Thorens TD 166Mk2 + WTA

[stein]

Još malo sa vinylengine foruma...

Antiskate is much more important to good reproduction than is often thought, because the forces we need to counteract are created by the music, not just the track of the groove. It’s a very complicated subject.Why do we need it? Passing the stylus through the record groove causes drag. If the cartridge were aligned straight down the arm and at a perfect tangent to the groove this force would act squarely on the bearings with no sideways component at all. This, rather than the lack of tracking error, is what makes linear trackers so good.But it doesn’t work like that. The cartridge is at an angle to the armtube to make the geometry work, so the drag force becomes a torque on the arm that’s translated into a movement towards the centre of the record. This torque is transmitted to the arm bearings, the cause of chatter in poor bearings.If we don’t have any antiskating then the inner (left signal) groove of the record gets pushed against more strongly than the outer groove and we hear distortion in the right channel because that isn't loaded properly. So we must add a little counteracting force outward to stabilise it.The problem is how much.The amount of antiskating force we need to apply is affected by many things:- Groove friction. This is affected by the friction coefficient of the record and very much by the stylus profile. This effect is stronger at the outer grooves where velocity is highest.- Tracking error. Going across the record this starts high, reduces to zero, climbs, falls back to zero then finally climbs again. Just how much this affects the drag depends on the stylus profile.- Groove modulation. The more energy put into the stylus by the signal, the more drag. This is a reaction to the energy used to excite the cantilever and the energy used to create electrical current in the generator. This effect is more marked at the end of the side than on the outer grooves and low frequencies create the most drag.So we have a force constantly varying as the record is played that we have to counteract without knowing its exact value. Setting up on a blank disc is not accurate because it doesn’t reflect the real drag value of the cartridge in the groove or an average value of the dynamic drag. Setting up with a test record is much better but here it’s important to set up at a number of points across the record. Careful listening with a known record is the final test. Listen carefully at outer and inner grooves, around the null points and halfway between them. Distortion from bias setup can be identified because it appears on one channel: Right channel, underbiased, left channel, overbiased. A slight mismatch might be heard by stereo image moving to left (under) or right (over).

Friction between stylus tip and the groove wall produces a force tangent to the groove. This frictional force depends on tracking force Fv and the friction coefficient my [3].Ff = Fv x myWith 45 groove walls the load on each wall is 0.7 of the vertical or tracking force so that the friction force is 1.4 Fv x my [5].my varies with record material and amount of groove modulation. Values were found to be between 0.22 and 0.64 for Shibata at 1.5 g tracking force [10].The reaction force (to the friction force) of the tone arm passes through the arm pivot.These two forces combine as vectors and, due to the offset angle (better : angle phi between groove tangent and effective length) of the cartridge, leave an unbalanced force, the skating force. This force tends to pull the arm towards the record's center.The force is further determined by the magnitude of phi (or by the magnitude of offset angle and tracking error, respectively), tracking force, shape and condition of the diamond (new, worn), the cartridge’s mechanical resistance (cantilever damping) and record material.Skating force, when uncompensated, produces distortions in the right channel (outer groove wall). Tracking force on the inner groove wall is increased, on the outer groove wall decreased [2]. Uncompensated skating force results actually in the stylus mistracking the outer groove wall.Uncompensated skating force results in increased record and tip wear at the inner groove wall (hence the left channel).Skating force compensation enhances trackability by about 20-25 %. For obtaining equivalent trackability by increasing tracking force alone (without any compensation) an increase of 50 % would be required. This, however, would result in increased contact pressure and hence increased record wear.The following findings presented by Kogen [2] are based on experiments and measurements.Higher modulation velocities result in increased skating force [1, 2]. Wright [6] could show experimentally that the friction force increased for higher modulation velocities (for sinewaves). Snell and Rangabe [7] showed that the dependance of the friction force of modulation velocity was different for different cartridges (Decca, EMI, ADC, Goldring, Ortofon).In 1968 RCA determined the effect of modulation velocity on stylus drag [9]. It was found that for a tracking force of 1.5 grams the modulation velocity had little effect on measured groove speed as measured by means of a stroboscope. The same velocities had however a significant effect (factor 4) when a tracking force of 5 grams was applied. The measurements were performed on a lacquer test record. On a vinyl pressing the decrease in groove speed would be 0.7 of the one measured on the lacquer. The equipment used was not specified apart from weight and moment of inertia of the turntable.According to Gilson [5] the effect of groove modulation (modulation drag) is composed of three related elements, inertial drag, compliance drag, transducer drag.Inertial drag : energy absorbed in accelerating the stylus assembly (accelerations up to 1400 g have been observed). Since the deceleration force is lost in frictional loss and not fed back into the system, a constant torque is imposed on the turntable motor, such that the inertial drag is increasing towards the records centre.Compliance drag : energy absorbed in overcoming stiffness and damping of the cantilever suspension. Greatest at low frequencies where lateral stylus excursion is at maximum. Compliance drag increases towards the record’s centre. Damping (and hence mechanical resistance) can vary considerably among different cartridges and even between samples of he same cartridge [7].Transducer drag : energy absorbed in converting mechanical energy into electrical output from the generator system. It increases towards the record’s centre.According to Gilson the tangential friction force further pulls the cantilever into line with the arm pivot. This cantilever displacement force is substantially the same as the frictional force Ff.He concludes that by applying skating force compensation at the arm pivot bot the skating and the cantilever displacement force are compensated. Since on certain parts of the record there will be overcompensation and on the remaining parts undercompensation (see below), the cantilever will be displaced the record’s centre and towards the outer rim respectively. “The amount by which the cantilever/armature system is displaced will depend on the static compliance of the cartridge, and any ill-effects on sound quality will depend on the sensitivity of the transducer system to non-linearity due to displacement from the true dead-centre position.”It has been found that elliptical styli produce greater skating force than spherical styli [2].Groove velocity (for silent grooves) appears not to change skating force. [2]. This finding was later confirmed by Wright [6] with an experimental setup (for measuring skating force) similar to the one used by Kogen [2], namely a cartridge that could swivel on a micro-bearing attached to the headshell. Wright used a Decca International tonearm because of the very low friction of its unipivot whereas Kogen used a Shure-SME 3009 tonearm.Groove radius has an effect on skating force in that there is a minimum atabout 3.5 inch with maxima at outer an inner grooves, the value at the outer groove being higherthan at the inner groove [2], the curve being hence of parabolic shape. The skating force varies between 90 and 100 % of its maximum value.These two preceding statements appear to be in contradiction but according to Kogen [2] there are factors not completely understood that result in the skating force differences that could be measured for various radii.The skating force Fs is a function of R (groove radius), D (overhang) and L (effective arm length = linear distance arm pivot tip point) [2, 3].Formula : Fs = Ff tan phi [2, 3, 4]Ff = Frictional force = Fv x mySin Phi = (a + ; a = R/2L ; b=1/2RL x (2LD D*2)phi (angle between groove tangent and effective length,) varies across the record surface with a minimum at about 3.5 inch and maxima at inner and outer grooves, the outer maximum being higher than the inner.Skating force compensation is provided at the arm pivot. This means that a torque is applied at the pivot which results in a compensating force that is at right angles to the effective length. This compensation force isdetermined by F = Ff sin phi which is different from the skating force Fs =Ff tan phi (the tan phi vector is directed towards the record’s centre whereas the sin phi vector is at right angles to the effective length).A different way of calculating skating force is to use offset angle theta and tracking error alpha [8]. For groove radii greater than outer null and smaller than inner null, the skating force isFs = Ff x sin (theta + alpha)Between the two null points, the skating force isFs = Ff x sin (theta - alpha)You need a groove to produce that skating force, so you need also a groove to adjust anti skating. Try the Hifi News and Reviews test record. There is a track for anti skating adjustment (4 tracks at increasing signal levels). If you use another protractor or tone arm setup procedure than the one provided with the tone arm or recommended by XXX, respectively, the geometrical relations (offset angle) of arm cartridge record change. The skating compensation provided on the arm is designed for the arm being adjusted according to the manufacturer's specifications (or manufacturer's alignment tool).[1] Alexandrovitch : A stereo groove problem, JAES, 1961, Jan., p.166[2] Kogen : The skating force phenomenon, Audio, Oct.1967, p.53 ; Nov. 1967, p.38[3] Bauer : Tracking angle in phonograph pickups, Electronics, March 1945, p.110[4] Oakley : Skating force, mountain or molehill, Audio, March 1967, p.40[5] Gilson : The cartridge alignment problem, Wireless World, Oct.1981, p.59[6] Wright : Bias correction and dynamic conditions, Hi-Fi News, Oct.1969, p.1187[7] Snell, Rangabe : Frictional drag and bias compensation, Hi-Fi News, Feb. 1970, p.221[8] Randhawa : Pickup arm design techniques, Wireless World, March 1978, p.73 : April 1978, p.63[9] Halter : Letters to the editor, JAES 1968, p.354[10] Pardee : Determination of sliding friction between stylus and record groove, JAES 1981, p.890Further papers :Deane : Forward drag and stylus profile, Hi-Fi News, Oct.1969, p.1186

Ne zamerite što nemam snage da prevodim...

[Zen Mod]

Пуно јасније, хвала обојици......

kojoj dvojici ?kao i obicno - triker samo smeta ......

[Leonardo]

Leo - prouci malo onaj clanak o Biz Arm - princip je apsolutno isti

Da, razumem na šta mi ukazuješ.Princip sam razumeo igrajući se malo sa originalnom WTA.Nedoumica se odnosila na ukrštene končiće, kao što se da videti na ovoj fotki, deluje da je protivklizna sila koja se tako ostvari jako mala, gotovo ništavna.Moguće ja da je u nekim slučajevima i toliko sasvim dovoljno.

[Zen Mod]

ma princip je tu - sve ostalo je igranje ;test ploca , dovoljna kolicina najlonske pletenice ( za predvez - mnogo sam je nekad koristio za skale ) , starija igla/glava ........ bar dva dana igranja naravno - osciloskop ne bi smetao uz test plocu , ali moze i bez njega

[revox]

znam da nisam od vašeg zanata ali dok sam razmišljo da prvim čistač ploča sa ručkom pored ideje da ručka bude od vrha štapa za pecnje što se pokazalo i po Stonu kao dobra ideja od jednog ortaka dobio sam ovo

[revox]

on reče da je ovo neki ležaj koji koriste za žiroskope u avionima

ovaj moj je malo korodirao ali on mi reče kad je nov da se vrti u ležištu maltene ako se dune u njega

pretpostavljam da mu je onda trenje vrlo malo

Čisto kao ideja možda bi ovo moglo poslužiti kao ležaj i horizontalni i vertikalni za ručicu

Ako je glupo nema veze ne zna pravnik ništa oko meanike :(

[stein]

on reče da je ovo neki ležaj koji koriste za žiroskope u avionima

ovaj moj je malo korodirao ali on mi reče kad je nov da se vrti u ležištu maltene ako se dune u njega

pretpostavljam da mu je onda trenje vrlo malo

Čisto kao ideja možda bi ovo moglo poslužiti kao ležaj i horizontalni i vertikalni za ručicu

Ako je glupo nema veze ne zna pravnik ništa oko meanike :(

Ja imam ovih u po dve do tri izvedbe u 6, 8, 10 i 12mm prečniku. Svaki se teško pomera kad je nov. Za čistač bih stavio četkicu na unipivot ili čak kod zvučnice...

[Ја sam sam]

Ako je glupo nema veze ne zna pravnik ništa oko meanike.

Није глупо напротив!

Тај лежај је јако добар али за грамофонску употребу треба га опрати у нитро разређивачу или бензину да се спере маст.

Након тога је идеалан!

стоН_Колд

[stein]

Није глупо напротив!Тај лежај је јако добар али за грамофонску употребу треба га опрати у нитро разређивачу или бензину да се спере маст.Након тога је идеалан!стоН_Колд

Ne znam o kakvim je zglobovima tačno reč, ali od sijaset vrsta koje smo do sada koristili, probali i ugrađivali, ni jedna izvedba nije u sebi imala bilo kakvo mazivo. A baš ih je bilo i sa sinterovanim ležajem i sa teflonom i samopodmazujućom bronzom...

[stein]

Ručica postepeno napreduje.Stigla mi je, na žalost samo jedna Hyper Titanium golf loptica, naravno, tu ni T od titanijuma nema. Spoljašnji omotač je neka elastična plastika a unutra neka sunđerasto - penasta guma. Kao što sam već rekao, telo ručice je magnezijumska cev, a spojni elemenat kod zvučnice i spoj cevke i loptice Al. Gde će se i šta lepiti, videćemo. Headshell još treba doterati i ima još dosta da se polira, ali ćemo pre toga spremiti nosač tega, teg, elemente za vešanje ručice i rupice za provlačenje žičica od zvučnice...

[Zen Mod]

par postova divana o motyoru za sokocalo - prebaceni u DIY gramofon temu http://www.diyaudio.rs/topic/561-diy-gramofon-ii/

ZM

[Impuls]

Suvise je tema o gramofonima otvoreno u kratkom roku i ne mogu bas da se snadjem gde ste rucke tovarili. Evo ja prilazem jednu fotku rucice

[Zen Mod]

http://www.diyaudio.com/forums/analogue-source/144616-well-tempered-labs-tonearm.htmlpar informacija o origigi golfici

[mmilovan]

Ajmo sa konkretnim podacima - u jednoj reviziji naše WTA silikonsko ulje bilo je gustine 5000. Ne znam da li ulje iste gustine pogodno za konstrukciju sa golf lopticom, odnosno da li bi za ovu konstrukciju možda moralo da bude ređe. Ulje se moglo pre tri godine nabaviti u Bariču.