阿坤吻紫悦的胸部图片:A类放大器网站

JLH Class-A Update JLH类A更新

I had originally intended that this page would be a step-by-step record of the modifications carried out during the past year by one constructor – Tim Andrew.我原本打算这个页面将是一个在过去一年中，一个构造进行修改的一步一步的记录 - 添安德鲁。 However, recent ill health has meant that I have been unable to spend much time sitting at my pc so, rather than incur yet more delay in publishing the results, I have decided to write a short summary instead.然而，最近健康欠佳的意思，我一直坐在我的电脑，而不是产生更多的延迟??公布结果，不能花太多时间，我已经决定，而不是写一个简短的摘要。 I am very pleased that Tim has taken the time to supplement this with his own comments.我很高兴，添了所用的时间，用他自己的意见，以补充。 At the end of the page is a brief update on the higher power 'JLH for ESL' circuit.在页面的结尾是一个简短的更新更高的功率电路的ESL JLH。

Tim is a professional musician (a classical concert pianist) and so I trust his subjective judgement when it comes to assessing the accuracy and realism of sound reproduction.蒂姆是一个专业的音乐家（古典音乐会钢琴家），所以我相信他的主观判断，当涉及到评估的准确性和再现声音的真实感。 Before Tim first contacted me, he had built a kit version of the 1996 design, which he had subsequently upgraded with higher quality components.之前蒂姆第一次接触我，他已经建立了一个1996年设计的，他随后与更高质量的元件升级包版本。 Though Tim was happy with the results, he was keen to see if further improvements could be made to the sound quality and I was pleased to be able to suggest various circuit modifications, the majority of which subsequently proved to be very worthwhile.虽然添了对结果满意，他敏锐地看到可作出进一步改善音质，我很高兴能够到各种电路的修改，其中大部分后来被证明是非常有价值的建议。 Each of the modifications was carried out separately so that the results could be evaluated on an individual basis.每个修改是分开进行，使结果可在个别评估。

Rather than show schematics for each stage, I will start off with the penultimate circuit and include some appropriate comments.而不是对每个阶段的显示原理图，我将开始与倒数第二的电路，包括一些适当的评论。

Fig 1 – The Penultimate Circuit图1 - 倒数第二的电路

Transistor substitutions 晶体管换人

One of the first modifications was to try alternative output transistors.第一次修改之一是试图替代的输出晶体管。 The MJL3281A gave an audible indication of oscillation and was quickly rejected. MJL3281A了一个振荡的声音指示，很快就被否决了。 The MJ21194 sounded significantly better than the 2N3055 but, in Tim's layout, introduced a low-level hum. MJ21194响起明显比2N3055更好，但在Tim的布局，推出了低级别的嗡嗡声。 The MJ15003 gave a similar improvement to the MJ21194, but without the hum, and so was retained for future use.的MJ21194 MJ15003了类似的改进，但没有哼，等于是为将来使用保留。 At a later stage, the BC212 and 2N1711 (Q4 and Q3) were replaced with the 2SA970 and 2SC3421.在稍后的阶段，BC212和2N1711（Q4和Q3）2SA970和2SC3421取代。

Output dc offset control 输出直流偏移控制

The standard dc offset control circuitry (7815 and associated components) was replaced with a two transistor constant current source (Q5/Q6).标准的直流偏置控制电路（7815和相关组件）是两个晶体管恒流源（Q5/Q6）取代。 I had various reasons for suggesting this change.我已经表明这种变化的各种原因。 Firstly, three terminal regulators are not renown for their quietness and so it did not seem like a good idea to inject the noisy output from one directly into the feedback loop.第一，三端稳压器是不是他们安静知名，所以不喜欢一个好主意，似乎从一个直接注入到反馈回路的噪声输出。 Also, I had received reports that certain 7815s oscillated due to the low current conditions under which they were being operated.另外，我已经收到报告，由于低电流条件下，他们正在运作的某些7815s振荡。

However, one of the main benefits of the ccs is that the output dc offset variation as the amp warms up is greatly reduced.但是，CCS的主要好处之一是大大降低，输出直流偏移的变化，如放热身。 This is because the temperature coefficient of the ccs acts in the opposite direction to that of the input transistor (Q4) and negates the effect of temperature changes in Q4 (assuming that the temperature of Q5 follows that of Q4).这是因为在相反方向的CCS行为的温度系数的输入晶体管（Q4）和否定的温度变化的影响，在第四季度（假设第四季度，Q5的温度如下）。 This cancellation of temperature coefficient effects can be put to further good use as will be seen later.取消这种温度系数效应，可以进一步用好，后面将会看到。

