I just looked in storage and pulled out a Technics SL-B2 that I had purchased for near-nothing many years ago. It appears to work fine after cleaning up the speed control pot and 33/45 switch, and adjusting the internal trimmer to put the 45 speed in range. The strobe looks stable, but I should put an actual record on it an play it (stylus appears there, but is in unknown condition - I have some LPs in the same condition).
Pulling the platter off shows the same green pole pieces and other motor characteristics I've seen on every other Technics direct drive. A custom-designed motor controller would run any of the SL-1xxx drives, presuming these all have the same number of pole pieces and same speed sensing mechanism.
As for stylus drag ... if I lightly touch the edge of the rotating platter, the strobe pattern shifts, indicating a temporary change in speed. When I let my finger off, it shifts back, indicating another temporary change. I've noticed this on every other DD I've tried it on (at least two that I recall), so this lag-with-drag seems to be a common "characteristic." My "finger drag" is surely ten times what an LP stylus drag would be, but a stylus still might be enough to measurably change the speed between silence and a loud passage. I must try the bristles of a small paint brush, that should make a "light drag" within the same magnitude as a stylus.
Then there's the larger size "78" stylus, needed to play acetates, whether they're curt at 33, 45, or 78RPM. The one I have tracks at about 5 grams, and would surely have proportionally more drag as well.
Pulling the platter off shows the same green pole pieces and other motor characteristics I've seen on every other Technics direct drive. A custom-designed motor controller would run any of the SL-1xxx drives, presuming these all have the same number of pole pieces and same speed sensing mechanism.
As for stylus drag ... if I lightly touch the edge of the rotating platter, the strobe pattern shifts, indicating a temporary change in speed. When I let my finger off, it shifts back, indicating another temporary change. I've noticed this on every other DD I've tried it on (at least two that I recall), so this lag-with-drag seems to be a common "characteristic." My "finger drag" is surely ten times what an LP stylus drag would be, but a stylus still might be enough to measurably change the speed between silence and a loud passage. I must try the bristles of a small paint brush, that should make a "light drag" within the same magnitude as a stylus.
Then there's the larger size "78" stylus, needed to play acetates, whether they're curt at 33, 45, or 78RPM. The one I have tracks at about 5 grams, and would surely have proportionally more drag as well.
The idea is an oil bath ( as said ATF ? ). Some sort of reliable sine wave with finger load and no load to get bench marks. Then add oil. Ideally voltage to coils lifts by perhaps 30%. Do the circular test you showed to see if wow and flutter etc OK. Veridier conjecture says if an imposed drag ( not frivtion, think canal boat ) is ten times greater than any stylus force then the stylus force is nullified. If you like the vector changes and the reactive load looks resistive. The Technics itself will have alogrithms to make a soft circuit. However making it mecahnically soft will be helpful ( one hopes, it might sound like an LP12 if too soft ). About too soft. I recently cured an echo resonance in a speaker unit with a phase plug. At first I didn't like it as the energy and verve was less. Now use to it I think it would be bonkers to go back. What it now needs is active EQ to add the sparkle back and doubtles restore the small peak I like. Listening to opera it is obvous the sound would suffer to go back to how it was. The drive unit has a wizzer cone so to have it this good is already something remarkable. The point being that often hi fi is one step forwards and two steps back.
Looking at it from other points of view. Most ideas seem to risk making it worse or kill the electronics. The drag factor is compensated so we can safely play with that. One way would be to fit a belt drive to a small acrylic platter on the platter top. It could use a Gyrodek belt or clone. If it was already good when belt then between the systems a hybrid drive could both enchance and damp. The games played on the belt drive as that would be easier.
How I discovered the drag was trying to get rid of it. Garrard 401 etc seem to take 10 minutes to come to speed. As best I know it is drag. Once discovered to be a friend a bearing was made to a tighter spec. It took 12 hours to reach speed. If switched off for 10 minutes it seemed to need another 12 hours so not just heat related. The Garrard motor is large so not a lack of power. The tribology seems to have tadpole shaped molecules in the oil. When they flow in a lamina way around the beaing shaft a stassis is arrived at. Perhaps the damping of an amplifier is simialr. You can test it amplifier on and off by gently pushing the cone. It should feel damped when on. Some say negative impedance to a motor will do the same. I have doubts. When Garrard I proposed a motional feedback system or pre-distotion. It might work on valve amps. I doubt it would for a motor. Having said that the 501 motor is almost identical cycle to cycle as was pointed out in it's world record test report. That is an excellent candidate for pre distortion. I would only exspect 3 dB vibration improvement on that motor.
