I only made one attempt and I offer only one peice of advice. Don't go to Briggs&Stratton for a motor.
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I built a table and arm a few years back. Wanted something I couldn't afford so I built the damn thing. Analog rules in my book and this table is a testament to that. Images can be viewed at: http://forum.audiogon.com/cgi-bin/fr.pl?vevol&1058201145&read&3&4&. If it spurs your curiosity, email me with questions and I'll be happy to answer and help any way I can.
Ill take some time here and give a brief description of the table, arm and cart.
First, I must confess Im not a mechanical engineer. My expertise and current passion lies in designing and building audio cabling. Uhm .you should buy some. The table is still a work in progress as I have time to work and play with it. My inspiration for this project largely came from Bill Firebaugh of Well Tempered fame. While little of his innovations are employed to any extent in this table, I highly admire his simple genius and approach to TT design. What a guy!
My Table goals were to build a table that was immune to feedback and the surrounding environment, a highly stable suspension system with a very low Q (highly damped) both in the lateral and horizontal plain and that would inflict no discernable signature from the sub-chassis platform to music signal. Resonant frequency target of the suspension is about 12hz.
Drive and rotational goals were for rotation to be driven by a powerful, stable and electrically low impedance source, and to maintain rotational stability regardless of the drag from the grove/stylus interface.
Project took me not quite a year. Materials used for this project had to be readily and easily accessible as, at the time, I was strictly a hobbyist on a mission. Materials include:
· 1.25 MDF
· Misc. viscosities of Dow Corning silicone samples ( no longer available due to this stuff worked better for TTs than for girl breasts at the time. Fortunately, my partner and I still have a pretty good boat load of this stuff to mess with.)
And rare, high end esoteric parts:
· Peanut butter jars (really!)
· Balloons (really!)
· Rubber Os
· Electrical Duct Seal
· Expanding Springs
· Rare Jelly Bean Magic extracted from Snake Oil (not really!)
Some of these materials are not optimal but they were what I could work with at the time. Hell, if I was doing it over again ( and I plan to in the not too distant future ) I probably wouldnt use most of these materials. I will use a new product that is a synthetic granite or marble. Its acoustical properties and mass are more desirable than the stone equivalent. The PVC's gotta go too.
The Arm is, by and large, after Well Tempered however more substantial. Briefly, the arm proper is suspended using Spider Wire, a sportsmans product for fishermen. This stuff is braided for good damping, 10 times stronger than Kevlar, has 0 stretch compared to Kevlar or standard mono filament and a smaller gauge can be used for less horizontal and vertical travel impedance. Im still waiting for someone to make speaker cones from this stuff but so far, no one has that Im aware of. Based on what I know about this stuff, seems like it would work much better than even Kevlar for driver cones lighter, stronger but green. Green maybe thats why nobodys using it. Fish must love green though.
Anyway .the arm tube uses two diameter sizes of high tempered light aluminum alloy used in the archer industry for high quality arrows. I got these free at the local sports store because they were drops for custom arrow lengths. Plus, at the end of an LP play, when I bring the arm back, it makes a cool sswwuuussshhhhhhh sound like an arrow shot through the air that just impresses the hell out everybody! Uh .not really. The two diameter sizes at two different lengths form a constrained damped arm tube while keeping the weight down and balance optimum. The arm tube employs further internal damping and polyophelien shrink tubing for external damping. The counter weight is lead and is designed to simulate its center of gravity and balance at the vertical pivot plane. The counter weight is held in place with blue tack for damping purposes. VTA, azimuth, pivot damping, and anti-skate are adjustable during play. All parts except for the arm tube and counter weight were fabricated at the local high school machine shop during a night class my partner and I enrolled in. We told the instructor we werent much interested in making a horse shoe for Mothers Day or one of those little knurled handled hammers. We wanted to make parts for tone arms. After seeing our plans, he was intrigued enough to let us do what we wanted. The rest of the students thought we were privileged nuts .we were.