Quiescent current control 静态电流控制

I first suggested that Tim try the 1969 bootstrap Iq control circuit, partly because the simulated distortion figures were half those for the 1996 version but mainly because I wanted to know how the two methods of Iq control compared in the same amplifier.我第一次建议添尝试，部分是因为1969年引导IQ控制电路的模拟失真数字分别为1996年版的一半，但主要是因为我想知道如何IQ控制两种方法相比，在相同的放大器。 I had received reports that the 1969 circuit (modified to dual supply rails) sounded better than the 1996 version, but I could not be sure that there were no other variables involved.我收到的报告，1969年的电路（修改双电源轨）听起来比1996年的版本好，但我不能肯定有没有涉及其他变数。 As it turned out, the bootstrap circuit was a retrograde step and Tim immediately reverted to the original 1996 arrangement.事实证明，自举电路是一种倒退和蒂姆立即恢复到原来的1996年安排。

I still had some nagging doubts about the 1996 Iq control circuit and so I suggested introducing another constant current source (Q7/Q8).我还有一些关于1996年IQ控制电路唠叨怀疑，所以我建议引入另一个恒流源（Q7/Q8）。 As with the bootstrap circuit, the simulated distortion figures were still half those for the 1996 version but with the added advantage that the distortion did not increase at low frequencies due to a reduction in capacitor effectiveness.自举电路，模拟失真数字仍然为1996年版的一半，但失真由于减少电容器效益低频率没有增加额外的好处。 A further advantage was an increase in amplifier efficiency (or maximum output).还有一个好处是增加（或最大输出功率）放大器的效率。 The maximum output voltage swing with the ccs is greater than that for the standard 1996 circuit and the maximum output current increases from around 1.35 to about 1.5 times the quiescent current.与CCS的最大输出电压摆幅大于1996年的标准电路的最大输出电流从1.35左右提高到约1.5倍的静态电流。

When carrying out this modification, Tim reused the existing MJE371 for Q8.当进行修改，添重用现有MJE371为Q8。 R10 has been retained to provide an easy means of measuring the quiescent current.一直保留到R10的静态电流测量提供一种简单的方法。 To my relief, Tim found the second ccs to be worthwhile improvement.我的救济，添发现的第二个CCS是值得的改善。

Power supply 电源

Whilst making the other alterations, Tim also took the opportunity to upgrade his power supply, initially by fitting larger bridge rectifiers and snubber capacitors and then by replacing the LM338s with 'follower' type discrete regulators, in line with my desire to remove unnecessary feedback loops from the overall circuit.其他改动的同时，Tim也借机升级自己的电源，最初是由装修取代“跟随者”型离散监管LM338s更大的桥式整流器，缓冲电容器，然后在我的愿望，以消除不必要的反馈回路从整体电路。 The 'follower' regulators, basically a capacitance multiplier circuit with a fixed voltage reference (derived from a resistor fed by a ccs), gave a small improvement. “跟随者”的监管机构，基本上是一个电容与一个固定的参考电压（由CCS美联储一个电阻所得）乘法器电路，给了一个小小的改进。 A much greater improvement was obtained when separate regulators were provided for each amplifier, whilst retaining a common transformer, rectifier bridges and reservoir capacitors.得到更大的改善时，每个放大器提供独立的监管机构，同时保留了一个共同的变压器，整流桥和水库电容器。

Fig 2 – The Final Circuit图2 - 最终电路

Removal of the feedback capacitor 去除反馈电容

I had received emails from a couple of constructors reporting on the beneficial effects of removing the feedback capacitor (C4).我已经收到了几个取消反馈电容（C4）的有利影响报告的构造函数的电子邮件。 I passed these comments on to Tim and he decided to try this modification for himself.我通过添了这些意见，并他决定尝试为自己的这一修改。

This modification should be treated with caution.这种修改应谨慎对待。 I would not recommend trying it unless the dc offset ccs (Q5/Q6) modification has been done first because otherwise the output dc offset variation during the warm-up period is likely to be in the order of several hundred millivolts.我不建议尝试，除非直流偏移CCS（Q5/Q6）的修改已经完成第一，因为否则输出直流偏移在热身期间的变化很可能在几百毫伏的顺序。 In Tim's case, with the dc offset ccs fitted, the output dc offset variation with the feedback capacitor removed was only slightly higher than that which he had previously with the standard 1996 circuit.在Tim的情况下，直流偏移CCS安装，输出直流偏移删除与反馈电容的变化，只略高于，这是他以前与1996年的标准电路。

I believed that the offset variation could be reduced further by utilising the temperature coefficient of the Q5/Q6 ccs.我相信，偏移量的变化可以进一步减少利用Q5/Q6 CCS温度系数。 I therefore suggested that R11 be made adjustable so that the temperature rise of Q5 could be varied.因此，我建议，R11的调节，使Q5的温度上升可能是多种多样的。 In this way, the output dc offset variation due to temperature changes in all stages of the amplifier could be compensated for, though this requires a lengthy, iterative process.在这种方式中，输出直流偏移的变化可以补偿由于温度变化在放大器的各个阶段，尽管这需要一个漫长的，反复的过程。 With the amp at its normal operating temperature, the offset is adjusted to near zero using VR1.在其正常工作温度放大器，偏移量调整到接近零使用VR1。 The offset when the amp is cold is then measured.偏移量时，放大器是冷的，然后测量。 VR3 is adjusted slightly, the amp is allowed to warm up and the offset is re-zeroed using VR1. VR3的调整小，放大器允许热身和偏移量是重新归零使用VR1。 The offset is then rechecked when the amp is cold and the process repeated until the minimum offset variation has been obtained.这个偏移接着复查时，放大器是寒冷和反复的过程，直到最低的偏移变化已获得。 Tim has been able to achieve an output dc offset variation between switch-on and normal operating temperature of less than 50mV.蒂姆已经能够实现输出直流偏移不大于50mV之间切换和正常工作温度的变化。

