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78 RPM for very expensive tables - DDS/PLL?

Discussion in 'Audio Hardware' started by milwaukeeshellac, Jun 4, 2021.

  1. milwaukeeshellac

    milwaukeeshellac Active Member Thread Starter

    Location:
    Milwaukee, WI
    Hi, all, I'm a 78 collector, and my equipment is about as close to the top of the 'food chain' as it gets. I'm at the point where I'm seeking solutions to problems that I don't really have. My current table is a Rek-O-Kut Rondine 3, which has infinitely-adjustable speed from 16-90 RPM. I also have a strobe disc that locks in the speed pretty well.

    I'm curious, though, if it's possible to get more precise. Dave Cawley in the UK makes modded Technics 1200 tables, and has designed a DDS (Direct Digital Synthesiser) PLL (Phase Locked Loop) control system that can make the table run with frightening accuracy. See here:

    78 RPM, 78RPM, 78's and how to play them, Technics SL-100, Technics SP-15
    http://www.soundhifi.com/images/T-01DDS.pdf

    I'm told that it only works with the Technics, and he's also having some issues with it at the moment.

    I'd like to possibly upgrade someday to a more sturdy table, e.g. a Nottingham Analogue Spacedeck or 294, with a massive sturdy platter and more quiet motor, and better all-around specs. Nothing urgent.

    Questions:
    - Are there other products out there that can deal with infinitely-adjustable speed? Everything else I've seen does only 33.3 and 45.
    - Are there any engineers out there who could purpose-build something like this? Dave charges $3k for his Technics-specific box, and I'd probably pay about the same or thereabouts if someone can build a quality product to make a high-end rig run from 16-120 RPM or anywhere in between and with extreme accuracy. A collector friend had one made for his Nottingham deck, but the engineer is no longer with us.
     
  2. vinylontubes

    vinylontubes Forum Resident

    Location:
    Katy, TX
    Considering 78 rpm records were never cut with the best accuracy, pitch control is really what you want. I'm not sure why accuracy is so important. If you can set the turntable to 34 and get perfect 33-1/3 rpm, I think that's fine. I wouldn't care about the readout as long as I can get the desired results. Precision is more important than accuracy if you have infinitely adjustable controls.
     
    Mmmark likes this.
  3. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    The motor is 12V DC on your turntable. The input to a DC motor is only voltage, and only variable by voltage. The amount of power output from the motor is also determined by the input voltage, below which it outputs less torque, above it's operating point it overheats. The rotation speed is affected by drag.

    Then, it's a belt drive. Technics belt drive uses AC servo controlled motors driven similarly to direct drive, but still need a pitch control. VPI uses motors locked to the AC wall power phase, but apparently can't make a turntable that turns at the right speed... Rega can't seem to make a speed controller work right..

    It is certainly possible to built a very precise voltage output controller, giving you 11.04V when you specify that, however the DC motor and platter drive drag will not respond in a linear way to voltage with speed. One would need to program in the specific turntable's results in a lookup table, and then still you aren't absolutely controlling the speed.

    A feedback mechanism is required which can detect the frequency of the platter, perhaps an optical sensor placed viewing the platter dots. However, it still can't control a DC motor with the versatility of an AC motor of a Technics, which can handle 10x as much current as its typical operation point to make speed corrections. Standard AC feedback motor speed controllers would have no hysteresis allowance for belt drive with the speed detected at the platter not being exactly what they command, potentially causing oscillations.

    [​IMG]

    5 minutes of looking at the Time Step doesn't tell me where they've inserted themselves in the circuit. It's easy to blindly drive an AC motor at a particular RPM, not so easy to commutate it or provide the feedback to command only as much current as needed for corrections. Maybe they replace the 4.193MHz quartz lock crystal with the generator, but that would be essentially like broadcasting radio into the turntable.

    Speed controllers for re-released Technics are essentially locked out of the market, because the turntables calibrate themselves with the microprocessor. The onboard technology could be capable of displaying and specify any speed, but the frequency generator is still voltage controlled.

    If transcribing, software will allow you any speed correction and any equalization. A reasonable person can implement that.
     
    Last edited: Jun 4, 2021
  4. MrRom92

    MrRom92 Forum Supermodel

    Location:
    Long Island, NY
    Technics SP-10R has a very sophisticated speed control as part of the power supply, though not with that kind of range. I believe it’s 28-90 RPM. I wish it were a bit more capable than this, but it does at least allow you to dial this in accurately down to 2 decimal points.
     
  5. drh

    drh Talking Machine

    Yes, I have a Technics SP-15, and I've been lusting after that controller myself, but the logistical issues and expense involved mean it will remain unrequited lust for now, at least.

    When I did a survey of tables for 78s a few years back (series of article starting here [TNT-Audio Vintage column] On an Overgrown Pathé - [English] and supplemented here [Vintage column] On an Overgrown Pathé - [English] ), these were the models I found that would handle the full range of speeds or close to it. Most are "vintage"; I don't have much experience with the "specialist" (like your Rondine) or "DJ" (like the Numark below) models currently on the market.

    Strathclyde STD 305D. Belt drive. Digital readout in RPM. Covers the full range. Speed controls are somewhat fussy, and the electronics, cutting-edge when the tables were new, are now a source of potential repair problems.

    Fons CQ30/International Mk. I. Two names for functionally the same table (CQ30 is in a nicer plinth). Belt drive. Covers the full range. No readout, but control ergonomics are better than with the CQ-30. Less to go wrong, but changing the belt is not a trivial operation.

    Lenco. Idler drive. Has a devoted niche following that mods them to the hilt and claims so treated they rival top-end modern tables.

    Technics SP-10 mk. 3. Direct drive, covers much but not all the range. Digital readout, but I think it's in per cent, not RPM.

    Dr. Feickert Analogue Volare. Covers the range; no speed readout, and on the basis of very brief, very hurried exposure I have the impression the process for making the adjustments and going back to "standard" speed is fussy. Nonetheless, we should not minimize that it's a modern table with suitable speed flexibility from a top-end maker. For some strange reason, the mfr. does not promote this capability or even offer much info about it.

    Numark TTX-1. My one foray into the "DJ" table market. Direct drive. Covers the range. Digital readout, but in per cent, not RPM. I had one; it developed a fatal problem after only a few years, although I gather subsequent models fix the issue. Alas, they also mostly lack the readout. Unlike with the Strathclyde, Fons, and Lenco, you're stuck with the built-in arm.

    possibly Thorens TD 524, TD 738; EMT. Professional grade tables. Have never seen any in the flesh, but (scant) material I've read suggests they may cover most of the desired range, albeit not quite all at the top.

    [edit] For what it's worth, I should add that my two in-service tables are a Fons Int'l I (for electric recordings; Graham Slee Jazz Club phono preamp) and Strathclyde (for acoustic records; Graham Slee Accession phono preamp), each fitted with an SME 3009 arm. I've been very happy with both. The Technics serves for now as a backup; some day, if I get it the speed controller and a thorough workover, it will probably take over for both.
     
    Last edited: Jun 6, 2021
  6. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Would it be enough that you just know the speed when you have a knob to dial it in? It occurs to me that with 216 dots going past a laser every 3/4 a second, and twice that many light-to-dark transitions, one could simply design a laser illuminator and optical pickup system to measure the platter's speed indicator, averaging over the last revolution in case of off-center platter, to give you as many combined speed measurements per second to display your speed. Could be precise enough to tell you how wide your dots are.

    Frequency and Duty Cycle Measurement Using Arduino - Arduino Project Hub
     
  7. 4-2-7

    4-2-7 Forum Resident

    Location:
    SF Peninsula
    Not really even close
    Your listening to 78s, every record is cut with different EQ curves and the speed cut can very from label to label over many years.

    Anyway not that your ready for something like this, any of their tables can be built for the speeds you want.
    Sota Turntables – Full-line of U.S. made turntables and accessories

    And have the Total Eclipse Package put in it
    Total Eclipse Package – Sota Turntables
     
  8. drh

    drh Talking Machine

    If by that you mean, is a built-in display necessary, well, no, it isn't; for instance, with the Fons, I make adjustments by consulting an outboard digital tachometer, which bounces a laser off a strip of reflective tape stuck to the edge of the platter. A built-in display, however, is a major convenience when one is playing acoustic and very early electric "78s," which were all over the map for actual speed but do follow some patterns. For example, Victor records very often run at around 75 or 76 RPM. Columbia nominally ran at 80, although that's not a hard and fast rule by any means. Pathe paper label ran nominally but not reliably at 80; the company helpfully "specified" its etched label, center-start discs as running at "90 to 100 RPM." And so on. With an onboard speed display, checking out a few speeds is simply a matter of adjusting one knob, and if you've figured out the speed before and made note in your catalogue or whatnot you can just dial in that speed without fuss from then on. With the outboard gizmo, it's "hold the tach and depress its "read" button with one hand while working the turntable controls with the other." Doesn't sound like much, but in practice it can get fussy, especially if the turntable is set in a place where holding the tach up to it is awkward.