The cartridge is a Sumiko Blue Point Special that has been rebuilt by Van den Hul with further structural modifications performed by me .one of which was performed on a table saw (wont forget that part, it was kind of scary!) and has also been cryo-tempered. Great little cartridge made better!
The table. The table is made from microwave-tempered 137n pure cast silver mined from Humps dairy farm here in Indiana and insulated with Belgian Mountain Teflon extracted from the Tefoliage Tree by mountain foliage masters. All materials were aged until it formed a turntable. Wait, that cant be right! The base of the table is 1.25 MDF supported by heavy brass cones. The sub-chassis is lead loaded and is 2 pieces of 1.25 MDF bolted together for constrained damping. The table utilizes a hung suspension.
The suspension towers are made from PVC and house the modified peanut butter jars that contain silicone fluid. The expansion springs are hung from the top of the suspension towers and have a custom paddle system affixed to them for damping in both the lateral and vertical plains as this system suspends in the silicone fluid. At the end of the springs is a steel rod that protrudes out of the bottom of the silicon housing. The balloons are used in such a way to keep the silicone from leaking out and allow for the suspension to operate freely. The steel rods are threaded at the exposed ends and are long enough to extend through the sub-chassis corners. Audiophile approved wing nuts and fender washers are threaded onto the steel bars from underneath the sub-chassis to allow the sub-chassis to hang. Leveling can be adjusted by rotating the tops of the suspension towers.
One thing that was fun in the building and testing of the suspension towers was that with preliminary operational set up and running of the table, I wanted to see if there was any instability or vibration being introduced to the suspension via the motor-belt-platter interface. I couldnt detect any with the naked eye but I wanted to be sure. Before adding the silicone damping system, I had the table running with just the springs suspending the sub-chassis. I took a flash light (before lasers were popular), mounted it to a stand, set it at an angle about 3 away from the table shining onto a 1 round mirror I attached to the sub-chassis. The light reflected onto a board I set up at an opposite angle about 3 away. Sure enough, what I couldnt see with the eye, the light revealed. It was wigglin! I added the silicone system to the towers and nothing! No movement whatsoever! My partner and I hi-fived and we was happy! There may be an easier way to do this but it was the best I could figure out with what I had and it worked! As the platter rests on top of the sub-chassis, (I guess Ive never seen a table where the platter rests underneath.) I made sure its center of gravity was below the suspensions hang(?) point to facilitate better suspension stability.
The platter came from a 1964 Marantz linear tracking turntable. For the time, it was a pretty hi-end table and today is collectable to some .all I could see was a big heavy platter for free so I trashed the rest of the table. Regardless, the platter needed work. 10lbs of what I considered ringing mass with little fly wheel action of its own. I fixed that. I damped the under part with a sand loaded cement like product that I acquired from my Mother who owns a ceramic business. Cant remember what its called but the stuff hardens fast (it even gets hot within minutes) and has slight expansion properties. Its pretty inert and even more so with the sand loading. Towards the circumference of the platter are a series of small compartments which lent themselves well for loading lead shot, sand and the cement like stuff. That provided the fly wheel affect I wanted to accomplish. I further incorporated a steel rod shaped to form a circle slightly larger than the platter. It is press fitted against some open cell rubber that I placed against the inside wall of the platter. This further adds to the fly wheel affect but more importantly, it offers constrained damping to the platter and eliminated any further ringing. Run out was checked and refined at a local professional machine shop. Platter has also been checked for balance. I must be really pretty good because it required no balancing. Done!
The spindle is the original but has been threaded to accommodate a record clamp I made and I had the machine shop grind a section out so the well would hold more oil. Because of the fly wheel affect and the now aprox. 20lb weight of the platter, I was able to use a fairly heavy viscosity oil to help stable the spindle surface/well wall interface. I tried using a very light viscosity silicone but it tended to compress some of the musics dynamics. I have a new spindle and well that I made to use but I havent had time to install it yet. Its a modified and refined version of Bill Firebaughs design. Im anxious to get it in.
