• 03-17-2012, 06:30 AM
    Feanor
    Trying a famous Magneplanar tweak
    I'm trying the famous tweak for Magneplanar quasi-ribbon drivers, in my case my MG 1.6QR's tweeter. This consists of putting a low-value inductor (choke) in series with the quasi-ribbon drive to prevent RFI from entering or leaving the driver.

    The notion here is that the quasi-ribbon is an excellent radio frequency antenna and that the RFI will feed back into the amplifier causing distortion, e.g. grain and degraded sound, especially high frequencies. If a person is using a class D amp as I am, the potential to improve sound would seem very good given the reputed sensitivity of these amps to RFI/EMI.

    I selected a Bourns JW Miller high current ckoke, the 5502-RC, whose specs are 10 microHenry, .017 ohms, 9 amps. Note: any higher inductance than 10 uH will attenuated in the audible range.

    So far I don't hear much difference but I'll listen some more. Other folks, notably Dawnrazor, have claimed huge improvements. Of course it would depend on one's RFI/EMI environment and associated equipment.
  • 03-17-2012, 08:00 AM
    blackraven
    Very interesting! My CDA-254 puts out a lot of RFI but it is in a wood case. I am going to put it in a Par Metal Aluminum Alodine case vs the Anodized because it has better RFI/EMI blocking. Plus I may line it with copper foil. In addition, I am going to use IC's with very good shielding..
  • 03-17-2012, 08:19 PM
    E-Stat
    Quote:
    Originally Posted by blackraven View Post
    Very interesting! My CDA-254 puts out a lot of RFI but it is in a wood case. .
    Tune an AM radio off station near the unit. I suspect you'll hear the interference.
  • 03-17-2012, 10:02 PM
    blackraven
    Quote:
    Originally Posted by E-Stat View Post
    Tune an AM radio off station near the unit. I suspect you'll hear the interference.
    I have already heard the interference when my Tuner was placed underneath it. It caused very loud interference when the tuner was within 6 feet of the amp. It makes me wonder if that's the reason the guy I bought it from sold it. We will see what happens when it is in the EMI/RFI shielding Alodine chassis.
  • 03-18-2012, 05:27 AM
    E-Stat
    Quote:
    Originally Posted by blackraven View Post
    It makes me wonder if that's the reason the guy I bought it from sold it.
    That's what all switching amps do.

    Quote:
    Originally Posted by blackraven View Post
    We will see what happens when it is in the EMI/RFI shielding Alodine chassis.
    My passive consists of DACT attenuators in a Par-Metals cabinet. Prices have gone up a bit in nine years though!

    Good luck with your project.
  • 03-18-2012, 11:01 AM
    Feanor
    Quote:
    Originally Posted by blackraven View Post
    I have already heard the interference when my Tuner was placed underneath it. It caused very loud interference when the tuner was within 6 feet of the amp. It makes me wonder if that's the reason the guy I bought it from sold it. We will see what happens when it is in the EMI/RFI shielding Alodine chassis.
    My FM tuner is located about 3.5' above my SDS-258 amp and it causes no interference. Is AM different? AM is at lower radio frequencies of course.

    I use a Belkin PureAV PF60 that has outlet banks isolated for RFI/EMI; my SDS, DAC, and CD player are on different banks. Also, I use a shielded PS Audio power cord for the amp.

    My amp is in a wood & MDF case. I lined the top cover with aluminum foil held in place with spray contact cement. (The amp is located several feet below other components as intimated.) Aluminum foil is supposed to work quite well according to some sources so maybe copper foil is a bit over the top.
  • 03-21-2012, 12:15 PM
    JoeE SP9
    Aluminum foil works quite well keeping these alien voices from interfering with my brain.:devil:
  • 03-21-2012, 01:38 PM
    Feanor
    I'm endorsing this tweak. For the small money involved it's no-brainer for folks with Magneplanar quasi-ribbons. If it works for your great; if it makes no difference you aren't out much.

    My system has never sounded better than in the last few days. Granted, I made two concurrent changes: (1) this RFI choke tweak, and (2) a new DAC. To a limited extent I've tried the choke with and without the DAC and vice versa. Though I'm inclined to say that most of the improvement is from the DAC, I can safely say the choke did no harm and likely added a bit to the improvement I heard. See the "Cheap DAC" thread here for my update.
  • 03-22-2012, 09:08 AM
    GMichael
    Hmmm.... Interesting. I'm glad to read that this tweak works for you. I wonder how much difference it makes if you live near a large city with many radio stations or far from any city.
  • 03-22-2012, 12:45 PM
    Feanor
    Quote:
    Originally Posted by GMichael View Post
    Hmmm.... Interesting. I'm glad to read that this tweak works for you. I wonder how much difference it makes if you live near a large city with many radio stations or far from any city.
    Yeah, I wonder. On the other hand I suspect it would have more to do with the radio frequency devices you have in your house and their proximity to the speakers.