    I've actually thought of hiring someone to install the guts of a similar tach into the Fons, setting up the laser to read the underside of the platter and cutting a little window in the plinth for the display, but I've never managed to get a technician interested and haven't quite worked up the courage (or willingness to spend $$$ for customizing) to force the issue.
     
  9. Daddy Dom

    Daddy Dom Lodger

    Location:
    New Zealand
    I would like to help as I am also a 78-user. I don't know much about the Rondine 3 but after a quick look online, I have to say I think there's a way to go yet before you even approach the middle of the food-chain. I honestly don't want to appear rude in saying this but if it cost $1300 in 2010 there are many turntables - old and new - higher up that you might aspire to. Even the trusty Garrard 301/401. These play 33/45/78 and are +/- adjustable to a point.

    Good luck!
     
  10. drh

    drh Talking Machine

    Not enough for acoustic records, though. If you want an idler drive table for those, a Lenco (aka Bogen, aka Goldring) is your best bet. A Garrard would be fine for about anything after ca. 1930.
     
    Daddy Dom likes this.
  11. milwaukeeshellac

    milwaukeeshellac Active Member Thread Starter

    Location:
    Milwaukee, WI
    Thanks all! A lot to consider. After digging further, the specs on the Rondine 3 aren't quite as nice as I'd originally thought. I think I'm going to save up and invest in Technics SP-10R--looks like an amazing reference-grade table. 90RPM is more than enough. Just need to find a good plinth. I think for an arm I'll go with something like a 12" Jelco SA-750. Archiving of 78s requires a cartridge with swappable stylii, e.g. Shure M75 or V-15 Vx, and a 12" arm allows for playback of 16" records.

    I've looked at a lot of tables over the past week, and most of them only allow for a modest amount of pitch control. I wouldn't be able to play a lot of oddball 78s at the correct speed. Quite a few field recordings in my collection with recorded as fast as 88 RPM and would sound like a dirge played on most high-end tables.
     
    Daddy Dom and McLover like this.
  12. milwaukeeshellac

    milwaukeeshellac Active Member Thread Starter

    Location:
    Milwaukee, WI
    Not to worry, I have a Timestep T-03 EQ A+, which is the best archiving EQ on the market for 78s. It has every conceivable EQ curve and allows for archiving in stereo, compensates for cartridge voltage, and a number of other vital bells and whistles.
     
  13. McLover

    McLover Senior Member

    Location:
    Athens, Tennessee
    SOTA is best used for modern LP and 45 RPM use. Also, typical tonearms used on a SOTA favor one cartridge mounted and not easily interchanged. I like a SOTA very well, but they are expensive, and more delicate than average if you move them carelessly (those ruby platter bearings can get knackered).
     
  14. McLover

    McLover Senior Member

    Location:
    Athens, Tennessee
    The Stanton 500/Pickering V 15 or the Shure M 44 family are the most commonly used cartridges by record collectors, archivists, and broadcast facilities. There is a wide selection of custom stylus options for those.
     
  15. milwaukeeshellac

    milwaukeeshellac Active Member Thread Starter

    Location:
    Milwaukee, WI
    Yes, although neither the Stanton nor the Shure are made anymore, and it's getting harder to find proper stylii and cantilevers. It's true that the Shure M44 was favored for a long time by restoration professionals (and I have a full set of stylii for it), but the best engineers have been moving away from it. The M75 is superior. There are still a lot of options out there for custom stylii as long as Expert Stylus can retip them.
     
    McLover likes this.
  16. JohnO

    JohnO Forum Resident

    Location:
    Washington, DC
    An excellent current cart with lots of easily available current factory made stylus sizes, Nagaoka MP-100 or MP-110 or any of the MP series.
     
    McLover likes this.
  17. drh

    drh Talking Machine

    For what it's worth, I've been using Shure V15Vx cartridges for 78s for years now. Agreed, Shure's exit from the business complicates matters, as does Stanton's. Have never tried Nagaoka, but for now, having not too long back outfitted a set of Pickering XV15/625E carts with the Rek-o-kut stylus set as an alternative option to the Shures, I expect I'll be standing pat for a while.
     