15/03/2003 Addendum 15/03/2003增编

It has been brought to my attention (thanks Mietek and Rudy) that removing the feedback capacitor increases the hum level at the amplifier output, which is particularly noticeable with high sensitivity speakers and if a simple rectifier/capacitor power supply is used.它已经引起了我的注意（感谢Mietek和Rudy），取消反馈电容增加在放大器的输出，这一点尤其明显，高灵敏度扬声器，如果是使用一个简单的整流/电容电源的嗡嗡声电平。 I had not anticipated this, but some quick simulations soon indicated that removal of the feedback capacitor reduces the PSRR of the amp by a factor of about 3, causing any supply rail ripple to become more audible.我没有预料到这，但一些快速的模拟很快表明，去除反馈电容减少了约3倍的放大器的PSRR，导致的任何电源轨纹波变得更加发声。

Fortunately, the cure for this problem is relatively simple.幸运的是，对于这个问题的治疗相对简单。 The PSRR of the input stage ccs can be improved by the addition of a single capacitor, connected between the junction of VR3/R11 (Fig 2) and the +ve supply rail. VR3/R11（图2）交界处和+ VE电源轨之间的连接，除了单个电容器可以改善输入级CCS的PSRR。 Doug Self's 'Audio Power Amplifier Design Handbook' indicates that this modification will improve the PSRR of the ccs by about 10dB.格自我的“音频功率放大器设计手册”指出，这一修改将提高约10dB的PSRR的CCS。 A capacitor value of 47uF will suffice, but higher values (within reason) can be used.一个47UF的电容值就足够了，但可以使用更高的值（在合理的范围内）。

The higher power ('JLH for ESL') circuit can be similarly modified by splitting R11 (Fig 3) into two 4k7 resistors in series and connecting the capacitor from the mid-point of these resistors to the +ve supply rail.高功率的电路（“ESL JLH”）可以同样修改R11（图3）分裂成两个系列的4K7电阻和连接这些电阻的中点电容+ VE电源轨。

This modification can also be carried out even if the feedback capacitor is not removed, and will give an improvement in PSRR with the corresponding reduction in hum.也可以进行这种修改的反馈电容，即使不会被删除，并且将给予相应减少在哼哼的PSRR改善。

17/08/2003 Addendum 17/08/2003增编

Several constructors have found that adding the 47uF capacitor to the input stage ccs after having removed the dc blocking capacitor from the feedback network has caused the ccs to become unstable.几个构造发现后拆除隔直电容的反馈网络，增加47uF电容器的输入级CCS，已引起了CCS变得不稳定。 This has manifest itself by relatively large output dc offset variations when taking voltage readings around the input circuit or when a hand is moved near to the ccs components.这有相对较大的输出直流偏移的变化反映出来时，周围的输入电路的电压读数或手搬到附近的CCS组件。

In Tim's case, a successful solution to this problem has been to replace Q5 and Q6 with 'slower' transistors.在Tim的情况下，一个成功的解决了这个问题已经被替换为“慢”的晶体管Q5和Q6。 The MPSA56 appears to work well in the ccs. MPSA56出现在CCS工作。 Alternatively, the 47uF capacitor could be removed and the PSRR of the ccs improved by omitting VR3 and replacing R11 with a 1mA constant current diode (or an FET wired as a ccs to give a similar current).另外，47uF电容器可以被删除，并改善了CCS的PSRR省略VR3和取代R11的同一个1毫安恒流二极管（或有线作为CCS给予了类似的电流的FET）。

Adding base resistors (100R to 1k) to Q5 and Q6 and/or a 1k resistor between Q6c and Q4e should also help to improve stability.基地添加的电阻（100R 1K）Q5和Q6和/或Q6c和Q4e之间的1K的电阻也应有助于提高稳定性。

Tim's comments on the modifications (Updated 17/08/2003) Tim的修改意见（17/08/2003更新）

A few years ago I built the 1996 version JLH Class-A amplifier.几年前，我建的1996年版JLH类一个放大器。 Constructors of this amplifier have commented about its smooth sound, with many favourable comments and comparisons against valve designs and a few not so favourable comments with regard to its limited power output.这个放大器的构造有关其光滑的声音，具有许多有利的意见和对阀的设计和一些不那么有利的意见，考虑到其有限的输出功率进行比较。 In its standard 1996 form, which I built from a kit using cheap components, my first impressions of its sound were of smoothness coupled with a relaxed liquid musical flow which I found far preferable to anything else which I had previously heard.在其1996年形成标准，这是我从一个工具包，使用廉价元件内置，它的声音我的第一印象是一个宽松的液体，我发现远远优于任何东西，我以前听说过的音乐流加上平滑。 In the context of my system with speaker efficiency somewhere around 87dB/W and with volume set correctly such as is appropriate for the perspective as recorded, or in other words "at a realistic level", its limited power output has never been a problem.在我的系统与扬声器的效率大约87分贝/ W和量设置是否正确，如适当的记录，或在“换句话说，在合理的水平”的角度来看，其输出功率有限从来就不是一个问题。 The amplifier and its power supply have since been subject to extensive component substitutions and substantial circuit modifications.放大器及其电源，至今已受到广泛的组件替换和大量的电路修改。

