I used Sutherland engineering time line speed measurement device:
http://www.sutherlandengineering.com/time.html
to check the speed of a newly upgraded Linn LP 12 with the Radikal DC motor, which does not have speed adjustment available (automatic adjustment by tachemeter and low jitter clock) contrary to the AC motor.
To my disappointment, it appears that the speed is too slow (-0.045%), but still within specifications of the Radikal (0.05%). The timeline has a time-base accuracy of 2 parts per million (accurate to 00.0002%).
Can the weight of Timeline affect speed, possibly moving the belt up/down over motor pulley?
Is there a way to adjust very slightly Radikal speed? If the top of the DC motor is not flat, the Radikal installation manual says it affects speed but if the Radikal is slightly too slow can you play with the top plate of Radikal motor to tilt it to a desired position (which one?) by pressuring its top against the foam?
Can this problem come from a not fully perfect installation? Radikal installation guide states that the :
- flat of the housing should be up with the side of the Keel
- motor should be positionned centrally in the hole
what is the influence of these two parameters on the speed if any?
LP12: Radikal installation
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yours in music
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As the motor pulley on Radikal is not tapered (as on the old AC motor), there is no way of fine tuning speed with its angle or position. Linn only points out that if the installation is incorrect, you will get a speed error. The main parameter is most likely the motor axis angle; when it's correct, the belt should ride centered on the ridge on the motor pulley.
I haven't measured the exact speed of any Radikal LP12. Does it matter at all if it differs by less than 0.1%? I don't think so. At least I never notice any performance boost after I fine tune the speed on Lingo LP12's.
I haven't measured the exact speed of any Radikal LP12. Does it matter at all if it differs by less than 0.1%? I don't think so. At least I never notice any performance boost after I fine tune the speed on Lingo LP12's.
I came to think of something, yours in music. I adjusted an LP12 today and listened to which way the belt is best oriented. There are four possible ways (excluding twists, which don't sound any good) and I normally start with which side should go in and which out. This is also visible, but I wanted to make sure so I gave it a listen.
Next I change the direction of the belt. Usually a smaller difference, but today I felt it was at least as important.
Now, as you have access to that "unnecessarily exact"
speed measurement device, could you perhaps make an experiment and report your findings? This isn't anything important, just do it if you think it's fun!
If you have left your LP12 running for a good while, Radikal will have reached its steady DC value, set by the measured time it takes for the black felt piece on the inside of the outer platter to rotate one revolution. Now, if your Timeline says speed is exactly -0.045%, could you then please do the following:
Turn the LP12 off, remove the outer platter, turn the belt inside out (using clean fingers), put the platter back on, switch the LP12 on and measure again. Please measure right from the start (as soon as the red LED in the LP12 on/off button dims). Because IF the speed is now slightly altered, the timing circuit of Radikal will start adjusting it, probably ending up at -0.045% again.
Did the measured speed differ from your original value of -0.045%, or was it the exact same?
Could you then do the same thing with the belt reversed in direction (turning it upside down)? Any (initial) speed change from that?
As I just mentioned, I suspect the timing circuit of Radikal will gradually adjust your speed back to the value you originally measured (-0.045%). But the purpose of the experiment is that I'm curious whether the orientation of the belt can affect the efficiency of the belt drive. Higher initial speed would indicate a more efficient transmission.
If there is any noticeable speed change resulting from the belt position, my next query is whether the most efficient belt direction is also the best sounding.
Next I change the direction of the belt. Usually a smaller difference, but today I felt it was at least as important.
Now, as you have access to that "unnecessarily exact"
speed measurement device, could you perhaps make an experiment and report your findings? This isn't anything important, just do it if you think it's fun!If you have left your LP12 running for a good while, Radikal will have reached its steady DC value, set by the measured time it takes for the black felt piece on the inside of the outer platter to rotate one revolution. Now, if your Timeline says speed is exactly -0.045%, could you then please do the following:
Turn the LP12 off, remove the outer platter, turn the belt inside out (using clean fingers), put the platter back on, switch the LP12 on and measure again. Please measure right from the start (as soon as the red LED in the LP12 on/off button dims). Because IF the speed is now slightly altered, the timing circuit of Radikal will start adjusting it, probably ending up at -0.045% again.
Did the measured speed differ from your original value of -0.045%, or was it the exact same?
Could you then do the same thing with the belt reversed in direction (turning it upside down)? Any (initial) speed change from that?
As I just mentioned, I suspect the timing circuit of Radikal will gradually adjust your speed back to the value you originally measured (-0.045%). But the purpose of the experiment is that I'm curious whether the orientation of the belt can affect the efficiency of the belt drive. Higher initial speed would indicate a more efficient transmission.
If there is any noticeable speed change resulting from the belt position, my next query is whether the most efficient belt direction is also the best sounding.
