Mod: Sl1200mk2 Improving Wow And Flutter

[Khom]

The LowPass filter can be further improved.
C210 was 220nF should be 1240nF
C211 was 220nF no change
.......................................
R207 was 56k should be 9k
.......................................

Did you simulate and measure this change? Looks like this is 'step back' to the more sharp response of LPF. And my simulation shows oscillation process.

(Later I will check the original value of C211 in my MkII-A)

[alfonso]

Interesting...

I recall the service manual has plots of the waveforms for calibrating the system, maybe you would like to perform such calibration with an oscilloscope.

As for flutter itself, adding more platter mass always helps...

As has been proved Flutter is not an issue with the sl1210...

Flutter _figures_ are not an issue with the Technics SL1200... when tested in the conventional DIN/IEC way.

Go compare it with an idler drive with a 4Kg platter mass and for sure you will hear a difference.

The flutter test they are carrying (1) applies weighting (2) it's limited to one fixed frequency (1KHz or 3KHz) and (3) cannot measure lower flutter than 0.05% because of the test records' limitation.

Please don't assume i have anything against the SL1200, as i've defended and keep defending it (and it's related models) on this forum.

Yes, but i do not agree that flutter is an issue on the sl1200.You are the only person who seems to think so.

No, not the only one. I we have an old thread on this very same subject, and i was just defending the SL1200 flutter as you were doing; while other people were telling me that the 1200 (and similar DDs) weren't as stable as commonly thought.

Now i see i was wrong.

Just search for "direct drive" and "cogging".

The "cogging" is something related to every thing has a motor spinning...and so is related to every kind of tt's too...and the fact that is more present in dd's (as bd lovers state) has yet to be proven

No. There are motors whose poles overlap. Those are cogless motors. Such the ones typically used... in idler drive tables.

The motor of the 1200 has poles that do not overlap.

The sl1200 motor,as you know, is quartz-locked:that means that you can slow the platter down or speed it up with your finger and you'll find the motor fighting against your finger to keep the platter at the speed selected.The rotation of the platter is under total control of the quartz,so no speed drift caused by inertia etc.And if you look at the specs of better dd's technics made you'll see that in those models even the speed drift that should happen when you switch between 33/45 while the platter is spinning is non-existing!In those cases the motor really has total control of the platter! Also,as you stated in the past,to hear difference in speed accuracy under 0,06% is quite a challenge...and,also,if the cogging (if present) isn't visible neither by looking at the strobe i think that really there's no reason to worry Of course is always good to know that things can be always improved...and very interesting things are being discovered in this 3d!

[OneyedK]

Did you simulate and measure this change? Looks like this is 'step back' to the more sharp response of LPF. And my simulation shows oscillation process.

Welcome Khom!

Yes, I did simulate, but no measurements yet.
Indeed there is a very small oscillation at 3Hz,
but this time, I optimised the filter for group delay.
Step response is now twice as fast as with the original mod.

With the original modification, I noticed the speed corrections
were better bringing the speed up, than bringing the speed down.
(this was during measurements, I'd have to make a movie instead of a screenshot)

Next measurement will be a logging of the control voltage.
So I'll be able to see how the response of the loop is in comparison with actual speed variations.

[flavio81]

If you go to the Library the Technics had 10x lower wow and flutter than most idler drives and changing the testing method will not help that.

My dear friend, you're comparing turntables tested in about 1965-1969 to turntables tested in 1977-1981. In late 70s you could measure standard (weighted) flutter with more precision. Also you're comparing measurements done the DIN way with measurements doing the IEC/JIS way, which will typically give lower numbers.

So "the Technics had 10x lower wow and flutter than most idler drives"... Hmmm... Let's see:

Technics SL1200MK2 W&F: 0.010% weighted RMS (JIS) and (here comes the trick) +-0.035% weighted peak (IEC 98A).

So Technics W&F= from 0.015% to max 0.060%, weighted.

Now for a standard Lenco L75... Measured real-life by a user:


Lenco W&F = +/- 0.020% weighted.

I fail to see the claimed "10x difference". Linear (unweighted) W&F is 0.10% which is what i would expect from the SL1200MK2 too. The difference is in the flutter frequency components and i'm afraid none of those tests will reveal the difference between such a Lenco and such a Technics. But they do sound different in terms of rotation stability.

[missan]

I think a good evaluation is to look at the frequency peaks, how they look like, and how the sidebands look like. We should not pay to much inportance at (in), from manufacterer, presented figures.

Most figures presented do not come from an independant lab.
missan

[OneyedK]

Now for a standard Lenco L75... Measured real-life by a user:

Did he mention how long it took him to get 33,33rpm?
On a Technics it's pushing a button, on a Lenco it's blood sweat and tears...
And connection only one channel to Adjust+ is a neat trick I didn't think of before

AGAIN, THIS IS NOT THE PLACE TO DISCUSS RUMBLER DRIVE PERFORMANCE,
THIS IS THE PLACE WHERE WE DISCUSS ELECTRONIC MODIFICATIONS TO IMPROVE THE SL1200 W&F SPECS.

