A tube would be better than an l beam in my opinion. If you used the carbon strips to form a box section around a balsa core you can improve the performance over that of a straight forward tube. A balsa carbon construction has excellent self damping properties. As balsa has a very low density, 0.16g/cc, very little mass is added Furthermore you can taper the box section to maximise the armtubes properties. Much easier than finding or making a tapered tube. Additionally the cartridge can be attached directly to the bottom of the box section eliminating the need for a headshell.
Niffy
TT Noise
Lest anyone get the idea that my TT and LT arm do not have any vibration problems I went on an expedition to try finding what kind of noise my setup actually has and where/how it was being generated All my testing was being audited through headphones to break any feedback loop there. Then I put a record on the platter. Next to the platter and on the top plinth I placed a hard stone cylinder tall enough to reach record level Then I set the needle on the stone cylinder and turned up the volume just under full gain. The sound was deafening! At normal listening levels there was some noise but easily covered up with music playing (needle on record now). What triggered this investigation was this discussion in the DIYaudio forum and the fact my old motor was starting to generate unwanted amounts of noise. Now to answer my previous question "where is all this noise coming from" let me identify the primary sources. So I had needle coupled to the top plinth through a stone pillar, turntable and motor not running and gain set way up. In my ears I could identify the oil burner in the basement, the motors on the hot water circulator, the hot water circulating in the pipes, my tapping on the floor in front of the TT and the shelf on which it stands and all the other timber frame house noises. Then I switched the stylus to the non rotating platter with a record on it. Noise levels were reduced some but still objectionable. Then I went back to the stone pillar and fired up the motor which by now is outboard mounted and sitting on some plumbers putty isolators. I could hear the motor running and some very low level AC hum. With the drive belt removed and spinning the platter by hand I think there was just a faint sound (maybe) from the bearing. At normal listening levels this would be inaudible.
My previous remark, more or less in jest, was about the turntable and peripheral furniture and construction stuff being a giant microphone looks like that is indeed what we have. The cartridge stylus and generator coils are just sitting there on the record held there by mass and inertia but the entire environment which it is coupled to is vibrating like crazy. It hears very last sound and vibe in that environment. What does the generator do? It faithfully generates the electrical analog of the physical stimulus. Fortunately it is all way below the level of the recorded music etc.
SO what am I to do about this. Clearly I can't eliminate the vibration short of moving to the garage and placing everything on a concrete pillar weighing a few tons. Making the glass rod somewhat isolated with washers riding on a threaded rod will provide some isolation and or damping. How effective will this be as it is probably a minor part of the disturbance?
For starters Since my arm is not fixed mounted yet and held down by weight I lifted it up and placed a drink coaster made from mouse pad material under it. Virtually all the noise from all the sources just about dissapeared. Music is way better in the bass and low mid range but all sounds richer and fuller but doesn't show any peakiness to the ears. A purely subjective description indeed.
One last thing. When I built the arm I used a piece of 1/8 dia aluminum tubing for the arm lift rod. It rang badly when tappped. Filled it with fine sand and it was better. Now with all the other racket under control I tapped the arm lift rod again. It still rings like a bell but less. Shrink tube Maybe fill it with RTV and hear what happens. Tapping on the glass rod now gives a very low level but clearly glassy sound in spite of the sand fill. Again this is with very high gain. Maybe dump the sand and coat the inside with RTV or threaded rod and washers.
Thanks for reading this far.
BillG
Went fishing last night for noise. Well I found some!
Lest anyone get the idea that my TT and LT arm do not have any vibration problems I went on an expedition to try finding what kind of noise my setup actually has and where/how it was being generated All my testing was being audited through headphones to break any feedback loop there. Then I put a record on the platter. Next to the platter and on the top plinth I placed a hard stone cylinder tall enough to reach record level Then I set the needle on the stone cylinder and turned up the volume just under full gain. The sound was deafening! At normal listening levels there was some noise but easily covered up with music playing (needle on record now). What triggered this investigation was this discussion in the DIYaudio forum and the fact my old motor was starting to generate unwanted amounts of noise. Now to answer my previous question "where is all this noise coming from" let me identify the primary sources. So I had needle coupled to the top plinth through a stone pillar, turntable and motor not running and gain set way up. In my ears I could identify the oil burner in the basement, the motors on the hot water circulator, the hot water circulating in the pipes, my tapping on the floor in front of the TT and the shelf on which it stands and all the other timber frame house noises. Then I switched the stylus to the non rotating platter with a record on it. Noise levels were reduced some but still objectionable. Then I went back to the stone pillar and fired up the motor which by now is outboard mounted and sitting on some plumbers putty isolators. I could hear the motor running and some very low level AC hum. With the drive belt removed and spinning the platter by hand I think there was just a faint sound (maybe) from the bearing. At normal listening levels this would be inaudible.