The Technics motor when damped might be very stable regardless of load. It might once understood have ways of offering pre-distortion as anti vibration. A notch filter might be used to work in the flutter region . As the coils are shaped to fit a hole it is doubtful they draw current sinusoidally. Some will infer they do as they see a near perfect sine wave in the voltage input. Don't forget the output impedance of the chip will be mOhms and mask the true current use. Personally I wouldn't give this much time as the mechanical route seems assumed. The measurements no matter how far from the absolute truth can be useful if repeatable. Whatever daft waveform you get as long as repeatable will say if wrong on a conjcture. The old Sony video manuals never said what the waveform meant. Just if good or bad.
1+1= 2 that's the only logic used. As I said before my living is doing this and I do OK. £20 000 000 turnover in 10 years and perhaps a bit more. I never read the exact acounts so go on what I am told. PCB about 133 in ten years. All went to market.
As far as I can see is all you dislike is your collecting bug added to . If direct drives are liked why ? I feel some guilt over slagging off DD in the Linn era. Now I would like to know more. I have no idea what you do for a living and no idea if you run rings around me with sucess you have had. If you do then I should take note of you. I am a time served engineer of about 50 years experiance and made money from it for about 40 of them. The work I did with Garrard was a hobby. I was offered to run BSR once. Wish I had. They were nearly finished at the time so I doubt it would have been fun. One thing I learned a long time ago. Knowing things is unimportant. It is knowing people. Knowing who will get the job done. It's team work and finding peoples good qualities. I never suffer not knowing things. The answer arrives or is found. If I don't know I ask. Not wanting to know will never solve anything. Whatever troubles you fellow ????????????
As far as I can see is all you dislike is your collecting bug added to . If direct drives are liked why ? I feel some guilt over slagging off DD in the Linn era. Now I would like to know more. I have no idea what you do for a living and no idea if you run rings around me with sucess you have had. If you do then I should take note of you. I am a time served engineer of about 50 years experiance and made money from it for about 40 of them. The work I did with Garrard was a hobby. I was offered to run BSR once. Wish I had. They were nearly finished at the time so I doubt it would have been fun. One thing I learned a long time ago. Knowing things is unimportant. It is knowing people. Knowing who will get the job done. It's team work and finding peoples good qualities. I never suffer not knowing things. The answer arrives or is found. If I don't know I ask. Not wanting to know will never solve anything. Whatever troubles you fellow ????????????
OK, may be some other day about torque required to overcome stylus drag.
Can Linear turntables can be used as motor unit ? Arm can be discarded. But I doubt if platter and motor with electronics will be any good.
regards
Can Linear turntables can be used as motor unit ? Arm can be discarded. But I doubt if platter and motor with electronics will be any good.
regards
@Hiten, there was this (contentious) thread over at Lenco Heaven where people noted down the spin down times of their respective Lencos. This was usually done by switching off a turntable that is playing, and allowing it to spin till it stops on its own, the brake being disengaged. An offshoot of this exercise was to test how much the stylus drag affects the spin down time. IIRC, the stylus reduced the spin down time by as much as half. Typical numbers were 30-32 spins without (@33 rpm), and half that with stylus engaged. So I would say stylus drag is not inconsequential.
Nigel. We do not give a Fark how much you earn or how many companies you were asked to run. Not impressed as you do not contribute anything of ANY USE to this thread. Please stop or will ask for removal to keep this thread on topic!
That's a good idea. Don't assume to run for as long as possible is best. It is as a test of bearing health. Sometimes to increase drag then change pully size a fraction helps. Often more rumble and other noise. It still might be something you like. Keep an open mind.
This happens in a practical example. The grease bearing Garrard 301 runs about 3 % fast if changed to oil. This is ideal for Japan at 95 to 105 V . In fact the speed will be about right just doing this. In the UK a new pulley needs to be made to suit. From this a false idea that the early ones are best has come about. Mostly it is the Japanese wanting them. S No circa 60 000 and above are the nicer ones. The rumble was less at about 60000 as when stereo arrived it had to be changed ( it was said to be - 35 dB in early examples ). In time the 401 was designed from all the ideas put together. For some reason 401 took years to become almost as good as the 301. This is daft as 90 % of the parts can be swapped. It is not difficult to make 401's work just as well. The 501 is 90 % the same as 301 in the hidden parts. The motor is larger and built in house. It is 24 watt and the older ones 12 to 16 watts. All of these problems can be solved with a Variac if wanting a simple root. My Variac is Indain called Voltsmart. It uses a LM324N to control a very beautiful synchonus motor. Alas I messed it up by " improving " the servo. Now working fine. It gives me 200 to 300 VAC 10 amps. If anyone ever needs that servo circuit I traced it out. Well done India.