I think a good evaluation is to look at the frequency peaks, how they look like, and how the sidebands look like. We should not pay to much inportance at (in), from manufacterer, presented figures.

Most figures presented do not come from an independant lab.
missan

You make a valid point there.
But it would be very difficult to distinguish between errors from the test record and errors from the drive system.
I have no knowledge of the existance of a measurement tool that can display what we want to see.
afaik even Audio Prescision stopped development for w&f measurement on their latest analysers.
The older ones didn't have a decent visualisation, just industry standard measurement protocols...

[alfonso]

If you go to the Library the Technics had 10x lower wow and flutter than most idler drives and changing the testing method will not help that.

My dear friend, you're comparing turntables tested in about 1965-1969 to turntables tested in 1977-1981. In late 70s you could measure standard (weighted) flutter with more precision. Also you're comparing measurements done the DIN way with measurements doing the IEC/JIS way, which will typically give lower numbers.

So "the Technics had 10x lower wow and flutter than most idler drives"... Hmmm... Let's see:

Technics SL1200MK2 W&F: 0.010% weighted RMS (JIS) and (here comes the trick) +-0.035% weighted peak (IEC 98A).

So Technics W&F= from 0.015% to max 0.060%, weighted.

Now for a standard Lenco L75... Measured real-life by a user:


Lenco W&F = +/- 0.020% weighted.

I fail to see the claimed "10x difference". Linear (unweighted) W&F is 0.10% which is what i would expect from the SL1200MK2 too. The difference is in the flutter frequency components and i'm afraid none of those tests will reveal the difference between such a Lenco and such a Technics. But they do sound different in terms of rotation stability.

mmm...it's the first time i hear that a lenco l75 has better speed stability than a sl1200...maybe it has lower rumble too?!

[flavio81]

mmm...it's the first time i hear that a lenco l75 has better speed stability than a sl1200...maybe it has lower rumble too?!

On a TT you can consider rumble sources:
(1) motor rumble
(2) bearing rumble
(3) uneveness of the record surface

Discarding (3), we have (1) and (2). On the SL-1200 and practically all direct drive turntables, motor (1) is never going to be a significant source of rumble since the motor rotates at slow speed (33RPM) and it's on the same mass as the bearing and the platter. So here the direct drives have a clear advantage, and in fact this is the #1 reason to consider Direct-drive as a turntable drive system.

For an idler drive, such as the Lenco, the motor rotates at much more rpm (1800RPM in case of the lenco) and vibrates more. Thus the motor (1) has the potential to be a source of rumble. Both in Lenco L75 and Garrard 301/401, the motor is suspended by springs. The motor rumble transmission path is as follows:

motor -> springs -> top plate (& plinth)

If the plinth is massive enough, motor rumble (1) is eliminated on an idler drive, and the residual rumble is (2) bearing rumble. More on this later.

Bearing rumble (2) is down to the fit, finish and overall quality of the rumble, and maybe to the platter balance too. I'm afraid the bearings on the SL-1200/1300/1400/1700/1800 are not as massive as the ones in a Lenco L75 or Garrard 301. I recall my SL-1401 having a significant rumble problem that simply wouldn't go even after i relubricated the bearing and moved the thrust plate so the bearing contacted a new part of the thrust plate.

Thus an upgraded bearing is a modification to seriously consider for a SL1200 enthusiast.

So, down to the answer: A correctly lubricated and adjusted Lenco L75/78 on it's stock plinth has generally nonintrusive rumble levels, but i would guess higher than the ones on a good condition Technics SL1200. Right now i'm listening to a stock L78 on my desk, on the worse setup possible (rumble-wise): Suspended by springs on a flimsy wood plinth. No rumble to worry about so far, and the turntable is 100% stock. But the motor has been relubed and recalibrated by me.

All the lenco rumble problems i've seen so far are mainly to miscalibrated motors or weak/incorrectly mounted motor springs.

By all accounts, a Lenco L75/78 on a heavy plinth has "no rumble". the same can be said of Garrard 301 turntables on a heavy plinth: The silence passages are black. How black? None more black.

AGAIN, THIS IS NOT THE PLACE TO DISCUSS RUMBLER DRIVE PERFORMANCE,
THIS IS THE PLACE WHERE WE DISCUSS ELECTRONIC MODIFICATIONS TO IMPROVE THE SL1200 W&F SPECS.

Stay cool.

[missan]

Just for some info. I have tried different combinations of cap. values for C210 and C211.
I have a heavier platter than original which might make a distinctive difference. Anyway I ended up with 220n/220n as the best combination for me, which was the original values on mine.
So I just changed them to much higher quality caps, which was a good thing.
missan

[OneyedK]

Hello missan,

I have no idea how much your platter+mat actually weights and no clue about how good your bearing is.
But given the fact that you increased flywheel mass and increased bearing drag, the overshoot of the 220/220 combination could be very well compensated by these things.

Don't get you hopes up about the "higher quality" caps in those locations, as long as the capacity was ok and no leakage current, the improvement would not be measurable nor audible.

Any idea how much your platter/mat/clamp actually weights?
(if it's at least 25% more than the original, my theory above is likely to be true)
Did you measure performance in some way?

I'm sorry I didn't get around changing the components to my last calculated values. Culprit is that darn good 103R, keeps me wanting to play records instead of working under the hood

Hope to finish the mod this week as I will be away from my decks until the second half of July after that... (you haul 16 tons and what do you get...)

Thus an upgraded bearing is a modification to seriously consider for a SL1200 enthusiast.

Absolutely true...
I'll try the thrust plate from Joel myself, as most "aftermarket" bearings go for crazy prices.
Maybe it's time to design one, together with some savvy engineers.

[missan]

Hi OneyedK

My platter weighs 40% more than original platter. Could very well be the reason.
My evaluation has been looking at frequency peeks and sidebands, using different frequencies. The peeks are sharpest with original values of caps.
I have cleaned the bearings, they are still perfect after long use. I see no benefit in another bearing if not making the plinth much more rigid.
missan

[OneyedK]

My platter weighs 40% more than original platter. Could very well be the reason.

Yes, that somehow dampens the response of the loop filter.

My evaluation has been looking at frequency peeks and sidebands, using different frequencies.
The peeks are sharpest with original values of caps.

Auch, that's misinterpreting what you measured.
I'll try to explain, but bear in mind that my English might not be good enough to be clear.
What you are looking at is an FM modulated spectrum.
Amplitude is not important, frequency deviation is.
The best possible loop filter will keep those deviations as small as possible.
However, if you look at the classical spectrum, smaller variations will show up
as a larger amplitude. Once the deviations are big enough (further from the original
signal) they will have no measurable amplitude, they will become invisible.
Now that is what you are seeing.
Small frequency variations will somehow thicken the peak,
while bigger variations will have no influence on the peak.
This is exactly what the original filter values do,
and that's the reason why I wanted to change them.
The difficulty is to keep the small deviations well under control,
while eliminating the larger deviations (something the original filter
simply does not do, as it doesn't improve the weighted w&f values)

I have cleaned the bearings, they are still perfect after long use.
I see no benefit in another bearing if not making the plinth much more rigid.

The bearing well simply doesn't last long on the stock Technics bearing.
And it will create noise.
I cleaned and relubed my bearing several times, visually inspecting it.
It felt still good... But then I changed it to a new (stock) bearing
and you don't need good ears to immediately notice the difference in background noise.

[flavio81]

The bearing well simply doesn't last long on the stock Technics bearing.
And it will create noise.
I cleaned and relubed my bearing several times, visually inspecting it.
It felt still good... But then I changed it to a new (stock) bearing
and you don't need good ears to immediately notice the difference in background noise.

With "bearing well" do you refer to the bottom thrust plate? If it's worn, you can offset the bottom thrust plate a little, so the turntable pivot touches a "fresh" part of the thrust plate.

The good thing with the SL-1200 and its cousins is that usually the bearings are interchangeable within all models (of course the automatic models have a slight opening in the bearing so the turntable pivot can engage the sprockets of the automatic mechanism.

[missan]

Auch, that's misinterpreting what you measured.
I'll try to explain, but bear in mind that my English might not be good enough to be clear.
What you are looking at is an FM modulated spectrum.
Amplitude is not important, frequency deviation is.
The best possible loop filter will keep those deviations as small as possible.
However, if you look at the classical spectrum, smaller variations will show up
as a larger amplitude. Once the deviations are big enough (further from the original
signal) they will have no measurable amplitude, they will become invisible.
Now that is what you are seeing.
Small frequency variations will somehow thicken the peak,
while bigger variations will have no influence on the peak.
This is exactly what the original filter values do,
and that's the reason why I wanted to change them.
The difficulty is to keep the small deviations well under control,
while eliminating the larger deviations (something the original filter
simply does not do, as it doesn't improve the weighted w&f values)

I have cleaned the bearings, they are still perfect after long use.
I see no benefit in another bearing if not making the plinth much more rigid.

The bearing well simply doesn't last long on the stock Technics bearing.
And it will create noise.
I cleaned and relubed my bearing several times, visually inspecting it.
It felt still good... But then I changed it to a new (stock) bearing
and you don't need good ears to immediately notice the difference in background noise.

My English could definitely be better, and what I don´t know about frequency analysis could fill a mall.

My thinking is that how broad the frequency peak is depends on the variation in frequency one is getting from W&F. With high enough sampling rate and an inert TT you will get only a very thin sharp response at exact frequency. With high FM this response will be much broader, and can relatively be looked at as one parameter.
missan