My previous remark, more or less in jest, was about the turntable and peripheral furniture and construction stuff being a giant microphone looks like that is indeed what we have. The cartridge stylus and generator coils are just sitting there on the record held there by mass and inertia but the entire environment which it is coupled to is vibrating like crazy. It hears very last sound and vibe in that environment. What does the generator do? It faithfully generates the electrical analog of the physical stimulus. Fortunately it is all way below the level of the recorded music etc.
SO what am I to do about this. Clearly I can't eliminate the vibration short of moving to the garage and placing everything on a concrete pillar weighing a few tons. Making the glass rod somewhat isolated with washers riding on a threaded rod will provide some isolation and or damping. How effective will this be as it is probably a minor part of the disturbance?
For starters Since my arm is not fixed mounted yet and held down by weight I lifted it up and placed a drink coaster made from mouse pad material under it. Virtually all the noise from all the sources just about dissapeared. Music is way better in the bass and low mid range but all sounds richer and fuller but doesn't show any peakiness to the ears. A purely subjective description indeed.
One last thing. When I built the arm I used a piece of 1/8 dia aluminum tubing for the arm lift rod. It rang badly when tappped. Filled it with fine sand and it was better. Now with all the other racket under control I tapped the arm lift rod again. It still rings like a bell but less. Shrink tube Maybe fill it with RTV and hear what happens. Tapping on the glass rod now gives a very low level but clearly glassy sound in spite of the sand fill. Again this is with very high gain. Maybe dump the sand and coat the inside with RTV or threaded rod and washers.
Thanks for reading this far.
BillG
Last edited:
A friend of mine came up with a really neat and cheap turntable isolation platform that almost entirely eliminated environmental noise. Two paving slabs with a motorcycle innertube between them. A bit of experimentation with pressure and moving the tube around to get it level and you have an air suspension system. Work brilliantly with any type of equipment, and can take almost any weight of equipment. He got the idea ffrom a laboratory laser platform, half ton block of granite sat on lorry tubes. If you can get the look of the thing past the wife you're onto a winner.
Niffy
Nifty,
I see where you are going, @ 3" the arm is pretty darn short. For the size of tube .220 mm this would equate rigidity wise to a roughly 3/4" tube one a 9" arm. All was selected by hand selection and ear, it's very hard to bend a 3" to 6" piece of carbon fiber by hand, almost impossible at .220" without first breaking it. The resonant frequency will show itself on a frequency sweep record, the rf is definately above 2k.
Colin
I see where you are going, @ 3" the arm is pretty darn short. For the size of tube .220 mm this would equate rigidity wise to a roughly 3/4" tube one a 9" arm. All was selected by hand selection and ear, it's very hard to bend a 3" to 6" piece of carbon fiber by hand, almost impossible at .220" without first breaking it. The resonant frequency will show itself on a frequency sweep record, the rf is definately above 2k.
Colin
Just did another test, similar to Bill's, keeping in mind that the turntable is also a design of my own. Putting the stylus on a non rotating record yields noise at full volume mostly dominate by phono stage noise floor, but I am on a concrete foundation floor so it is quiet in itself. However if I put my ear to the top plinth with a spinning record and no volume I can hear sound transferred into the top plinth, very quiet though. This tells me that decoupling is working at drawing excess energy away from the cartridge vs sending energy to and smearing the detail retrieval, whatever energy the cart doesn't produce into sound we want drawn away anyways, right?.
Colin
Colin
Colin,
Hi, Thanks for making that test. Last night I tried another test, but not on my good arm. From bits and pieces that could be assembled into a working arm I mounted a spare track tube using rubber washers and a threaded steel rod. This arm did not have a cartridge lift rod, just the track rod/tube. The stylus was resting on the non rotating record and the gain was up but not all the way.Tapping on the plinth, the table, the record, anything, set the threaded rod into vibrating with a very low base tone that rang loudly for quite a few seconds. Totally unusable. That steel threaded rod was doing its best to be a chime rod and succeeding. How did you get around that one? I've not tried it yet but your overhead support rod tied to the far end of the track tube probably could reduce or kill kill the chiming rod resonance. So far my solidly mounted sand damped cantilevered track rod is winning by furlongs.
Colin said above: "However if I put my ear to the top plinth with a spinning record and no volume I can hear sound transferred into the top plinth, very quiet though. This tells me that decoupling is working at drawing excess energy away from the cartridge vs sending energy to and smearing the detail retrieval, whatever energy the cart doesn't produce into sound we want drawn away anyways, right?."