For my sins the 401 I have is the worst type. It is 301 parts in the first production about 1964. I was told when ready to go the bosses insisted on using up 301 parts. They then killed it by using a 12 watt winding . Later it was made 16 watts as 301 after protests from reviwers. Ralph West effectively said 401 was rubbish in his review. He had forgotten to put the supplied oil in the bearing and would never admit it. As Terry O'Sullivan said the factory should have visited him and done the job. He possibly felt a bit upset they didn't, as terry said you might also take him to lunch. Charles Austen pumps have been known to. John Borwick confirmed that Ralph was less than happy to talk about it as he might have been a bit harsh and a bit wrong. I think he pointed to Thorens TD 124 and said time to stop buying British. Ironic as TD 124 has more problems than 401 I feel and of the same type. John is still alive. I can not change my deck as it was a gift from a friend who would be upset. So I will raise the voltage instead. I am rather happy it has 301 parts. I can put the later coils in of which I have plenty ( that I don't count as wrong ). The symptom of the " awful " 401's is they never stay on speed very long. Although subtle the 16 watt ones are less fussy. We are only talking 0.1% so not vast. All the same the better ones are more stable. Raising the voltage has limits. In time the iron saturates and that is not good. Thus a 16 watt coil will always be better.
Anyway guys time to sign off. You now know all I know so over to you. Be open minded. I was and found the JVC L3-E to be better than my wildest dreams. I only bought it because the guy said he didn't want to take it home and give him £35. I bought it as it is so small. I then fell in love with it. I am still friends with Paul Stewart ex of JVC. He was genuinely over the mooon when I said how I liked it as it was one of his babies. JAS 11 and VHS also. Paul told me how he launched VHS. It would now be less than OK. He sold tapes to the film industry at a prices they could not resist. The rest is history. I worked with VHS and Beta. I never really saw Beta as anything special. If a Beta was set up for hours it would win on bandwidth. LP12 the same, 4 hours work Linn should have engineered out. Generally the JVC were better as found in the box. JVC X1 is a great pick up. It's Shibata tip was the start of modern types. The Z1 somehow nothing special.
Today I helped design the Loricraft PRC 7. This is to clean 20 inch records. My input was insisting it looks good which was a headache until the F word was exchanged a few times which made everyone laugh. The problem being a new layout. As I said " Remember guys all drawings in the dustbin and don't make a spare". Often I get phone calls " Nige , do you remember how we did this or that"? 90% of the time I have a drawing. We could clean 21 inch if they exist. I suspect over time the PRC 5 which can do the same has sold 20. It's not much but nice to be part of cleaning records from as far back at 1928. I would guess Loricaft has sold 2 000 machines in the last 10 years of which I built 1500 ? I don't get paid now. It's my baby as I hated it so much when I first built them. No two ever worked the same although all were made to work. It took years to get all of it right. Now they just work and are fantastic in build quality. Someone cloned one recently. It was a famous company. They had one to copy. It ruins records. How can that be ? The clone has an inclined PTFE tip. Any fool can see that won't work. The arm is long and no offset. As the Loricarft is a clone of the 1968 Audio and Design Ltd we never really understood that. It is simply to stop the nylon working as a stylus. That would be a disaster. This was one of us who isn't very interested who worked that out. Peter usually only understands being paid, he thinks record cleaning machines a daft waste of money. He builds the arms after Guy at 84 said it was time to give it up. Guy has offered to help when needed ! I love working with older people. At 58 I was the youngest at Loricarft by some years. Steve who took my job about 44.
Hooray!
Ref drag clearly few opened the link, but it matches what was measured on lencoheaven. So they could have saved themself the effort as it was worked out 30 years ago! But is it significant?
Ref drag clearly few opened the link, but it matches what was measured on lencoheaven. So they could have saved themself the effort as it was worked out 30 years ago! But is it significant?
Is stylus drag significant?
For the heavy platter-ed Lencos, it's probably not significant to produce speed variations. Especially if a regular mat is used. I once tried an acrylic mat on my Lenco and I was surprised to observe that using a record cleaning brush to clean a spinning record was enough to slow down the record. I observed it more carefully and saw that the acrylic mat was slipping on the platter with the application of some force from the record brush. This was instantly cured by reverting to a rubber mat. Now I use a rubber or felt mat below the acrylic mat because I somehow like the sound of the acrylic mat.
And now back to regular programming......🙂
For the heavy platter-ed Lencos, it's probably not significant to produce speed variations. Especially if a regular mat is used. I once tried an acrylic mat on my Lenco and I was surprised to observe that using a record cleaning brush to clean a spinning record was enough to slow down the record. I observed it more carefully and saw that the acrylic mat was slipping on the platter with the application of some force from the record brush. This was instantly cured by reverting to a rubber mat. Now I use a rubber or felt mat below the acrylic mat because I somehow like the sound of the acrylic mat.
