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  • Stabilizing VPI unipivots with magnets

    This is an analog-heavy site, so I hope a few will appreciate my approach to stabilizing my JMW 10.5i with magnets, for truly exceptional results. The following are copied from my posts on vpiindustries.com and whatsbestforum.com

    The specs are:

    1) Two Stock 3mmx1.5mm (3/16" x 1/16") N52 Neodymium round magnets in the arm base from K&J Magnetics (https://www.kjmagnetics.com/proddetail. ... 52&cat=168); and

    2) Two Custom 20.7mm inner diameter, 31mm outer diameter, 0.8mm (1/32") thick N35 Neodymium ring magnets from SM Magnetics (https://supermagnetman.com/collections/neodymium/rings)

    All magnets are axially magnetized. Because the various VPI arms may slightly differ, it's important to accurately measure the inner diameter with a caliper - and I measured 20.64mm for the base, hence the 20.7mm ID spec - and for the outer diameter, the goal was to place the opposing magnets right over the outer edge of the ring magnets (hence the 31mm OD spec).

    Keep in mind that K&J Magnetics does not make 0.8mm thick magnets, only as low as 1.6mm, and that's why I went to SM Magnetics. The reason for going for 0.8mm thick rings is to be able to stack them up, if need be, and it was necessary (quicker and stronger stabilization).

    Azimuth adjustment can still be achieved by severe rotation of the counterweight, or by moving the round magnets a tiny bit off center. VTF impact was minimal, because of where the round magnets were placed.

    I would not go lower than N35 grade rings, so N28 for example won't do. I feel that any VPI unipivot arm can be stabilized with this technique.

    A quick demonstration movie can be found at https://youtu.be/Y2z3g6xyshM

    One of the additional benefits of using repulsive forces is how quickly VTF stabilizes on the gauge, something that is not true with the original arm. The other not so obvious benefit is that the arm's azimuth is no longer affected by the wires sticking out of the arm, because of the considerable repulsive force. The obvious benefit is that the arm is extremely stable during play. And the sonic results: stable imaging, much more accurate timbre, very taught and tight bass.


    Analog: VPI Aries 3, custom suspension + platter interface || Magnetically stabilized JMW 10.5i || Ortofon A90 || Modded & fully shielded Pass XP-25 || Last gen VPI SDS speed controller || Magnum Dynalab MD-90SE/105 Digital: Spectral 3000SL || Fully shielded Yggdrasil 2 Amplification: Spectral DMC-30SV || DMA-500AR Speakers: Heavily modded MartinLogan (custom Mundorf dual xover, cabling, woofers, xformer; structural mods) || Modded REL sub Cabling: Fully shielded MIT Oracle 50ic,MA-X,90.1 || Shunyata Alpha v2,Omega AES/EBU Power: Shunyata Denali 6000/S v2, Venom XC and NR cords, SR-Z1 outlets, Typhon. Tweaks: Isodamp, mumetal, 3M AB5100, Dynamat, Copper foil; Vishay diodes, resistors, Mundorf coils & capacitors

    Link

  • #2
    Elegant and effective design. Kudos.
    Speakers/Amps: Genesis G2.2 Jr with Powered Servo-Sub Bass, Genesis GR1440 Mono Amps, 5,000 watts total power
    Preamp: SMc Audio VRE-1C Preamp (fully balanced inputs and output)
    Analog 1: VPI Signature 21 Belt-Drive Turntable w/ 10” 3D Printed Fatboy Gimbal Arm and Ortofon MC Windfeld Ti Phono Cartridge driving Lehmann Silver Cube Phono Preamp
    Analog 2: VPI HW-40 Direct-Drive Turntable w/ 12” 3D Printed Fatboy Gimbal Arm and Ortofon MC Anna Diamond Phono Cartridge driving Genesis Gold Phono Preamp
    Analog 3: Studer A810 R2R tape w/ Bridge Console. Using built-in tape preamp
    Digital: Lumin Network Player with Lumin NAS
    Cables: Genesis Advanced Technologies/Absolute Fidelity Interface Interconnects, Speaker, Phono and Power
    A/C Power: Extensive System Upgrades, Sub-panel w/hard-wired power cables, and IsoTek Super Titan Passive Power Conditioning for Amplifiers
    Accessories: Custom Acrylic Equipment Stands, Klaudio Ultrasonic RCM

    Comment


    • #3
      Thanks for the post Ack! But wouldn't this be redundant in light of the new dual pivot version of the 3D arm?
      Myles B. Astor, PhD, Administrator
      Senior Editor, Positive-Feedback.com
      ________________________________________

