Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

DIY linear tonearm
DIY linear tonearm
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 31st January 2019, 04:19 PM   #2661
Coolerooney is offline Coolerooney
diyAudio Member
 
Join Date: Dec 2018
Default Groovvy

Hi all

As the record is cut, the position of the “stylus” cutter is determined by the cutting program that controls the linear speed. (Of the cutter arm)
I am assuming that the density of the grooves is uniform across the record (save for the spaces between songs) -any takers?

Thought experiment
The distance between the start and end groove is 100 mm- and is the lineair distance travelled by the stylus

If the playtime of the music is 10 min (one music piece), there are 333 rotations of the record
The nr of grooves are then is 333 and the groove size 0,3003003 mm (groove+land)
I call this the “groove map” a bit like a mountain range seen from the side
With this information the steppermotor speed for the TA can be set, without sensor information for/of the cartridge- and the record played- a bit like base pitch and servo integrated- Ralf- post2630/2641


Application-multi song
The number of music pieces and the spaces between the music are known, so is the duration of each music piece- the size of the spaces is unknown

By mapping the groove density across the complete record would allow to get the same situation as when the record is cut.- we know where the groove is relative to the stylus at any time
A few tricks can be used to reduce the difference vs the original “cutting map”
If only we could have the cutting map......

The mapping is conceivably done independent of the normal listening experience, and is different for each record

Problems: inconsistent manufacturing standards, spaces, accuracy of measurement, replicating the cutting linear motion-but for the rest, we’re fine

Look forward to your ideas

Greetz

Coolerooney

Last edited by Coolerooney; 31st January 2019 at 04:43 PM.
  Reply With Quote
Old 31st January 2019, 05:10 PM   #2662
niffy is offline niffy  England
diyAudio Member
 
Join Date: Nov 2013
Location: Dartmoor
Hi Coolerooney,

I believe that most records are cut with a variable pitch. With analogue tape masters a second head reads the tape before the main head in order to determine the levels. Depending on the output from this second head the cutter slows or speeds up its rate of movement. This is to prevent one groove from breaking into or distorting the previous groove. This could be achieved by just having a wider groove spacing but this would limit the length of playback per side or would cause the record to be cut closer to the spindle where quality is lower. With digital masters the levels can be predetermined.

You could map the groove pitch for an entire side but you would have to account for even the slightest variation in platter rotation. This could be achieved by having an optical encoder on the platter and counting the exact number of revolutions. You would also have to make sure that you queue the record in exactly the same place, into the same groove each time. (I know that it is technically only one groove but you get my meaning) I think the typical groove spacing is closer to 100um.
You would probably need to account for the slight variation in the position of the record on the platter due to variation in the size of the central hole.

Niffy
  Reply With Quote
Old 31st January 2019, 06:37 PM   #2663
Coolerooney is offline Coolerooney
diyAudio Member
 
Join Date: Dec 2018
Bummer
  Reply With Quote
Old 1st February 2019, 06:28 AM   #2664
nocdplz is offline nocdplz
diyAudio Member
 
nocdplz's Avatar
 
Join Date: May 2010
Location: italy
Groove pitch - variable since Neumann lathe invention - 1950 ca. Sound engineers decide only average spacing due the length of music content to be cut on lacquer. Together with stereo and Riaa curve is what made Vinyl the great medium we love.
carlo
  Reply With Quote
Old 1st February 2019, 01:28 PM   #2665
lcsaszar is offline lcsaszar  Hungary
diyAudio Member
 
Join Date: Mar 2004
Location: Budapest, Hungary
It has been puzzled me since I first played Philip Glass' soundtrack titled Powaqqatsi on vinyl, how the cutting people could manage to squeeze 68 minutes on it (Side A 33'27", side B 34'35"), and with great dynamics, good bass and all.
  Reply With Quote
Old 1st February 2019, 02:38 PM   #2666
super10018 is offline super10018  United States
diyAudio Member
 
Join Date: May 2010
Let's assume you can map the groove for specific record for a specific table at particular moment perfectly. The driving mechanism can trace the map perfectly. Who wants to wait for completion of mapping before you play a record every time? I don't.
  Reply With Quote
Old 1st February 2019, 03:14 PM   #2667
Coolerooney is offline Coolerooney
diyAudio Member
 
Join Date: Dec 2018
Quote:
Originally Posted by super10018 View Post
Let's assume you can map the groove for specific record for a specific table at particular moment perfectly. The driving mechanism can trace the map perfectly. Who wants to wait for completion of mapping before you play a record every time? I don't.
Hi Super

The idea is to store the map, and pull it up when you play the record- yes you will have to select the appropriate map prior to playing

Best

Coolerooney
  Reply With Quote
Old 1st February 2019, 03:23 PM   #2668
super10018 is offline super10018  United States
diyAudio Member
 
Join Date: May 2010
Quote:
Originally Posted by Coolerooney View Post
Hi Super

The idea is to store the map, and pull it up when you play the record- yes you will have to select the appropriate map prior to playing

Best

Coolerooney
Problem is there is no single map to fit all records even on same table. Even for same record on same table, a single map is not good enough because center hole of record doesn't always fit spindle tightly.
  Reply With Quote
Old 1st February 2019, 03:40 PM   #2669
koldby is offline koldby  Denmark
diyAudio Member
 
koldby's Avatar
 
Join Date: Jun 2003
Location: Ruds Vedby
Maybe there could be a "predict the future" system :
If we have a sensing device that travels ,say 2 groves, BEFORE the cartridge and tells a positioning system , where the pick-up should be , when it arrives to that position. Sort of a FIFO system with a delay. It could tell both horizontal and vertical position...
Could it be done?
And would it solve all the error correction of a normal servo arm?
__________________
What is Home Theatre without good sound?
  Reply With Quote
Old 1st February 2019, 03:46 PM   #2670
Coolerooney is offline Coolerooney
diyAudio Member
 
Join Date: Dec 2018
Quote:
Originally Posted by super10018 View Post
Problem is there is no single map to fit all records even on same table. Even for same record on same table, a single map is not good enough because center hole of record doesn't always fit spindle tightly.
Hi Super- good point- working on that one btw- but difficult to get below 0,1mm, even then there a 1 groove width variance (about)
  Reply With Quote

Reply


DIY linear tonearmHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Linear tracking tonearm vs. Pivoting tonearm Don Nebel Analogue Source 5 31st May 2015 03:55 AM
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
Magnetic suspension linear-tracking tonearm? Shaun Analogue Source 5 4th June 2003 10:21 PM


New To Site? Need Help?

All times are GMT. The time now is 10:18 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki