalab "Split-Rollers" for sale?