      -Zellaton Plural Evo speakers
      -Goldmund Telos 300 stereo amp
      -Goldmund Mimesis 37S Nextgen preamplifier
      -Doshi EVO and Goldmund PH3.8 phonostage
      -VPI Vanquish direct-drive turntable
      -VPI 12-inch 3D Fat Boy dual pivot tonearm, VPI 12-inch 3D Fat Boy gimballed and SAT LM-12 arm
      -Lyra Atlas SL Lambda, Fuuga Mk. 2, vdh Colibri Master Signature, MutechHayabusa, MOFI Master Tracker, Sumiko Songbird cartridges
      -Technics RS1506 with Flux Magnetic heads, Doshi V3.0 tape stage (balanced)
      -Assorted cables including Transparent XL Gen. 6, Skogrand, Viero, Kubala-Sosna, Audience Au24SX, Genesis Advanced Technologies and Ensemble Power Cords
      -Accessories including Stillpoint Aperture panels, Cathedral Sound panels, Furutech NCF Nano AC receptacles; Silver Circle Tchaik 6 PLC, Symposium ISIS and SRA Craz 3 racks, Audiodharma Cable Cooker, Symposium Ultra and assorted SRA OHIO Class 2.1+ platforms.

      Comment


      • #4
        I don't think so - smaller [smallest] contact area
        Analog: VPI Aries 3, custom suspension + platter interface || Magnetically stabilized JMW 10.5i || Ortofon A90 || Modded & fully shielded Pass XP-25 || Last gen VPI SDS speed controller || Magnum Dynalab MD-90SE/105 Digital: Spectral 3000SL || Fully shielded Yggdrasil 2 Amplification: Spectral DMC-30SV || DMA-500AR Speakers: Heavily modded MartinLogan (custom Mundorf dual xover, cabling, woofers, xformer; structural mods) || Modded REL sub Cabling: Fully shielded MIT Oracle 50ic,MA-X,90.1 || Shunyata Alpha v2,Omega AES/EBU Power: Shunyata Denali 6000/S v2, Venom XC and NR cords, SR-Z1 outlets, Typhon. Tweaks: Isodamp, mumetal, 3M AB5100, Dynamat, Copper foil; Vishay diodes, resistors, Mundorf coils & capacitors

        Link

        Comment


        • #5
          Wouldn't this be kind of defeating the purpose of the unipivot arm itself? It is a great idea but seems like it detracks from the original design...

          Comment


          • #6
            Side-to-side stability/wabble has always been an issue with unipivots, thats why I don't use them. There are several strategies to deal with the wabble issue. A magnetic approach is good, effective and maintains the single point/low friction bearing. Ack's approach is simple, and economical = excellent value.

            The ultimate solution is to set the unipivot with a bias to one side and slide along a bearing surface. The first time I saw this is with the SPJ arm on the Spotheim La Luce table. And with Durand's latest arm. It is very expensive to manufacture. These designs should not be confused with knife edge or twin point bearings.
            Speakers/Amps: Genesis G2.2 Jr with Powered Servo-Sub Bass, Genesis GR1440 Mono Amps, 5,000 watts total power
            Preamp: SMc Audio VRE-1C Preamp (fully balanced inputs and output)
            Analog 1: VPI Signature 21 Belt-Drive Turntable w/ 10” 3D Printed Fatboy Gimbal Arm and Ortofon MC Windfeld Ti Phono Cartridge driving Lehmann Silver Cube Phono Preamp
            Analog 2: VPI HW-40 Direct-Drive Turntable w/ 12” 3D Printed Fatboy Gimbal Arm and Ortofon MC Anna Diamond Phono Cartridge driving Genesis Gold Phono Preamp
            Analog 3: Studer A810 R2R tape w/ Bridge Console. Using built-in tape preamp
            Digital: Lumin Network Player with Lumin NAS
            Cables: Genesis Advanced Technologies/Absolute Fidelity Interface Interconnects, Speaker, Phono and Power
            A/C Power: Extensive System Upgrades, Sub-panel w/hard-wired power cables, and IsoTek Super Titan Passive Power Conditioning for Amplifiers
            Accessories: Custom Acrylic Equipment Stands, Klaudio Ultrasonic RCM

            Comment


            • #7
              the graham phantom supreme uses magnets to stabilize side to side wobble
              Magnepan 1.6 QR Loudspeakers, Amherst A-2000 MOSFET 150 WPC Amp, Conrad Johnson PV-10A Modded Tube Line & Phono Stage, Electrocompaniet MC II Class A Head Amp, Audio Technica AT-OC9XML Cart (Stereo) , Graham Engineering 2.2 Tonearm (Stereo) , VPI Aries-1 Turntable (Stereo) , VPI Clamp, Denon DL-102 Cart, (Mono) , Luxman Tonearm (Mono) , Kenwood KD-500 Turntable (Mono) , Michell Clamp, Marantz 20B Analog FM Tuner, Pioneer SACD, Onkyo DX-6800 CD Transport, DIY 24B/192K DAC, Sennheiser HD-650 Headphones, Headroom Max Balanced Headphone Amp, DIY Silver Interconnects

