Some questions have been ask regarding the platter mass possible with the SP-10 Mk2 motor unit. I have a Mk 2A and here are specifications from the factory manual:
Platter = 2.9 kg
Speed fluctuation with load changes = 0% within 5 kg
The AT-666 Disc Stabilizer was a popular accessory for SP-10 tables, at least in Japan. That weighs 1.4 kg and due to the close relationship of Technics and AT, it is not likely they would have designed an accessory that would cause malfunction or failure of the SP-10.
So from this my conclusion would be that any mat or added mass with the stock platter should not cause substandard performance so long as it is less than 2 kg.
Now, can anyone direct me to warnings against the Mk 2A that Rich121 mentions?
Platter = 2.9 kg
Speed fluctuation with load changes = 0% within 5 kg
The AT-666 Disc Stabilizer was a popular accessory for SP-10 tables, at least in Japan. That weighs 1.4 kg and due to the close relationship of Technics and AT, it is not likely they would have designed an accessory that would cause malfunction or failure of the SP-10.
So from this my conclusion would be that any mat or added mass with the stock platter should not cause substandard performance so long as it is less than 2 kg.
Now, can anyone direct me to warnings against the Mk 2A that Rich121 mentions?
"Jas
engine room
Posts: 5057
Posted: Mon Jan 15, 2007 8:30 am
Post subject:
Hi,
The 140V line just powers the strobe so I wouldn't worry about that. Without test gear it would be difficult to diagnose the problem. Out of interest which variant of the mkII is it? The mkIIa is known to have some problems with failing IC's.
Regards,
JaS"
Here is the only reference that I could find from Vinyl Engine.
From what I understand, Technics upgraded the controller in the MKIIa and used "less" electronics by using more IC's... I guess some of these have a problem failing and cannot be sourced.
I don't have "first hand" knowledge of this, just from what I have read in posts from others.
I used to have a file with alot of SP-10 info such as this, but I can't find it.. must have deleted it.
Just another reason to get a new controller/power supply design and built
Rick
engine room
Posts: 5057
Posted: Mon Jan 15, 2007 8:30 am
Post subject:
Hi,
The 140V line just powers the strobe so I wouldn't worry about that. Without test gear it would be difficult to diagnose the problem. Out of interest which variant of the mkII is it? The mkIIa is known to have some problems with failing IC's.
Regards,
JaS"
Here is the only reference that I could find from Vinyl Engine.
From what I understand, Technics upgraded the controller in the MKIIa and used "less" electronics by using more IC's... I guess some of these have a problem failing and cannot be sourced.
I don't have "first hand" knowledge of this, just from what I have read in posts from others.
I used to have a file with alot of SP-10 info such as this, but I can't find it.. must have deleted it.
Just another reason to get a new controller/power supply design and built
Rick
function of SP10 with altered platter mass
Hi Pryso, I would like your estimate to be true, but can you tell me how you arrived at it (the idea that one could alter the SP10 platter mass by up to 2 kg with zero deleterious effect on speed stability)? The factory statement that one can add 5kg with "0%" effect on speed is/was a way of bragging about the motor torque. But it tells me little about how such a large increase in mass might affect speed stability and the ability of the controller/motor/platter to cope with transient effects of stylus drag. If I understand the rudimentary mechanism of the servo, any change in mass would alter damping and cause either sluggish response to transients (if too heavy) or oscillation (if too light). (The extreme example of this is seen when you remove the platter totally; the motor just cogs along in a herky jerky way.) I am sure there IS a certain allowable change in total mass that has no practical negative effect (given the torque of the motor, etc); I just wondered how you came to the conclusion that the magic amount is 2kg.
I did not see where Rich said anything specifically negative about the MkIIA. As I recall, somewhere upstream in this thread, he said it is "unreliable". Possibly it is or was thought to be less reliable than the MkII, because it uses more op amps. Somewhere else I think I read something about the strobe being run off a circuit that also runs the motor controller, thus permitting electrical noise from the strobe to muck up the latter. That's just from dim memory.
Hi Pryso, I would like your estimate to be true, but can you tell me how you arrived at it (the idea that one could alter the SP10 platter mass by up to 2 kg with zero deleterious effect on speed stability)? The factory statement that one can add 5kg with "0%" effect on speed is/was a way of bragging about the motor torque. But it tells me little about how such a large increase in mass might affect speed stability and the ability of the controller/motor/platter to cope with transient effects of stylus drag. If I understand the rudimentary mechanism of the servo, any change in mass would alter damping and cause either sluggish response to transients (if too heavy) or oscillation (if too light). (The extreme example of this is seen when you remove the platter totally; the motor just cogs along in a herky jerky way.) I am sure there IS a certain allowable change in total mass that has no practical negative effect (given the torque of the motor, etc); I just wondered how you came to the conclusion that the magic amount is 2kg.
