diy turntable project... advice needed

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hmm... that 9 inches, is that measures from the point of balance above the unipivot to the beginning of the headshell, end of the headshell, or overall including the balance section?... and what is the purpose of the angled heads?, thats what im curious about

i dont know how i would go about making the pin location adjustable, my idea would be to cut the head off a screw or bolt and sharpen it, then i could drive it into a threaded bushing thats glued into a hole drilled in my table so i can adjust the height of the pin...

i was planning to find the optimal location to mount the pin before drilling the hole... i COULD maybe make a block of wood that houses the pin... hollow out the bottom of that block for some lead weights, and maybe cover that with a rubber mat to prevent it from slipping... then have a tonearm i could just physically pick up and move... would that be a good idea for the tonearm?.. then i could just place it wherever i want... if the base was heavy enough, and the rubber mat had enough tack to it, it shouldnt move even if the table holding the player is accidently bumped

IF thats a good idea, i guess all i would need to know is if that 9 inches is measured from the unipivot joint to the needle, or where its measured at, and the purpose of the angled heads and i should have pretty much all the info i need to get started

and although this first tonearm will be unipivot, at this point im convinced it will be a good idea to continue experimentation with linear tonearms as well
 
before i left school for medical reasons.. i was majoring in mechanical engineering, and well, the more i learned, the more i favor simplicity above all else... so i look for a balance of usefulness, quality, and simplicity, if something definitely offers a better result, but at the cost of low reliability and high cost due to being too complicated of a design, i dont see it being worth it..

so in the end, even if some highly complicated air bearing linear system offered a better sound i would have to ask myself... is that small increase worth the great increase in cost and parts count?... the more parts something has, the more likely it is to break... its why ive decided to go with the simplicity of unipivot

i dont believe the unipivot HAS to be a sharp point fitted into a sharp pocket.. they can be rounded i believe, but the important thing is that the pin has a smaller radius than the pocket... that being said, even if a pointed drill bit isnt going to yield a perfectly pointed pocket, as long as the pin itsel was a close match, only a little steeper of an angle, i think it would work just fine... that being said, im probably going to make a few tonearms out of different materials, and different unipivot joints and see which one i like best

one will be laminated balsa core with thin hardwood on the top and bottom, overall rectangular in cross section, the other is going to be a balsa dowel rod glued inside a piece of aluminum tubing

if i go with a 9 inch tonearm, i think the straight angle of the headshell would probably be best and i can position this probably 2/3 of the way towards the center of the record.. since this one ill make as simple as possible, im going to try the drilled picket with this one, and this 9 inch tonearm will be the balsa dowel glued inside a piece of aluminum (or many even rigid plastic) tubing

other tonearm will be 12 inches with an angled head since the length will over extend the area where the cartridge would normally sit.. giving it the tilt would give it the proper parallel angle to the grooves and will probably be neccessary unless i move the tonearm further away in which case, the overall phonograph would have to be larger... so ill try the angled head on this one... this one will look like a more conventional tonearm, rectangular in cross section with integrated wooden headshell, and be the one made of laminated balsa and red oak

i will model both of these later with textures added so that you can see how i layer the materials... and for the balsa dowel inside the tube, im going to cut a groove along the length of it for the wire, so the wiring will still be inside it all
 
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makes sense

I thought of an easy way to make the arm length adjustable
its simply a brass rod, bent into two paralel
thicker material for gass welding might do it

if the mounting point of your armbase doesn't fit the angle, you can instead adjust with angle pickup headshell

somewhere in the middle of music grooves the needle/headshell should be perfectly angled in relation to groove
its the only point where you have near perfect tracking
in all other positions you have tracking error
its about finding best compromise

antiskating is another issue
some like to deal with it
other don't
depends
it can be tricky to make a good antiskating device
many have negative 'side effects' on arm function
 

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hmm.. you call that length adjustable... i call that a reminder that i played trombone in gradeschool... so im assuming your idea of length adjustable was inspired by a trombone?... it would work... you could make a single tube length adjustable just by making it telescoping... if you cut a piece out of one side of the end piece, fixed a screw on the piece attached to the base, the presence of the screw would prevent the forward piece from twisting in relation to it... and you could just tighten the screw to lock it in place

trombone idea works too, but surely you would need some way of holding it at a desired length so the act of tracking doesnt pull it out...

