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Thread: Custom Arm Mounting Collar for Jelco SA-750 - essential for setting correct azimuth

  1. #1
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Exclamation Custom Arm Mounting Collar for Jelco SA-750 - essential for setting correct azimuth

    Many watchers here will be aware that I have a bit of a bugbear with the arm mounting collar for my Jelco SA-750D. Specifically, there is vertical wobble of the arm pillar that can (and does) result in quite significant azimuth errors as the arm tracks the record. The fault lies in the design of the Jelco collar, which has an undersize hemispherical cutout to one side of the pillar hole, which should ensure that the arm pillar fits snugly and vertically, when pressed against this cutout. This is very similar to the design of my Ittok LVII's collar, but in the case of the Linn it works faultlessly, every time, because the securing grub screw is more or less in the middle of the collar (heightwise); in the Jelco collar, the grub screw is tiny and located right at the top, so it pushes the pillar over at the top, rather than pushing the whole thing against the cutout. Setting the arm up with the Jelco collar is impossible without the aid of a headshell spirit level; and even then the silly small screw has to be overtightened against the soft alloy of the arm pillar. The collar is a hateful piece of design that is quite at odds with the good engineering of the rest of the arm. So, the only thing to do was to have a new collar made up along more sensible design principles. Here it is:



    The top (visible) part of the collar is 5mm taller to allow the set screw to be located as far from the top as possible; also that screw is now M6 with a nylon stub at the end. The hole in the pillar does not have a cutout, but it is just the right size for the arm pillar to move up and down freely with virtually no movement in any other plane. The bottom part of the collar has been extended to give as much support below as possible (slightly too far, as it happens, which would be a problem with a Neglex cable rather than my Audio Origami/Cardas one). Otherwise it's a drop-in replacement for the Jelco collar.

    Setting up the arm is now a breeze - there is absolutely no movement other than up and down, and azimuth is consistent across the record. The grub screw can be just 'nipped up' or cranked tight without it digging into the arm pillar. As a design exercise this has been a great success, at modest cost. The collar that you see above has been bead-blasted but not anodised, but the quality of machining and finish is exceptional. As I sit here typing, the Kenwood is sounding very good indeed. It did before, but required a great deal of faffing around to get the proper setup - now it's as fit-and-forget as I could have wished. I'm very pleased!

  2. #2
    Join Date: Nov 2008

    Location: North Down /Northern Ireland/ UK

    Posts: 19,484
    I'm Neil.

    Default

    Nice job, very nice job.

    Now all you need to do is make them and sell to Jeleco customers.

    The stock Technics arm has similar issues though for different reasons. When you adjust the arm height unless you push the locking arm full across there is side to side and front to back rock in the arm. Fine when locked though but not as rigid as I would like to see.

    Regards D S D L
    Regards Neil

  3. #3
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Default

    Actually, the few design alterations are a matter of getting the CAD drawing changed and it would be a straightforward matter to have a batch made up if there was demand.

  4. #4
    Join Date: Nov 2008

    Location: North Down /Northern Ireland/ UK

    Posts: 19,484
    I'm Neil.

    Default

    Quote Originally Posted by Shuggie View Post
    Actually, the few design alterations are a matter of getting the CAD drawing changed and it would be a straightforward matter to have a batch made up if there was demand.
    I would have a think about it and maybe look at getting a patent on the design, if you can be bothered. Wee things like these can have a big effect on how the arm would sound other than improving how VTA works, has there been an improvement in sound ?

    Regards D S D L
    Regards Neil

  5. #5
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 110,012
    I'm AudioAl'sArbiterForPISHANTO.

    Thumbs up

    Hi Hugo,

    Great work. As far as I'm concerned, every Jelco SA-750 owner should have one, as since you mentioned this problem the last time I've investigated it myself and discovered that it is a very real issue which *must* be resolved. Setting correct azimuth is essential in order to get the best sound!

    Therefore, can we have info please on how to obtain one of these collars and how much they are?

    Even if there isn't sufficient interest to get a batch made (which I doubt), I definitely want one, so in the meantime whilst ascertaining the demand, please PM me with the cost of having one made like yours - cheers!

    Marco.