Colin, what is the sound you hear transferred into the top plinth? How do you know it is getting into the plinth or just coming straight through the air to your ears. What is the excess energy? Is it coming direct from the cartridge vibrating and getting into the arm? I thought that was the energy we are trying to drain off. The longer I'm with this project the more suspicious I become of this draining energy concept. This closed loop theory of TT design. It may be that the correct answer to your "-----we want drawn away anyways, right" question may be "wrong" I'm nowhere near far enough along to say that "right" is "wrong" .
Give it some real thought please.
BillG
Bill,
If I put my ear right on, think stethoscope to the top plinth while a record is playing I can hear vibration transferred into the plinth. This top plinth is isolated from the bottom constrained layer motor plinth. If I tap the lower plinth there isn't much transferred to the top plinth at all, and anything is a very very low thud with volume cranked.
On the arm, my top bar which is only damped internally with foam to kill hf ringing help rigidity but also moves the bar resonance lower and more out of the audio band, the hf resonance is actually above 4khz, between 6-8khz. The loop is broken by the way I've dealt with platter/vinyl decoupling via foam/cork/inert resin compound.
I believe in limited decoupling, rigidity on smaller contact area that is placed for maximum rigidity while still loosing some energy transfer to be dealt with at another point, in this case sunk into and changed, dissipated into the top plinth.
Colin
If I put my ear right on, think stethoscope to the top plinth while a record is playing I can hear vibration transferred into the plinth. This top plinth is isolated from the bottom constrained layer motor plinth. If I tap the lower plinth there isn't much transferred to the top plinth at all, and anything is a very very low thud with volume cranked.
On the arm, my top bar which is only damped internally with foam to kill hf ringing help rigidity but also moves the bar resonance lower and more out of the audio band, the hf resonance is actually above 4khz, between 6-8khz. The loop is broken by the way I've dealt with platter/vinyl decoupling via foam/cork/inert resin compound.
I believe in limited decoupling, rigidity on smaller contact area that is placed for maximum rigidity while still loosing some energy transfer to be dealt with at another point, in this case sunk into and changed, dissipated into the top plinth.
Colin
Hi All,
Haven't had time to do much with the threaded rod mount with all the Holiday preparations etc. But I did get a piece of shrink tube put on the resonating carriage lift rod. This helped tame it a great deal. There is still some there but it is much lower in amplitude. Nothing that can be heard at normal to high listening levels. Also made a 60HZ 2 phase cd to drive the newly acquired stepper motor. Got that driving the TT with no trouble at all. It is on a temporary mount, an old red brick. An old 30WPC amp and a cd player comprise the power unit. I must say I'm amazed with the lack of wow, and there is next to no motor noise getting into the TT. The motor is mounted outboard from the TT proper. For $2.50 you can't get better bang for the buck.
BillG
Haven't had time to do much with the threaded rod mount with all the Holiday preparations etc. But I did get a piece of shrink tube put on the resonating carriage lift rod. This helped tame it a great deal. There is still some there but it is much lower in amplitude. Nothing that can be heard at normal to high listening levels. Also made a 60HZ 2 phase cd to drive the newly acquired stepper motor. Got that driving the TT with no trouble at all. It is on a temporary mount, an old red brick. An old 30WPC amp and a cd player comprise the power unit. I must say I'm amazed with the lack of wow, and there is next to no motor noise getting into the TT. The motor is mounted outboard from the TT proper. For $2.50 you can't get better bang for the buck.
BillG
Not much to elaborate on. The base for the motor is a red brick from the garden. On one broad side there are 2 3/8" x 2" scraps of softwood hotglued to the brick as mounts and spacers for the motor. Then the motor was hotglued to the wood pieces. Direct glue to the motor shell. The motor comes with a brass gear on the shaft. This was removed by grinding away enough of the gear to permit easy removal. I used a Dremel cutoff disk. Be careful not to grind all the way through the brass. Leave a thin skin. Then I turned an aluminum pulley, can be anything to the right diameter. Measured a pulley from a previous motor. The actual working diameter was cut as a small groove in the pulley for the very thin .003" dia nylon sewing thread I use for a belt. This keeps the thread running true. It runs around the outside diameter of the TT platter. The pulley was drilled for a tight fit to the motor shaft. You can easily make it a looser slip fit and put some super glue on the shaft to fasten it. A few thousandths of an inch clearance will not bother the pulley action one whit. Next comes the belt which comes straight off a spool of sewing thread. Well Tempered TT uses this system. Make it long enough so you have to stretch it a bit. Tight but not real tight. Pushing on the mounted belt it should give one to two inches. Here is another trick I use. So that there will not be excessive slippage I hold a piece of violin rosin against the thread for a short time. These rosin coated nylon thread belts have incredible life and performance.