I did not see where Rich said anything specifically negative about the MkIIA. As I recall, somewhere upstream in this thread, he said it is "unreliable". Possibly it is or was thought to be less reliable than the MkII, because it uses more op amps. Somewhere else I think I read something about the strobe being run off a circuit that also runs the motor controller, thus permitting electrical noise from the strobe to muck up the latter. That's just from dim memory.
Thanks for your input, Rich. I recently had good luck sourcing a no-longer-available IC for my Denon DP80, from a company in Hong Kong. (A part that had not been made since 1983 but without which the DP80 is dead in the water.) I am planning to find out whether they can also source any of the ICs used in the SP10 MkII and IIA, just to have spares available. If anyone wants to do the same, let me know by e-mail.
This idle back and forth will pass the time and keep the thread going until Steerpike and/or Mark Kelly can get up to speed on the motor controller.
This idle back and forth will pass the time and keep the thread going until Steerpike and/or Mark Kelly can get up to speed on the motor controller.
Hi Lew, let's see if I can explain myself.
When I got my Mk 2A and read the owner manual, I was impressed to see Technics' claim that if they could be fitted, 500 tonearms could track at 2 g. each without affecting any rated speed. OK, that would be 1 kg. Now since the platter itself weighs 2.9 kg, the record mat 543 g. (mine is the heavy, flat Technics mat), and the record weight from 120 to 200 g., this suggests a total mass of roughly 4.6 kg (2.9 + 1.0 + 0.54 + 0.2). The +/- 2.0 g. tracking of a single arm was considered too small to include. Another way to consider this would be that in place of the 500 arms and standard mat, 1.6 kg of any other mass could be added to the platter without affecting performance.
But then after reading some of the questions and comments on this site, I went back to the manual to reread the specifications. Here I found the statement for speed fluctuation (not starting torque) of 0% within a limit of a 5 kg. load. Now subtracting the 2.9 kg. platter mass we have a 2.1 kg. variable to deal with. So with the addition of a record, we would have something less than 2.0 kg. margin to play with. This could be in the form of a metal mat such as the AT aluminum or MS copper, a spindle weight, and or a ring weight.
If I've made a mistake in these calculations I would like to be shown my error.
Thanks for your interest.
When I got my Mk 2A and read the owner manual, I was impressed to see Technics' claim that if they could be fitted, 500 tonearms could track at 2 g. each without affecting any rated speed. OK, that would be 1 kg. Now since the platter itself weighs 2.9 kg, the record mat 543 g. (mine is the heavy, flat Technics mat), and the record weight from 120 to 200 g., this suggests a total mass of roughly 4.6 kg (2.9 + 1.0 + 0.54 + 0.2). The +/- 2.0 g. tracking of a single arm was considered too small to include. Another way to consider this would be that in place of the 500 arms and standard mat, 1.6 kg of any other mass could be added to the platter without affecting performance.
But then after reading some of the questions and comments on this site, I went back to the manual to reread the specifications. Here I found the statement for speed fluctuation (not starting torque) of 0% within a limit of a 5 kg. load. Now subtracting the 2.9 kg. platter mass we have a 2.1 kg. variable to deal with. So with the addition of a record, we would have something less than 2.0 kg. margin to play with. This could be in the form of a metal mat such as the AT aluminum or MS copper, a spindle weight, and or a ring weight.
If I've made a mistake in these calculations I would like to be shown my error.
Thanks for your interest.
Pryso,
I think there might be an error in your reasoning in that a 2g stylus (for instance) does not produce 2g of drag on the platter.
An anology: you can put a 50kg bag of cement on a rug, and drag the rug across a smooth floor, with considerably less force than "50kg".
(strictly speaking we ought to convert masses in kg to forces in Newtons, but the idea remains the same)
Whatever the actual drag on the platter produced by a tracking force of X, the drag is also going to vary depending on the radius at which the arm is playing. Much more drag at the periphery tan close to the centre (torque is the product of force by radius)
Aside from the above, a large platter mass (what I like to call inertial mass) is not going to affect the magnitude of the speed error, but rather the recovery time.
