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找了个偷懒的办法，ocr了一把，得到英文稿，实在懒得翻译了，再google翻译了一把，得到了驴唇不对马嘴的中文翻译，对照着看看基本还能理解。
A Direct-Coupled Amplifier with Cathode Follower - Raymond H. Bates - Radio & Television News, Nov. 1949
Two novel circuits in a single audio amplifier provide wide frequency response with a minimum of distortion.
THE construction of the amplifier to be described in this article was actually initiated a little over two years ago, at which time I became an enthusiastic audio ham. During the recent war I was associated with radar in a practical way and so became acquainted with the cathode-follower which was used extensively in radar as an inexpensive medium for matching a high impedance to a low impedance in voltage amplifier stages. At that time, it appeared to me that the cathode-follower might be ideally suited for audio output stages where the problem of getting a good impedance match is generally difficult and usually expensive. With this in the back of my mind, I began experimenting with all types of audio amplifiers, searching for a circuit that would provide a lot of performance for a minimum of parts. Previous issues of RADIO & TELEVISION NEWS, I discovered, had described both cathode-follower and direct-coupled amplifiers as separate circuits. I could not find any articles that described an audio amplifier with both direct coupling between stages and cathode-follower output. So, using old issues of RADIO & TELEVISION NEWS as source material, I proceeded to construct this amplifier.
As can be seen in the schematic diagram, the circuitry is extremely simple.
Complete schematic diagram of direct-coupled 6V6 cathode-follower amplifier.
There are two features that give this amplifier its superior performance. One is direct coupling between the plate of the 6SJ7 and the grid of the 6V6. The other is the cathode-follower output from the 6V6.
In addition to its simplicity, direct coupling eliminates the undesirable characteristics that are inherent in ordinary resistance-capacitance coupling, such as short circuiting of weak signals and grid blocking of strong signals.
The cathode-follower output, in addition to its simplicity, provides both improved high and low frequency response, damping out of all the peaks in both the output transformer and speaker, less distortion, and 100 percent degenerative feedback.
In order to determine the circuit values in the schematic, free use was made of the tube manuals and Kirchoff's and Ohm's laws. Commencing with the output stage in the conventional manner, the tube manuals indicate that for a single-stage output, a 6L6, 6V6, 6F6, or 6K6 are likely output tubes. The 6V6 was selected because of its ready availability and relatively lower percentage harmonic distortion rating. The 6SJ7 was chosen mainly because of its high gain and low percent distortion.
In order to keep power requirements down, I chose a 350 volt, center-tapped, 120 mA (53 mA only required) power transformer which is readily available at moderate cost. Allowing for a 15 volt drop in the filter choke and a 250 volt drop from the plate to the cathode of the 6V6, 85 volts is available at the cathode of the 6V6. Since in a direct coupled circuit the grid bias, 12.5 volts in this case, is obtained by the voltage differential between the cathode and grid, approximately 73 volts is required at the grid of the 6V6 (and at the plate of the 6SJ7, inasmuch as these two tube elements are connected directly together). With 73 volts at the plate and 55 volts at the screen of the 6SJ7, a voltage amplification of 115 can be obtained at only 0.8 percent distortion. This means that a 0.1 volt signal at the grid of the 6SJ7 will provide a 11.5 volt signal at the grid of the 6V6 which is considered adequate.
In accordance with Kirchoff's law, the voltage and current distribution around the circuit is indicated in the schematic. Note that there is a 12.5 volt drop through the DC resistance of the primary of the output transformer which was measured to be approximately 250 ohms. The cathode-follower output is obtained simply by connecting the transformer to the cathode of the 6V6 and tying the plate and screen of the 6V6 together to the "B plus" supply, as shown.
The output of the amplifier is approximately 4.5 watts. While this figure may seem low to those accustomed to dealing with amplifiers having output of 20 or more watts, it is entirely adequate for home use when an efficient speaker system is used.
Tests made by various organizations have shown that for listening in the average home living room, an output of less than one watt is generally used. The only reason for providing more power than this is to allow for the peak passages that occur in some classical compositions.
The input sensitivity is such that even the high-quality, low-output crystal pickups will provide sufficient drive.
No provision has been made for the use of variable reluctance pickups, although there is no reason why such units could not be used if a preamplifier stage were added. There have been many satisfactory preamplifiers described in various issues of this magazine.
In the event a preamplifier is used for the magnetic pickups, great care should be exercised in the shielding and placement of parts to avoid hum pickup. The careful selection of the tube used in the preamplifier will aid materially in the reduction of hum.
There is sufficient reserve capacity in the power supply to take care of almost any type of preamplifier without any trouble.
No provision for tone controls has been made, although they could be added with little difficulty. There is a great deal of controversy as to the best type of tone control, and it was felt that they could be added at a later date when the most satisfactory type had been determined by experiment.
It is essential that the primary of the output transformer, T1 have a resistance of approximately 250 ohms, as the resistance of this winding determines the grid bias for the 6V6. A check of the various types of transformers on the dealers' shelves by means of an ohmmeter will be sufficient. The primary impedance of this transformer should be from 5000 to 6000 ohms, with the higher value giving slightly less distortion.
The voice coil winding should be selected to match the speaker in use. Most of the better speakers have an impedance in the vicinity of 8 ohms, and for that reason t his value is specified.
It is not essential that this transformer be of the sealed type, but it should be of good quality so that the full benefit of the amplifier may be realized. Poor transformers are usually deficient in frequency response at the upper and lower frequencies.
The power supply, being conventional, needs no explanation.
Under-chassis view shows relative placement of miscellaneous components.
As can be seen in the photographs, the construction of the amplifier is simple and straightforward, with point to point wiring being used throughout. All the parts used are of good quality, all chokes and transformers being shielded and/or hermetically sealed. The total cost is slightly less than ten dollars. By observing the usual preCautions, twisting filament leads, etc., hum is inaudible at full gain.
When used with a good-quality tuner or record reproducer and a well baffled extended range speaker, the performance of this amplifier is superior for average living-room listening. The author used a Pilotuner for FM programs, a Webster dual speed record player for reproducing the conventional 78 r.p.m. and Columbia 33-1/3 r.p.m. records, an RCA player for the new 45 r.p.m. records, and a Jensen bass reflex reproducer.
Lacking laboratory test equipment, the author could not conduct the usual harmonic and intermodulation distortion tests on this amplifier. However, judging from extensive living-room listening tests, using recordings ranging from the RCA Victor Red Seal version of "Night on Bald Mountain" to the Capital Stan Kenton rendition of "Peanut Vendor," this amplifier leaves little to be desired.