The motor is from Wayne Merrils Underground Sound inventory of souped up AR motors. I threw away the stock power supply for this and built a low impedance version of the same. At its heart, it uses a 120/18V 4VA toriodal transformer and Film and Foil 600V caps. I had the belt pulley for the motor made custom for the platter diameter. Took me a while to figure out the math to get the pulley/platter speeds right but it worked just fine. Damn though that I cant find that formula. Im gonna need it again. Not sure if I could find where I originally got it. If someone knows the equation, maybe you would be willing to help me out? I want to make another pulley that incorporates its own fly wheel but I may use a different motor. The motor is bolted to 15lbs of lead that I poured into a Van Camps baked bean can and stands alone on three points from the table. The motor exhibits no vibration whatsoever when mounted like this. The belt used for this comes from Sota Industries they make good high tolerance belts.
Finally, the sound or, better put, its portrayal of the groove. I believe I did good if I say so myself. People who are only familiar with digital playback who have heard this analog front end just kind of shake their head. One of my local customers was so inspired he went out and got a VPI TNT rig.
This table is mechanically and sonically quiet as confirmed with my audiophile, cryo-treated, DC biased active shielding, Teflon tubed stethoscope and is unaffected by its environment. This table throws an appropriately huge sound stage that simply allows the other components to disappear if they are capable. Everything hangs together, nothing is emphasized at the expense of another aspect. Dynamics are first class and startling at times.
One of my favorite recordings is the John Marks label of Songs My Mother Taught Me Beautiful violin and piano music recorded in fairly intimate acoustic. Ohio street, which can be seen out the windows from my listening seat, runs right along side my listening room. One night while listening to this music, I heard the low rumble of a truck go by the side of our house. I didnt think much of it until about five minutes later when it occurred to me I hadnt seen any headlights come down Ohio street. Either somebody really stupid was driving a truck at night with no headlights on or .it was in the recording and I had never heard it before I started using this table. I played the cut back and another idiot drove down Ohio street with no headlights! It sounded that real! When I played the cut backwards it said Paul McCartney nine times very slow and in a deep voice. Couldnt believe it.
Another recording I enjoy much is Opus 3s Depth of Image. Maybe the lead fumes have messed me up but I actually have grown to like the music on this LP. Theres one cut that features a trombone and Im telling you, that damn trombonist is out on Ohio street at midnight. My neighborhood to the west of me has just gone freaky headlightless trucks and tromboners its like a damn horror film. I wont go into the listening room at night anymore without my wife. Well, really, the trombonist is not that far out but the blat of the instrument just hits you and the mix is very convincing of where hes at on the soundstage the speakers just arent there. You can hear him fairly deep and far right and his playing even reveals image height because of ceiling reflections from the recording venue. It seems good analog can do this kind of stuff. At the least, I enjoy very much this tables portrayal of any well recorded performance.
Another enjoyable example of this tables performance is illustrated on Belafonte at Carnegie Hall. I have an original of this LP set and have heard the CD version of this recording on several digital front ends. The CD sucks! With my LP on this table, Im at the concert and in the audience as Belafonte entertains. Its an awesome experience. I dont usually lean to this type of music but hes so entertaining and the portrayal is so live. Ive found no one, myself included, that isnt captivated by this performance as reproduced on this table. My Bic lighter shines brightly when I spin this record and I've gone through 3 lighters designated just for the playing of this LP.
Anyway, its a good table that allows me to enjoy my small but treasured LP collection to the max. Its still about the music and the gear is only there to allow me to experience the performance in the home to whatever degree I can attain.
BTW, with some of the above, I talk as in the present. Not so. This room has gone away as weve moved recently. The Ohio street incidents are to blame. I dearly miss that room and my workshop as well as there were many fond memories there but Im off to bigger and better room(s) to better serve my customers and my music enjoyment and I trust some richer memories of which some of you will be a part of.
Brief description? Yea right. One of these days Ill learn I dont know how to do brief. Sorry if I kept you up late or crashed your computer.