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Thread: Rega RB-300 tonearm on Technics SL-1200Mk2

  1. #1
    Join Date: Sep 2015

    Location: Minsk, Belarus

    Posts: 30
    I'm Valera.

    Default Rega RB-300 tonearm on Technics SL-1200Mk2

    Inspired by Qwinn. Origin see here: https://www.jkwynn.co.uk//Tech2_HTML/Tech2_14.html

    Part 1 - Tonearm base and fitting

    I posted early my DIY silicon fluid damper for SL-1200Mk2 tonearms https://theartofsound.net/forum/show...704#post848704 . Despite it works perfect, I decided to replace the whole tonearm, RB-300 or -250 was the best performance/price choise for me. Bought RB-300 on e-bay in good condition (-250 could be cheaper choise but I didn't find suitable offer).

    Loading spring was tuned to zero force and damped by small soft textil pieces (I leave backdoor).

    The first issue is the tonearm base. All necessary calculations already made by Qwinn, see link abowe. I've make several top view photos/measurements and by simple geometry calculations got absolutely the same (no wonder).

    Ok, all drawings are ready, tonearm base will be made from oak. Simple rotary attachment to mini-mill, some lathe finish, varnishing and base is done.

    1 base_tn.jpg 2_bas_finish_tn.jpg

    The next issue is tonearm height adjustment. Classical Techie has perfectly designed (really perfectly) hight adjustment mechanics but it can't fit RB-300 tonearms. I turned out aluminium hub (upper part) and nut (both have metric thread with 1 mm pitch) according to tonearm 'leg' thread. Don't ask me why british tonearm has metric thread, I expected something like 15/16-20. BTW, there is one of prototype of tonearm base I've made by 3D printer on photo (3D print is very useful for prototyping).

    3 lift mechanics_tn.jpg

    The next point is internal and external wiring. Of course, default ones should be replaced. Internal wirings replaced with litz, external - with Klotz shielded twisted pair, it requires new wires holder on the tonearm 'leg'. Lathe again, drill press... done. Sure, I fitted balanced XLR connectors instead of RCA.

    5 cables soldering_tn.jpg 6 sll details_tn.jpg

    Again - many thanks to Quinn. Next is new couterweight.
    Analog: Technics SL-1200MkII (RB300 tonearm, external PSU, separated power supply for all stages, improved bearing), MC Goldring Eroica LX, custom SUT 1:10, Balanced input J-FET DIY phonostage
    Digital: Cubietruck (headless Debian server, i2s output, external masterclock from DAC), content on HDD. DAC: Lynx D29v4 (Altera FPGA digital stream separator, 2*AD1853, 2*3 OP42 LPF)
    PA: DIY composite amplifier YES-3, schematic by Gennady Bragin
    Acoustic: DIY floorstanding 3-way SB Acoustics

  2. #2
    Join Date: Sep 2015

    Location: Minsk, Belarus

    Posts: 30
    I'm Valera.

    Default

    Part 2 - new couterweight

    Further upgrade of RB-300 is counterweight. The main requirements are correct weight and mass center which should be as low as possible relating tonearm longitudial axes, I decided to make something like this:

    AL.jpg

    Again - drawings, calculations, drawings, calculations and machining. Counterweight body is made from pure aluminium (aluminium, not Al alloy), two additional masses turned from copper and glued to main part. Both metals are acoustically inert enough.

    IMG_2416_tn.jpg

    Total weihgt is about 102 g, I coated it with laquer to prevent of corrosion.

    IMG_2455_tn.jpg

    Now new tonearm and it base are ready to install. Not so complicated work, special protractor for RB-300 was printed earlier.

    IMG_2464_tn.jpg IMG_2479_tn.jpg

    Sound. It's definitely much better than stock SL-1200Mk2 tonearm (even with silicon fluid damper). Sound is solid and clean, so this upgrade definitely worth it.

    https://www.youtube.com/watch?v=u1cIle6QHnw

    PS My Techie works with self-made step-up transformer 1:10 made on Fe-based toroidal nanocrystal core (1.1 H, 100 Ohm), folloved by self-made fonostage described here https://theartofsound.net/forum/show...balanced-input
    Last edited by Khom; 04-06-2023 at 13:06.
    Analog: Technics SL-1200MkII (RB300 tonearm, external PSU, separated power supply for all stages, improved bearing), MC Goldring Eroica LX, custom SUT 1:10, Balanced input J-FET DIY phonostage
    Digital: Cubietruck (headless Debian server, i2s output, external masterclock from DAC), content on HDD. DAC: Lynx D29v4 (Altera FPGA digital stream separator, 2*AD1853, 2*3 OP42 LPF)
    PA: DIY composite amplifier YES-3, schematic by Gennady Bragin
    Acoustic: DIY floorstanding 3-way SB Acoustics

  3. #3
    Join Date: Apr 2014

    Location: swansea

    Posts: 485
    I'm gerald.

    Default

    Love your counter weight do you have the cnc file for it by any chance ?

  4. #4
    Join Date: Sep 2015

    Location: Minsk, Belarus

    Posts: 30
    I'm Valera.

    Default

    Thanks. No, I haven't CNC machines, all parts are made using desktop mini-lathe and mini-mill (you can see it at the end of my video). This is not so hard work even on these diy-class machines. If you want I can leave here dravings of countermass details.
    Analog: Technics SL-1200MkII (RB300 tonearm, external PSU, separated power supply for all stages, improved bearing), MC Goldring Eroica LX, custom SUT 1:10, Balanced input J-FET DIY phonostage
    Digital: Cubietruck (headless Debian server, i2s output, external masterclock from DAC), content on HDD. DAC: Lynx D29v4 (Altera FPGA digital stream separator, 2*AD1853, 2*3 OP42 LPF)
    PA: DIY composite amplifier YES-3, schematic by Gennady Bragin
    Acoustic: DIY floorstanding 3-way SB Acoustics

  5. #5
    Join Date: Apr 2014

    Location: swansea

    Posts: 485
    I'm gerald.