              Comment


              • #8
                What Joe Pittman said - the modified arm is still a unipivot, and wobble is a real sonic issue and has always been with unstabilized unipivots. My WBF thread includes a video of the wobble problem.
                Analog: VPI Aries 3, custom suspension + platter interface || Magnetically stabilized JMW 10.5i || Ortofon A90 || Modded & fully shielded Pass XP-25 || Last gen VPI SDS speed controller || Magnum Dynalab MD-90SE/105 Digital: Spectral 3000SL || Fully shielded Yggdrasil 2 Amplification: Spectral DMC-30SV || DMA-500AR Speakers: Heavily modded MartinLogan (custom Mundorf dual xover, cabling, woofers, xformer; structural mods) || Modded REL sub Cabling: Fully shielded MIT Oracle 50ic,MA-X,90.1 || Shunyata Alpha v2,Omega AES/EBU Power: Shunyata Denali 6000/S v2, Venom XC and NR cords, SR-Z1 outlets, Typhon. Tweaks: Isodamp, mumetal, 3M AB5100, Dynamat, Copper foil; Vishay diodes, resistors, Mundorf coils & capacitors

                Link

                Comment


                • MylesBAstor
                  MylesBAstor commented
                  Editing a comment
                  Do you have wobble on your arm? I don't see wobble on my arm.

                • ack
                  ack commented
                  Editing a comment
                  There are a number of factors that can cause wobble, e.g. off-center disc, heavy bass or passages, vertical undulations. If you observe the arm carefully, especially from the rear, you can easily see it wobble. I can easily hear it with a 1kHz tone by standing right in the middle of the speakers at the speaker plane, and the image constantly shifts L/R/L/R/L/R... it's quite evident on the Revox's VU meters too.

              • #9
                My graham 2.2 uses weights and silicone fluid to minimize wobble.
                Magnepan 1.6 QR Loudspeakers, Amherst A-2000 MOSFET 150 WPC Amp, Conrad Johnson PV-10A Modded Tube Line & Phono Stage, Electrocompaniet MC II Class A Head Amp, Audio Technica AT-OC9XML Cart (Stereo) , Graham Engineering 2.2 Tonearm (Stereo) , VPI Aries-1 Turntable (Stereo) , VPI Clamp, Denon DL-102 Cart, (Mono) , Luxman Tonearm (Mono) , Kenwood KD-500 Turntable (Mono) , Michell Clamp, Marantz 20B Analog FM Tuner, Pioneer SACD, Onkyo DX-6800 CD Transport, DIY 24B/192K DAC, Sennheiser HD-650 Headphones, Headroom Max Balanced Headphone Amp, DIY Silver Interconnects

                Comment


                • ack
                  ack commented
                  Editing a comment
                  Yes, damping by viscous action

              • #10
                Well I have a VPI for years, now I have the Triplanar and there is no going back. The ability to adjust the Triplanar to no end is the cat's meow for me!!!

                Comment


                • #11
                  Originally posted by JCOConnell View Post
                  the graham phantom supreme uses magnets to stabilize side to side wobble
                  And I might add, ladies and gentlemen, that the design is patented..! So hobbyists can do as they wish, but anyone with ideas of produciton should be aware that we spent a lot of time and $$ in this design, and would not smile favorably on any commercial pretenders... The Phantom (AKA Bob Graham, hisself....)

                  Comment


                  • #12
                    Bob, what's your patent's number? Would love to read what you have done. The results of my stabilization are a little short of astonishing
                    Analog: VPI Aries 3, custom suspension + platter interface || Magnetically stabilized JMW 10.5i || Ortofon A90 || Modded & fully shielded Pass XP-25 || Last gen VPI SDS speed controller || Magnum Dynalab MD-90SE/105 Digital: Spectral 3000SL || Fully shielded Yggdrasil 2 Amplification: Spectral DMC-30SV || DMA-500AR Speakers: Heavily modded MartinLogan (custom Mundorf dual xover, cabling, woofers, xformer; structural mods) || Modded REL sub Cabling: Fully shielded MIT Oracle 50ic,MA-X,90.1 || Shunyata Alpha v2,Omega AES/EBU Power: Shunyata Denali 6000/S v2, Venom XC and NR cords, SR-Z1 outlets, Typhon. Tweaks: Isodamp, mumetal, 3M AB5100, Dynamat, Copper foil; Vishay diodes, resistors, Mundorf coils & capacitors

                    Link

                    Comment


                    • #13
                      I think this is it:
                      https://www.google.com/patents/US7382713
                      Analog: Holbo Turntable, Transfiguration Proteus; Forsell Air Reference, Transfiguration Phoenix S; Rega RP-8, VdH Crimson XGW; VPI Prime Signature, VAS Nova Mono, VAS Nova Signature, Symphonic Line RG-8
                      Digital: Mac mini 6,2 with YFS PS-12M LPS; Exogal Comet Plus, Exogal Ion PowerDAC
                      Electronics: Aurorasound Vida, Channel D Lino C; Merrill Cara, Gryphon M-100 Mkii (pair)
                      Cables: Morrow, Gryphon interconnects; YFS USB cable; Morrow, XLO, Channel D phono cables; Morrow, Gryphon, Goertz speaker cables

                      Comment


                      • #14
                        JCMusic....just wondering.....what adjustment does your TriPlaner provide that the VPI is wanting?

                        Comment

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