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yours in music
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- Location: Pays-Bas
That's an interesting idea, but I don't know if this time line device, rightly called unnecessarily exact :mrgreen: can allow you to get an idea of the initial speed adjustment using different belt configuration in order to determine which belt drive configuration has better efficiency (higher initial speed).
I show you a video illustrating how this time line works.
http://www.youtube.com/watch?v=RF2XieUlzvk
For each revolution, the Timeline will flash out 8 lines on the wall. Choose only ONE of the locations (ignoring the other 7). That one location will get a new line every time the turntable rotates completely around. If speed is correct, the new line will hit the same spot for every revolution. otherwise it will drift in position.
I show you a video illustrating how this time line works.
http://www.youtube.com/watch?v=RF2XieUlzvk
For each revolution, the Timeline will flash out 8 lines on the wall. Choose only ONE of the locations (ignoring the other 7). That one location will get a new line every time the turntable rotates completely around. If speed is correct, the new line will hit the same spot for every revolution. otherwise it will drift in position.
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yours in music
- Member
- Posts: 18
- Joined: 2010-05-17 11:53
- Location: Pays-Bas
This is how to determine the speed deviation:
First, you measure the drift from the laser light, in my case (excert from an email):
I used the time line to check the speed of a newly upgraded Linn LP 12 with the Radikal DC motor, no speed adjustment available (automatic adjustment by tachemeter and low jitter clock).
To my disappointment, it appears that the speed is too slow.
I put a reference vertical line on the wall behind my turntable, on the perpendicular line to the wall from the central spindle point, distance is 48,4 cm between the spindle and thewall. I measured how many rotations are necessary to move the laser 10 cm (5 cm from each side of the reference point ). It took 75 rotations to move 10 cm. I did it also for a drift of 14 cm (7 cm from each side of the reference point). It took 100 rotations (less than the expected 105 rotations necessary if you have an average rotation of 7.5 for each cm as in the first measure, but I believe this is because the wall is flat not a circular shape). I would like to know how to derive from these measurements what is the actual speed of the turntable or the % deviation from the reference 33 1/3? If you know please tell me!!!
The radikal DC motor speed of Linn is specified accurate at 0,05%.
Could it be also that when you put the timeline on the spindle to do these measures, since the weight that the motor has to drive is higher, this slows the tt much like the stylus drag?
Also the drift is not regular, for example the first 1cm drift needed 9 rotations, the secon one 6, the third one 8 and the fourth one 7...
Second, you make some calculations:, for example in my case (quote from an answer to my previous email by sutherland):
if the drift is 1 revolution over a time period of 100 turntable revolutions, that would be an error of 1%
with a wall distance of 50 cm, the circumference of the circle would be pi x d about 3 x 100 = 300 cm
so a drift of 300 cm over 100 revolutions would be 1%.
Linns specs 0.05% that would be drift of 300cm x 0.05 = 15 cm
I think the speed change by belt position could be measured in terms of how many rotations necessary to have a drift of X cm on the back wall? Problem is that as indicated earlier the speed variation is not time constant...
First, you measure the drift from the laser light, in my case (excert from an email):
I used the time line to check the speed of a newly upgraded Linn LP 12 with the Radikal DC motor, no speed adjustment available (automatic adjustment by tachemeter and low jitter clock).
To my disappointment, it appears that the speed is too slow.
I put a reference vertical line on the wall behind my turntable, on the perpendicular line to the wall from the central spindle point, distance is 48,4 cm between the spindle and thewall. I measured how many rotations are necessary to move the laser 10 cm (5 cm from each side of the reference point ). It took 75 rotations to move 10 cm. I did it also for a drift of 14 cm (7 cm from each side of the reference point). It took 100 rotations (less than the expected 105 rotations necessary if you have an average rotation of 7.5 for each cm as in the first measure, but I believe this is because the wall is flat not a circular shape). I would like to know how to derive from these measurements what is the actual speed of the turntable or the % deviation from the reference 33 1/3? If you know please tell me!!!
The radikal DC motor speed of Linn is specified accurate at 0,05%.
Could it be also that when you put the timeline on the spindle to do these measures, since the weight that the motor has to drive is higher, this slows the tt much like the stylus drag?
Also the drift is not regular, for example the first 1cm drift needed 9 rotations, the secon one 6, the third one 8 and the fourth one 7...
Second, you make some calculations:, for example in my case (quote from an answer to my previous email by sutherland):
if the drift is 1 revolution over a time period of 100 turntable revolutions, that would be an error of 1%
with a wall distance of 50 cm, the circumference of the circle would be pi x d about 3 x 100 = 300 cm
so a drift of 300 cm over 100 revolutions would be 1%.
Linns specs 0.05% that would be drift of 300cm x 0.05 = 15 cm
I think the speed change by belt position could be measured in terms of how many rotations necessary to have a drift of X cm on the back wall? Problem is that as indicated earlier the speed variation is not time constant...