Vertical Tracking Angles - Rega's A Vibration Measuring Machine

Vertical Tracking Angles - Rega's A Vibration Measuring Machine

Posted by The Sound Organisation on Oct 4th 2018

Carefully Reproduced From The Rega Book "A Vibration Measuring Machine"

The world of turntable design is riddled with myths, all the more so since the turntable's vital role in system sound quality was established during the 1970s. Obsessive consumers often seem to suffer enormous (albeit quite unnecessary) angst over cartridge and stylus alignment, making minute adjustments to tonearms and cartridges in order to optimise the vertical tracking angle (VTA) and/ or stylus rake angle, azimuth, and overhang.

 

시스템 음질에서 턴테이블의 중요한 역할이 1970년대에 확립되었기 때문에 턴테이블 디자인의 세계는 신화로 가득 차 있습니다. 강박적인 소비자들은 종종 카트리지와 스타일러스 정렬에 대해 엄청난 (불필요한) 불안을 겪으며 수직 추적 각도(VTA) 및/또는 스타일러스 레이크 각도, 방위각, 오버행을 최적화하기 위해 톤암과 카트리지를 미세하게 조정하는 것처럼 보입니다.

 

Rega has measured the vertical tracking angles of more than 100 different cartridge models, and has found that their actual VTAs vary between 20 and 36 degrees (with downforce), and most fell between 23 and 28 degrees. (Rega itself has opted for 27 degrees, without downforce, and 23 degrees at normal downforce.) The overall figures may therefore be up to 10 degrees greater than that required to meet the current (and nominal) 20 degree disc-cutting standard. (In practice, reducing the VTA of the cartridge cantilever to less than 23 degrees risks the rear of the cartridge fouling the disc surface.)

 

레가는 100개 이상의 다양한 카트리지 모델의 수직 트래킹 각도를 측정한 결과, 실제 VTA는 20도에서 36도(다운포스 포함) 사이이며 대부분 23도에서 28도 사이라는 것을 발견했습니다. (레가 자체는 다운포스 없이 27도, 일반 다운포스에서는 23도를 선택했습니다.) 따라서 전체 수치는 현재 (그리고 공칭) 20도 디스크 커팅 표준을 충족하는 데 필요한 것보다 최대 10도 더 높을 수 있습니다. (실제로 카트리지 캔틸레버의 VTA를 23도 미만으로 줄이면 카트리지 후방이 디스크 표면을 오염시킬 위험이 있습니다.)

 

Furthermore, talk to the cutting engineers that are actually responsible for making the discs, and it's clear that they pay very little attention to so-called cutting 'standards' . One reason is simply because the VTA is defined by the mechanics of the cutter head, and is not normally changed by the cutting engineer. It may also vary by at least 7 degrees across a single disc, depending on frequency, cutting depth and lacquer springback. (Indeed, the standard itself was changed from 1958's 15 degrees to 20 degrees in 1975.) 

 

또한 실제로 디스크 제작을 담당하는 커팅 엔지니어들과 이야기를 나눠보면, 그들이 소위 커팅 '표준'에 거의 신경을 쓰지 않는다는 것을 알 수 있습니다. 한 가지 이유는 단순히 VTA가 커터 헤드의 역학에 의해 정의되며 일반적으로 커팅 엔지니어가 변경하지 않기 때문입니다. 또한 주파수, 커팅 깊이 및 래커 스프링백에 따라 단일 디스크에서 최소 7도 이상 다를 수 있습니다. (실제로 이 표준 자체는 1958년의 15도에서 1975년에 20도로 변경되었습니다.)

 

Enthusiasts' favourite way of changing VTA 1s to adjust the height of the arm pillar, but a quick examination of the geometry involved clearly shows that a 0.5-inch variation in arm pillar height (probably the maximum possible in practice) will only change the VTA by 3 degrees (±1.5 degrees). Crucially, making the pillar adjustable in the first place is very undesirable from an overall rigidity perspective, since this joint is the turntable/arm's core reference point from which all system vibrations are measured. 

 

매니아들은 암 필러의 높이를 조정하기 위해 VTA 1을 변경하는 방법을 가장 선호하지만, 관련 지오메트리를 간단히 살펴보면 암 필러 높이의 0.5인치 변화(아마도 실제로 가능한 최대치)는 VTA를 3도(±1.5도) 정도만 변경한다는 것을 분명히 알 수 있습니다. 결정적으로, 이 조인트는 모든 시스템 진동이 측정되는 턴테이블/암의 핵심 기준점이기 때문에 처음부터 필러를 조절 가능하게 만드는 것은 전체 강성 관점에서 매우 바람직하지 않습니다.

Note that all formal disc-cutting parameters in practice fall below 18 degrees, whereas arm/ cartridge replay usually occurs above 24 degrees to avoid any risk of fouling the disc surface. That fact alone means that fiddling around with VTA adjustment is entirely futile. (In reality, the rear of the arm needs to be as close to the surface of the disc as possible. Any adjustment upward can only increase the unavoidable VTA inaccuracy.)

 

실제로 모든 공식적인 디스크 커팅 매개변수는 18도 이하로 떨어지지만, 암/카트리지 재생은 디스크 표면이 오염될 위험을 피하기 위해 일반적으로 24도 이상에서 이루어집니다. 이 사실만으로도 VTA를 조정하는 것은 전혀 쓸모가 없다는 것을 알 수 있습니다. (실제로는 암의 뒤쪽이 디스크 표면에 최대한 가까이 있어야 합니다. 위쪽으로 조정하면 피할 수 없는 VTA 부정확성만 증가시킬 수 있습니다.)

 

One method of measuring distortion due to VTA variation is to use a test record (in this case the CBS STR160 VTA test). A test tone of 400Hz is played and the second harmonic distortion is measured at 800Hz.

 

VTA 변화로 인한 왜곡을 측정하는 한 가지 방법은 테스트 레코드(이 경우 CBS STR160 VTA 테스트)를 사용하는 것입니다. 400Hz의 테스트 톤을 재생하고 800Hz에서 두 번째 고조파 왜곡을 측정합니다.

 

Rega electronic design engineer, Terry Bateman, carried out this test using audio precision test equipment. The following four graphs show the test results as follows:

 

레가 전자 설계 엔지니어인 테리 베이트먼이 오디오 정밀 테스트 장비를 사용하여 이 테스트를 수행했습니다. 다음 네 개의 그래프는 테스트 결과를 보여줍니다:

1. The test record played on the standard Rega mat. 테스트 레코드는 표준 레가 매트에서 재생되었습니다.
2. The arm height increased by 3mm using a spacer. 스페이서를 사용하여 암 높이를 3mm 늘렸습니다.
3. The test record played on the platter without a mat. 테스트 레코드는 매트 없이 플래터에서 재생되었습니다.
4. The test record raised off the platter by 6.5mm. 테스트 레코드는 플래터에서 6.5mm 정도 올랐습니다.

It can be seen that the graphs show no significant change to the second harmonic distortion even though the total effective change in the arm height is 9.5mm. Also note that the SRA is changing as well as the VTA.

 

그래프에서 암 높이의 총 유효 변화가 9.5mm임에도 불구하고 두 번째 고조파 왜곡에는 큰 변화가 없음을 알 수 있습니다. 또한 SRA도 VTA와 마찬가지로 변화하고 있음을 알 수 있습니다.

 

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Want to read more? Check out "A Vibration Measuring Machine" here.