DIY tensioned string suspended tonearm - Page 3 - 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 24th March 2010, 03:06 PM   #21
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
This is a message that was sent to me:
“I was thinking about your thread suspension idea and I like it a lot. I was wondering if you used a mono filament thread like a polyester or nylon fishing line? I thought of a twist on this idea to build a linear arm. The horizontal bearing would be two paralleled and tensioned threads spread apart by some small distance. The vertical bearing would be a horizontal thread held in a small “U” shaped frame to which a small plate is clamped to the tread and from which are mounted two small hollow steel tubes that would make up the tonearm assembly. So the tone arm can rotate on the tensioned thread in the “U” channel and the “U” channel would have small groves on the underside which registered to and slide upon the two horizontal filaments. I hope that this makes sense. The tonearm rotates on the short thread and that assembly slides upon the two parallel threads. Let me know what you think about this idea. Thanks for posting your thought provoking idea. Best regards Moray James.”


The thread I used is described in post #5
My bearing is build based on believing that tensioned string solidly connected to the wand can drain out (into the post) vibrations induced in the wand by stylus, so these vibrations don’t get back to cartridge. Like in tight gimbal bearing but without the noise caused by friction. In your proposed model wand assembly slides loosely on 2 parallel threads which is opposite to what I believe. There are reports from air suspended linear arm builders that lowering air pressure (which lowers solidity of coupling between wand assembly and support) lowers sound dynamics, bass quality and output.
It will work but it is hard to say how it will sound.

Marek
  Reply With Quote
Old 30th March 2010, 01:12 AM   #22
diyAudio Member
 
sumaudioguy's Avatar
 
Join Date: Jan 2010
Location: Midwest U.S.A.
This just reminds me of the "well tempered tonearm" by Bill Firebaugh (sp?). I really liked his business practice but not the arm. Every change in level meant a different drag load on the stylus which pulled on the arm a very slightly different amount which resulted in pitch shift at the front of every note. This effect drove me crazy! I could not handle it and made my skin want to jump off my body. Suppose being overly sensitive to FM which is the big can this type of distortion fits in. Singing springs in tonearms was my next big annoyance. -cheers
__________________
What the other guy said----Standing on the shoulders of giants.
New avatar- no more little array
  Reply With Quote
Old 30th March 2010, 09:26 PM   #23
dtut is offline dtut  United States
diyAudio Member
 
Join Date: Feb 2007
Location: California Central Coast
Recently, while I was listening to some Bach sonatas, I heard distortion during string crescendo passages. Sound familiar, Marek? The string - on my suspension, not the instruments - had stretched and loosened.
After I retightened the string, the distortion mostly disappeared confirming, for me, that Marek's theory that tensioned string carries resonances to the frame where it's damped. But that leaves the problem of where the resonance originated. There are plenty of suspects. This arm was pretty much thrown together with whatever was on the bench at the time so the type of string, wand material, cartridge, and counter-weight design all need to be re-examined. Marek's find that additional weight at the head shell is helpful is a good starting point. Beyond that, despite my allergy to math, I'd like this to get a little more formal and check out more about effective mass and the causes/cures of resonance.

Before I built this arm, I was considering a tensioned string linear arm. My idea was to use glass beads for the sliding surface, but after buying beads and sliding them on string, teflon insulated wire, and guitar string, I decided there was too much friction/noise and I wasn't sure about how to avoid/damp the noise and string resonances.

Regardless, I urge Moray James to go ahead with developing his idea and reporting back. I hope my experience was misleading and he comes up with something viable.
__________________
Doug Tuthill
  Reply With Quote
Old 31st March 2010, 12:13 AM   #24
diyAudio Member
 
Join Date: Aug 2003
Location: Calgary on the Bow
Doug thanks I appreciate your support, projects such as this can take on a life of their own. I only wish that I had a fraction of the DIY talent that I see most every day in these forums. I would be most interested in seeing any pictures you might have of your arm projects linear or pivoted.
__________________
moray james
  Reply With Quote
Old 31st March 2010, 01:01 AM   #25
dtut is offline dtut  United States
diyAudio Member
 
Join Date: Feb 2007
Location: California Central Coast
Moray,

You're welcome.