Now download the free trial version of "COOL EDIT" music editing software. It has the ability to generate and save wave forms. Use that to make a stereo file, left and right channels, having 60Hz sine wave specs. You can specify where to start the wave. One channel starts at the beginning, the other channel starts 90 degrees later. Specify a long enough play time to get you through long records with out interuption. 40 minutes will do for the longest LPs. Use a workable CD player and any functional receiver /amplifier to play back the 60 (or 50) Hz into the motor. The loudspeaker outputs drive the motor. One channel to one motor coil, the other channel to the other coil. I place the brick alongside the TT and run the thread. Position the brick, or mount of your own choice to tension the belt, turn on, and turn up the volume to where the motor runs smoothly.
Select the volume and balance on the amp for smoothest and quietest
running. Now for the motor. Go to the "AllElectronics" website and find their stepper motor with 7.5 degrees per step and 24 volt rating for USD 2.5. Order a couple so you will have a spare. It will show up in a few days.
I'm going to build this up into a nice power unit. Don't feel compelled to duplicate my sticks and stones from the garden approach.
BillG
Last edited:
SGregory, In my last answer to this request, I did elaborate but didn't say anything about weight and drive torque. Sorry about that. My platter is a 5 pound Corian disk. The stepper motor hardly knew it was there. Just enough for a good motor load. Those steppers have gobs of torque, should handle many times greater load than 5 lbs. My spindle is running in 100.000 Cs silicone fluid as well. If you find one motor marginal for your platter it would be easy to use two motors (that spare one I suggested) with 2 belts. Just be careful to have both pulleys very close to identical diameter. Also if the amp doesn't like two motors in parallel, run them in series. A 20W per channel amp should handle 2 motors with ease.
BillG
Hi there, that's my turntable. The bearing is SKF LBBR6. It was quite hard to get my hands on these...
I'm playing with a different solution now...
Hi there Stein2 , please let us know about your different solution ! thx Paul
I was trying to get the **mn thing work with the 623 bearings (10x3x4mm), sets of two, four, but it woudn't work without problems - it just keeps making trouble... So, I decided to try my luck with linear bearings... Not much luck with these as well, THK or chinese, same problem. I polished the shaft, burned, removed the rubber sealings - nothing helped -it just kept skipping - lagging...
Ended up with a pair of these SKF bearings and finally got it to work.
In the meantime I was so frustrated that I made WT clone to listen to records and got back to the drawing board...
Now I'm testing the much heavier version - 8mm shaft with a matching 8mm linear bearing. The version with the LBBR6 bearing was merely pushing 18.84 grams including the Grado Silver and counterweight. I'm not sure about the current weight but it's working against all odds... Of course, the test cartridge is an old NAD9200
Ended up with a pair of these SKF bearings and finally got it to work.
In the meantime I was so frustrated that I made WT clone to listen to records and got back to the drawing board...
Now I'm testing the much heavier version - 8mm shaft with a matching 8mm linear bearing. The version with the LBBR6 bearing was merely pushing 18.84 grams including the Grado Silver and counterweight. I'm not sure about the current weight but it's working against all odds... Of course, the test cartridge is an old NAD9200
Attachments
I know that this is going to be a bit OT - but I'll do it anyway I built a completely new TT with a larger plinth especially for testing purposes -to test various tonearm ideas. The first arm I built to test was a clone of the Well Tempered Arm @10.5" and it works like a charm. Both technically, and sonically. I spent about a week of my spare time and the results are more than satisfactory. That is why not succeeding completely with the linear tracking tonearm becomes so frustrating...
The problem with the SKF LBBR6 bearing is that it doesn't get stuck, however, there's a significant amount of play, so, if the hole on the record is eccentric, the arm works rather like a screen wiper than moving the arm left-right - thus it's not really tangential - more like a very short ... wiper?
The TT/tonearm topic @ vinylengine: http://www.vinylengine.com/turntable_forum/viewtopic.php?f=87&t=63983
I built a completely new TT with a larger plinth especially for testing purposes -to test various tonearm ideas. The first arm I built to test was a clone of the Well Tempered Arm @10.5" and it works like a charm. Both technically, and sonically. I spent about a week of my spare time and the results are more than satisfactory. That is why not succeeding completely with the linear tracking tonearm becomes so frustrating... The problem with the SKF LBBR6 bearing is that it doesn't get stuck, however, there's a significant amount of play, so, if the hole on the record is eccentric, the arm works rather like a screen wiper than moving the arm left-right - thus it's not really tangential - more like a very short ... wiper?
The TT/tonearm topic @ vinylengine: http://www.vinylengine.com/turntable_forum/viewtopic.php?f=87&t=63983
Last edited: