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Pro-Ject Debut III SB - vibration in tone arm

 

New member
Username: Jon6000

London, London 44

Post Number: 1
Registered: May-11
Hi everyone,

I've had this table for around three years and generally think it's good value, however an annoying problem has recently started to manifest itself. When spinning at 33rpm I can feel a slight vibration when I lift the tonearm. Not every time, but mostly. Sometimes it goes away if the motor has been on for a while. If I change the speed (via the Speed Box) to 45rpm there is no discernable vibration.

The problem still occurs if I remove the platter. However if I remove the belt I can barely feel any vibration. If I switch off the motor and just spin the hub by hand with the belt off I can feel no vibration.

My guess is that tiny vibrations from the motor are being amplified by the hub when the belt is on. Is this something I could solve with a little grease? If so, where exactly should it be applied. Or is it something I pretty much just have to live with given that it's a budget table?

Any thoughts or comments appreciated. Thanks,

Jon
 

Platinum Member
Username: Artk

Albany, Oregon USA

Post Number: 14377
Registered: Feb-05
Do you feel the vibration without the speedbox? Are you using the stock cartridge and counterweight?
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16141
Registered: May-04
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I think you'd be far better off consulting the manufacturer than a forum on this issue. If this is a common problem, the manufacturer should be aware of it and should have come up with some sort of fix - even for a budget table. As far as this forum is concerned, this is not a commonly reported problem so anything said will be nothing more than guesswork.


Consider first that a turntable is a closed loop system which implies that any unwanted vibration within the system will result in degraded sound quality. Then consider that the closed loop system must exist within the hostile environment of the average listening room. With that in mind placement of the table is crucial to high quality playback. You state this problem has "recently started to manifest itself". This then suggests you should think back and try to realize what might have changed just prior to your first noticing this problem. This would particularly apply to any changes in location or set up of the deck. Certainly, if you've recently changed cartridges, this would be a suspect in the "incorrect set up" category of investigation. If you can identify something that changed, either reverse it or rectify it and then determine whether the problem still exists.


If the problem persists after you've exhausted all possible changes made to the system, then we move on to the closed loop system itself. Discounting any outside vibration which might be entering the table through its feet, there are only two sources of vibration which would account for the problem as you describe it. The first is the motor and the second is the main bearing which supports the platter. The motor is an AC synchronous type which latches on to the pulsing of the 50/60 cycles of the incoming AC voltage in order to set its speed. While the basic motor on all budget belt drive tables would be fairly cheap, most do not suffer from any sort of "cogging" issues which would result in reasonably large (for a turntable) pulses in the motor. This should be even more the case after the addition of the Speedbox. You can check a few things here just to minimize the possibility of a motor problem. First, reverse the AC plug from the Speedbox at the wall outlet. This may or may not be possible depending on whether the plug is of a polarized design. If the plug is polarized and this is a problem that you are certain did not exist when you first set up the table, then assume the problem doesn't exist within the Speedbox to the degree you can remedy the issue yourself. Next, remove the Speedbox from the AC line and plug the table directly into the wall outlet. If the problem still persists, then you can eliminate the box as the problem with 99% certainty.

The other location for vibration to enter the system would be the main bearing/motor interface - which in this case is the belt drive system. The most significant advantage to a belt drive table is the inherent isolation of the two working elements of the table. The one link between the two pieces is the belt and this is where you should first look for a remedy to your problem. After three years time the belt has probably worn out and stretched itself out of shape. A new belt would be the first thing I would suggest if you don't feel like contacting the manufacturer. My guess would be this will completely solve the problem.

If you'd like to troubleshoot a bit before you order a belt, you can pull the main bearing to check for sufficient grease. You do this just like you would check a dipstick on a motor by pulling straight up and being careful not to mar the surface of the bearing or its supporting well. With the bearing out of the well there should be noticeable lubricant up to the top 1/2 to 7/8 of the bearing shaft. There's no reason for the original lubricant to have left the bearing as long as you've handled the table properly over time. So my guess is levels here are not your problem. If they are, order some bearing grease from your dealer since you do not want to mix lubricants in the bearing well. The dealer will instruct you on how to top off the bearing.

Unless the problem exists within the Speedbox, my feeling is the switch to 45 RPM is a red herring and doesn't have anything to do with the problem. By increasing the rotational speed of the system you've also changed the resonant frequency of the system and the tonearm problem doesn't exhibit itself quite so well at the higher resonant frequency. The same reasoning applies to spinning the hub by hand.

Keep in mind the table is a resonant system; if it were not, there would be no sound produced by the cartridge. As a resonant system, the problem could be the result of several minimal problems which, accumulated, are building up a single higher resonant frequency which you are detecting in the arm. To track this sort of problem you would first try to isolate the table more effectively from external vibration. Move the table to a different support shelf or to the floor and check for problems.

