My previous TT was a Rega RP8 with Apheta 2 MC and the Needle talk could be heard from the listening position with the volume turned down. I didn't have this TT very long.
Rocking I assume you mean Azimuth tilt. Looking at the photo of the back IMO this is most likely caused by the play in the bearings. Preload the bearings to remove most of the play. Too much preload and the bearings will bind.
Great news Mike, congratulations: you have given a big push forward to the radial rail concept, and I think you can go on even further.
First step: keep the cartridge as leveled as possible to the rail, eliminating the distance (= the lever) that may bring issues with the stilus drag. A rail with a larger, steadier section* may be helpful
Second step: separate the lifter from the vertical articulation. (with a mechanism that implements lift plus rotation of the rail itself - far safer). This can further reduce the moving masses. One of the most interesting and good sounding features of the LC is a very light carriage with no shaft and no chattering - this one instead has the vertical movement, with small shafts + CW, so it resembles more a traditional LTA carriage)
Third step: eliminate the parallelogram: on LC the parallelogram is used mainly to avoid the VTF variation, despite the travel of the carriage (=CG shift) along the mobile rail. But here the rail is fixed so the parallelogram is not needed; it is complicated and has too many bearings in the wrong place, right above the cartridge.
So how to do the vert joint? I don't know, but there are many possible ways, the corkscrew was just a first suggestion; Now are needed brilliant inventors like you.
carlo
*rocking: that's why I named the Cantus rail; this too allows some vertical rotation
First step: keep the cartridge as leveled as possible to the rail, eliminating the distance (= the lever) that may bring issues with the stilus drag. A rail with a larger, steadier section* may be helpful
Second step: separate the lifter from the vertical articulation. (with a mechanism that implements lift plus rotation of the rail itself - far safer). This can further reduce the moving masses. One of the most interesting and good sounding features of the LC is a very light carriage with no shaft and no chattering - this one instead has the vertical movement, with small shafts + CW, so it resembles more a traditional LTA carriage)
Third step: eliminate the parallelogram: on LC the parallelogram is used mainly to avoid the VTF variation, despite the travel of the carriage (=CG shift) along the mobile rail. But here the rail is fixed so the parallelogram is not needed; it is complicated and has too many bearings in the wrong place, right above the cartridge.
So how to do the vert joint? I don't know, but there are many possible ways, the corkscrew was just a first suggestion; Now are needed brilliant inventors like you.
carlo
*rocking: that's why I named the Cantus rail; this too allows some vertical rotation
Last edited:
I mustn't get too exited yet, i still have those problems to resolve before its usable and to judge if it exceeds my current arm at all......BTW, i never noticed needle talk with the OL arm, doesn't mean it wasn't there, but i never noticed it, but hopefully his arms are better than the Rega as that's what he aims for and has a good reputation, and i have been happy with his, my motivation started as a lockdown project!
No, sorry, my poor description, its rocking along the groove varying VTA by swinging around the rail viewed from the side. It seems pretty solid in lateral across the record and azimuth consistency also looks ok at a first glance.
The bearings get a little preload from needle drag i guess in the direction i am describing.
This may also be because in warp the length of the vertical lever around the rail varies and cartridge drag will rotate it but with the varying lever the moment varies.
Being radial rail as opposed to vertical pivot this is more critical and must be because this variation exceeds the resistance to rotation from the bearings sat on the rails and the moment of the weight below the rail.
Many thanks for your support Carlo, i am not sure if i have added anything to radial rail ideas yet, perhaps publicity on a tiny scale but that's all, when it rocks in musical terms as opposed to physically i will feel i am getting somewhere, at the moment it wows, but again in the wrong sense!!
I see that now with this rocking problem, but also felt the weight lower below the rail was helping negate it, maybe the two moments simply cancel as the lever varies. Steadier rail is definitely on my radar, but without increasing drag or friction, also if the rail gains width does it go out of radial at some point. Actually i have two bearings each with two contact points, so 4 contact points in total, i don't know whether the bearing friction or the contact friction is more significant but will be thinking how to simply improve that next.
I have quite liked so far that the rail is high enough to get the record in when the carriage and stylus are parked outboard of the platter, it avoids turning the rail away or equivalent
Another good thought, i enjoy reading how your mind works with experience, knowledge and clarity, not surprising LC variants look and work so good, i enjoy to keep mine simple and cheap as well.
I think your hopes for me exceed capability Carlo! - i shall move forward stage by stage and hope for advice and/or revelation over the weeks!
Resistance to that rotation without drag and variation in drag eludes me this morning, it reminds me of your good advice to concentrate on vectors and geometry but the solution is less obvious.
Rearrangement of wiring brings a great improvement, tracks the side straight off, no glitches or skips, taking the spring of the wires backwards, instead of sideways, even though its small, improves lots of things including the rocking motion, i now cannot audibly hear the wow and visually its already much reduced, i now need to readjust VTA: stylus drag with the forward counterweight and then will play some test records.
I guess its obvious the wires and tower could be much shorter! - but i will leave some tolerance for now.
Then reconsider all the earlier input,
mike
I guess its obvious the wires and tower could be much shorter! - but i will leave some tolerance for now.