Post 14 in this thread.

Edison said something about "90% perspiration and 10% inspiration." I've noticed that persistence, inquisitiveness, and a willingness to royally screw up seem to really count in DIY. Oh, yeah, and a penchant for hanging out in and with the weird.
__________________
Doug Tuthill
  Reply With Quote
Old 1st April 2010, 02:09 AM   #26
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
Sumadioguy,
I am saddened that my tonearm reminds you of an unpleasant experience.
I only saw a picture of “well tempered tonearm” and I don’t like the design. My tonearm is mechanically different. My bearing is practically a unipivot. I am not sure what to call the bearing of “well tempered” – a floating swing? My string is under tension, it is solidly anchored to the support above and below the wand and string’s horizontal movement and vibration is limited. My antiskate force is adjustable and proportional to skating force. I use different materials etc. And don’t forget that my tonearm is home made, not for sale but free to be copied for any reason.
I don’t hear the singing of the spring, you might. With your experience, you probably could calculate resonance and without building anything find out if the spring sings in audible frequency. I prefer to build my toys and if they sound good to me I share the design.

Doug,
I use test LP to check mechanical resonance of the tonearm with given cartridge, so far I was only a couple of grams off the target. Sound waves behavior in the wand and other parts of the tonearm is a different matter - unless you have lab equipment you have to trust your ears. The only “complicated” calculation I did was the effect of different distance between magnets’ gap and string attachment point on stiffness of the Schroeder type bearing, but that does not apply to our designs.

Moray,
I also was dreaming about linear arm, it was string suspended unipivot mounted on brass bearings sliding on two stainless steel bars. The wand assembly was motorized and wand was pivoting only to compensate for crooked records.

Marek
  Reply With Quote
Old 1st April 2010, 03:37 AM   #27
diyAudio Member
 
sumaudioguy's Avatar
 
Join Date: Jan 2010
Location: Midwest U.S.A.
I am probably all wrong about the comparison of yours to the well tempered. Sorry for that as everyone makes errors. Shall study both further.
__________________
What the other guy said----Standing on the shoulders of giants.
New avatar- no more little array
  Reply With Quote
Old 1st April 2010, 04:49 PM   #28
EC8010 is offline EC8010  United Kingdom
diyAudio Moderator Emeritus
 
EC8010's Avatar
 
Join Date: Jan 2003
Location: Near London. UK
Default Bizarm

I see the Well-Tempered arm has been mentioned a number of times. Here's its progenitor.
Attached Images
File Type: png Biz1 copy.png (65.7 KB, 628 views)
File Type: png Biz2 copy.png (51.1 KB, 623 views)
File Type: png Biz3 copy.png (95.1 KB, 619 views)
File Type: png Biz4 copy.png (87.5 KB, 577 views)
__________________
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 4th April 2010, 03:39 PM   #29
diyAudio Member
 
directdriver's Avatar
 
Join Date: Nov 2005
Perhaps another way to do the tension is to use the magnet again? Just a thought.
Attached Images
File Type: jpg string_diagram_alt.jpg (17.9 KB, 563 views)

Last edited by directdriver; 4th April 2010 at 03:49 PM.
  Reply With Quote
Old 5th April 2010, 04:57 PM   #30
marekst is offline marekst  Poland
diyAudio Member
 
marekst's Avatar
 
Join Date: Oct 2006
Location: Central Florida
Directdriver,
You missed my point - I wanted both ends of the string solidly attached to the support!
I don’t like patented designs, because then you have to bury your toys with you to avoid a patent attorney showing up on the widow’s doorstep...

I am busy growing food now in my veggie garden, but when spring is over I will make my second tonearm; I already thought out different vertical geometry for it.
Marek
  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 07:27 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