    Default

    Quote Originally Posted by Khom View Post
    Thanks. No, I haven't CNC machines, all parts are made using desktop mini-lathe and mini-mill (you can see it at the end of my video). This is not so hard work even on these diy-class machines. If you want I can leave here dravings of countermass details.
    If you would please

  6. #6
    Join Date: Sep 2015

    Location: Minsk, Belarus

    Posts: 30
    I'm Valera.

    Default

    See the attached drawings. There is no hard tolerancies, all parts can be mashined easy with small ('desktop') DIY-mashines, like mine.
    countermass_draw.jpg copper_parts_draw.jpg
    Analog: Technics SL-1200MkII (RB300 tonearm, external PSU, separated power supply for all stages, improved bearing), MC Goldring Eroica LX, custom SUT 1:10, Balanced input J-FET DIY phonostage
    Digital: Cubietruck (headless Debian server, i2s output, external masterclock from DAC), content on HDD. DAC: Lynx D29v4 (Altera FPGA digital stream separator, 2*AD1853, 2*3 OP42 LPF)
    PA: DIY composite amplifier YES-3, schematic by Gennady Bragin
    Acoustic: DIY floorstanding 3-way SB Acoustics

  7. #7
    Join Date: Jan 2009

    Location: Essex

    Posts: 32,504
    I'm openingabottleofwine.

    Default

    Quote Originally Posted by Khom View Post
    Part 2 - new couterweight

    Further upgrade of RB-300 is counterweight. The main requirements are correct weight and mass center which should be as low as possible relating tonearm longitudial axes, I decided to make something like this:

    AL.jpg

    Again - drawings, calculations, drawings, calculations and machining. Counterweight body is made from pure aluminium (aluminium, not Al alloy), two additional masses turned from copper and glued to main part. Both metals are acoustically inert enough.

    IMG_2416_tn.jpg

    Total weihgt is about 102 g, I coated it with laquer to prevent of corrosion.

    IMG_2455_tn.jpg

    Now new tonearm and it base are ready to install. Not so complicated work, special protractor for RB-300 was printed earlier.

    IMG_2464_tn.jpg IMG_2479_tn.jpg

    Sound. It's definitely much better than stock SL-1200Mk2 tonearm (even with silicon fluid damper). Sound is solid and clean, so this upgrade definitely worth it.

    https://www.youtube.com/watch?v=u1cIle6QHnw
    Excellent work Valera - well done!
    Barry

  8. #8
    Join Date: Oct 2008

    Location: Glasgowshire

    Posts: 9,697
    I'm Gary.

    Default

    Great Job!
    AC POWER
    Hardwired 10kVA balanced mains powering entire system
    AMPS
    Meridian 557 power Amp (Modded) / PS Audio BHK Preamp (Modded)
    SPEAKERS
    Wharfedale Evo 4.4
    DAC
    PS Audio Directstream (Modded)
    TURNTABLE
    Pro-Ject X8 balanced output via XLR / Ortofon Quintet Blue cartridge
    PHONOSTAGE
    Pro-Ject DS3 B balanced Input (TT and Phonostage powered by Pro-Ject Power box RS2 linear psu)
    DIGITAL
    OPPO 203 (Modded: Linear PSU, i2s output to Dac) - Roon Endpoint, HDMI input used for all things Streaming/ PS5 /AppleTV ... also good for movies apparently?
    MUSIC PLAYBACK
    Tweaked AP-Linux based Roon Server into Oppo 203 as Roon endpoint
    Ipad Roon Remote.
    Apple Music/ YouTube via AppleTV, fed to Dac via Oppo HDMI input/i2s output to Dac.
    SPEAKER CABLES
    Biwired: Duelund DCA10GA (Bass) Duelund DCA16GA (mid & treble) Duelund 12DCA used as jumpers (On
    "Blackcat Cable" Chris Sommivigo's advice - yup, even with biwire it sounds better - and it does)
    INTERCONNECTS
    All Balanced: Ghost+ recording studio XLR cables

  9. #9
    Join Date: Apr 2014

    Location: swansea

    Posts: 485
    I'm gerald.

    Default

    See the attached drawings. There is no hard tolerancies, all parts can be mashined easy with small ('desktop') DIY-mashines, like mine.
    Do you have a better image of the sizes cant make them out ?

    Cheers Gerry

  10. #10
    Join Date: Sep 2015

    Location: Minsk, Belarus

    Posts: 30
    I'm Valera.

    Default

    Sorry, something was wrong with my attachment - forum engine compressed pictures to small volume. See here on google: https://drive.google.com/drive/folde...kmK0LfS8NpAwJL
    Analog: Technics SL-1200MkII (RB300 tonearm, external PSU, separated power supply for all stages, improved bearing), MC Goldring Eroica LX, custom SUT 1:10, Balanced input J-FET DIY phonostage
    Digital: Cubietruck (headless Debian server, i2s output, external masterclock from DAC), content on HDD. DAC: Lynx D29v4 (Altera FPGA digital stream separator, 2*AD1853, 2*3 OP42 LPF)
    PA: DIY composite amplifier YES-3, schematic by Gennady Bragin
    Acoustic: DIY floorstanding 3-way SB Acoustics

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