Then reconsider all the earlier input,
mike
Attachments
As soon as i got VTA back in range the wow returns i guess because there is no rotational moment when the weight is brought directly under the rail, so i need to find rail stability next i think, a wider bearing and rail spacing is one idea, but i would like to find it with the current components where i can........
your big kick is to do without a mobile rail - thing i had considered at the beginning, thinking of it as unfeasible: i was evidently wrong.
After making 3 LC I may assure you that it is a really nice jump, in term of simplification:
cables: if thin cables may alter significantly the carriage motion it means that your carriage is really good, so keep them even thinner, long, and with one or two loops.
large rail section: same single bearing centered on two large diam wheels, to increase the advantage on the axle. The double rod rail is not really self centering because the bearing has to slide (not rotate) to go back, while probably it likes more to reach a lower potential position
c
After making 3 LC I may assure you that it is a really nice jump, in term of simplification:
cables: if thin cables may alter significantly the carriage motion it means that your carriage is really good, so keep them even thinner, long, and with one or two loops.
large rail section: same single bearing centered on two large diam wheels, to increase the advantage on the axle. The double rod rail is not really self centering because the bearing has to slide (not rotate) to go back, while probably it likes more to reach a lower potential position
c
Thanks for your continual encouragement Carlo
Cables are done, took them back in line and left them high and long and they don't drag it around or spring it back, cartridge tracks the record side fine, no jumps and sounds solid tracking at 1.8, same as with my OL arm
So i scribbled 3 ideas, (apologies again to those i offend with these sketches!) first two to lower rail to stylus height, but i have a feeling the weight being low relative to the rail is also nice, Stage 1 i can do more easily than stage 2
3rd idea is my interpretation of your suggestion of larger rail, can be done with the other parts the same, are such wheels readily available, easy to centre etc?
This way the cart can still rotate (no self centering). Think instead to put the cartridge + parallelogram between a two rods rail (round, square, angular, who knows) hollow in the middle. And at the same level, trying to reduce at most all harmful torques, horizontally and vertically.
The ideal would be the stylus tip no more than 1 cm under.
c
i simply like when ideas begin to flow around, whoever they belong to
The ideal would be the stylus tip no more than 1 cm under.
c
i simply like when ideas begin to flow around, whoever they belong to
I can see the appeal to get stability and also to reduce the moments and torques. The two are not necessarily related so starting with the rail and runners:
At the moment i am struggling to think of the rail system that will give stability without increasing friction and contact points.
I could simply add a second rail where my crash rail is and dispose the running bearings (1 or 2, yellow or blue respectively) and i would have stability, but would only be good if i could get the rails really flat, one relative to the other, or i would create VTA change as well.....and friction may also take over.....but if that worked i could then move on to other areas, mike
At the moment i am struggling to think of the rail system that will give stability without increasing friction and contact points.
I could simply add a second rail where my crash rail is and dispose the running bearings (1 or 2, yellow or blue respectively) and i would have stability, but would only be good if i could get the rails really flat, one relative to the other, or i would create VTA change as well.....and friction may also take over.....but if that worked i could then move on to other areas, mike
Attachments
From that pic I can see why you have pitching issues. you have 2 vertical pivots. Adding 1 bearing in the middle on the opposite side to the other 2 and another rail would solve the issue. You will need to make the rear rail adjustable so it becomes parallel with the front any miss alignment (either vertically or horizontally) between the rails will tilt the cartridge by a multiplication factor of the distance from the rail to the cartridge.
Thanks Warren, i can implement that most easily and then consider further refinements as time goes on.
i will make a new pair of rails and bolt the two bases together each end to ensure alignment. the works will then hang through the centre.
By two vertical pivots, do you mean the pitch on the rail and the parallelogram please? - and acting under the same force or moment they get into instability?
If i do that the rear bearing and rail will not then be radial. which brings me to question which rail and bearing is considered the principal one and where between them to i best centre the weights?
Or, i could not change any of that just add the rear rail with current arrangement and see! - i recall sound advice about don't over think it.....
i will make a new pair of rails and bolt the two bases together each end to ensure alignment. the works will then hang through the centre.
By two vertical pivots, do you mean the pitch on the rail and the parallelogram please? - and acting under the same force or moment they get into instability?
If i do that the rear bearing and rail will not then be radial. which brings me to question which rail and bearing is considered the principal one and where between them to i best centre the weights?
Or, i could not change any of that just add the rear rail with current arrangement and see! - i recall sound advice about don't over think it.....
So Carlo, now that Warren is talking about pitching i am more in my element, i was a naval architect (see Seawardboat.com - also an ex sailor).
So if i have a dual rail ultimately, the stylus must run on the radial line, but which part of the rail and where is the weight best centred fore and aft.
i imagine weight over the stylus and equidistant between rails..........
if i do this three bearing version i will then be able later to possibly miniaturise the parallelogram, reduce bearing to stylus height and change the cueing to something that lifts the entire rail assembly. i can also get VTA later as well.
one thing at a time though.
I would start with the COM centered between the 2 rails. If you use 3 bearings the rear will have higher contact pressure, will this cause issues, I don't know. I would not use 4 bearings as any miss alignment however slight could have one or 2 bearings lifting off the rail. A 3 legged stool is firmly planted no matter the ground profile.