If you've never listened to a direct coupled cathode-follower amplifier, then you have a pleasure to look forward to while constructing this one.
的直接耦合放大器与阴极跟随 - 雷蒙德H.贝茨 - 广播电视新闻， 1949年11月
在一个单一的音频放大器的两个新颖电路提供具有最小失真的宽的频率响应。
这篇文章中所描述的放大器的建设实际上是启动了两年多前，当时我成为一个热心的音频火腿。在最近的战争中我与雷达相关的以务实的方式，因此结识了阴极跟随这是广泛用于雷达作为一种廉价的介质相匹配的高阻抗电压放大级的低阻抗。当时，它似乎我，阴极跟随器可能会非常适合于音频输出级在那里得到一个良好的阻抗匹配的问题是一般人很难，通常价格昂贵。有了这个在我的脑海，我开始与所有类型音频放大器的实验，寻找一个电路，用于将至少部分提供了大量的性能。广播电视大学新闻以前的问题，我发现，描述了两个阴极跟随器和直接耦合放大器作为单独的电路。我无法找到所描述的音频放大器，这两个阶段和阴极跟随器输出之间的直接耦合的任何物品。因此，使用广播电视大学新闻源材料的老问题，我着手兴建这个放大器。
作为所用的示意图可以看出，该电路是非常简单的。
完整的原理图直接耦合6V6阴极跟随器放大器的示意图。
有两个功能，使该放大器以其优越的性能。一个是6SJ7的板和6V6的栅极之间的直接耦合。另一种是从6V6输出阴极跟随器。
除了它的简单，直接耦合消除了不期望的特性所固有的普通电阻 - 电容耦合，如弱信号和强信号栅阻挡短路。
阴极跟随器输出，除了它的简单性，同时提供了改进的高频和低频响应，阻尼出来的同时在输出变压器和扬声器，变形较少，而100％的负反馈的所有峰。
为了确定在原理图中的电路值，免费使用作出的管手册和基尔霍夫和欧姆定律。以常规方式，输出级起，管手册显示，对于单级输出， 6L6 ， 6V6 ， 6F6 ，或者6K6有可能输出管。在6V6被选择的，因为它易于获得和相对较低百分比的谐波失真的评估。该6SJ7被选中，是因为它的高增益和低失真的百分之主要。
为了保持电源的要求下，我选择了一个350伏，中心抽头， 120毫安（ 53毫安只需要）电源变压器，很容易在成本适中。允许在滤波器扼流一个15伏的压降，并从板250伏的压降到6V6的阴极， 85伏电压可在6V6的阴极。因为在直接耦合电路中的栅极偏置， 12.5伏在这种情况下，是通过在阴极和栅极之间的电压差得到的，大约73伏，需要在6V6的网格（并在6SJ7的板，生死时刻作为这两个管元件被直接连接在一起） 。用73伏板和55伏在6SJ7的屏幕，可以在只有0.8 ％的失真获得的115的电压放大。这意味着在6SJ7的网格中的0.1伏的信号将在这被认为是足够的6V6的栅极提供一个11.5伏的信号。
根据基尔霍夫定律，电压和周围电路的电流分布是表示在示意图。需要注意的是，通过该测定结果为约250欧姆的输出变压器的初级直流电阻12.5伏的压降。简单地通过变压器连接到6V6的阴极和绑6V6的板和屏幕一起到“B加”供应所获得的阴极跟随器输出，如图所示。
放大器的输出是约4.5瓦。虽然这个数字看起来可能低到那些习惯于处理具有20个或更多瓦的输出放大器，它是完全足够家庭使用，当一个高效扬声器系统使用。
通过各种组织所做的试验表明，对于收听在家里的起居室平均，小于1瓦特的输出通常使用。提供比这更多的权力的唯一原因，是让那发生在一些古典乐曲的峰值通道。
输入灵敏度是这样的，即使是高品质，低产出的晶体皮卡将提供足够的驱动。
故并无作出使用可变磁阻拾音器，虽然没有理由，如果一个前置放大器中加入这样的单位不能使用。目前已在这本杂志的各种问题，描述了许多令人满意的前置放大器。
在前置放大器用于磁性拾音器时，应十分注意在部分的屏蔽和安置的做法，以避免嗡嗡声拾音。谨慎选择在前置放大器中使用的管子将嗡嗡声的还原物质帮助。
有足够的备用容量在电源采取几乎任何类型的前置放大器的照顾，没有任何麻烦。
不计提音调控制已经取得了，但他们可以用很少的难度补充说。有一个很大的争议，以音调控制的最好的类型，因此有人认为他们可以在日后添加的时候最满意的类型已经由实验确定。
至关重要的是，该输出变压器， T1的初级具有大约250欧姆的电阻，由于该绕组的电阻决定了栅极偏置为6V6 。各类在经销商的货架变压器由一个欧姆表的方式的检查就足够了。这个变压器的初级阻抗应为5000〜 6000欧姆时，具有较高的值赋予略少的失真。
音圈绕组应选择的扬声器匹配使用。大多数的更好的扬声器具有在8欧姆附近的阻抗，并且由于这个原因吨指定他的值。
它不是必需的，该变压器是密封型的，但它应该是高质量的，使得放大器的全部好处，可以实现。穷变压器通常是在上部和下部的频率缺陷型的频率响应。
电源供应器，即传统的，不需要解释。
在机箱视图显示各种元件的相对位置。
如在这些照片中可以看出，该放大器的结构是简单的和直接的，具有点对点各处所使用的布线。所有使用的部件的质量是好的，被屏蔽和/或密封所有的电抗器和变压器。总成本略小于十块钱。通过观察平时的预防措施，扭丝引线等，哼哼是听不见的在全增益。
当与优质调谐器或记录重放以及一个莫名其妙扩展音域扬声器使用，该放大器的性能优越于普通客厅听。笔者使用了Pilotuner调频节目，韦伯斯特双速电唱机再现传统的78转和哥伦比亚33-1/3每分钟转数记录，一个RCA播放器新45每分钟转数记录和詹森低音反射重放。
缺乏实验室测试设备，笔者无法进行通常的谐波和互调失真测试，在此放大器。然而，从粗放客厅判断听力测试，使用录音不等RCA维克多红印章版“夜在秃头山”来的**斯坦·肯顿演绎“花生供应商， ”这个放大器留下一点不理想。
如果你从来没有听过的直接耦合的阴极跟随器放大器，那么你有一个快乐的期待，同时建设这一个。
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发表于 2014-1-4 21:30
楼主