As this section is about my impressions of the modifications that have been made to the circuit, a brief word on what I consider to be an "improvement" might be in order.由于这部分已作出修改的电路??，一个简短的字，我认为是一个“改善”我的印象是，可能是为了。 I want to hear, with ease, the ambient signature of the recording venue, with a distinct impression of the space between its walls.我想听到的，轻松的录音场地的环境签名，与它的墙壁之间的空间的一个鲜明的印象，。 Also, I want to notice, for example, the sound of the felt hammer of a piano hit the string, followed not only by the sound of the string vibrating but also the more subtle reflected and attenuated sounds of the hammer and its mechanism as these reverberate between the walls of the recording venue.另外，我要注意，例如，钢琴的感觉锤的声音击中的字符串，不仅其次是振动的弦的声音，但也因为这些锤子和其作用机制的更加微妙的反射和衰减的声音之间的录音场地的墙壁上回荡。 This is sometimes more noticeable in larger venues where the reflected sound arrives later, albeit weaker.这是有时在较大的反射声到达地点后，虽然弱，更引人注意。 Those delicate piano harmonics must be reproduced with the greatest accuracy, enabling subtle shadings of timbre to be noticed, again with ease.这些微妙的钢琴谐波必须复制最大的准确度，使音色的微妙的阴影被察觉，再次轻松。 As a pianist, I want to hear the "pitch" of the note as it decays through to its quietest moment as acutely as possible, but I want no hint of hardness or roughness.作为一个钢琴家，我想听到的“间距”的注意，因为它通过最安静的时刻敏锐地尽可能衰变，但我想没有一丝的硬度和粗糙度。 With orchestral strings for example, where there are many instruments playing together, I don't want to hear one homogeneous group, and I want transparency, not brightness.例如管弦乐字符串，那里有许多文书一起玩，我不希望听到一个同质的群体，和我想的是透明度，而不是亮度。

Professionally, I have a very close affinity with the piano.专业，我有一个非常密切的亲和力与钢琴。 A difficult instrument to reproduce, it is perhaps more revealing of faults in the reproduction chain than can be the case with other instruments although the human voice is also very useful, for obvious reasons.一个困难的仪器重现，这或许可以与其他文书的情况下，虽然人类的声音也是非常有用的，原因很明显，更揭示再生产链中的故障。 It is my view that any modification that produces a more realistic rendition of the complex sound of this instrument, and the very subtle structure of its over-tones, will also represent an improvement in the accuracy of the amplifier overall.这是我认为，任何修改，产生了复杂的声音本仪器更加逼真再现，非常微妙的结构和其对色调，也将代表整体改善放大器的准确性。 This has been the case during all my listening trials.这期间一直都是我听试验的情况下。 It is worth mentioning that any modification which leads to an apparent decrease, for example in the level of the treble, will not necessarily be deemed to be an improvement, even if the new treble level is a welcome one, unless it is accompanied by an improvement elsewhere, improved detail or portrayal of nuance for example.值得一提的明显减少而导致的任何修改，例如在高音水平，??并不一定被视为是改善，即使新的高音水平是一个值得欢迎的的，除非它是伴随着由其他地方的改进，例如改进的细节或细微之处的写照。 From this, you will gather that I am not in the habit of 'voicing' the system, adjusting one thing to correct for another, but that I prefer to address the transparency of the system as a whole, with the aim of neutrality.由此看来，你会收集，我在“清浊”制度，调整一件事情，以正确的另一个的习惯，但我喜欢中立的目的，以解决系统作为一个整体的透明度，。 Only then will I look at altering the balance, perhaps with a slight adjustment to the treble.只有到那时，我期待在改变平衡，或许有轻微的调整高音。 It is through this approach (transparency first, followed by tonal balance) that I am now able to enjoy the vast majority of recordings in my collection, previously I had found many of these to be deficient in one way or another.正是通过这种方式（透明度第一，音调平衡），我现在能够享受在我的收藏绝大多数唱片，以前我已经发现其中许多这样或那样的不足。 Almost without exception, each modification has improved "difficult" recordings, whilst further improving others, often revealing a warmth and atmosphere, the previous lack of which had been wrongly attributed to the recording.几乎没有例外，每次修改完善“困难”的录音，同时进一步改善他人，常常露出了温暖和氛围，以前的缺乏已被错误地归因于录音。

Though considerable time has been expended on both the amplifier and its power supply, I find it sobering to say the least that improvements made to power supply, specifically to the method of its delivery into various parts of the amplifier circuit have been so rewarding.虽然放大器和电源上都花费相当长的时间，我觉得很发人深省的，至少可以说，改善电源，特别是其传递到各个部分的放大电路的方法已使奖励。 The following is a list of the modifications that, with considerable help from Geoff, I have been able to carry out on the 1996 version of the JLH.下面是一个清单，从Geoff相当大的帮助，我已经能够进行的1996年版的JLH修改。 Also included are my opinions of the results of these.此外，还包括这些结果我的意见。 Each substitution has been carried out individually, this has enabled subsequent and hopefully accurate (but not always positive!) evaluation.每个替代已进行单独，这使以后希望准确（但并不总是积极的！）评价。 ! ！

The Amplifier 放大器

Input capacitor. 输入电容。

The cheap polycarbonate(?) 1uF input capacitor was replaced with a 470nF Mcap "Audiophile" polypropylene type.廉价的聚碳酸酯（？）1uF的输入电容是一个470nF MCAP“发烧”聚丙烯类型取代。 This led to an improvement in both bass firmness and in detail, treble sounded less bright.这导致了两个低音的坚定性和详细的改善，高音听起来不那么明亮。 Later, I replaced the Mcap 470nF with Audio Note paper-in-oil 470nF.后来，我与音频便条纸油中470nF取代MCAP 470nF。 This sounds very different, smooth, warm and open with much more textural detail and firmness in the bass.这听起来很不同，很光滑，温暖和开放得多的纹理细节和中低音的坚定性。 There is some loss of focus when compared with the better plastic types and the positioning of instruments within the stage is not as precise as it could be, however none of the plastic types I have tried has approached the naturalness and openness of the paper-in-oil, particularly in the treble, and any shortcomings are easily forgiven in light of considerable improvements elsewhere.时相比并不精确，因为它可以更好的塑料类型和阶段的定位仪器内，有一些失去重心，不过我已经试过的塑料类型没有走近的自然性和开放性的文件中在其他地方相当大的改善，石油，特别是在高音，和任何缺点很容易原谅。 This simple modification has since proved to be one of the most effective.这个简单的修改以来被证明是一个最有效的。 I have also tried a polystyrene type (333nF) which sounds more detailed and focussed than anything else tried previously, though there is a tendency to sound a little "squeaky" on occasions (placing a small paper-in-oil capacitor across it improves this considerably), nevertheless I prefer this to most polypropylene types, many of which sound hard and slightly blurred to me.我也曾尝试聚苯乙烯类型（333nF）听起来比什么都尝试以前更详细，更集中，虽然有一种倾向，声音，有时一个小小的“吱吱响”（小造纸，石油电容放置跨越，提高这相当），但我更喜欢这个最聚丙烯类型，其中有不少声音硬，有点模糊，我。

Resistors. 电阻器。

All standard grade metal film resistors in both critical and semi-critical parts of the circuit were replaced with tantalum film types.所有标准的高档金属膜电阻器在电路的关键和半关键的部分取代钽薄膜类型。

Improved smoothness and texture, with a more fluid sound.改进的平滑度和质感，更流畅的声音。 A slight "mumbling" quality has been removed.轻微的“喃喃自语”的质量已被删除。

Output transistors. 输出晶体管。

The 2N3055s were replaced with MJ21194. MJ21194 2N3055s被替换。 In comparison with these the 2N3055s sound grey and rather diffused with less sense of authority, less detail and a more prominent treble quality.在比较这些2N3055s声音灰色，而用更少的权威感，细节较少和更加突出的高音质量扩散。 In contrast, the MJ21194s have a noticeably firmer sound with more ambience in the treble and greater detail.相比之下，MJ21194s有一??个明显更坚定的声音，在高音和更详细的更氛围。 More natural generally.更自然普遍。 Reluctantly, they were removed from the circuit due to a faint hum which was not present with the 2N3055s.不情愿，他们从一个微弱的嗡嗡声，这是不是与2N3055s目前由于电路。

Wanting to try something else, and now with the strong impression that the 2N3055s were less than ideal, I tried some MJ15003s.想尝试别的东西，现在的2N3055s不太理想与强烈的印象，我尝试了一些MJ15003s。

This time, a substantial improvement over the 2N3055s.这个时候，比的2N3055s大幅改善。 The MJ15003's bass is both tauter and more authoritative, with cleaner treble and greater textural detail. MJ15003的低音tauter和更权威，更清洁的高音和更大的纹理细节。

DC offset control. 直流偏移控制。

Replace 7815 with constant current source.恒流源替换7815。

Result...Cleaner, smoother and weightier, with what can only be described as an organic flow.结果... ...更清洁，更顺畅，重，只能被描述为一个有机的流动，。 It was obviously all there before, but I suppose it was masked somewhat by the noise of the regulator.显然这是所有有前，但我想这是稳压器的噪声所掩盖有点。 The volume can be increased further without sounding "loud".体积可进一步增加而冠冕堂皇的“大声”。 A substantial improvement in all respects.在各方面的显着改善。