    McLover likes this.
  18. drh

    drh Talking Machine

    Not familiar with them, but sound interesting. What's the profile of those styli? Conical? Elliptical? Truncated elliptical? Some or all of the above? And what's the recommended tracking force? Thanks for calling our attention to them.
     
  19. Classicrock

    Classicrock Forum Resident

    Location:
    South West, UK.
    Cawley's power supply will not give greater speed accuracy than a stock Technics 1200G. It's more about supposed noise reduction by substituting the inbuilt Switch mode supply. On the old 1200II there were advantages for MC cartridges mainly just by moving the PS outside the deck. If you want to play 78s I think the 1200G is an ideal tool and you can vary speed using the pitch control. Not infinitely adjustable but enough options to correct the speed for any non standard 78 rpm disc I would think. Another possibility would be the old Lenco rim drive turntables. The speed slider control actually adjusts speed on a continuous graduation basis though there are notches for the various standard speeds.
     
  20. qwerty

    qwerty A resident of the SH_Forums.

    For 78s I would suggest an old transcription idler - they have the mass and momentum to give the music life. Some have user-adjustable speed control, others don't. I'm not familiar with the old idlers in your land. Where I am the Orpheus Silex (hybrid belt/idler) has an adjustable speed and is great for 78 playback (sorry, I don't know the range but I would be confident it would go to 90rpm).
     
  21. drh

    drh Talking Machine

    According to this Orpheus Silex 4-Speed Belt-Drive Turntable Manual | Vinyl Engine the pitch variability is 7%, or around 5.5 RPM. That figure, which I think actually is pretty generous as they go for turntables of that sort, would get you from ca. 72.5 to ca. 83.5, which would be enough for many, but by no means all, acoustic recordings. For instance, an Edison Bell set that I transferred a while back needed to go at 84 RPM, just beyond that 7% level, to be on pitch, and center start Pathes would be well above it. For that matter, I transferred an early electric set in which all sides ran at 82 RPM (just within the Orpheus Silex's range) but one odd man out was at 84 (just outside).
     
    qwerty likes this.
  22. qwerty

    qwerty A resident of the SH_Forums.

    Good research. In the context of the Silex, not many many Edison Bell and Pathe disks are around here, so unlikely to be a problem. The Silex was given as an example, I would be confident that there are idlers out there with the full speed variability range.
     
  23. 4-2-7

    4-2-7 Forum Resident

    Location:
    SF Peninsula
    :confused: Who Knew
    :confused: A table that comes without a tone arm, can have any tonearm mounted on it. The comment above and this one is totally nonsensical. While the SOTA Sapphire is geared to higher end audiophile use and systems, and arms people choose will be higher end non removable head shells, it doesn't limit the use of any arm. In fact the table is designed and will accommodate any arm one wants to uses. The fact is SOTA sold their tables with tonearms that where s shape removable head shell arms. Not that one needs to change the cartridge every record, but I'v even had SME 3009 arms on my tables.

    I didn't know the OP had planed on doing DJ work and carrying the table around from show to show. Me I just set it up in my system and it's there to stay for many years. When I need to move it, I just stand it on it side and lock the bearing, it's very simple.

    Anyway your post was pretty off the wall and doesn't make much sense. Not only can you order a SOTA with what ever speeds you want, you can have an old used one converted. They have also teamed up with Phoenix Engineering for the power supplies and Roadrunner. They also sell it to work on other tables like the VIP, you can get the motor, PSU and Roadrunner tack.

    Lately you can pick up older SOTA Sapphires and Star Sapphires pretty cheap, the total eclipse package cost $1100. You can build a SOTA any way you want to use it and have a killer table that will play what ever records one wants.
     
  24. Pinknik

    Pinknik Senior Member

  25. JohnO

    JohnO Forum Resident

    Location:
    Washington, DC
    The MP-100 is .7 conical, the MP-110 is .4 x .7 elliptical, and there is a 1 mil stylus. These are for around 2g tracking force. The cart sounds close to an XV-15/680, no high peaking like a S500 or high rolloff like a Shure.
    The 2.5 mil, 3.0, 3.5, 4.0, 4.5 are all conical and 2-5g, and all of these styli are in-stock items at the two main US stylus sellers, company L and company T. The 4.5 may not always be, but that is easily on the auction site sold from Japan.
    The archival stylus makers would do well to start supporting this very nice and current cart from a classic manufacturer that cares and supports such work.
    It's a fine cart for normal use too.
     

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