DIY tensioned string suspended tonearm - Page 2 - diyAudio
Go Back   Home > Forums > Source & Line > Analogue Source

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 27th January 2010, 04:14 PM   #11
dtut is offline dtut  United States
diyAudio Member
 
Join Date: Feb 2007
Location: California Central Coast
Marek,

I've been working along similar lines trying to design a tensioned string alternative to Schroeder's magnets. I was stuck about how to position the arm on the string if I was going to use a single string. Your bar idea is an elegant solution. Thanks for posting.
__________________
Doug Tuthill
  Reply With Quote
Old 8th March 2010, 03:21 PM   #12
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
Hi, I am back home, thanks for comments.
I am including a sketch (diagram) of the bearing.

What is the advantage over conventional unipivot design?
These are my personal, unprofessional opinions:
Tensioned string drains sound waves out of wand more efficiently than the needle point.The wand is lighter around pivot point than wand of a conventional unipivot - it stores less energy. The sound is more dynamic, detailed and cleaner.
Compared with gimbeled tonearm there is a lot less friction and no bearing rattle.
Compared with magnetically suspended tonearm, there is no advantage but my new bearing has less tension (resistance), the pivot point is not imaginary
and i believe the tonearm is not protected by patents, but I may be wrong.

Marek
  Reply With Quote
Old 8th March 2010, 03:24 PM   #13
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
nt
Attached Images
File Type: jpg 001.JPG (55.5 KB, 875 views)
  Reply With Quote
Old 12th March 2010, 06:36 PM   #14
dtut is offline dtut  United States
diyAudio Member
 
Join Date: Feb 2007
Location: California Central Coast
Default another tensioned string arm

This is a prototype I've come up with that uses an expansion of Marek's string tensioner. It's appearance-challenged, but works surprisingly well. There are two strings, upper and lower, which support and pivot both the outer ring and the wand. It's critical that the strings at each pivot point be quite close together or they become a parallelogram, which causes unwanted stray tensions. The strings, in this case, are dial strings, which I had available. They're a bit stiff, but don't stretch much. The arm is salvage and the cartridge is a Shure. The outer ring is PVC pipe.

My conclusions about this kind of arm are the same as Marek's, despite the different approaches. My immediate reaction to hearing this arm was that the sound is delicate - it is transparent and nuanced, the notes are made by instruments played by musicians.
Attached Images
File Type: jpg P1030115.JPG.jpg (135.4 KB, 819 views)
File Type: jpg P1030109.JPG.jpg (105.8 KB, 821 views)
__________________
Doug Tuthill
  Reply With Quote
Old 12th March 2010, 08:57 PM   #15
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
Ingenius design. I see you maneged to make gimbal tonearm without rattling bearings -congratulations. You are right about unwanted stray tensions, that's why I made 1/32" holes for the string. If you make a metal version with vectran string, dampened spring and well treated wooden wand it could outperform anyting out there. One question: why two springs?

Marek
  Reply With Quote
Old 12th March 2010, 10:16 PM   #16
dtut is offline dtut  United States
diyAudio Member
 
Join Date: Feb 2007
Location: California Central Coast
Thank you, Marek,

I'm guessing that your question is 'why two "strings?"' There are no springs in this design. I did figure out a single string version, but the tension was huge in order to make all the connections. Some string broke - radio dial string - and some - nylon kite string - introduced stray tensions, which moved the wand horizontally. I still like the idea of a single string gimbal and I'll keep working on it with high tech string and better machined surfaces that will reduce friction on the string as it's being tensioned. I haven't explored your damped spring, yet, but I plan to.

I work mostly in wood because that's what I'm used to and my shop is set up for. On the other hand, there's this machinist here who likes to do audio related work - - -

You and I seem to be all alone out here in Tension String Land and that's a shame because it's such a great way to DIY an arm.
__________________
Doug Tuthill
  Reply With Quote
Old 13th March 2010, 08:51 AM   #17
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default Excellent stuff.

This looks like a very interesting idea. I've always used unipivots (ball point pen into PTFE block) because I felt that rattling bearings could be heard, but your string-driven-thing idea solves the rattling bearings of gimbals and wobble of unipivots whilst retaining the unipivot's manufacturing simplicity.

