New Technics SP10 motor controller specification

[brianco]

Shaun,

Thank you....I have a similar plinth concept, only somewhat larger....that way it can be reduced, but if it is to hide the electronics it may well remain large!

Has anyone got a good power supply schematic designed to produce the raw voltages needed to supply the control and drive sections? Such a design, using today's components should be more stable than the original and easy to build.

Many thanks

[jlevro]

[QUOTE]Originally posted by brianco

Has anyone got a good power supply schematic designed to produce the raw voltages needed to supply the control and drive sections? Such a design, using today's components should be more stable than the original and easy to build.

Hi, Brian.

I'm new to this thread, but I thought it was time to jump in. I recently procured an SP-10MkII without the power supply. I designed a new supply that seems to make the platter spin properly (!) and the lights light. I won't have a plinth constructed for another week or 2, so I can't say how it sounds on an absolute basis. However, I will be able to compare it to my Teac TN-400 "MagneFloat" TT on a similar plinth, which I like better than my HW-19MkIV+.

Anyway, the supply is pretty straight-forward. The current demands aren't all that great (+32.5V @ 220ma, +5V @ 280ma, and +140V @ 5ma). However, I did observe that the motor current spikes up to around 1A for about a second at startup and for about 1/2 second at turnoff, so be advised.

The supply uses transformers I had on hand. The 30VAC transformer is probably a bit of overkill, but this is audio, right? The +140V supply is very sleazy. I've done this "reverse connection" thing for bias supplies in a tube amp and low current tube guitar preamps, which is what gave me the idea. There aren't a lot of 100-120V low current transformers around. I get about 85VAC out of the reverse-connected transformer, which I feed into a voltage doubler. Crude but effective. At some point, I'd like to remove the neon lamp in the strobe and replace it with an LED so I can run it off a low voltage.

Those are Fairchild "Stealth" diodes for rectifiers. I also use Panasonic FC's for the low voltage filtering and ED's for the HV. Can't wait to hear it.

JL

[brianco]

....for taking the trouble. I'll let you know how it goes!

Any comments from anyone on JL's schematic?

[mikkelbreiler]

Originally posted by Steerpike


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!

I read your post and to me you come off as if you do not know what scratching really is.

It can be done and has been done to death on less capable decks than the SP-10MkII, the SL12x0 for instance.

"Scratching" is a lousy term for the activity itself.
Scratching means to momentarily halt or manually turn the vinyl opposite the playing direction for artistic reasons.
The way this is accomplish probably defers a LOT from your perception:
A special thin mat is used called a slip mat. This mat has a very slippery surface facing down on the turntable platter and a grippy surface facing up against the vinyl record.
Thus stopping the vinyls movement requires a lot of less effort than I think you give this principle credit for.
And moving the vinyl in the direction opposite playing does not require a whole lot of power either. This is done routinely by DJs using the soft part the their fingers, just under the nail.
The SP-10 family gives the principle of letting the vinyl go and quickly letting it pick up speed to play a section very good properties to work with. it is the analog way to sample and repeat in the old days.
Look around I am confident that several videos on the internet show this principle.
Technics manufactures slipmats for professionals, and decks that can stand up to this. Technics is also one the main sponsors of the annual International DJ Championship competition.
I really do not see this as something bad, ill or not to do.
There are countelss reason why you do not want to do this. ranging from, the cost of the stylus/cart or record all the way up to you're not good enough at it to warrant keeping up doing it.
I have seen and heard some truly amazing stuff done using turntables and a mixer.
This is USUALLY not the type of use you employ using your fathers Koetsu MC cartridge and his rare collection of 1st issue half-speed mastered classical music. But a DJ will have another take on it and use any snippet for effect.

I never DJs myself and never tried my hand at mixing. With arthritis in family gene pool this would probably not be a long career anyway. And I should have started when I was a kid in the 80s.
For now I will hope this thread ends up in more pictures of working stuff and resort to fixing my gear up as best as I can.

Vinyl would not be this popular today without DJs. So go and hug your local DJ. Keep saving old decks from waste deposits, neglect and people who do not know what they are doing.

-Mikkel

[mikkelbreiler]

There is a seller on eBay who is selling new after market Power Supplies for the SP-10 Mk II. I forget which seller ID he has but it looks small and can probably be built into at least just as many plinths as the factory one.

I have recently read an article about the Rubato turntable mat, from England. It is in the current issue of High Fidelity in Denmark (4-2009). it is a 1.7 Kilos copper plate which look good and is reported to improve the sound. I might go for one on next month budget.
No words anywhere about the added mass of the platter and any start up difficulties. But then you're talking about using the 10Kilo MkIII platter with the electronics designed to pull a 2,9 stock Mk II platter so 1.7 Kilo really isn't much I guess.

I have two SP-10MkII in my Technics collection and I am in the process of getting the SH-10B3 plinths completed for them. I am afraid I am not hard core enough to tell the tiny differences of playing a record with a blue label or an orange label like I suspect some people claim to can. But the engineer spirit of this thread is a good factor that kept me reading all the pages of the thread.

Btw the same Highi Fidelity mag 4-2009 also has an article about a swedish guy who secured himself a pair of Technics AFS-100 speakers. 175 kilo each. They'd be scraping the ceiling in my apartment and I am struggling to have enough room for my current collection as it is not everything can be set up up for use at the same time.


-Mikkel

[Steerpike]

I've started a web write-up of the project developments. So far, not much that hasn't been posted in this forum already.

(I will mention updates to my web page here in this forum, so no need to go check my page every day to see if its changed, you can rely on the email notifications from DIYAUDIO.COM)

http://web.eject.co.za/s8nspawn/sp10web/sp10.htm (a few internal cross-reference bugs still, and somehow my editor decided to eliminate every occurrence of the word 'the' - I may not have spotted all when I put them back! )

[bernard991]

Steerpike

for a dedicated page to the project , which hopefully will move forward
also an impressive array of projects on your toys page as well ...
pretty good credentials ..!

[Steerpike]

A bit more maths on my page 2:

Page 2

[Steerpike]

More maths on my page 2 - I've redone it as PDF instead of GIF images.

page 2

And more circuitry of the power driver stage:

Page 3

[Brett]

I'm not posting much, but am following this with great interest.

Excellent work.