or did you want it to be able to pulled out so that the tracking can dictate the length needed to remain parallel to the groove? in which case you would get fluctuations in pitch due to it...

now what if you had a headshell that could pivot as the arm tracked... maybe have some kind of a pulley mounted to the base of the table and the headshell... so as the arm moves, the headshell would be automatically turned to counter that, resulting in a static angle relative to the groove being played, and atleast reduce much of the tracking error
 
ill admit.. theres a lot more to this tonearm than i had thought... the platter, maintaining its speed, tuning it.. thats the easy stuff.. but the tonearm is where the real science and engineering come into a good record player, and where it seems most the options are, and where any choice is going to change the tone of the music...

all of that being said, i think its best for now that i take previous advice, by an inexpensive pre-existing unipivot turntable, and experiment with different diy tonearms... that being said, im looking at the audio technica LP60 and the pioneer PL-990 which has that built in strobe, and from what i can tell with that one all i have to do is mount a switch in place of a single jumper to make a switch to turn the preamp on or off...

anyone have a better idea for for what i could use as a good test bed to test out my tone arm ideas prior to making my own turntable?
 
ive actually been working on speaker design and construction and was thinking of taking a metal, maybe copper rod or tube, wrapping it in copper wire, and hooking that up to a DC power supply to generate a cylindrical electromagnetic field, then create a bushing that uses the doughnut shaped neodymium magnets on each end to ride on top of the electromagnetic field as an attempt to make my own passive mag-lev linear tonearm along side my two unipivot ideas.. if for some reason the cylindrical idea doesnt work, i could get some neodymium bar magnetcs set into a long bar triangular in cross section.. then a bushing to ride over that and i probably wouldnt even need the electricity for that.. so im going to experiment with mag-lev bearings too
 
actually.. i found some cylinder neodymium magnets 1 inch in length about 1/4 inch diameter that are magnetized along the edge... if i packed about 8 of these into a plastic tube... then used thin bar magnets placed inside a wooden bushing in atleast an octagonal pattern, it should ride pretty effortlessly on the rod.. what do you guys think of that idea for a mag-lev linear tonearm?
 
actually.. i found some cylinder neodymium magnets 1 inch in length about 1/4 inch diameter that are magnetized along the edge... if i packed about 8 of these into a plastic tube... then used thin bar magnets placed inside a wooden bushing in atleast an octagonal pattern, it should ride pretty effortlessly on the rod.. what do you guys think of that idea for a mag-lev linear tonearm?

Great Idea! Where's the pictures?

One little question though, how are you shielding the cartridge?
 
are you asking how am i shielding it from the magnetic interference?... well similar designs of similar systems as well as mag-lev platters suggest the cartrige is typically outside the range of the magnetic field... so with a 6-8 inch arm on the bearing, it shouldnt reach that far.. if it did, i guess i could just make the arm longer, pushing the bearing further away from the table, but i dont think id have to
 
i went to a thrift store and got a cheap POS turntable for $9 just to play with... its nothing im going to keep or play my good records on, but just a toy i can throw away if need be... platter for it isnt even full size and i doubt the platters bearing is useful either

but anyway, i got an idea of building the table from hardwood painted like a red or blue color.. a light maple colored wooden platter, i will route out a cavity for the switches, potentiometer, and electronics to mount into.. however, i will cover it with a white plastic cover made out of the material like a pickguard on a fender strat is... the toggle switch will be that of one used on a stratocaster guitar, as well as the pots and knobs.. also, im thinking of using the output jack deep dish plates to connect the speakers :-D

in all, its going to have many of the design features of a stratocaster guitar.. but still be my phonograph :D...

now what would be REALLY cool is if i could design my tonearm to look like a whammy bar
 
I thought I should share pics of the turntable I built just to show how simply it can be done. I started with a pioneer belt drive TT I bought off of some guy from craigslist. I just screwed/bolted/glued the relevant parts to a big chunk of oak. I did it in my kitchen. Antiskate/tracking/downforce I'm sure were all horrible. But not having any resonances from a cheap turntable body and tonearm produced really great sound.
 

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