    P.S This thread will be (slightly) renamed and made into a sticky, so that as many people as possible know about this issue and also the product which resolves it.
    Main System

    Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.

    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

    Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.

    CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.

    Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.

    Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.

    Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.

    Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.

    Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.


    Protect your HUMAN RIGHTS and REFUSE ANY *MANDATORY* VACCINE FOR COVID-19!

    Also **SAY NO** to unjust 'vaccine passports' or certificates, which are totally incompatible with a FREE society!!!


  6. #6
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Default

    Marco

    I will find out about getting a number made up; and how much they would cost. In the meantime, it would need a Technics user to try my collar out to be sure of all aspects of the design, particularly with regard to the range of height adjustment required and whether the lower part needs to be shortened at all to prevent the cable plug from fouling the bottom.

    Cheers

    Hugo
    Last edited by Ammonite Audio; 14-08-2010 at 08:15. Reason: Factual correction

  7. #7
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 110,012
    I'm AudioAl'sArbiterForPISHANTO.

    Default

    Why not bring it up then, Hugo? Would be good to meet up again, and interesting to evaluate the collar's efficacy on my deck

    Marco.
    Main System

    Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.

    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

    Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.

    CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.

    Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.

    Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.

    Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.

    Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.

    Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.


    Protect your HUMAN RIGHTS and REFUSE ANY *MANDATORY* VACCINE FOR COVID-19!

    Also **SAY NO** to unjust 'vaccine passports' or certificates, which are totally incompatible with a FREE society!!!


  8. #8
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,814
    I'm Hugo.

    Default

    I might just do that - it would provide an opportunity to find that errant OEM Stillpoint that's lurking somewhere in your towers of Mana!

  9. #9
    Join Date: Jan 2008

    Location: Wrexham, North Wales, UK

    Posts: 110,012
    I'm AudioAl'sArbiterForPISHANTO.

    Default

    Hehehe... Indeed!

    Marco.
    Main System

    Turntable: Heavily-modified Technics SL-1210MK5G [Mike New bearing/ETP platter/Paul Hynes SR7 PSU & reg mods]. Funk Firm APM Achromat/Nagaoka GL-601 Crystal Record Weight/Isonoe feet & boots/Ortofon RS-212D/Denon DL-103GL in Denon PCL-300 headshell with Funk Firm Houdini/Kondo SL-115 pure-silver cartridge leads.

    Paul Hynes MC head amp/SR5 PSU. Also modded Lentek head amp/Denon AU-310 SUT.

    Other Cartridges: Nippon Columbia (NOS 1987) Denon DL-103. USA-made Shure SC35C with NOS stylus. Goldring G820 with NOS stylus. Shure M55E with NOS stylus.

    CD Player: Audiocom-modified Sony X-777ES/DAS-R1 DAC.

    Tape Deck: Tandberg TCD 310, fully restored and recalibrated as new, by RDE, plus upgraded with heads from the TCD-420a. Also with matching TM4 Norway microphones.

    Preamps: Heavily-modified Croft Charisma-X. LDR Stereo Coffee. Power Amps: Tube Distinctions Copper Amp fitted with Tungsol KT-150s. Quad 306.

    Cables & Sundries: Mark Grant HDX1 interconnects and digital coaxial cable, plus Mark Grant 6mm UP-LCOFC Van Damme speaker cable. MCRU 'Ultimate' mains leads. Lehmann clone headphone amp with vintage Koss PRO-4AAA headphones.

    Tube Distinctions digital noise filter. VPI HW16.5 record cleaning machine.

    Speakers: Tannoy 15MGs in Lockwood cabinets with modified crossovers. 1967 Celestion Ditton 15.


    Protect your HUMAN RIGHTS and REFUSE ANY *MANDATORY* VACCINE FOR COVID-19!

    Also **SAY NO** to unjust 'vaccine passports' or certificates, which are totally incompatible with a FREE society!!!


  10. #10
    Join Date: Feb 2008

    Location: SW England, UK

    Posts: 76

    Default

    I would be interested in one of your arm collars for my 12" Jelco, I agree the original supplied is not really good enough.

    How is the collar fitted, with a couple of screws?

    Can you PM with some idea of the cost.

    Many thanks

    Roger
    Roger.

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