Iq control circuit. IQ控制电路。

The Iq control circuit was replaced with a bootstrap circuit (using an Elna "Silmic"). IQ控制电路的自举电路（使用Elna的“SILMIC”）取代。 Less clarity was the result, with less tonal variety and focus, sounding more shut-in.减清晰的结果，音调较低的品种和重点，听起来更关。 The bootstrap simply doesn't sound as detailed.引导根本不健全，详细。 I assume this is due to the presence of the bootstrap capacitor connected to the signal path.我想这是由于连接到信号路径的自举电容的存在。 Perhaps a Black Gate might improve things, but I suspect not enough to equal the MJE371 circuit which is more transparent, open, dynamic and uncoloured, the female voice sounds less "female" with the bootstrap circuit.也许一个黑色的门，可能提高的东西，但我怀疑没有足够的平等MJE371电路，这是更透明，更开放，动态和无色的，女性的声音自举电路“女性”。 It strengthens my theory that those who prefer the earlier version of the JLH do so because of the absence of the 7815 in the earlier circuit.它加强了我的理论，那些喜欢早期版本的JLH的，因为在前面的电路的情况下的7815。 I would go further and say that due to the absence of both a bootstrap capacitor, and an output capacitor, and with the ccs in place of the 7815, they might well prefer the 1996 version, all other things being equal.我要进一步说，由于自举电容和输出电容的情况下，CCS的7815，他们可能更喜欢1996年的版本中，所有其他条件不变。 My original Iq control circuit was very quickly re-instated!我原来的IQ控制电路非常迅速地重新恢复！

It was not long until the original Iq control circuit was removed again, this time replaced with a constant current source and with better results this time.时间不长，直到原来的IQ控制电路再次被拆除，取而代之的这个时候，一个恒流源，效果会更好时间。 The initial reaction is to think that the treble detail and "air" have been diminished with a reduction of transparency.在最初的反应是认为高音细节和“空气”的透明度，减少减弱。 On prolonged listening things are rather different.在长时间聆听的东西是相当不同的。 There is actually more detail coming across, coupled with a growing sense of "rightness".其实是有更详细的跨越，再加上越来越多的“正确性”意识。 Sounds are presented in a more natural light, gone is the spotlight effect with its admittedly pleasant but artificial treble detail.声音在更多的自然光，走的是其诚然愉快，但人工的高音详细的聚光灯效果。 String harmonics are more balanced and proportioned with a sense that they now belong to the fundamental, part of the whole.字符串谐波更加平衡和匀称，从某种意义上说，他们现在都属于根本，是整体的一部分。 The gaps between rapid piano notes are often missed by amplifiers, the JLH reproduces these well and they are even clearer now than before. JLH繁殖快速的钢琴音符之间的差距往往是由放大器错过，这些，他们现在比以前更清楚。 Familiar recordings of woodwind and brass instruments sound remarkably smooth and natural.熟悉木管乐器和铜管乐器录音的声音明显流畅自然。 Differences in scale between smaller chamber music recordings and larger scale works are now more clearly conveyed.在规模较小的室内乐录音和较大规模的工程之间的差异，现在更清楚地传达。 It is interesting to compare the sound of the Iq ccs circuit with that of the bootstrap which shared many of the attributes of the ccs but had a lumpy and coloured, slightly congested characteristic which I found unpleasant.有趣的是，比较与共享CCS的许多属性，但我发现不愉快的波诡云谲，有色，略微拥挤的特点，引导的IQ CCS电路的声音。 Returning to the standard 1996 Iq circuit the next day was quite a relief, this time I have no plans return.返回到1996年的标准Iq的电路的第二天是相当的救济，这时候我已经不打算返回。 I would miss the qualities that the Iq ccs circuit has brought to the amplifier.我会想念IQ CCS电路放大器的素质。 Final thought........Recommended for those who want to sit down for an evening of good music and a fine wine.最后想到........推荐那些要坐一个晚上的好音乐和美酒。

Feedback capacitor. 反馈电容。

The 470uF Oscon (previously a very similar sounding 220uF Silmic) feedback capacitor was replaced with link (needing a small change in value to the DC offset ccs preset).反馈电容470UF OSCON（以前一个非常类似的冠冕堂皇的220UF SILMIC）的链接（需要在直流偏移CCS预设值小的变化??）所取代。 The result of this change was a more open and natural treble with an increased sense of fluidity, depth and ease.这种变化的结果是一个更开放，更自然的高音与一个增加的流动性，深度和缓解感。 Hot/cold offset variation are much greater without the feedback capacitor, in my circuit a variation of 150mV was observed (with the feedback capacitor it was around 65mV), this was reduced by controlling the current through the ccs in an effort to adjust the temperature compensation, but on a recent re-build of the circuit this arrangement proved ineffective and was subsequently removed.热/冷偏移的变化是在我的电路没有反馈电容要大得多，一个150mV的变化观察（大约65mV与反馈电容），这是减少通过努力CCS控制电流，调节温度赔偿，但在最近的一个重新构建的电路，这样的安排被证明是无效的，随后被删除。

