Some Cartridge and tonearm input please

[mashaffer]

EC, I think you have it right. I'll add it to my history collection (rather than the round file) and start studying up on rolling my own.

mike

[SY]

Just for pedagogical purposes (EC is right, it's worth a minute but not much more), the best way to check for pivot friction is to balance out the arm to zero grams downforce, then very gently blow it from side-to-side and up-and-down.

[mashaffer]

I have started to do some research on this new and exciting project. I suppose that I can use some parts from the old tonearm to make my job easier.

I suppose I can use the old flange and mounting point and just make the arm length proper for that mounting point (easier than making arbitrary length arm and cutting a new mounting board). I could also incorporate the existing headshell too.

I assume that a rigid material is best for the arm but I am not sure that I could explain why I think that. It could just as easilly be the case that the tonearm should be designed to dampen certain vibrations. What say you? Is it even an important consideration?

Should I aim to have the pivot point above both the counter weight and the headshell?

mike

[EC8010]

No, you want the pivot height at record height. To make the arm stable, you want the counterwieght below pivot height so that the arm's centre of gravity is just below pivot height. I suggested balsa because it's light and has good damping. Oh, and it's easy to work. I posted a thread about unipivot arm design together with pictures of my arm on this forum, but I can't quite remember where...

Ditch the headshell. You want minimum mass (but not at the expense of rigidity) at the business end.

[scooby300]

Originally posted by mashaffer
EC, I think you have it right. I'll add it to my history collection (rather than the round file) and start studying up on rolling my own.

mike

Don`t get rid of it yet put some oil on the pivot and the rest of the joints. Then put a old cartrigde in it and a not so good lp if sound ok that will do . Untill u buy a new or make one

Remember if you don`t listen to it you won`t know how bad it sounds or good maybe. One TT is better than no TT

[EC8010]

No, no, no! A poor arm/cartridge can damage an expensive collection of LPs in short order. I've always had much better cartridges and arms than the rest of my system, and as a consequence, the LPs I bought as a student are still perfectly listenable. It's just not worth taking risks with your LPs.

[scooby300]

Come on everybody has some lps that or ready for the bin that’s in their collection even i have. If just you only play one track of the lp .

If you haven’t got any bad lps in your collection go to a charity shop and buy one. some of my lps come from such shops some you can get in mint condition.

[EC8010]

Charity shops can be a good source of LPs. I picked up a pressing of the Cantelli Beethoven Symphony No 7 the other week...

The thing is, a flat LP with low recorded level won't stress an arm much. Put a warped LP with high levels on and it won't move as it should, forcing the cartridge to mistrack and wreck an otherwise OK LP. Worse, the friction could easily be different from day to day and at different angles (probably is). I made my first arm when I was 14 in a double period (80 minutes) one morning at school and have never looked back.

[scooby300]

You did not state that your build your own arms before . But if didn’t have any tonearms available to i would try it .

So i would bin it

[mashaffer]

I went looking through my scrap bins and a plan is beginning to form. I cut a section of 1" motor shaft on the horizontal band saw for the bearing cup. I dont have access to drill press or milling machine right now but I think I can find someone to true the ends and cut a pilot hole for me.

For the post I could grind a proper point on an old drill bit or I have an extra dimond tipped grinding wheel dressing tool (used to level worn grinding wheels). The dressing tool might be overkill but it would be kind of cool to say I have a diamond bearing.

I have some flat copper rods (about 1/16" thick, 1/4" wide and 3+" long) that look like they came out of a motor arm. I figure on using one of those for the outriggers for azmuth stabilization (with suitable weights attached). The idea is to notch the top of the bearing cup so that the rod fits on top between the cup and the tonearm itself.

Here is my idea for antiskate. The bearing cup will be drilled half way through so I was thinking that I could cut a groove around the cup that was even with where the tip of the post will be and then cut two vertical grooves 180 degrees from each other. Each vertical groove would have a small screw installed just below the circular groove. A fishing line is then attached to one screw, fed up the vertical groove to the circular groove and wrapped around the bearing. The fishing line is then slung over a pully with appropriate weight attached. I don't know if this will work but the idea is to apply the torque in such a way as to not upset the arm balance or dynamics as a line to the arm itself would.

Any thoughts on these plans?

mike