The operation of the servo system is all about timing. If the platter doesn't react fast enough (or too fast, if mass is removed), when the motor works harder, the servo electronics can over-compensate - because it doesn't sense the expected speed correction that it requested. This sensitivity is reduced (though not eliminated ) by using a combination controller - a velocity feedback loop as well as a phase feedback loop.
I think there might be an error in your reasoning in that a 2g stylus (for instance) does not produce 2g of drag on the platter.
An anology: you can put a 50kg bag of cement on a rug, and drag the rug across a smooth floor, with considerably less force than "50kg".
(strictly speaking we ought to convert masses in kg to forces in Newtons, but the idea remains the same)
Whatever the actual drag on the platter produced by a tracking force of X, the drag is also going to vary depending on the radius at which the arm is playing. Much more drag at the periphery tan close to the centre (torque is the product of force by radius)
Aside from the above, a large platter mass (what I like to call inertial mass) is not going to affect the magnitude of the speed error, but rather the recovery time.
The operation of the servo system is all about timing. If the platter doesn't react fast enough (or too fast, if mass is removed), when the motor works harder, the servo electronics can over-compensate - because it doesn't sense the expected speed correction that it requested. This sensitivity is reduced (though not eliminated ) by using a combination controller - a velocity feedback loop as well as a phase feedback loop.
This sensitivity is reduced (though not eliminated ) by using a combination controller - a velocity feedback loop as well as a phase feedback loop."
Would there be a way to add adjustability to this somehow, so that different masses could be used with the new controller/turntable?
Thanks...
Rick
Would there be a way to add adjustability to this somehow, so that different masses could be used with the new controller/turntable?
Thanks...
Rick
With a higher mass platter wouldn't the inertia be higher & therefore more immune to speed fluctuations as a result of drag & therefore less work for the servo to do? How does this get factored into the feedback scheme - i.e does it result in an optimum platter weight that balances inertia Vs response time to servo control?
Yes, definately. Most easily when designing a new controller.
To add this facillity to the existing controllers would require some reverse engineering - but its not impossible.
What I want - always dreaming big - is that my controller will have a 'setup mode', so that it can auto-tune itself to any (reasonable) platter mass. This is not particularly difficult, because you get all the info you need buy timing the platter run-up period - something a micro-controller is easily able to do.
Higher mass means longer time periods for changes to occur, but it doesn't reduce the MAGNITUDE of the speed reduction for a particular level of drag. Bigger mass is great for rejecting impulse disturbances (stylus drag due to say music transients), but has little advantage when the disturbances are constant (bearing drag for example).
A larger mass means MORE work for the motor, WHEN the error has occured - or rather an error large enough to be detected.
Yes there is an optimum platter weight, based on the motor power, and the desired response time. But any feedback loop reduces the system's sensitivity to errors in the so called 'plant model'. (in the same way that feedback in an amplifier lets you use transistors with widely varying gains, and no overall effect of the amplifiers gain).
I.e., one of the functions of feedback is to smooth over uncertainties (eg. manufactring variations, or aging processes) in the drive system model.
Thus limited variations in the platter mass have no effect on the response / performance. Change the mass TOO much though, and the controller runs out of headroom, or slewrate.
(the analogy is an amplifier trying to drive a 'difficult' impedance speaker)
Wow...this has slipped to page 3...very very slow...
What do we need to do to breath some life into this project?
I don't see this going anywhere, honestly...there has not been any substantial posts since long before Xmas 2008
Seriously, what needs to be done to get this rolling, started and finished?
Everyones suggestions appreciated...
Rick
What do we need to do to breath some life into this project?
I don't see this going anywhere, honestly...there has not been any substantial posts since long before Xmas 2008
Seriously, what needs to be done to get this rolling, started and finished?
Everyones suggestions appreciated...
Rick
I'd like to see a copy of the Kaneta power supply for the mk I done with some modern equivalents. The schematics I've seen are so blurry I can hardly tell what a lot of that stuff is. The values seem to be missing on most of the resistors as well.
Anybody out there ever built a mk I Kaneta motor controller?
Anybody out there ever built a mk I Kaneta motor controller?
Platter Mass.......
Having been 'off sick' for several months I am trying to catch up on what is happening re the proposed new PS ideas.
The whole matter of 'total platter' weight also interests me as I intend using a heavy pure carbon mat. Has ANYONE actually attempted to add say 0.75 Kilo or more?? If so were there any issues?
Many thanks.