Driver transistor (2N1711). 驱动晶体管（2N1711）。

This was replaced with a 2SC3421.这是一个2SC3421替换。 As with the other transistor substitutions I have made in the JLH, the actual pitch of a note is more easily heard with the 2SC3421s.与其他的晶体管替换我JLH，音符的实际音高是更容易与2SC3421s听到。 The same characteristics introduced by the Iq ccs circuit are still there but each single note now conveys more "meaning", more clearly defined in time. IQ CCS电路相同的特征仍然存在，但现在每个单注表现出更多的“意义”，更明确的时间定义。 Timing, of course, is a musician's greatest asset!时机，当然，是一个音乐家最大的资产！ The Iq ccs circuit introduced a smoother, rounder sound with a somewhat darker hue, the extra transparency and openness brought about by the 2SC3421s has lifted that slight darkness away whilst apparently retaining the smoothness and naturalness of the Iq ccs. IQ CCS电路引入了一个较深的色调更顺畅，更圆的声音，额外的透明度和公开性所带来的2SC3421s已解除轻微的黑暗，而显然是保留的平滑性和自然的智商CCS。

Input transistor. 输入晶体管。

The BC212 was replaced with 2SA970 with similar improvements to those noticed with the 2SC3421. BC212是取代2SA970的2SC3421注意到类似的改进。

The Power supply. 电源。

Rectifier diodes. 整流二极管。

Having tried snubber capacitors across the original "standard" diodes with no noticeable improvement, the originals (and snubbers) were replaced with schottky types.在试图跨越原来的“标准”没有明显改善二极管的缓冲电容器，原稿（缓冲器）取代肖特基类型。 This seemed to be beneficial with more smoothness and an improved "woody" quality with woodwind.这似乎是有利于更多的平滑性和改进的“木本”质量与木管乐器。

Regulators. 稳压器。

The LM338K regulator circuit was replaced with a capacitance multiplier. LM338K稳压电路电容倍增器代替。 The bass now conveys more authority and the amplifier sounds a little warmer, also with more detail.低音表现出更多的权力，放大器的声音一点点温暖，也更详细，。

Dual regulators. 双稳压器。

The single capacitance multiplier was replaced with a new (adapted) dual version allowing separate regulation for each channel.单电容倍增器是一个新的（改编）允许对每个通道单独调节的双版本取代。 This warrants a detailed write-up so I shall list my observations in the order in which I noticed them and in descending order of their magnitude.这是值得一个详细的写，所以我将我的观察名单中我注意到他们的顺序，其规模降序排列。

It is only now that I have heard the new dual power supply, that I can identify the sonic effects of the single supply.只是现在我听到的新的双电源供电，我可以识别单电源供电的声音效果。 For the first, and most important observation, I shall use a single piano note as an illustration.第一，也是最重要的观察，我将使用一个单一的钢琴说明，作为一个例证。 With the single supply, when the note is struck there is an initial transient 'bump' as the hammer hits the string, followed by the decay, which starts after the initial 'bump' has subsided.随着单电源，被击中时注意有一个初始瞬态的“凸点”，凿打的字符串，由最初的“凸点”已经消退后开始衰减，。 With the dual supply, this initial transient is less 'loud' (better controlled?) and it carries more weight and meaning, this is followed by the decay which not only conveys better pitch, leading to more emotion and tunefulness, but the decay starts sooner, its first moments not masked by the apparently exaggerated impact of the hammer blow introduced by the single supply.随着双电源供电，这种最初的瞬态少“响亮”（更好的控制？），它承载更多的重量和意义，这是其次，它不仅传达更好的间距由衰变，导致更多的情感和tunefulness，但开始的衰变越早，其第一时刻没有蒙面介绍，由单电源供电的槌击，显然夸大的影响。 Also, due to the increased definition, the note seems to decay more slowly, incidentally this is one of the more significant differences between a small grand piano, and a large 'concert' grand where, due to the increased string length of the larger instrument, its sustaining power is much greater.此外，由于增加的定义，似乎说明衰减更慢，顺带之间的小三角钢琴的显着性差异，以及一个大型的“音乐会”隆重，由于较大的仪器增加字符串的长度，其底气大得多。 A single note can therefore be followed more easily from start to finish.一个音符，因此可以更容易从开始到结束。 The tonal signature and real colour of all instruments are now better conveyed.现在有更好的传达音调的所有文书的签名和真实的色彩。

There is also a significant improvement in the quality of the treble where there is greater transparency.还有一个显着改善的高音的质量有更大的透明度。 For most of the time, it is less obvious than before, and smoother, but little details previously almost un-noticed are conveyed more clearly and with improved texture.对于大多数的时间，这是不太明显的比以前顺畅，但以前几乎未注意到的小细节更清楚地传达和改善质地。 This treble improvement was unexpected and is a constant pleasure!这高音改善感到意外，是一个常数的乐趣！