The more important question would be whether the arm is in motion only when you are holding it above the disc surface or also when it is in a play position. The former would be somewhat inconsequential to the table's performance and might only be a slight annoyance to you. The latter would result in somewhat devastating effects to the performance of the cartridge. If the latter were the case, then I might suspect the stylus is in need of replacement. The cantiliever of the stylus assembly acts as a spring and, as we all know, springs have multiple resonant frequencies. As the stylus assembly wears, the resonating points of the assembly change with time.

Overall, I'd do a quick check of the incoming voltage as described above. If this doesn't locate the source of the problem, then I would go with a new belt. If this doesn't solve the problem and the bearing lubricant is at a sufficient level and you can come up with no other changes which have recently ccurred, then it's definitely time to contact the manufacturer.


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Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16142
Registered: May-04
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One more question about the table, is the vibration cyclical in nature? In other words, can you detect a pattern to the vibration which you could relate to a certain position, or positions, on the motor or the bearing? If you suspect this is the case, mark the bearing hub in some manner - a piece of tape would do - and pay attention to the position of the tape relative to, say, the tonearm base, which each pusle you feel in the arm. How rapid is the vibration? More than twice during a single revolution of the hub? Or more often than that?


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New member
Username: Jon6000

London, London 44

Post Number: 2
Registered: May-11
Hello Jan,

Thank you very much for taking the time to respond. In answer to some of your points:

The table has always been in the same place since I bought it (actually around four years ago, not three as I stated) and I'm almost certain that the issue has not always been present. However I have moved it to a different location in order to try and diagnose the problem and the vibration is still there. One environmental factor that could have played a part is room temperature, the room can be very warm during summer mornings, and cold at other times. Unfortunately there isn't much I can do about this.

The turntable I have actually has the Speedbox integrated, so it runs from the same power supply as the turntable. Therefore it's a bit difficult to test it in isolation, or remove it from the loop. I actually had started to think the belt may be the issue, so it was good to hear that the problem could potentially be fixed by replacing a relatively cheap component.

The vibration is not cyclical, but constant, and doesn't vary according to the position of the tonearm. Therefore I can only assume the problem is still occuring during playback. The cartridge is the one that came with the table (Ortofon OM5E), although the stylus has been replaced a couple of times. I will double check that it is correctly fitted.

I will hopefully have some spare time tomorrow evening to check the bearing, although I'm starting to doubt whether this is the problem for the reasons you mentioned. After that I think I'll go ahead and order a new belt.

Thanks again for your thoughtful response, I will report back any progress.

Jon
 

New member
Username: Jon6000

London, London 44

Post Number: 3
Registered: May-11
Hi Art,

The speedbox is integrated so I'm not sure how to test without it. The cartridge is the standard OM5E that comes fitted, the stylus has been replaced with an OM10. It looks correctly aligned as far as I can tell using the cardboard protractor that came with the table. The counterweight is standard.

Jon
 

Platinum Member
Username: Artk

Albany, Oregon USA

Post Number: 14378
Registered: Feb-05
That you are using the stock counterweight and cartridge eliminates one common cause of vibration with that table.

Jan knows more about this than I do so I'll give her the floor.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16143
Registered: May-04
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http://www.project-audio.com/main.php?info=kontakt&cat=default&lang=en

https://www.ecoustics.com/cgi-bin/bbs/show.pl?tpc=1&post=1826889#POST1826889

"What I have noticed on my system, the speedbox seems to create vibrations on the motor.
(Speedbox is manipulating the frequency, right?)
This vibration travels via the plinth to the tone arm and finally to the cartridge. And if you lower the needle to the silent part of the record you will hear hum (because the cartridge is vibrating...).
I can actually feel the vibration on different parts of the turntable: in the motor, plinth and tonearm bearing.
Is this what you experience too?.
My solution was to put two soft rubber washers on both sides (four in total) to the motor's transportation mounting brackets and gently tighten the securing screws back were they originally were.
The result is a floating but more dampened fixture, and this seems to cure the hum in my turntable."
; http://www.vinylengine.com/phpBB2/viewtopic.php?t=20607&start=30



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Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16147
Registered: May-04
.

Jon, take that suggestion from vinylengine as a last resort. It certainly doesn't appear to be an "approved" modification of the table's design and I would be a bit concerned should that come from anyone at Project.

I'm not that familiar with the configuration of motor to plinth mounting on the Project table so I can only provide basic information here and you'll have to put it in the perspective of a budget table. However, the shift in recent years has been away from softly suspended components in the closed loop of the table. Higher quality tables most often will separate the motor from the plinth and use a rigidly mounted motor assembly as you would see on a VPI Scout for example.