Having been 'off sick' for several months I am trying to catch up on what is happening re the proposed new PS ideas.
The whole matter of 'total platter' weight also interests me as I intend using a heavy pure carbon mat. Has ANYONE actually attempted to add say 0.75 Kilo or more?? If so were there any issues?
Many thanks.
Steerpike said:
Please tell us more!
Is your design for both a controller and a power supply?
If yes with the controller, what capabilities will it have, and can you tell us more about its design?
If yes on the power supply, can you tell more about the design? Will it have adjustable supply voltage like the origional, or at least, will it be easy to wire to whatever voltage is required?
This is good news...
Looking forward to your next post!
Rick
Both. If you have followed this from the start, you'll read that I have ONLY the motor, so my circuitry will replace everything electronic in the original SP10.
The actual PFD (phase frequency detector) controller is still in in the theory stage - I have to build the power supply and 3-phase drive circuits first, to make measurements on the mechanical properties of the motor. I have two possible PLL types I want to test, (i) a logic state machine, and (ii) a more conventional sample/hold phase-to voltage converter.
Both types are to include a microprocessor. (PIC 16F series)
Are you referring to AC mains voltage? This is entirely dependant the transformer you use. My circuitry will requires a centre-tapped 18 to 24v AC. That's a very common transformer. (There is the option to use dual tranformers if one wanted to be exoic and really isolate the different sections. In fact, the first thing that the PSU does is rectify the AC, so you could run it happily from 4 Pb-acid accumulators)
Sounds like you have it thought out and have a good idea what you want to accomplish.
I am assuming, that since you only have the SP-10 motor, that you will also have a means for adjusting the controller to accomodate different platter masses?
This would be very helpful to be able to add heavier ring type record clamps and spindle clamp...or use higher mass platters.
Also, being able to trim the speed for certain recordings would be nice.
But, if just a controller/power supply for 33/45/78 RPM Lps, that would be an improvement in parts and parts management for the future, over the aging stock components.
My comment:
"Will it have adjustable supply voltage like the origional, or at least, will it be easy to wire to whatever voltage is required?"
Yes, I was relating to supply voltage. Nice to see that all it will take is the appropriate transformers, very simple to do.
As for me, I very much appreciate your indeavor, and I have been posting and following this since last Fall at least... I am glad it is materializing and again, appreciate your efforts and time.
Rick
I am assuming, that since you only have the SP-10 motor, that you will also have a means for adjusting the controller to accomodate different platter masses?
This would be very helpful to be able to add heavier ring type record clamps and spindle clamp...or use higher mass platters.
Also, being able to trim the speed for certain recordings would be nice.
But, if just a controller/power supply for 33/45/78 RPM Lps, that would be an improvement in parts and parts management for the future, over the aging stock components.
My comment:
"Will it have adjustable supply voltage like the origional, or at least, will it be easy to wire to whatever voltage is required?"
Yes, I was relating to supply voltage. Nice to see that all it will take is the appropriate transformers, very simple to do.
As for me, I very much appreciate your indeavor, and I have been posting and following this since last Fall at least... I am glad it is materializing and again, appreciate your efforts and time.
Rick
For the moment, it's just a figure that appears in an equation to determine the value of certain capacitors and resistors. What I want to do eventually is have the microprocessor automatically take measurements of the motor mechanics all by itself, and then compute its own feedback parameters accordingly. So after changing mats, or platters etc. you'd just push the 'align' button, and it would do its thing - much like tape decks that do automatic bias alignment.
And 16-2/3 RPM is a requirement for me, so it will be a 4 speed.
I think the software should have a 'feature' that if anyone tries to 'scratch' with the turntable, it shuts off and won't re-start for 24 hours!
For my part I would be perfectly happy if a simple 33rpm function - with no frills other than say an on-board =/- 5% speed adjuster, were to be the outcome of this project. I also would require that the PS+Controller were capable of being cabinet mounted at say 3' distance from the turntable itself. My present TT is a SP10Mk11P (ex.BBC) and all on board electronics were successfully mounted as an out-board unit connected by an umbilical. (It worked for five years this way but now has a 'dead' problem which I am not qualified to diagnose. A new, simpler, DIY unit would be the more economic option to rebuilding the existing boards.)
The difference between on and off TT electronics is very big indeed and the extra trouble is far outweighed by the improvement in all aspects of the resultant sound quality.
The difference between on and off TT electronics is very big indeed and the extra trouble is far outweighed by the improvement in all aspects of the resultant sound quality.