Opus 3 Cantus parallel tracking arm

[moray james]

Originally Posted by JRKO

Thanks for that Moray James - I need to pose some questions so I can better grasp the fundamentals.

I understand that the surface of say, copper is more easily damaged, and so softer than glass and I think(?) that and acrylic tube would be harder than the copper.

1)What would be the difference in sound in this application? The whole carriage weighs very little and the total contact/friction area between bearing and tube must be a single square millimetre or so.

2)Isn't bearing choice a greater issue as they have the major contact/friction area internally and so the change to ceramic outweigh the benefit of a change of tube from copper to glass?

3)Would't a harder material like glass be more susceptible to ringing from the music than a softer material? Could that be an issue of the tube passing vibration back to the arm assembly?

4)If you minimise contact friction between bearing and tube too much wont the bearing simply be dragged along the tube and be worse than a softer material anyway?

Thanks in advance for bearing (pun intended) with me!

1) different materials will have different sonic qualities. You will have to experiment and see for yourself. In this application bearings which are intended for ultra low friction would be my first choice though I would also be temped to experiment with bearings which are intended for ultra low noise as well.

2) Generally when you design parts that move you design one part to be sorter so that part will wear first. This part is generally the less expensive or the easier part to get to to replace. I think that using a glass tube with a mohs hardness of about 6 and a bearing with a harder material makes thee most sense. I am not sure that I understand your question so if I have missed the point please reword it for me.

3) If you mount your glass tube into a material of similar hardness you can divert the energy some and then deal with it. A layer of shrink tube on the glass will damp it significantly especially if the shrink tube is adhesive lined. It does not always take a lot to damp things at high frequencies. You might have success with a few layers of clear lacquer on the outside of the tube. I see this as a design tweak rather than a major issue as bare glass works extremely well.

4) If you could reduce the drag or friction to zero sure the sled would just be dragged along and that would be fine. I think that some attention to sled geometry with respect to bearing contact and the sleds ability to track in a straight line would be beneficial. When the arm rides a warp the sled is literally dragged up the wall of the tube and gravity pulls it back down for you this is where riding the inside of a tube is so much better than riding on the outside of a tube. Inside gravity works for you and outside it just helps you to fall off. This design of Bo's is so clever and so very simple so very well thought out.

I hope this helps and is of some use. Best regards Moray James.

[JRKO]

Haha! what a dumb question my no.4 was - if its frictionless its nirvana, not a problem!!!

Right - Nuf talky - more buildy!

[midwifecrisis]

Hi everyone,

I learned from this thread about the passing of Bo Hansson, very sorry about this. Does anyone here know whether his company is still selling his Cantus tonearm or parts for it? I've emailed to the address on his website, but my message as returned to me as undeliverable.

Thanks for any news,
Sean

[JRKO]

see if you can find a reseller maybe.

Or build you own

[midwifecrisis]

Originally Posted by JRKO

see if you can find a reseller maybe.

Or build you own

Well, I'm gathering parts to do exactly that. Thought about buying the support block part, though. Trying to figure out having decent VTA adjustment, my solutions aren't so elegant yet...

cheers

[JRKO]

off the top of my head the only VTA built in on the DIY versions I can remember is to mount the tube 'block' on a large threaded bar.

how about allowing the block to slide up a delrin rod and shim it out as needed?

I'm just going to set mine within my cartridges ideal a be done. Guess it depends o the compliance but thats been discussed a few pages back.

[bgruhn]

Originally Posted by JRKO

off the top of my head the only VTA built in on the DIY versions I can remember is to mount the tube 'block' on a large threaded bar.

how about allowing the block to slide up a delrin rod and shim it out as needed?

I'm just going to set mine within my cartridges ideal a be done. Guess it depends o the compliance but thats been discussed a few pages back.

Originally Posted by JRKO

Haha! what a dumb question my no.4 was - if its frictionless its nirvana, not a problem!!!

Right - Nuf talky - more buildy!

Hi gang,
Just checking in to let you all know I'm still here. Been busy around the house and there were a few clocks to tend to. So nothing much with the Cantus Clone save listening to some music with supper or other odd moments. I'm still very pleased with the LT arm and a polished design is shaping up in my mind. Got to find some good wire soon and come up with a good support for it so that there is no, or at least uniform, drag on the carriage. What I'm using now occasionally causes skips. Most of the time though, no problem. I'm anxious to see some more results on these projects.

BillG

[dtut]

VTA,

The screw head is captured between the t-nut and the cap. Screwing it in lowers the arm, screwing it out raises it. I thought the pictures would do a better job of showing how things work. If there are questions, I'll be glad to help.

[Sourdingue]

Hello everyone, I take this post in progress and will try to make my small contribution.
Here is an arm that I made inspired by the design of "cantus", except that the arm is pneumatic, decoupling and damping of the arm support is provided by a viscous liquid ..

[midwifecrisis]

Originally Posted by dtut

VTA,

The screw head is captured between the t-nut and the cap. Screwing it in lowers the arm, screwing it out raises it. I thought the pictures would do a better job of showing how things work. If there are questions, I'll be glad to help.

Thanks for sharing your system, that's a terrific solution. My version is leaning a bit heavier in terms of materials, and it's nice to see how simply it can work.

Are the other two screws in the top plate holding/leveling the copper tube? I was trying to figure out how to accomplish leveling the tube, the mounting plate and VTA altogether, seems like your version manages it nicely.

Thanks!