Technics SL1200/1210 debate

Having said that, it's really great to have an expert journalist like David Price posting here for everybody's benefit. Perhaps more research will shed some more light on this PSU conundrum. It's certainly complicated stuff, that's for certain, and completely beyond an ignorant fool like me.

 

Hi Devil - John Borwick in his original review of the SP10/II gives a good basic explanation of the SL1200 motor. It works just as the SP10/II but is the slightly lower torque version. This motor (Matsushita) went into most DD t/ts, with the notable exception of Sony who had their own BSL design, I believe. The principle is the same on all DDs, except Sony and Denon used speed references via magnetic tape heads reading real-time speed pulses from a magnetic strip on the inside of the platter.

DD was a good system, but like belt drive depends on how well you do it. It just being DD doesn't make it good or bad; depends on the implementation. What you can say is that it has a 'sound' which is very different to BD. DD is super taut and tight (almost fidgety on bad decks), BD is smooth and languid (and certainly wobbly on bad decks).

What you can say is that the best DDs measured far better than the best BDs of the day; speed stability was demonstrably better than even the best decks of the day like the Linn LP12.

Find the review here:

cheers,

David
http://www.vinylengine.com/technics-sp10-mk2.shtml

 

Thanks, yes I have read that before. The standard-issue PSU gives very good speed measurements. What I am struggling with is the notion that an aftermarket PSU will improve on these.

I think that's a bit of a tough one to answer.

Obviously, there are other issues as well, but this PSU thing is quite baffling.

 

...yes - I'll see if we can measure a stock SL1200 vs. the Timestep PSU one at the mag sometime.

I have to say that you can never have too good a PSU on anything. It's easy to demonstrate almost universally across the board. Ideally, the deck (and indeed our entire hi-fi systems) should be run off a car battery, or suchlike. AC mains can be very noisy, and the easiest way to fix it is to eliminate it altogether!

 

Only a motor when all said and done.
If the new PSU is bringing about any improvement it must be measurable.

Reduce noise? - measurable
Change torque? - measurable
Alter wow performance? - measurable
Flutter performance? - measurable
Performance under load ? - measurable
Resistance to feedback - measurable.

Far too much shit passing for fact in audio generally.
Would be nice to see some hard evidence backing up these changes for what is simply a motor drive.

Since these decks have a detachable shell it wouldn't be difficult, using the same shell and cartridge, to record a nice high res 24/96 sample from a standard 1200 and one that has been breathed on. Stick them up blind and let the people decide.

 

I recall years ago one of the engineers at Naim stated they *thought* the difference between a Valhalla and Armageddon was with torque. I got the impression that couldn't be measured at the time or they didn't want to discuss details.

How do you measure the torque, Rob?

 

I think that you can indirectly measure it, for example by measuring variation under load - both constant and dynamic.
It used to be measured in the uk magazines pretty regularly.

Naim may well be right.
I recall that the Linn Axis would back-off the drive to the motor once the platter was up to speed, and IIRC the Lingo did the same?

 

There's no reason at all why any type of aftermarket PSU should influence a motor with this type of control system. And this is the real reason why Technics have never upgraded it - it can't in fact ever be upgraded.

 

I figured this would be one way you could measure but it really was just a guess-thanks for confirming the possibilty.

IIRC, you're correct about the Axis and Lingo controllers. I believe one of the differences between Axis and Lingo are two class A amps producing a cleaner output for the motor with the Lingo. Can't recall exactly how the Axis does it (crystal oscillator maybe??)

regards,

dave

 

Fully agree James. I'm certainly not an engineer but I'd think if this were the key to a TT's sound then the original design's performance as described in JB's review linked by DP would mean this table sounds far better in any fashion than an LP-12. It doesn't IMO, more like x generations further away from the master tape compared to an LP-12 regardless of the Linn's colorations. Same with the SL-1100 A.

Changing between my 3009s and EPA-110 tonearm didn't alter the basic limitations in sound with these two Technics turntables as well.

regards,

dave

 

At the very least the PSU takes the transformer out of the deck.

 

Yes. That's exactly what it means

Although not the only issue, it does help to have a platter that can go round constantly at the right speed in a structure that doesn't sing along.

 

MJ Hi did Technics use an optical encoder, would you know how many 'snapshots' it takes per revolution?
Very best Keith.

 

From the Timestep site -

The SL-1200 has three problems with its power supply and regulator a) the transformer mechanically hums and this is audible through the cartridge, b) the transformer has an electromagnetic field also audible though the cartridge, and c) the existing power supply dips on some motor demands giving variable and poor dynamics to the feedback system.


They seem to agree with you Rob.

Perhaps Timestep could supply a power supply, for testing as you've described?

Sounds like Dean might have a deck that could be used?

Just thoughts.

 

Rob

they have a trace on their site actually -

http://www.soundhifi.com/sl1200/SL1200 PSU.htm


any thoughts on it?

 

They use a frequency generator. In the SP10/2 at 33.3rpm it produces about 105Hz. Which is about 189 'snapshots' per rev. the SL12x0 is similar.

The clever bit is that they phaselock the rotation to the frequency generator.

Paul

 

They don't specify the load they've applied. I'd like to see that trace under normal just playing a record conditions. And I'd like to see evidence that the ripple then manifests itself in the cartridge output.

Paul

 

As Paul says, an electromagnetic (not optical) frequency generator within the moving platter produces a waveform which is compared with a reference waveform.

The function of the various elements of motor control are loosely described in the service manual. See the part in the orange box.


Actually, looking back at some pictures I took of mine, I'd guess that the effect of the copper foil strip on this magnetic hub, passing the 3 pairs of small coils (as indicated in the 2nd picture) are what acts as the frequency generator.

 

Certainly looks impressive but as Paul says, we need to know the load being applied to the platter.
I suspect that graph looks quite different with say the load from a cartridge tracking at 2g against someone trying to stop the platter with their hand.

Getting the frame transformer away from the cartridge can only be a good thing though IMO.

 

I think those are the 'position detector' coils, which drive the switching to the drive coils as the magnet poles pass.

Paul