Finally, I have almost everything
Next step is to connect cable to cartridge pins in headshell and connectors on the back, to modify a lift and to finalize a headshell to accept a cartridge, more pictures will follow (once it is done).
Nice work
Hi tabarddn,
No need for the ball bearing
Other than than, the layout looks o.k.
The ratio between exit point of the thread and diameter of the magnets is crucial. Ringmagnets are to be aligned with absolute precision or else Azimuth and VTF changes over the usable radius of the record will occur.
The thread should not have any "play" at the exit point.
Good luck with your project!
Frank
No need for the ball bearing
Other than than, the layout looks o.k.
The ratio between exit point of the thread and diameter of the magnets is crucial. Ringmagnets are to be aligned with absolute precision or else Azimuth and VTF changes over the usable radius of the record will occur.
The thread should not have any "play" at the exit point.
Good luck with your project!
Frank
...idea was to if magnetic field is not even when tone arm moves across the record the bottom magnet will move along with it.
Regards.
An externally hosted image should be here but it was not working when we last tested it.
Regards.
Hi Hiten,
I was going to mention that, but it makes the entire assembly quite a bit more complicated to produce as now the lower magnet has to be very well centered vs the center of the bearing underneath. And a perfectly vertical/perpendicular orientation/alignment is still necessary to avoid azymuth changes across the record.
Nevertheless, a design variation worth trying.
Cheers,
Frank
I was going to mention that, but it makes the entire assembly quite a bit more complicated to produce as now the lower magnet has to be very well centered vs the center of the bearing underneath. And a perfectly vertical/perpendicular orientation/alignment is still necessary to avoid azymuth changes across the record.
Nevertheless, a design variation worth trying.
Cheers,
Frank
Yes sir, it will be little complicated to align. I guess we can align the disc magnet precisely on ball bearing when it is separate and then treat the assembly as one when aligning to tonearm magnet. I also like simple things
. This is just to discuss variations and probable improvements.Regards
VTF Deviations
Hi all ,
Have followed this thread for years and decided to have a go at building one of Franks marvellous creations . Having spent months machining parts I decided to run a few tests on the bench before mounting the arm on the turntable .
Rotating the arm horizontally the VTF remains stable Across the surface of the record what I have noticed is a slight change in VTF when altering VTA .
I know from some of the earlier posts other people have encountered this and wondered if there was a acceptable tolerance to look for.
On my build Raising the arm about 3mm at the measuring scale causes the VTF to increase about 0.06gram .i realise that this harks back to what Frank was mentioning about the stable balance and neutral balance .Ideally no deviation would be desirable but is the small increase I measured acceptable .My balance weight is drilled slightly off centre I tried a centre drilled weight and ran the same tests there was very little difference .
Hi all ,
Have followed this thread for years and decided to have a go at building one of Franks marvellous creations . Having spent months machining parts I decided to run a few tests on the bench before mounting the arm on the turntable .
Rotating the arm horizontally the VTF remains stable Across the surface of the record what I have noticed is a slight change in VTF when altering VTA .
I know from some of the earlier posts other people have encountered this and wondered if there was a acceptable tolerance to look for.
On my build Raising the arm about 3mm at the measuring scale causes the VTF to increase about 0.06gram .i realise that this harks back to what Frank was mentioning about the stable balance and neutral balance .Ideally no deviation would be desirable but is the small increase I measured acceptable .My balance weight is drilled slightly off centre I tried a centre drilled weight and ran the same tests there was very little difference .
Hi Michael,
Congrats, the measured ratio VTA/height to VTF is much better than what most DIY efforts(that I've seen or physically checked) achieved.
It isn't just the geometry of the bearing and the displacement of the counterweight, but also the strength/size of the magnets used that will affect said ratio.
If your arm exhibits a restoring force along the armwand axis when a centrally drilled counterweight(= no mass offset) is used, then the bearing ist more or less on the stable balance side.
An arm that is close to or in neutral balance will make it a lot easier to adjust so that there are no VTF differences along the usable record radius.
Cheers,
Frank
Congrats, the measured ratio VTA/height to VTF is much better than what most DIY efforts(that I've seen or physically checked) achieved.
It isn't just the geometry of the bearing and the displacement of the counterweight, but also the strength/size of the magnets used that will affect said ratio.
If your arm exhibits a restoring force along the armwand axis when a centrally drilled counterweight(= no mass offset) is used, then the bearing ist more or less on the stable balance side.
An arm that is close to or in neutral balance will make it a lot easier to adjust so that there are no VTF differences along the usable record radius.
Cheers,
Frank
Hi Frank. Do you think the 15 and 20 degree VTA arguement is important? As I understand it 15 degrees was the springback of a cut disc when using a zero degree cutting stylus angle. As the springback exists 5 was added to have a better result ( 5 added to the cutter ). I bet the real answer is different? I bet even the zero degree cutting is not right? I must stop reading Hi Fi mags and ask an expert.
A friend Martin Renwick is ( was? ) showing his very posh bicycle in Berlin. I should have told you. His bicycles have much in common with your pick up arms. That is, long after the job is finished Martin wants it better.
A friend Martin Renwick is ( was? ) showing his very posh bicycle in Berlin. I should have told you. His bicycles have much in common with your pick up arms. That is, long after the job is finished Martin wants it better.
Hi Nigel,
For whatever reason, people will always play with the relative position ("height" )of the arm bearing. Many do so to optimize the setup and attribute the sonic changes to the change in VTA or SRA(the only factor worth considering when one is dealing with cartridges with line-contact stylus profiles) , and not the change in VTF(which in itself affects VTA/SRA). So the VTA debate is usually based on the wrong assumptions, but historically, the figure is a standard that never was put into practice universally. Measured VTA for historic("classic") and modern cartridges varies between 4° and >30°.
Do not mistake the VTA with what is the basis for many cartridge designs: building a generator cantilever assembly that offers enough clearance between record and cartridge. A Dynavector Karat 17D CAN'T adhere to the standard of 20° VTA. And as long as the vertical orientation of the stylus and therefore the SRA in operation is close to or on the same line as the cutting edge(haha...) of the cutting stylus, the claimed advantages of, say, a super short cantilever seem to outweigh(at least for the designer) the disadvantage connected with a non-standard VTA(higher intermodulation distorsion).
Here's a link to a pretty good article on VTA incl. the switch from 15° to 23^/25° and then back to 20°(our current "standard")
Vertical Tracking Angle
Now try to figure out whether your record is of the 15° or a later type and then account for that by raising or lowering the arm to increase/decrease VTA by at least 5°... oops, you can't get it down far enough with your modern cartridge?...
Vinyl replay will always involve compromises... and still remains the greatest format
But all of that is a topic for another thread....
Cheers,
Frank
For whatever reason, people will always play with the relative position ("height" )of the arm bearing. Many do so to optimize the setup and attribute the sonic changes to the change in VTA or SRA(the only factor worth considering when one is dealing with cartridges with line-contact stylus profiles) , and not the change in VTF(which in itself affects VTA/SRA). So the VTA debate is usually based on the wrong assumptions, but historically, the figure is a standard that never was put into practice universally. Measured VTA for historic("classic") and modern cartridges varies between 4° and >30°.
Do not mistake the VTA with what is the basis for many cartridge designs: building a generator cantilever assembly that offers enough clearance between record and cartridge. A Dynavector Karat 17D CAN'T adhere to the standard of 20° VTA. And as long as the vertical orientation of the stylus and therefore the SRA in operation is close to or on the same line as the cutting edge(haha...) of the cutting stylus, the claimed advantages of, say, a super short cantilever seem to outweigh(at least for the designer) the disadvantage connected with a non-standard VTA(higher intermodulation distorsion).
Here's a link to a pretty good article on VTA incl. the switch from 15° to 23^/25° and then back to 20°(our current "standard")
Vertical Tracking Angle
Now try to figure out whether your record is of the 15° or a later type and then account for that by raising or lowering the arm to increase/decrease VTA by at least 5°... oops, you can't get it down far enough with your modern cartridge?...
Vinyl replay will always involve compromises... and still remains the greatest format
But all of that is a topic for another thread....
Cheers,
Frank