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Old 23rd December 2013, 05:34 PM   #641
Tom Bloem is offline Tom Bloem  Netherlands
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Join Date: Oct 2013
@Walterwalter,

Sorry, after all it was a very simple problem.

Take a hand drilling machine and a drill of 8,0, 8,5 or 9.0 mm and make the hole in the eccentric record wider. Put the record on the platter, the stylus in the most inner groove and turn the platter by hand so you can observe the eccentricity (see drawing). Now correct the eccentricity with some careful “tick’s” with your finger. The longer the attached bar (2 sided tape), the more accurate the centricity of the record (an inflexible carbon tube – 500 x 4 x 1 mm – weights 3,7 gram and costs about 3 euro).

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Before, you have to drill the diameter of the spindle with a pillar drill machine in a small and thin metal or hard plastic disk. Modern glues fasten within one or two seconds so everything is ready now. The eccentric record will be perfect centric. Every owner of a pile of vinyl records can do the job.

Last edited by Tom Bloem; 23rd December 2013 at 05:49 PM.
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Old 23rd December 2013, 09:25 PM   #642
Mark Kelly is offline Mark Kelly  Australia
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Only works on one side. Eccentricities rarely align.
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Old 23rd December 2013, 10:56 PM   #643
berlinta is offline berlinta  Germany
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Hi Tom,
Unfortunately I can only second Marks experience with non-aligned stampers.

For a cheap solution of this problem check the spindle design of the Artemis Labs turntable that I designed in 2006. You'll find the spindle to have a "waist" from mat level to about 3mm above. The waist is 6.5mm in diameter(iIrc) and the spindle above the waist has a "standard" diameter of 7.15mm. When dropped, the record "lands" centered, but your aforementioned "tick" with a finger(with some practice) will get you much closer to perfect concentricity.

The other, rather important advantage is that (fairly)well centered records will not make physical contact with the spindle. One less source of noise.....

@ Ralf. Won't be making it to CES in Jan (BUMMER!). The servo just needs a second(cue and runout groove) mode that, when a displacement over time > x is sensed, switches to pure servo(sans pitch factor). That's doable :-)
But it is a problem in general to allow for the user to cue a servo-controlled linear tracking arm "free-handedly" and not à la Pioneer PL-L1000 or similar...

All the best to all the best :-)

Frank
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Old 24th December 2013, 06:30 PM   #644
Tom Bloem is offline Tom Bloem  Netherlands
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Join Date: Oct 2013
@Mark Kelly,

Because of the explanation of Berlinta I now understand what you mean. And your massage is: when the manufacturer of the record spends too few attention to the centricity of the record, they also will take insufficient care to align the grooves on both sides of the record.

Well, because of your warning I inspected the centricity of a new jazz album I bought recently: Trichotomy – Fact finding mission – of the NAIM label. The NAIM-label is advertising themselves as the “exclusive top hifi”, but the record is not exactly centric on both sides and the eccentricity of both sides differs...

The designer of a tonearm cannot wipe out the influence of warped and eccentric records. You can “smear it out” over the frequency spectrum so it is hardly observable with the spectrum analyzer. But it is impossible to eliminate the influence of the wiggling to the stylus and cantilever of the phono cartridge. A well fabricated record is the foundation that underlies vinyl hifi. Bad centred records are simply no high fidelity...

Conclusion: everyone who spends more than about 1000 euro for a new turntable with tonearm and cartridge is in fact a dumb consumer. Because for 1000 euro he can buy a quality CD-player and enjoy real hifi. Moreover, every hifi shop must have a warning on their website: all the state of the art turntables, tonearms and cartridges can only reproduce high quality music if the record is a high quality fabricated vinyl record. These records are not widely available!

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Well, let us see what can be done. The question is how we can centre a record when the grooves of both sides of the record have not the same centre point. First, it must be comfortable for the person who wants to play a vinyl record. Second, side one and side two must be centred separately. So we have to make a choice. For example the red pawls are side one of the record and the blue ones side two. So we have to mark them separately with nice appropriate stickers on both sides of the record.

Centring the record – after widening the centre hole – can be done according to my previous post. Next, one needs a mould/matrix to drill the holes at the right place from the spindle and at right angles to each other (so the spindle have to be the point of reference). Not by using a big drilling machine (3,1 mm holes are fine), but by a small electro motor that fits into two concentric pipes with a loose spring. The thickness of the middle section of a record is 2,0 – 2,8 mm so one AA battery is more than enough power to drive the small electro motor with attached drill (a small collet to fetch the small and short drill is enough).

I realize that the suggested way to centre the record is “really shameful” in modern times. So it is great there are really small gadgets that can project a small red dot on the wall (Power point gadgets). The pawls are not rarely: a lot of technical/mechanical equipment is suited with this kind of alignment (the spring must be loose so the record is not lifted by the invisible pawls for side two of the disk). Fetching these pawls in a acrylic platter is just drilling 4 holes with the mould/matrix (next step is to drill the correct diameter and depth). And metal platters? If there is enough room beneath just glue them at the other side (increasing the surface of the glue with one or more rings that fit).

Last edited by Tom Bloem; 24th December 2013 at 06:54 PM.
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Old 26th December 2013, 07:41 PM   #645
Tom Bloem is offline Tom Bloem  Netherlands
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Suppose, I make a tangential tonearm (the tangential movement of the tonearm is done by the stylus). I put an high quality record on the platter, start playing the music and watch the cartridge slowly moving to the inner side of the record. Everything is just fine!

Back to reality. Because I have a lot of really lightweight tubes, I attached a carbon tube of 0,7 mm x 500 mm to my fixed pivot tone arm. When I looked up the specifications of 30 cm vinyl records (IEC98-1987) I read the tolerance of the diameter of the spindle hole in relation to the spiral of the groove: 0,2 mm.

I have measured the (ec)centricity of a lot of the best quality records, but none of them showed a steady movement of the tonearm when I observed the moving point of the carbon tube all along the groove. However, is this all eccentricity or is it partly the vibration of the cartridge, caused by the stylus and cantilever?

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I have checked this (finishing groove) and the “score” is about 40% vibrations by the cartridge and 60% eccentricity. The smallest eccentricity at the tip of the stylus – at both sides of the record – at the finishing groove was 0,2 mm (for example the Argo label). Remember: these are high quality classical music records and not popular music records. Nevertheless, there are popular music records that meet the IEC98-1987 specifications too.

Back to the imaginary tangential tonearm. The eccentricity of the record is equal for this type of tonearm so the cartridge is moving to and fro for 0,2 mm and more. The observed vibrations of the cartridge are not reserved for fixed pivot tonearms: the cartridge in the tangential tonearm will resonance in the same way and these vibrations (!) are not restricted to very low frequencies. Conclusion: what looks – from a distance – like a smooth train is – from close up – a fan that’s bumping over an unpaved road. And these were all high quality records...

So, what is the profit of a tangential tonearm when the stylus have to move the mass en friction of the tonearm at right angles? There is no tracking error and there is no offset angle, that is right. So this tangential tonearm is not bad in comparison to a fixed pivot tonearm. But this type of tangential tonearm cannot estimate the quality of a cd.

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Suppose I want to centre all my eccentric records by myself. What will be the maximum precision I can met? Well, I can use a small laser that projects a red dot on the wall at a distance of 2 or 3 meter. So I can measure differences of nearly 0,01 mm. Nevertheless, this is only possible when the tonearm and cartridge is very rigid. A little tolerance will ruin the accuracy. Because of this magnification of the wiggling of the stylus I can come far. But when I am ready adjusting the centre of the record I have to drill those 2 holes into the vinyl for this side of the record (pawls).

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I have to use a tool for this job and this tool is not available so I have to make it by myself. With other words: the precision of this tool – plus/minus the tolerance of my adjustment – will set the new (ec)centricity for this side of the record. Therefore, my question is: who can make this tool with a tolerance less than +/- 0,1 mm? Personally, I know a lot of tricks to get very close. But a tolerance less than 0,1 mm? That will only happen by accident. (Don’t worry about the vibrations of small DC motors; of course they will pulsate.)

When we will reach a higher level of the quality of the reproduced music of a vinyl record, we have to:
  • centre the records as good as we can;
  • forget all those fixed-pivot dogma’s;
  • damp a lot of the natural resonances of the cartridge, caused by the vibrations of the stylus and cantilever;
  • transfer the tonearm from the outer side to the inner side of the record by only one force (tracking force).
So we are back at post number #632.

Last edited by Tom Bloem; 26th December 2013 at 07:47 PM.
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Old 26th December 2013, 09:55 PM   #646
berlinta is offline berlinta  Germany
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Hi Tom,
All modern records are cut with "variable pitch", so the rate at which the cartridge moves towards the center is never constant. Even perfect centering can't get rid of this flaw, which, on the other hands yields longer max. playing time and less "bleed through" from groove to groove. Can't eat your cake and have it, too... :-)

Cheers,

Frank
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Old 27th December 2013, 10:48 AM   #647
Tom Bloem is offline Tom Bloem  Netherlands
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@Berlinta,

I am aware of the variable pitch, but the groove will never cross itself. Therefore, the lack of a straight movement (with variable speed) from the outer side to the inner side of any (!) record have to worry me (and others). Nevertheless, this was not the most accurate experiment. So I have ordered a nice laser to do a 100% non-disturbing experiment. We will see.
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Old 28th December 2013, 09:48 AM   #648
walterwalter is offline walterwalter  Ukraine
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@Tom Bloem
Your ideas as to centering holes look good. However, even with my humble collection of 1000 records, it is rather time and work consuming. That is why I personally would prefer something like Nakamichi automatic center search (if it ever be moderately priced ). Unfortunately, manufacturers are very busy with solving imaginary problems, as well as unsubstantial ones.
Let me explain my point. Due to special literature, eccentricity of central hole of 0,15 mm gives speed deviations (wow) of 0,1 t-0,25%. Together with recorded track eccentricity, in may give up to 0,27mm deviation, which brings wow up to 0,19-0,45%... Thinking logically, what is the point of making highly sophisticated TT with 30kg platter, magnet bearing, superb motors, etc, if as a result we still have up to 0, 25-0,5% of speed deviation with each record turn? Doesn't it look as an engineering absurd?
As for me, I see several other problems with LP gear, those rather substantial, ignored by manufacturers and audiophiles. Linear tracking seems to have least influence on sound reproduction quality, of all of them.
Or, maybe I'm wrong as to linear tracking? Actually I'm unable to hear sonic differences of 1,5 degree error with my Micro Seiki arm. However, I hear the difference with different cables, including power cables...
P.S. Still prefer LP sound to CD.

Last edited by walterwalter; 28th December 2013 at 09:55 AM.
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Old 28th December 2013, 06:36 PM   #649
Tom Bloem is offline Tom Bloem  Netherlands
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Join Date: Oct 2013
@Walterwalter,

Sorry, that I was a bit vague in earlier posts; I have nearly the same opinion about phono equipment as you have. Moreover, I am quite upset when I see video’s showing “magic” turntables and tonearms that cost 5.000 euro and more. Because a 1000 euro CD-player offers the buyer more quality.

I like vinyl records because I have to handle them with a lot of care. Just like precious things and that’s correct because beautiful music is precious for me. Nevertheless, it is very interesting to see how far we can come with this old technique. At the moment I can hardly hear the difference between a piece of music on a vinyl record and the same music on a CD. I know the quality of the CD is better, but I cannot hear that very well (and others who are listening agree with this). Therefore, I am afraid at the end the progress will be limited (just like you argued).

Audiophile magazines and high end audio shops do not agree with this. They advise me to spend a lot of money and they promise me a phenomenal audible sensation when I take home “one of those bargains”. Many people believe those tales. Recently, someone offered his Van den Hull phono cartridge (Colibri) because he wanted to buy a new Colibri with platinum wiring (pfffff).

[When I install my equipment in a room as big as the listening room of a high end audio shop, I will hear everything with far more detail than in my own living room. Just because of the possibility to increase the output of the amplifier in relation to the volume of the listening room (and less deformation caused by resonances from the walls, etc., etc.).]

Because I still buy new vinyl records, it is quite disappointing to clearly see the cartridge wiggling all along the trajectory; the eccentricity exceeds far the specifications of the RIAA/IEC. Moreover, the same music on CD is half the price... So I have to centre these new records just to show myself I am not a fool. That’s why I give it a try. But when the results are unsatisfactory, I immediately stop buying any new vinyl record.

Oh, by the way; some month ago I ordered a test LP in the UK for about 30 pounds (the only test LP I could find at the internet). It is the analogue test LP of Hi-Fi News, produced by Len Gregory, ‘The cartridge man’. Well, a test LP have be the most accurate LP that meets the RIAA standard, isn’t it? When I put the record on the turntable I can shuffle the record to and fro for 0,4 mm... The Needledoctor will sell you exactly the same test LP for only $49.99 (a bargain for this high quality record, so the costumers rated it with 5 stars! ;-))
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Old 28th December 2013, 09:55 PM   #650
berlinta is offline berlinta  Germany
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Hi Tom,
Somewhat off topic, but:
The Hi-fi News test record isn't worth the admission price for a number of reasons...
Listen with your own ears, take what reviewers (or other experts) say with more than just a grain of salt.
If you can't make out much of a difference between an LP and the equivalent CD, that's fine. But how can you then say: "I know the quality of the CD is better."?
If you were to come by my place and do a double blind listening comparison between LP and CD, you may revise your position. I've done it with musicians, men and women alike, students, "audiophiles", recording engineers and recently with the head of the music department of a local public broadcast station.
His words after listening to the LP versions: "You can't get quality like that from CD..."
His wife was completely flabbergasted as well. She too thought that CD was supposed to be superior...
Don't get me wrong. CD is a great format, measures well in many departments, but overall, still trails when we're looking at the state of the art products. To your consolation, one of the better 1000$ CD players will outperform a poorly put-together and sluggishly adjusted record deck with ease.

Then there is the question which type of recording/mixing/mastering method was used for the CD/LP. Some LPs are produced like mere afterthoughts with the CD actually sounding superior even when played back via a super turntable.

Here in Berlin, an LP cost about 10-20% more than the CD(sometimes the same!), but you get a CD copy and or a (hi-rez)download code with each LP. No question what I choose... :-)

Keep us posted on your arm design and sonic impressions, the medium itself is what it is.... :-)

Cheers,

Frank
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