The design philosophy of the rigid suspension you see on many of the top line tables is to minimize any random motion within the table's loop. By inserting soft washers between the motor and the plinth of the Project you will allow the motor to exhibit even more free motion (vibration) which will result in a greater deviation away from its centerline position relative to the main bearing of the platter. In other words, the physical distance between the centerline of the motor shaft and the centerline of the main bearing will constantly be shifting. And, while the exact physical distance between these two components is not critical to the performance of the table (when we are discussing a belt drive system), the constant shifting of the distance does become an issue. This shifting distance (vibration) creates a constant tugging on the belt which is then translated into a constant displacement of the bearing shaft and, therefore, also the platter. Given the microscopic dimensions of the record groove any sort of random motion in the platter will result in both lost information and additional noise as the stylus responds to the non-musical movement it is tracking.

Of course, if the movement in the arm is now sufficiently large enough that you can feel it through the arm, the movement is already there and the table's performance is already being compromised. This then becomes a d*mned if you do and d*mned if you don't situation. The motion of the softly suspended motor should be less than what you are detecting with the present arrangement. Either way, if the new belt doesn't solve this problem, and something like soft washers ends up being the answer from Project, then I would consider this a significant flaw in the design/construction of the table.



This isolation of motor to platter has been a consistent problem for turntable designers over the last half century. For many designers working from the 1950's through the 1990's the answer was a suspended subchassis as you would find on the original subchassis AR table or the current Linn Sondek LP12 (whose basic design dates back to the mid 1970's). As the understanding of just exactly how a table operates became more evident to designers, the shift gradually took place towards removing any sort of random motion in the drive system of the table. There really isn't a tremendous agreement on just how a drive system should be accomplished and this seems to be one of those issues where, if the designer is willing to devote enough time, money and resources to the issues, there can be several good solutions to the problems presented.

If this were my table, however, I would be looking for ways to minimize the vibration of the motor rather than simply making it less apparent through the plinth or arm. One approach I've used and which I felt was successful would be to use a lead weight as a vibration sink for the motor. For this modification you begin with a lead diving weight which you can find in any sporting goods store or any diving shop. Place the weight under the motor's center and insert an adjustable bolt and "T-nut" between the weight and the motor. (I used an extra speaker spike I had on hand but any bolt will do.) Place a very small bit of BluTak or non-permanent photo mounting tape on the broad top surface of the T-nut and position the top of the T-nut against the bottom of the motor mounting can. The other end of the bolt will rest on top of the weight. Slowly adjust the bolt against the T-nut until it provides a reasonably good fit and gradually reduces the vibration of the motor by sinking that vibration into the lead weight. Don't tighten too much or you can damage the mounting can in which the motor sits. The can has a mostly cosmetic function so there's no permanent damage done if you over tighten but there's no advantage to going that tight. The BluTak will keep the motor can from sliding round on the T-nut without being a permanent adhesive.

I had quite a bit of height to work with on the table since the table itself was supported by other diving weights. Whether this particular arrangement will work for you I can't say but, in any case, I would be looking to minimize motion rather than alllowing even greater motion in the motor and then trying to keep it away from the plinth/arm.



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New member
Username: Jon6000

London, London 44

Post Number: 4
Registered: May-11
Thanks Jan, I read with interest the various solutions in the links you posted - the washers solution was quite appealing, being fairly easy to implement, however I understand what you're saying about it increasing the motors ability to move around. I've read a couple of solutions involving replacing the transport screws however I'm convinced this would be extremely bad for the motor, and probably drastically reduce its life.

I've got a new belt on order, which I'm still hoping will be the "magic bullet" - in the meantime, I might try the washers just out of curiosity. If the new belt has no discernable effect I'll look into your fishing weight solution and see if it's feasible on the Debut.
 

New member
Username: Jon6000

London, London 44

Post Number: 5
Registered: May-11
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Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16153
Registered: May-04
.

" If the new belt has no discernable effect I'll look into your fishing weight solution and see if it's feasible on the Debut."


"For this modification you begin with a lead diving weight which you can find in any sporting goods store or any diving shop."


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New member
Username: Jon6000

London, London 44

Post Number: 6
Registered: May-11
D'oh!
 

New member
Username: Jon6000

London, London 44

Post Number: 7
Registered: May-11
Just to update, the new belt arrived but unfortunately does not seem to have resolved the issue.

I've experimented with various combinations of rubber washers and BluTack under the band that suspends the motor, however in most instances this actually made the vibrations worse. I did also try replacing the transport screws which appeared initially to remedy the problem, however after half an hour of spinning, I could once again feel the vibrations in the arm.

I was hoping to get at the bearing to see if I could apply a few drops of oil to it. I removed the rubber band and lifted out the motor, then removed the pulley from the top. I then tried to gently prise apart the motor however I didn't want to force it as I wasn't sure if it was designed to be re-openable.

Jan, regarding your diving weight solution, would the weight be sitting underneath the plinth or inside it, underneath the motor? I don't think there is room for the latter on the Debut, however there is a hole in the plinth around half an inch in diameter directly underneath where the engine is suspended. If I place the table on some rubber feet to give it some extra height, I could place the weight underneath the plinth, with the bolt going through this hole.

I'm going to contact Pro-Ject as well regarding the motor and to see what advice they can offer.
 

Platinum Member
Username: Jan_b_vigne

Dallas, TX

Post Number: 16185
Registered: May-04
.

"Jan, regarding your diving weight solution, would the weight be sitting underneath the plinth or inside it, underneath the motor?"


I'm not going to be much help with answers here, Jon. I can't recall ever seeing a Project table in a situation where I could get up close enough to know how it is laid out under the plinth. When you say "inside it", I don't really know where that would be. In general terms the weight would be stationed directly beneath the motor or the can which holds the motor. The "can" would be that portion of the mounting assembly which contains the "ears" to which the transport screws attach. Possibly the Project doesn't have such an arrangement but that would surprise me, I've never seen a turntable where the motor isn't held in some sort of mounting bracket (can). If I say the weight should be underneath the plinth, situated directly beneath the motor assembly, does that help? Unfortunately, I'm not seeing the hole you describe; http://www.project-audio.com/inhalt/en/manual/manual_debutphsb.pdf, so I can't say whether that would be an appropriate location or not. Generalizing again, the weight needs to be more or less centered under the motor itself to be most effective. How's that? The connecting bolt then forms a straight, vertical and perpendicular line between the weight and the bottom of the motor assembly.


"If I place the table on some rubber feet to give it some extra height, I could place the weight underneath the plinth, with the bolt going through this hole."


Due to the physical variations between tables it's not possible to say exactly how you should make this modification. For a temporary experiment rubber feet are acceptable. However, as a permanent fix, rubber feet are less than ideal since they also allow for extraneous, random motion within the table itself. Rubber feet have the advantage of being inexpensive for a manufacturer and, if there is no suspension to the table whatsoever, then rubber provides a bare minimum of isolation. Most high end designers will dispense with rubber feet or will be open to the user removing the O.E.M. feet and replacing them with a superior "footer" which further minimizes the "squishy" rubber effect. If the O.E.M. feet are of a harder rubber, they are providing virtually no isolation and are there simply to raise the table up and to not mar the shelf. Any aftermarket footer will include instructions which indicate proper placement is not in contact with the O.E.M. feet but directly in contact with the bottom of the unit and the supporting shelf.

We get back to the point where there are mulitple ways to manage the suspension of a turntable. IMO, the better approach with a table such as the Project would be to place a set of aftermarket footers underneath a platform/shelf (3/4 inch MDF would be a first choice here) and then place the table on another set of footers atop that platform. For the most part, avoid squishy materials in the suspension of these items as they tend not to interfere with the closed loop principles of a table. That said, suspension and footer mods are all too often a "suck it and see what comes out" sort of modification. What works for one situation might not work in another and certainly what works for a turntable is unlikely to be the appropriate solution when it comes to a power amplifier.

My suggestion for the Project, since it is a budget table designed to be roughly similar to the Rega products, would be something along the lines of a heavy, solid interface footer such as this; http://mapleshadestore.com/feedback_triplepoints.php Now, if you're like me and you read the copy and then see, "All of this for a mere $100.00!!!", you cough up your coffee. So use that example as nothing more than an example of the solid sort of footer I am suggesting. As I suggested in an earlier post, additional diving weights used as a footer would be acceptable as a diy device.

Most aftermarket modifications begin as someone simply recognizing a problem and then setting out to solve that problem. In most cases their solution begins with the sort of things you can find off the shelf and, if they prove successful, to then make a marketable product. In order to make a marketable product, the off the shelf device is dressed up a bit to make it appear to be worth "a mere $100.00!!!"

So use your imagination and come up with a few inexpensive devices which might work in your case. Suck it and see what comes out. If you are dissatisfied with one device, try another. If you're spending, say, five dollars on each device, you could try several before you reach the point where a "mere" $100 would have been a better solution. Get the idea?



And, yes, as I said in my first post here, calling Project is your best source for an answer to your specific problem. There certainly is the chance the motor is defective or that this is a consistent problem with Project. They would be your best source for a resolution at that point.

Finally, no, the motor itself is not meant to come apart. But, if the the vibration is so strong you feel it through the arm, it's doubtful additional lubricant in the motor would change the situation.



Good luck and let us know what Project has to say.



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