And now back to regular programming......🙂
I did start working through some numbers to present on this for discussion, but an emergency C-section got in the way so watch this space. I am convinced that, due to the way the control loop works platter inertia removes any variations as torque is being corrected for very rapidly. The SP-10 Mk3 which uses the same principles but biggyfied from all the cheaper quartz lock units can spin a 10Kg platter to lock in 0.25 seconds. The tacho on these turntables have a pulse around every 1.2degrees of rotation. Only the big rim drives can match that and they do not have the control loops.
Joshua,
Not sure about the motor on/off run down time with/without stylus, as motor is not involved. Lets say without stylus it takes 20 rotations and with stylus 10 rotations. Drive system has that much time (10 rotations just to exaggerate) to correct speed. That means platter inertia is a good thing.
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One more of my non-scientific crude torture test experiment. I replaced the stylus on my turntable with pointed plastic nail on clamp, tied with rubber band and counterweight on the headshell placed on not so good running record. The strobe was steady. Counterweight with rubber and dummy stylus was almost 100gms. Arguments about this being (1) constant fixed drag, (2) plastic stylus will have less friction and (3) How electronics handle the varying drag (if any) should be heartily contemplated. But at 60 times normal tracking force the turntable did very well.
Video : Drag Test
Not sure about the motor on/off run down time with/without stylus, as motor is not involved. Lets say without stylus it takes 20 rotations and with stylus 10 rotations. Drive system has that much time (10 rotations just to exaggerate) to correct speed. That means platter inertia is a good thing.
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One more of my non-scientific crude torture test experiment. I replaced the stylus on my turntable with pointed plastic nail on clamp, tied with rubber band and counterweight on the headshell placed on not so good running record. The strobe was steady. Counterweight with rubber and dummy stylus was almost 100gms. Arguments about this being (1) constant fixed drag, (2) plastic stylus will have less friction and (3) How electronics handle the varying drag (if any) should be heartily contemplated. But at 60 times normal tracking force the turntable did very well.
Video : Drag Test
Attachments
I ran some numbers last night and wrote some text then battery fell out of laptop 🙁
anyway, based on published figures with bearing drag and average stylus drag being roughly equivalent and stylus drag varying 3:1 between min and max, you end up with a 1.8:1 variation in torque requirement between min and max. If you double bearing drag that ratio drops to 1.5:1
So does it matter? Most turntables have no control loop. DD do have a control loop that can work very quickly. What I have yet to calculate is the effect of the drag changes when you take platter inertia into account. I suspect it will show that the DD is unperturbed by varying stylus drag, but cannot prove it yet.
anyway, based on published figures with bearing drag and average stylus drag being roughly equivalent and stylus drag varying 3:1 between min and max, you end up with a 1.8:1 variation in torque requirement between min and max. If you double bearing drag that ratio drops to 1.5:1
So does it matter? Most turntables have no control loop. DD do have a control loop that can work very quickly. What I have yet to calculate is the effect of the drag changes when you take platter inertia into account. I suspect it will show that the DD is unperturbed by varying stylus drag, but cannot prove it yet.
As I posted earlier (and in the old provocatively titled "Why is DD Bad" thread), the turntables I've seen DO have a changed speed/phase with something larger than stylus drag, and I presume it would react with a change proportionally smaller, but still there, with varying stylus drag.
If "unperturbed" means an inaudible change, then that would depend on the ears doing the listening, but I'm reasonably sure the effect could be measured.
If "unperturbed" means an inaudible change, then that would depend on the ears doing the listening, but I'm reasonably sure the effect could be measured.
Measure yes ( well not sure which test records would work for this) but the questions are
1. Is it audible
2. Are other methods better
3. How can it be minimised
1. Is it audible
2. Are other methods better
3. How can it be minimised
It is said that Direct Drive turntables are as good as the control system they are having. It would be wonderful if someone gives rough guidelines how to recognize them.
Regards.
Regards.
This is something that needs more research. The classic 70s/80s DD units had analogue control units, but these days you can do a lot more digitally. It's an area I want to research more. But I need to relearn a few bits of control theory. They say 'use it or lose it' sadly I didn't use it.
Been looking at some other options today and the SONY PS-LX22 and its ilk seem to go cheaply so having a flutter to see if I can pick one up for a gander. As with my technics the idea is to see if the motor can be reused in a better housing.
from pics Sony looks OK. Is electronics control system good ? Which control system would be good. Quartz or servo ? There were some Sony turntables with XTAL Lock. But I don't understand control systems.
Regards.
Regards.
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