New Technics SP10 motor controller specification

[Steerpike]

There are still refinements to be done; now I can finally take measurements on the real thing in operation and tweak the circuit parameters. Even in its rough state its showing W&F figures so low I'm rather amazed at what I'm seeing: 0.005%. But that is with no groove modulation drag, so it might in fact be right where it should be.

[Steerpike]

Been revising some maths I haven't done in years to get a few equations that will predict exactly how this thing behaves under various conditions. And writing some software scripts to draw root-locus diagrams for various loop filters. They are still messy, so I'm not showing them off yet!

[brianco]

But we are pleased that you are refining your work!

My no 1 SP10 is due home from a total rebuild incl. off chassis PS/Control unit this next week or so. No 2 will get your treatment but again off-board and comparisons will be very interesting as I will be able to eventually drive each motor from either power/control unit. The plinth is almost ready, slate sandwiched around alloy and a la Mr Kenyeta, i.e. no top plate, just motor and platter in the plinth.

Thanks for all you have done for the few who regularly follow this thread of yours. Pioneer work.

Good luck!

[Steerpike]

I'm also doing an experiment with an unexposed 35mm colour print film. I've cut the sprocket edge off this and affixed it to the platter (possibly other TT platters as well) to see how the sprocket holes will serve as a tacho generator, using a photo diode as pickup.

It seems the film is an easily obtainable source of very precicely punched holes. This could be useful for turntables that have no inherent tacho generator.

[Steerpike]

I've updated my page 5 with the details of PLL theory and the maths of optimising the control system behaviour, which I've been typing up and making drawing for over the past few days. It might be tediously abstract for those more interested in circuit boards, but as Carl Sagan said: "If you really want to make an apple pie from scratch, you must first create the universe."

Link --->PLL theory

It's a PDF file - only way I can get equations in.
The graphic on the last page (page 9) is a screen print from the software scripts I've been writing to plot the pole-zero motion (root locus) of the system as the loop gain is adjusted.

The direct link to the PDF ---> http://web.eject.co.za/s8nspawn/sp10web/sp10pllg.pdf

This isn't quite complete; it only covers linear phase detectors, and there is a bit extra on Z-transforms for digital systems, still to be added. The 'Z' in Z-transform is not indicative of the Z-Z-Z-Z-Zs I'l probably hear from readers.

[Triophile]

I am sooooo looking forward to the culmination of this project, given the W&F figures you've gotten so far. Be very interesting to see how it stacks up against my elderly Trio L-07D. Please keep up the very fine work!

Cheers, Jon.

[Dave Cawley]

I'm seeing: 0.005%

How did you measure this?

Thanks

Dave

[rich121]

Any news?


Rick

[Steerpike]

My internet has been out for a while - so I'm now just getting back to message board postings!

Originally Posted by rich121

Any news?

I'm currently PCBing/testing a frequency-to-voltage module to add in parallel to the existing digital PLL to see if I can get a wider lock range.
While the PLL as I have described so far works, it doesn't give a very wide control range, so under conditions where it does unlock (heavy load, or at start-up) it is quite slow to get re-locked.

The power-amp section I'm very happy with - I don't think I'll be changing that. But the direction reversal switching will be modified slightly in the future to give improved torqe in reverse.

[rich121]

Myself, Steerpike, and others first posted to this thread on June 15, 2008..... 2.5 years ago!

This thread receives very rare, and sporatic posting... at best.

Honestly, I don't see this thread going anywhere.

I know I have seen motor contoller units and power supplies built by professionals for the SP10 MKII.
I think it would be much more practical to make a list of these so that we could at least purchase them and get our turntables done.
I will do more searches and try to come up with what I have come across in the past, and hopefully others will chime in with their own sources and we may be able to find built from scratch equipment at affordable prices.

Anyways...I'm just expressing my thoughts....

Rick