| plysch |
Hallo anadicts.
Does anyone in this forum have any experience of the Nagaoka MP-50 p.u?? Is it good for 300$?
I´m looking for a new MM cartridge and don´t really know what to buy. Or do you have any suggestions on any other p.u in the pricerange of 300-500$.
I have a very limited posibitlity to test the p.u´s, becaues I live very far from a deasent audiodealer so I must trust your ears (or the reviews)...
THANX |
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| sreten |
As far as I know the MP50 is no longer made, I would
expect there to be more suitable choices available.
What cartridge you need depends first and
foremost on the quality of your turntable and arm.
Secondly the mass of the arm and to a degree
the type of arm fixed or detachable headshell.
Thirdly to a degree the sort of tonal balance you
want, rich, neutral or bright.
Fourthly to a degree practical issues, stylus
life, cost of spare styli, ease of mounting etc.
What turntable and arm do you have ?
What sort of sound are you looking for / expecting ?
:) sreten. |
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| plysch |
sreten: Today I´ve got a Thoréns TD320mkII, but I´m building an own designed table at the moment. It will be non suspension table with lots of mass and a glued birch platter (84mm thick, leadfilled) with external motor (teres) and a copy of there bearing.
The arm is an homemade 'Ladegaard's Air Bearing Tangential Tonearm' with a balsa arm (don´t know the word in english but it´s built with many small pieces crossing eachother, like bridges are built....hope you understand) so the arm is very lightweight.
I would like a natural sound, not to warm anyhow, I use tube amplifiers and they are quite rich in there sound. |
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| sreten |
Wow !
Not an easy thing to give an opinion on, but I will ;).
From what I remember the MP50 was a fairly heavy cartridge
and high compliance, too much for almost the cartridge itself
and a poor choice for a typical japanese turntable.
However your "lattice work" arm is very hard to picture,
except its like a crain arm, or as you say like a bridge.
You say it will be very low mass, fair enough but how much
the lateral mass is higher than the vertical mass is hard to
judge, assuming you do not have a lateral pivot.
For these types of arms a decent tracking weight is a positive
help but if it is low mass in both planes you need a high compliance.
Given the construction of the arm a low mass cartridge will help
the arm "have its own sound" compared to a heavy cartridge.
From what you've said and the application I think the Ortofon
OM 30 Super with the weight removed is a great choice for a
"blind" purchase, far more so than the Nagoaka.
It has an extended line contact stylus (which lasts more
than twice as long as and also sounds better than an
elliptical stylus) and allows decent tracking force without
record wear due to the extended contact.
It may be a little bright but you say that's not a problem.
Should also work well in your current Thorens, though
you may need the weight to balance the arm correctly.
As its not popular in the UK (we like the 530) from here :
http://www.mantra-audio.co.uk/mantraonline.htm
Its available for 137 euros which if you check european prices
also makes it extremely good value - its 200 to 250 in Europe.
:) sreten.
(P.S. given your arm balsa construction I'd check the model
plane making community as to how to add very lightweight
wrap around sheeting - its the way to do it ;) ) |
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| analog_sa |
$300 for a Nagaoka?! Daylight robbery. Unless that's Zimbabwean dollars.
For usd300 you can buy a real cart like a 103R |
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| sreten |
Just add an MP50 stylus is £140 in the UK, OM30 £75.
:) sreten. |
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| ingvar ahlberg |
The Nagaoka MP 50 is available NOS in Sweden but they are of course old and probably overpriced.
Sretens wiev on "covering" the arm is rigt, this is done with ricepaper glued onto the structure and then "doped" with a laquer shrinking the paper resulting in a very stiff and strong structure.
Add a little weigth and go for a good Grado, it will at least work good in the Thorens if You find it too "gentle" soundwise. |
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| sreten |
sorry IA,
but Grado's are rich sounding, which is not asked for, and extortionate prices for very mundane tip technology IMO.
Not that I don't like them, I do, they do sound nice, the Black in the States is fantastic VFM.
:) sreten. |
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| plysch |
Hmmm, "ricepaper glued onto the structure and then "doped" with a laquer shrinking", then it will kill the stunning looks and look more like a threewalled tube. I will give it a try naked first. :)
Should I put weight in the arm, if so should it be evenly spread from top to back, in apperance of ex. a brassrod?? How much is needed? I don´t want a too heavy arm, because then I must have a more powerful airpump.
Thankyou so far. |
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| sreten |
why consider weighting the arm ? surely destroys the point ?
:) sreten. |
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| plysch |
I was just woundering about the weight considering what IA wrote: "Add a little weigth and go for a good Grado".
If it´s not nessesary i won´t do it.
Summa summarum as we say in Sweden (The sum of it all):
I need a high compliance and a low mass cartridge, maybe some wrapping to damp and stiffen up the structure of the arm....
I´ll give the Ortofon a chance and see how it falls out. :)
Thanks for all, cheers |
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| sreten |
| quote: | Originally posted by plysch
I need a high compliance and a low mass cartridge, maybe some wrapping to damp and stiffen up the structure of the arm....
Thanks for all, cheers |
Hi,
just to clarify, your arms lateral mass will probably mean medium
compliance is better, if the arm does not have a lateral pivot.
Without a pivot lateral effective mass of the arm is its total
moving mass, whilst vertically is will be much lower, this is why
the LABTT shows 3Hz lateral and 10Hz vertical resonances.
Note that by having a relatively long counterweight stub and
therefore relatively low mass counterweight you can reduce
the lateral effective mass, all moving parts should be as
lightweight as possible.
:) sreten. |
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| plysch |
Xuse me, but I don´t follow, what is 'lateral mass' & 'lateral pivot'? :confused:
About the counterweight, should I have it mounted low, like in the horisontally plane of the bearing or lower (hanging down), or doesn´t it matter if it´s mounted straight out from the arm? Then it will be placed about 15mm above the bearingpoint. |
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| dice45 |
Hello Plysch,
(hoping i'm not cvaryiong water to the river :) )
concerning lateral mass:
the tonearm together with the cartridge forms a mass-spring-damper system capable of damped oscillations at a natural resonace frequency. Location of this resonace frequency is determined by the spring constant of the spring (the cartridge's cantilever susoension) and the effective mass: the lower the spring constant and the higher the mass, the lower the freqency will be.
So: the higher your tonearms mass, the lower the resonance freqency.
For lateral movement the tonearms full moving mass is the effective mass.
For vertical movement (rotation around the horizantally oriented tonearm pivot axis) we have the rotational equivalent of the mass: moment of inertia. And this moment of inertia J depends on the distribution of mass elements dm as well as on their radius r in respect ot the pivot axis:
J=integral(r^2*dm)
In any case the rot.inertia results into someting behaving like a point-shaped mass located at the stylus tip and the equivalent value of this mass point is called "effective mass" (in any direction for pivoted tonearms and in vertical direction for linear tracking tonearms). And yo can count on the vertically "effective mass" being considerably lower that the actual moving mass of the tonearm.
Lateral pivot:
for a pivoted arm it is effective tonearm length
for a liner tracker is is infinity.
Vertical pivot:
for both pivoted and linear tracking tonearms it is the effective tonearm length, measured form the stylus tip. It's the horizantally oriented tonearm pivot axis that i mentioned above.
So, now to your cartridge choice:
Your Ladegaard arm is air-borne but the the bearing is not alltoo stiff. A cartridge with high lateral compliance should be prone for hefty oscillations with this arm.
I would join the recommendation for medium compliance cartridges, no, i would go further and recommend low compliance cartridges. Hint: get yourself a medium stiff to stiff MC cartridge. There are some nice Ortofons around with 12-17 µm/mN and why not use a Denon 103 with 5 µm/mN. Denons are repute to cooperate well with Ladegaards, technically as well as sonically.
For my own tonearm (which has a very stiff bearing, BTW) i go on the same path: if i get the thing to make a Shure V15V (>40µm/mN) sing and swing, bingo. But i doubt this will happen and i'm happy using MC carts making life easier for a linear tracker.
BTW, i am glad that a passive linear tracker (like the Ladegaard and my design) has a lateral resonance frequency much lower that the vertical one. I think this provides better guidance for the cartridge (i know there are numerous experts out there fervently disagreeing with me and claiming this is an inherent drawback of the linear tracker... and fervently trying to find other proofs why a linear tracker cannot work ;) ).
I expect low frequency trackability to improve considerably by low lateral resonance: possibly the famous Telarc 1812 cannons become trackable with a plain ordinary MC cartridge :)
Concerning your tonearm wand design maybe you find some inspirations on my website, look at the pixes in the LT-2 section.
Hint: the material of the frame work is 7-layer plywood, about 2mm thick.
I would hesitate to cover my framework with paper or fabric tightened by contracting lacquer: the thought of designing a tambourine into my tonearm wand would certainly frighten me. :o |
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| sreten |
There are two types of air bearing arms :
type 1:
The LABTT only has a vertical pivot, laterally the whole
assembly moves as one piece along the air bearing,
as far as can tell.
For circular air bearing arms the air bearing is the
vertical pivot and the horizontal / lateral slide.
(e.g. the Rockport, Air Tangent)
These arms are very torsionally stiff.
Type 1 arms have very different effective masses seen
by the catridge in the vertical and lateral planes.
type 2 :
The arm has both a lateral and vertical pivot, could
even be a unipivot, as well as the air bearing slide.
Type 1 arms move the arm along the slide by a slight
deflection of the stylus (hopefully), whilst for type 2
the drag on the stylus pulls the arm straight.
Note that the lateral bearing only needs a few degrees
movement, and this is generally arranged to allow cueing.
Type 2 arms are very similar to normal arms in
terms of the effective mass seen at the catridge.
Most parallel trackers seem to be type 1 with
very different effective mass in the two planes.
Horizontally the cartridge sees the total moving mass
of the arm, vertically the mass seen is much less.
I've searched for an example of a homemade type 2 which
I've seen in the past on the web but can't find one, I'm sure
they exist though.
Nearly all servo controlled parallel trackers are type 2.
Hope this helps,
:) sreten.
P.S. IMO the hieght of the counterweight is not critical. |
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| plysch |
Yes indeed :) Now the pieces falls into place.:smash:
Thanks for your patient sreten, I think I´ve got it under control now. I´ll post some pictures and a rewiev when the TT is alive and kicking (hopefully before midsummer ;) , I´m still waiting for the bearing to be made). |
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| plysch |
dice45, are you some tonearmdoctor ;) that was an impressiv answer, I think I´ll print that out.
I just spoke with a bloke who said that I must try the Dynavector 10X5 (could that one be an option?) if I should use a MC cartridge it must be a high output. (don´t have the money for a desent mc-stage)
About your own tonearm: looks awsome :up:
My own arm looks very similar to your LT-2, but it is a bit higher at the rear.
Have you built it yet or is it in construction-phase???
Nice work!! |
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| sreten |
| quote: | Originally posted by dice45
So, now to your cartridge choice:
Your Ladegaard arm is air-borne but the the bearing is not alltoo stiff. A cartridge with high lateral compliance should be prone for hefty oscillations with this arm.
I would join the recommendation for medium compliance cartridges, no, i would go further and recommend low compliance cartridges. Hint: get yourself a medium stiff to stiff MC cartridge. There are some nice Ortofons around with 12-17 µm/mN and why not use a Denon 103 with 5 µm/mN. Denons are repute to cooperate well with Ladegaards, technically as well as sonically.
|
Hmmm......
I think we are the same page but I was thinking with a Balsa
arm keeping mass low is important, the counterweight becomes
less massive so supporting it less of issue etc.
For this to work keeping the slide mass low is very important.
The point is via very low total mass to make the medium
compliance OM 30 behave as if it had low compliance.
I completely agree for a more "normal" say aluminium arm with
an emphasis on rigidity not weight, low compliance is the only
option, but I'd still advise against heavy (10g) MC's.
:) sreten. |
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| sreten |
| quote: | Originally posted by dice45
BTW, i am glad that a passive linear tracker (like the Ladegaard and my design) has a lateral resonance frequency much lower that the vertical one. I think this provides better guidance for the cartridge (i know there are numerous experts out there fervently disagreeing with me and claiming this is an inherent drawback of the linear tracker... and fervently trying to find other proofs why a linear tracker cannot work ;) ).
I expect low frequency trackability to improve considerably by low lateral resonance: possibly the famous Telarc 1812 cannons become trackable with a plain ordinary MC cartridge :)
|
I'm not prepared to argue with your first statement other than
to point out it makes them completely unuseable with any form
of suspended subchassis deck, with main modes of 3 to 5Hz
and usually lateral and rotatational modes 2 to 10Hz, the
change of level as the arm moves across also doesn't help.
Your second point I will take issue with. Low frequency trackability
is directly proportional to compliance and the frequency of the
lateral resonance if below a reasonable value does not affect
trackability in the Audio range.
A reasonable estimate of low frequency tracking
capability is compliance times tracking weight.
:) sreten. |
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| sreten |
| quote: | Originally posted by plysch
I just spoke with a bloke who said that I must try the Dynavector 10X5 (could that one be an option?) if I should use a MC cartridge it must be a high output. (don´t have the money for a desent mc-stage)
|
IMO the OM30 suits the very low mass "Balsa lattice" approach.
IMO if your approach is higher mass and more rigidity then an MC
becomes your only option, for high ouput MC's the Denon DL110
and DL160, 4.8g, 8/10 cu become good choices, as does the
Dynavector 10X5 at 6.6g , 12cu on a higher budget.
You are looking at target masses twice those of the Ortofon.
They should work without problems in your Thorens.
Note that none of the MC's have a line contact tip like the
OM 30 and stylus life will be less than half of the OM 30.
:) sreten. |
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| sreten |
this may help - :) sreten.
Lets say for your arm vertical mass = 3.5g and lateral = 35g.
With the Ortofon 2.5g you have 6g total vertical, 37.5 total lateral.
25 cu = ~ 13Hz vertical and ~ 5Hz lateral.
Note adding the 2.5g weight would increase lateral mass much
more because your counterwieght would need to be 50% heavier.
Making the counterweight lighter and moving it out further is
one way of increasing vertical mass whilst reducing lateral mass. |
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| plysch |
Jesus!!! What have I got myself into....
I had no idea that it was so many parameters to take concern to.
I´m afraid I start loosing the grip just as I thought that things turned out to be clear :xeye:
It´s too much science for me to handle, maybe I shouldn´t have taken up the thread :D
However, I´m sure it all works out in the end.....
Now I have to continue eating my ravioli, that´s basic stuff ;) |
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| plysch |
Sreten : after reading your latest posts with my stomach full of ravioli and beer, I found it resonable to go for 'as light as possible'. It seems that the Resonance Frequency will end up under the audioable area:
| quote: | | 25 cu = ~ 13Hz vertical and ~ 5Hz lateral |
Your attached Resonance Frequency-tabel probably proves that, but I don´t know how to read it. :)
So I´ll try with the Ortofon OM 30 Super, it´s a cheap p.u & I must start somewhere. Better to test it all out first and upgrade later if it´s nessesary. And it´s certainly better than my old 'K9', but I wounder about this:
| quote: | | From what you've said and the application I think the Ortofon OM 30 Super with the weight removed is a great choice |
How do I remove the weight, is there a big risk to damage the p.u when doing it?
Best regards
:drink: |
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| sreten |
the axis are a little confusing,
left is from 6Cu up to 40cu,
the bottom is from 4g to 40 g.
The weight in the cartridge is the shiny bit you can see,
it simply falls out.
The compliance issue is fairly straight forward for the OM30.
If you make a lightweight arm, a lightweight slide and
use a spaced counterweight you'll be absolutely fine.
How you make a lightweight slide may take some thought.
But now you are aware that the mass of all the moving parts
are relevent laterally your unlikely to use say a too heavy slide,
which you may have done before, the relative mass of all the
parts will be obvious, if the slide weight is similar to the the
counterweight it will be fine, a lot more, not so good.
With a spaced counterweight the vertical mass should
fall out to be a reasonable value for the OM30.
:) sreten. |
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| sreten |
Regarding the graph
And assume a cartridge mass of 5g.
some Cu's - 10, 20, 30
some arm effective masses 5, 15, 25
which give total effective mass 10, 20, 30
You look where they intersect and at the nearest lines.
10 cu - 10g = ~ 16 Hz
10 cu - 20g = ~ 11 Hz
10 cu - 30g = ~ 9 Hz
20 cu - 10g = ~ 11 Hz
20 cu - 20g = ~ 8 Hz
20 cu - 30g = ~ 6.5 Hz
30 cu - 10g = ~ 9 Hz
30 cu - 20g = ~ 6.5 Hz
30 cu - 30g = ~ 5.3 Hz
On a turntable like your Thorens target is 10Hz.
:) sreten. |
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| plysch |
Thanks for filling the blaks about the graph, but why should 10Hz be good for my Thorens?
How do I know what will be right for my new table? That will be a non-suspention-table, if that makes any differances (it probably does, everything seems to matter).
Are there any place on the net where I can learn more about stuff like this, could be fun to know the theory behind the result. |
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| sreten |
Basically for your solid turntable and type of arm its a compromise.
All records are eccentric to some degree. At 33.3 rpm this means
the arm has to move side to side at ~ 2Hz, a lateral resonance
of 2Hz is not good , 3hz is not good for 45rpm records.
Whether the arm would actually work would depend on the
amount of damping in the system, but its obvious a higher
lateral resonant requency is a much better idea.
Record warps fortunately are in the vertical direction but again
nearly all records are not perfectly flat, so 2 Hz and 3Hz again.
Bad warps or ripples - you tell me - but obviously quite a bit
higher frequencies are generated, generally presumed to be
up to 6Hz.
Good turntable suspension design will also try to keep all
frequency modes below 6 Hz and its genarally accepted
3Hz to 4Hz is a good suspension frequency.
This means the lowest arm frequency generally useable is
~ 8 Hz. But 10Hz is better.
However the higher the frequency the lower the compliance
and the poorer the low frequency tracking, so basically you
don't want to raise the frequency too much.
8Hz to 13 Hz is a good range but the nearer 10Hz the better.
Note that DJ's typically use nearer 15Hz, with a coin on the headshell ;).
For your arm its a compromise between mass i.e. structural
integrity and the frequency of the lateral resonance. If the
vertical resonance is too high you start to get a bass boost
(but only for out of phase bass so not really an issue)
IMO the compromise for a medium compliance low mass MM
and a higher mass low compliance MC would roughly be the
same, with a stronger build for the MC the lateral frequency
would end up very similar.
My target for your arm would be 4.5Hz to 5Hz = 55g to 40g total mass,
if the total mass turns out lower great, up to to say 75g fine also.
:) sreten. |
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| peranders |
| quote: | Originally posted by plysch
dice45, are you some tonearmdoctor ;) that was an impressiv answer, I think I´ll print that out. |
:nod: and we are glad to have :dice:45 back here. |
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| sreten |
Some brainfade in my last post.
The eccentric frequency is ~ 0.5Hz for 33.3 rpm and 0.75Hz for 45
rpm not 2Hz and 3hz as I erroneously stated, what was I thinking ?
The 2Hz to 3hz region is were most record ripples warps reside.
A good "test" for an air bearing arm is taking the centre
out of a 45 rpm single and deliberately placing it eccentric.
:) sreten. |
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| dice45 |
sreten,
| quote: | Originally posted by sreten
I'm not prepared to argue with your first statement other than
to point out it makes them completely unuseable with any form
of suspended subchassis deck, with main modes of 3 to 5Hz
and usually lateral and rotatational modes 2 to 10Hz, the
change of level as the arm moves across also doesn't help.
|
well, as you corrected yoursellf already, lateral excitation happens at 0.55Hz@33rpm (and 1.32Hz@78rpm :) ... I'd say that a lower lateral resoncance at >3Hz is probably far enough apart from that to prevent oscillation or keep it within bearable limits (i always assume that the cartridge's cantilever supsension has a considably high amount of damping -- the suspension consists of rubber after all with a decent movement-2-friction-heat conversion .... and all possible hysteresis and relaxation effects take place too :xeye: )
Passive linear trackers and lightweight supension TTs don't cooperrate, agreed. But give your air-suspended TT plinth some weight, maybe 100kg?, and make the air springs reasonably low-damped and level the sucker and you may find you like the sonics very much .... :)
| quote: |
Your second point I will take issue with. Low frequency trackability
is directly proportional to compliance and the frequency of the
lateral resonance if below a reasonable value does not affect
trackability in the Audio range.
A reasonable estimate of low frequency tracking
capability is compliance times tracking weight.
|
Hmm, i em no ´neeetif speeka, do you mean by "take issue with" that you disagree?
My experience with low lateral tonearm resonance and low compliance: the cartridge may mistrack or not, in any case it doesn't loose track i.e.it jumps back into the same groove.
No question that an old, worn, weak-of-age MC cartridge which maybe manaages to track 60µm (or only 50µm?) on the ortofon 0002 will mistrack at the 1812 cannons.
But atleast the music goes on (rhythmically) uninterupted, due to the high lateral inertia of the tonearm. Yeah, i know, a dirty defintion of tracking ability :D
And a cartridge which is at its tracking limit in a usual pivoted arm marches around the edgy corners with stunning ease in a laterally low resonating linear tracker. I just tried that out.
But, admitted, i did not measure THD.
With your LT test (excentric 45rpm) i would not be happy (circus artistry :mad: ) : the linear tracker has much more lateral effective mass compared to a pivoted arm and the poor cartridge has to suffer. You do that with your own Koetsu Onyx Platinum, you hear me? :)
Volker Kühn from audioplan (he now runs BlackForestAudio and distributes Fertin speakers among others) used to demonstrate the Souther arm (now marketed by clearaudio): the arm did that test fine but the rail had (and still has :()to be cleaned 3 times a record side. ROTFLMAO :), excentric test made but real life test flunked .
DTopic, you provided a lot of useful info here, goes straight into my keep folder, THANXALOT! :)
Plysch,
thanx for the compliment.
My LT-2 (the project has suuuuch a long beard, i do not even call it LT-2 any more) evolved a bit from what your see on my site.
It is still in design state, a functional prototype is coming the next few months and i expect to have a preproduction prototype coming December. no idea if i manage that, my job i eating me and my head always feels like broken.
But LT-2 will have some more freatures than just a framework tonearm wand. I will have a lateral force compensation (call that an antiskate substitution mechanism -- i want to have my lateral bias defined as i like it, no as the tomearm prescribes), different wands for different cartridges, 2 minute cartridge exchange time, adjusting and measuring tools for any ****ing geometry parameter (thus providing 100% parameter reproducabliity) ... oh yes and i will have phono connectors without any magnetic components, just solid/massive 99.99% silver contacts and PEEK insulators. One of those connectors will be fully RCA/Cinch compatible (plug AND jack!), the other one will be my own thing, tinytiny, untra-leightweight and connecting the
LT-2 slider to the phono interconnect (which also will use silver wire, single-strand of course). I just hated the thought to loose in the connector what my tonearm just had sonically achieved. And 75µm single strand wire does not stand heavy connectors -- just let the plug slip out of your hand and the wires are ripped off.
All for now, gotta work |
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| sreten |
| quote: | Originally posted by dice45
Hmm, i em no ´neeetif speeka, do you mean by "take issue with" that you disagree?
My experience with low lateral tonearm resonance and low compliance: the cartridge may mistrack or not, in any case it doesn't loose track i.e.it jumps back into the same groove.
No question that an old, worn, weak-of-age MC cartridge which maybe manaages to track 60µm (or only 50µm?) on the ortofon 0002 will mistrack at the 1812 cannons.
But atleast the music goes on (rhythmically) uninterupted, due to the high lateral inertia of the tonearm. Yeah, i know, a dirty defintion of tracking ability :D
And a cartridge which is at its tracking limit in a usual pivoted arm marches around the edgy corners with stunning ease in a laterally low resonating linear tracker. I just tried that out.
But, admitted, i did not measure THD.
With your LT test (excentric 45rpm) i would not be happy (circus artistry :mad: ) : the linear tracker has much more lateral effective mass compared to a pivoted arm and the poor cartridge has to suffer. You do that with your own Koetsu Onyx Platinum, you hear me? :)
Volker Kühn from audioplan (he now runs BlackForestAudio and distributes Fertin speakers among others) used to demonstrate the Souther arm (now marketed by clearaudio): the arm did that test fine but the rail had (and still has :()to be cleaned 3 times a record side. ROTFLMAO :), excentric test made but real life test flunked .
DTopic, you provided a lot of useful info here, goes straight into my keep folder, THANXALOT! :)
|
By "take issue with" I meant prepared to argue the point.
By "tracking capability" I didn't realise you were referring to
nice mistracking characteristics, I took its meaning literally.
In the literal context the OM30 will be rather good.
The offset 45 comment was a little flippant. But an old LP
with a filed hole, say 2mm could be useful for checking the
arm at various points across the record.
:) sreten. |
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| dice45 |
| quote: | Originally posted by sreten
By "tracking capability" I didn't realise you were referring to
nice mistracking characteristics, I took its meaning literally.
In the literal context the OM30 will be rather good.
The offset 45 comment was a little flippant. But an old LP
with a filed hole, say 2mm could be useful for checking the
arm at various points across the record.
|
sreten,
:) i was often always grilled by rather scholastic, measuring-oriented guys with my preference for passive linear trackers and in particular in combination with MC cartridges.
No question, probably nothing beats the proper tracking of Shure V15V properly mounted into an SME3009/III.
And i doubt that high-compliant cartridges will feel fine in a passive linear tracker. BTW, my goal with LT-2 is to male a V15V atleast work in my LT-2. But i don't expect it to sing and swing and meake my feet tap and my body shake :) .... (i dont expect the V15V make me respond that way in any arm but in a passive linear tracker i expect it to sound particularly awful)
IMO the high lateral inertia in combination with disc excentricity ages a phono cartridge way before its time has come. Not to speak of the precious records. If one wants to be happy with a linear tracker on the long run, IMO it is vital to have some way to compensate excentricity of the canter hole in order make the arm's slider move spindlewards continuously and not inwards/outwards oscillating. The TT i have on my back-burner has such a device: the platter spindle pin is only 3mm dia and on excentic records the excentricity is marked by an open pencil-drawn circle having exactly the dia of the vacuum nozzle -- i have a jig for measuring and marking the excentricity of the groove pattern in repect to the center hole.
This is my 1st measure to make the linear tracker move uniformly. My 2nd measure is the lateral force compensation i mentioned above; this has a nice side effect: i can make sure the inner groove is under slightly more pressure than the outer one. I have described the sonic consequences of skating over-compensation in earlier posts.
Now with a passive linear tracker w/o lateral force compensation we always have plenty of skating over-compensation .. and i for my part do not want to have that, sonically (sounding like :apathic: ).
I want to do the whole job right if i have to do it.
Plysch,
i agree with sreten, the Ortofon OM30 indeed is a fine cartridge.
Please look for my earlier posts: how to glue an MM cartridge's cantilever plug-in into the cartridge's body.
I did it often with Ortofon OMB 5 and OMB 10. Makes a very nice improvement, sonically, and with those Ortofons it is comparatively easy to do. The plug-in costs about 70% of the complete cartridge but the cartridge is budget anyway so why not "pay" for the improvement by cancelling the cartridge body's re-usabliity once the stylus is down. |
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| plysch |
OK, Dice45, I´ll try to do the glueing of the cantilever into the body, it´ll be interesting to see (hear) if there is any improvment by doing that (I don´t doubt it is but you got to test your ears).