Love the "rustic" look.
__________________
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
  Reply With Quote
Old 13th March 2010, 02:07 PM   #18
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
Doug,
My mistake, I am seeing things, my brain assumed that inside that white thing on top of your screw is a small spring and another below the support. In your prototype the wooden support bends and acts as a spring. With stiff metal support and stiff string some kind of spring is necessary to compensate for thermal expansions and for changes of the length of the string when it twists as the arm moves. Otherwise tension will change, sound will change and antiskate force will change. By the way Schroeder tonearm is another string suspended design with a pair of magnets acting as a spring, many try to copy that, we are not alone.
Marek
  Reply With Quote
Old 13th March 2010, 05:46 PM   #19
dtut is offline dtut  United States
diyAudio Member
 
Join Date: Feb 2007
Location: California Central Coast
Good Morning EC8010 and Marek,

Thank you both for your responses.

I was interested in unipivots, but there's the wobble thing --- I built a wood version Schroeder arm (pg 31 "DIY Schroeder Tonearm?") which worked well, but there's the patent thing --- The yoke on the Schroeder led to the gimbal. Marek and an artist named di Suervo provided important positioning solutions.

As a very rough analogy, I think these arms are like the softer, better damped suspensions on modern cars - less bump and rattle, better control. Suspensions like that require strong, stiff frames as Marek correctly points out. The difference, and the critical factor, between tensioned and conventional arms may be that tensioned suspensions are unified - when under tension, they inherently become one piece instead of separate parts.

I hope more people get in on this idea because there is more potential still.

The small white things at the top and bottom are wood plugs with a vertical hole through them and a horizontal slot. A small metal bar drops into the slot and the string is tied over it. That's another reason I went with two strings - tying off one string made me nuts - I never got it figured out, really.

"Rustic" was kind and a good laugh this morning.
__________________
Doug Tuthill

Last edited by dtut; 13th March 2010 at 05:49 PM.
  Reply With Quote
Old 21st March 2010, 11:36 PM   #20
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
Because of wood cutting mishap my wand ended up shorter and consequently lighter than intended and I had to make a heavier cartridge mounting plate. I thought adding weight to the headshell is a cheap solution good only to make commercial tonearms universal, whereas on custom made tonearms the extra mass could be better used to make the arm stronger. I guess I was wrong, the results are better than I expected just from getting the effective mass right. I am not sure if the improvement is because the headshell plate is heavier or made of different material (brass in place of aluminum) or because consequently the counterweight was moved to different location where my interior counterweight shaft dampening is more effective, but I like what I hear. I never make things identical for A/B testing, I do not like changing cartridges back and forth for comparisons, but I know that now my baby sings like never before and it does it with inexpensive cartridge AT440MLa. A bit of glassines in the sound of violins disappeared, focus improved – the tonearm is ready.
On the picture is a new headshell plate - the plate is brass the threaded part is aluminum.

dtut,
Thanks for explanation. Your design has one advantage over mine: it doesn’t need counterweight with low center of gravity which positively changes the way tonearm reacts to record’s moguls. I could easily achieve that by making a bearing with enough restoring force (two points suspension, one couple millimeters above another) but I believe that that would be worse than low counterweight! The disadvantage of your concept is extra ring between the wand and the support (extra part, longer, more complicated string path, possible resonances etc). “The wobble thing” is not an issue as my tonearm is stable, some minimal friction of string around pivot point stops wobbling. Conventional unipivots have a heavy bell around pivot point which reinforces wobbling effect.

About the “patent thing” I don’t plan to sell anything but I have extremely strong opinion on it…well, I’m sure it would be erased by the moderator. I will soon rebuild my other magnetically suspended tonearm as string suspended, anyway.

About more people getting on this idea – it’s a shame that your original, ingeniously designed, totally DIY tonearm had almost no response... Hmmm… what does that say about our DIY forum which falls over expensive, commercial designs…

Good luck in developing your tonearm I am glad to share this thread with you,

Marek
Attached Images
File Type: jpg 035.JPG (53.7 KB, 710 views)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Magnetically suspended DIY tonearm marekst Analogue Source 76 16th April 2012 04:27 PM
Another DIY Tonearm johnmarkp Analogue Source 0 21st April 2008 11:07 PM
my DIY Turntables and DIY tonearm Roger Waters Analogue Source 57 22nd January 2008 06:05 PM
DIY Tonearm kitemap Analogue Source 6 1st December 2007 08:52 PM


New To Site? Need Help?

All times are GMT. The time now is 10:31 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2