7963 Phono Amp

위 R-core Power Trans 는 1V 당 9.6 Turn 으로 감았습니다.

LP 만들때 녹음시 진폭이 큰 저음은 Cutter 가 옆으로 튀여 나갑니다. 저음은 많이 줄여주고 

고음음 반대로 많이 강조합니다 (정확히는 RIAA표를 보십시요)

재생시 반대로 Pre-amp 에서 저음은 강조하고 고음은 줄입니다. 

이 역할을 하는 동조회로가 위의 RIAA Equalization 회로입니다.

이 동조회로는 이미 회로전문가가 만든 것으로 저는 그대로 사용 합니다.
물론 Parts 값을 바꾸면 고음/저음 균형이 달라집니다.

 

여기서는 주파수특성 교정으로 파형의 찌그러짐 (고조파 발생 --양념) 하고는 다릅니다

위와 같이 동작점을 Vg=0v 로 했습니다.

Plate Load 저항을 47K ohm로 더 높이고  Cathode 저항은 제거 합니다. 

(grid 의 + 영역에서의 동작 방지를 위해서 동작점은 약간 이동하지만 cathode 에 20-30 ohm 저항이 필요할수도 있습니다.) NFB 가 제거되서 발진 가능성이 있습니다.

RL 을 86 K ohm 로 해도 출력전압은 거의 변동 없습니다. 

동작점이 2.5 ma - 35 v 로 이동 합니다.

Sylvania's 1962 publication entitled "Sylvania Subminiature Strap Frame Grid Tubes for Military and Industrial Applications" describes the development of a new line of subminiature tubes as follows: 

"The advantages of the strap frame grid are quite well known and are attested to by the steady increase in the number of new electron tubes employing this innovation. The area of growth in the past, however, had been restricted to miniature and larger designs. About two years ago, Sylvania launched a program to develop a subminiature frame grid tube design for the Military and Industrial markets. 

The results of this program to date are ten new tube types. Each new type, when compared with its nearest conventional predecessor, shows a marked improvement in gain and operating efficiency of both the plate and heater. In addition, the new design offers the mechanical ruggedness, stability and reliability, characteristic of subminiature construction." 

The majority of subminiature tubes are downsized versions of existing miniature 7 and 9 pin types which, in turn, were smaller versions of existing octal types -- for example, the 6SN7/5691 beget the 5751, from which the 6112 was derived. The 7963, while claiming no octal forerunners (as t were no frame grid octal twin triodes), can trace its ancestry to the 6DJ8 family. 

In fact, with regard to audio applications, the 7963 offers performance in low level audio applications that is superior to all 6DJ8 variants, and to all other subminiature twin triodes as well. In a tube-to-tube comparison between the 6DJ8 and the 7963, the 7963 exhibits: 

A) superior transconductance -- 14,000 micromhos for the 7963, versus 12,500 for the 6DJ8; 
B) slightly lower plate resistance -- 3100 ohms for the 7963, versus 3200 for the 6DJ8; 
C) higher voltage gain -- 40 for the 7963, versus 33 for the 6DJ8. 
In addition, the 7963, is more linear than the 6DJ8, as a comparison of each tube's characteristic curves will attest. 

Perhaps the greatest advantage the 7963 has over the 6DJ8 is will be found in its reduced voltage requirements. T is a strong correlation between plate voltage and tube noise -- the lower the plate voltage, the lower the tube's noise figure. For line level applications, the 7963 requires no more than 75 volts dc; in most cases, 50 volts is quite adequate. For moving magnet phono, and for microphone preamplifier requirements, 30 to 50 volts dc will do the trick. For moving coil cartridge step-ups, 15 to 25 volts is all you'll need!