I must thank you & Sreten for an interesting thread, I´ve learned a lot by this and hoping to be able to use it in real life :)
Good Night..... |
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| fdegrove |
Hi,
| quote: | | IMO the high lateral inertia in combination with disc excentricity ages a phono cartridge way before its time has come. Not to speak of the precious records. If one wants to be happy with a linear tracker on the long run, IMO it is vital to have some way to compensate excentricity of the canter hole in order make the arm's slider move spindlewards continuously and not inwards/outwards oscillating. |
Not sure what you're talking about here but IMO at the speed a record is spinning and assuming lateral movement is not impeded by anything other than the arms' mass I fail to see how:
a) It would wear out a cartridge. Its cantilever doesn't flex laterally unless you have an extremely severe problem causing all sorts of other havoc anyway. In short it won't stay in the groove that way for long.
b) How on earth it can be compensated for as this drag will vary with the degree of excentricity of a record...
Come to think of it, in my entire collection I can't point to a single one being excentric enough to be visible to the naked eye anyway.
c) With a classic pivoted design the problem may well be worse as the excentricity will likely trigger a series of effects, tail wagging do style.
Cartridges such as the Shures being optimized for trackability inevitably lose out on a raft of other parameters.
As these are highly compliant they lose so much inner detail burried in those precious grooves that they're only just O.K. for casual listening.
Given that, I can't be bothered to put them in a LT tonearm design where it will likely be much overdamped no matter what.
Cheers,;) |
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| dice45 |
All,
i'd just like to mention a remark Wally Malewicz made to me.
He told me that he measured lateral forces on pivoted and passive linear tracking arms. He measured it as percentage of the tracking force, using his WallySkater.
He reported that most passive linear trackers have more than 3 times the lateral force of a pivoted arm with Anitskating adjusted to zero.
And .... Frank ....
you thought i would enter a discussion with you, didn't you? |
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| sreten |
| quote: | Originally posted by dice45
He reported that most passive linear trackers have more than 3 times the lateral force of a pivoted arm with Anitskating adjusted to zero.
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Which is exactly what you'd expect isn't it ?
Lateral force on a cartridge being related to lateral effective mass.
I'd expect a similar difference between high and low mass
pivoted arms, its the extra dynamic force needed that reduces
the resonant frequency for high mass pivoted arms.
Its quite easy to show the deflection angle of a stylus for an
eccentric record is inversely related to the lateral resonant
frequency.
And identical for different mass / compliance combinations as
long as the resonant frequency is the same.
(ignoring friction/stiction)
:) sreten. |
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| sreten |
| quote: | Originally posted by fdegrove
Come to think of it, in my entire collection I can't point to a single one being excentric enough to be visible to the naked eye anyway.
Cheers,;) |
I checked the record sitting on my turntable, budget blues label.
Its quite blatantly eccentric ~ 1mm.
So I'd tried another, CBS, much better and not
noticeable unless you look hard but still there.
So on went a third, here you couldn't see eccentricity as
some minor warp movement made it impossible to judge,
though it did appear to move laterally over the warp.
:) sreten. |
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| fdegrove |
Hi,
Sreten,
Unfortunately there are quite a few of those records around...
What I do, if possible, is replace them with a good copy.
All in all, I feel that's the most economic solution...Is there any other anyway?
Cheers,;) |
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| dice45 |
Sreten
| quote: | | Its quite easy to show the deflection angle of a stylus for an eccentric record is inversely related to the lateral resonant frequency. And identical for different mass / compliance combinations as long as the resonant frequency is the same. |
and the resonance Q is the same :)
BTW, i have one of those fancy side force checkers which are meant to replace a cartridge in the headshell and which measure and display lateral stylus force on a small analog instrument at the front. A nice help to check if the lateral force i applied via my LFCM is too big or pointing in the wrong direction (equivalent to antiskating over-compensation). No question, the LFCM only can deliver a constant force, an average lateral force compensation.
All,
about 1/3 of my record collection has an excentric center hole in respect to the groove pattern and considering the fact that most of them are unobtainable, original 1st/2nd pressings with otherwise VG+++ to pristine groove groove wear condition, i cannot even dream of being able to replace it with a comparable copy, after all i collect records since i left school.
And as we are on excentricity, we cannot even rely on the vector of excentricity having the same length and direction for both sides of a given record, quite the contrary. Excentricity of the groove pattern in respect to the center hole can be considerably different for each side of a given record (probably caused by too much backlash in the hinge of a record press and by the fact that the centerhole either is punched afterwards or is part of one half of the record press).
Geometric imperfections on vinyl records are simply an environment condition. Like record warp, pressing bubbles, excentricity, groove2groove Xtalk etc. . Something to be accepted as real life. Not something to be argued with.
Now if i find an easy way to reduce excentricity amplitude to 1 or 2 groove widths, why shouldn't i do it? Centered record sides reward me with a rock-solid imaging and better rhythmic stability. |
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| fdegrove |
Hi,
| quote: | | Now if i find an easy way to reduce excentricity amplitude to 1 or 2 groove widths, why shouldn't i do it? |
Sure...Why not.
The easiest way I can come up with is to device a tool to repunch the record.
Maybe it's a bit too simplistic or no one wants to touch his collectables this way....I don't know.
| quote: | | Centered record sides reward me with a rock-solid imaging and better rhythmic stability. |
Yes indeed, excentric ones give the exact opposite...
Cheers,;) |
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| sreten |
One way could be to ream out the centre holes and make a
set of press fit inserts with various eccentric offsets built in.
You can also buy a device for cutting out the centre of records to
allow use in jukebox's. This would allow a 45 adaptor to be used.
It won't get you to 1 or 2 groove widths though.
:) sreten. |
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| dice45 |
All,
it is not necessary to repunch the record.
The excentricity topic has been discussed here: http://diyaudio.com/forums/showthre...4784#post54784. and following
My initial idea was based on having a vacuum platter. Now i had some more ideas.
Let's assume our vacuum platter keeps the record strictly on its position once the vacuum is applied. The vacuum system does not need a puck or clamp sitting on top of the record as it has two sealing lips, one at the outer perimeter and one at about the radius of the inner groove. We apply the vacuum by a cylindric nozzle thru the center hole. The center pin has 3mm dia, allowing 2.1mm of excentricity. The nozzle has two ends, one flat and one with a shoulder centering the center hole (7.2mm dia) to the center pin. The vacuum hose is radially attached to the nozzle and the nozzle's center hole is drilled thru.
Let's assume we have a jig for measuring and marking record side excentricity. The jig has a platter and a beam carrying a groove microscope and a center puck having the same outer dia as the vacuum nozzle. The beam is radiallay oriented and has a hinge at its end and locates the µscope just over the lead-in groove; the center puck rests on the records surface at approx. the position of the center. The platter is mounted on a linear guide and can be adjusted to a certain amount of excentricity in respect to the center puck.
***
Remember, if you do not want to go vacuum but want to have centering, then any clamping device smaller than a record label which does avoid to rotate the disc while clamping will do instead.
Just make sure that the jig's center puck and the record's clamp outer dia are the same.
***
If we want to mark excentrcity of a record side, we put the disc on the platter and rest the beam with center puck on the record. we rotate the platter while looking thru the µscope and check whether the groove pattern is excentric. If yes, we search the excentricity maximum and adjust the platter away from the center until excentricity seems to have disappeared. We decide the record is excentric and needs correcting and and has to get a pencil mark around its center hole. We lock the jig so that no accidental misalignment is possible and draw a circle around the center puck, using the puck's cylindrical perimeter as drawing template. We know: the pencil circle is concentric to the groove pattern. Hence we don't have to pay attention to how much the record side is excentric or how the excentricity is oriented.
Now playing records:
Scenario 1: the record is centric.
We look for a circle and dont find any => record is centric => we need the shouldered side of the vacuum nozzle to center the record. We apply vacuum. Done.
Scenario 2: the record is off-center.
We look for a circle and find one => we need the flat side of the vacuum nozzle and center the pencil circle to the nozzle (the human eye is super-sensitive to concentricity; i'd expect less than 50µm centering error). We apply vacuum. Done.
It should be evident that we undergo the marking procedure only for records we like and/or find sonically rewarding.
All who find my procedure described below too complex and effort-loaded, please consider that you may need a similar jig and a similar procedure to locate the proper punching location. I prefer my method as i do not have to make permanent (and mistake-prone) changes to the records; i can erase and replace my pencil marking anytime.
Now you ask me how to get a ****ing groove µscope? :D
1st, illuminate the groove from almost level in radial direction using an ultra-bright green LED so that you see the grooves.
2 options:
1) use a 20x magnifier with big lens2focus distance instead, and have a pointer cut from paper slide on the record surface. Does a fine job ... all you need if you are careful
2) build yourself a µscope from optical components obtainable from companies like Edmund Scientific or from what you find at your local thrift store. Get a crosshair (preferably illuminated, too) in the intermediate image plane between objective lens and ocular lens. Now you have your pointer, the crosshair optically on the record surface but mechanically in safe distance.
Moreover, your head (don't forget your nose tip) is in safe distance from the record surface... after all you don't want to impregnate your record surface with the skin grease from your nose. :)
For the ocular You should get a lens system meant to be used as an ocular. For the objective any lens system with positve focus length is usable; you do not need hightech stuff with huge aperture and ultra-plane image plane. If you can project an image of an object on a screen, the lens system will do. Happy experimenting ! :) |
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