The third improvement I have noticed is an improvement in the positioning of individual instruments.我注意到第三个改进是在个别乐器的定位改进。 The perceived stage width is not obviously any wider than before, although I couldn't fault it before, on a good recording the stage width was almost limitless, on a bad recording it had definite limits.认为舞台的宽度没有明显比以前更宽，虽然我可能没有过错之前，一个很好的录音舞台的宽度几乎是无限的，它有一定的限制在一个糟糕的记录，。 This hasn't changed, what has improved is the positioning of instruments within the limitations of the stage width imposed by the recording, with instruments on the edge of the stage more clearly conveyed in space with a better "floating" feel to the acoustic coupled with a more acute sense of the venue.这并没有改变，有所改善的仪器定位在舞台的宽度的限制，对录音与舞台边缘仪器在太空中更清楚地传达一个更好的“浮动”的感觉的声学耦合，更敏锐的场地。

Filter capacitors. 滤波电容。

Having previously bypassed the standard grade electrolytics with Elna "Silmic" 100uF with little, if any improvement, this time the original capacitors (30,000uF per rail) were replaced entirely with "Silmics" (18,000uF per rail).以前绕过的Elna的“SILMIC”小100uF的标准级电解电容，如果任何改善，这完全取代“Silmics”（18,000每轨UF）原电容器（30000每轨UF）的时间。 A superb improvement in definition.一个高超的定义改善。 The scale of which came as quite a surprise.其中规模令人惊喜。

Conclusion. 结论。

I consider the JLH in its present form, to be a very special amplifier.我认为在目前的形式JLH，是一个非常特殊的放大器。 Its ability to portray the acute sense of emotion and excitement contained in a fine performance, through its accuracy and with such grace, coupled with its ability to scale music's dynamic heights so convincingly, is rare.它能够描绘的情感和包含在一个优良的性能，通过其准确性和这样的恩典，兴奋的敏锐，再加上其规模音乐的动态高度令人信服的能力，是罕见的。 My most sincere thanks to Geoff who, through spending so much time helping others like me, has so far not had time to carry out these modifications for himself *.我最诚挚的谢意，杰夫的人，通过花费了大量时间帮助其他像我这样的，到目前为止，还没有来得及为自己进行这些修改*.

* Unfortunately not the only reason - Geoff 不幸的是并非唯一的原因-杰夫

Higher power circuit 更高的电源电路

The 'JLH for ESL' circuit, which can be used with conventional speakers as well as electrostatics, already has a ccs for dc offset adjustment but it would benefit from the other modifications outlined above.电路“为ESL JLH”，它可以与传统的扬声器以及静电，已经有一个CCS直流偏移调整，但它会受益于上述其他修改。 In particular, the use of a ccs for quiescent current adjustment obviates the need for a high power preset, which can sometimes be hard to find.特别是，静态电流调整的一个CCS的使用，省却了高功率预设的需要，这有时很难找到。

Fig 3 – The Higher Power Circuit图3 - 高功率电路

When used with conventional speakers, this circuit can deliver over 40W provided the supply rail voltage and quiescent current are selected to suit a specific load impedance.与传统扬声器使用时，该电路可提供超过40W的电源轨的电压和静态电流的选择，以适应特定的负载阻抗。 The supply rail voltage needs to be a couple of volts higher than the peak output voltage swing and the total quiescent current should be about 0.7 times the maximum output current.电源轨的电压必须高于峰值输出电压摆幅和几个伏的总静态电流应约0.7倍的最大输出电流。 The power dissipated in each output transistor (supply rail voltage times half the quiescent current) should be limited to about 40 to 45W, assuming decent sized heatsinks are used (0.6 to 0.8degC/W per transistor).在每个输出晶体管的功耗（电源轨电压乘以一半的静态电流）应限制在40到45W左右，假设体面大小的散热器均采用（0.6 0.8degC / W的每个晶体管）。

The peak load voltage and current can be calculated from required power and the speaker's impedance in the normal way using:高峰负荷电压和电流可以计算出所需的电源和扬声器的阻抗，在正常使用方式：

Vpk = sqrt(2*Pwr*Rload) and Ipk = sqrt(2*Pwr/Rload) VPK = SQRT（2 * PWR * RLOAD）和电流峰值= SQRT（2 * PWR / RLOAD）

To allow for speaker impedance variations, I would suggest that current is calculated using ¾ of the speaker's nominal impedance and voltage using 1½ times the nominal value.为了让扬声器的阻抗变化，我会建议，目前的计算方法¾扬声器的标称阻抗和电压，采用1.5倍标称值。 Of course, you are free to make your own assumptions about speaker impedance variations and to calculate the required supply rail voltage and quiescent current accordingly.当然，你可以自由扬声器的阻抗变化使你自己的假设，并计算出所需的电源轨的电压和静态电流相应。 From feedback I have received, higher quiescent currents tend to sound better so you may wish to bias the compromise between voltage and current accordingly (whilst keeping the power dissipation in the output transistors at a safe level).从反馈意见，我已经收到，较高的静态电流往往会更好的声音，所以你不妨偏置电压和电流之间的妥协（输出晶体管的同时保持在一个安全的水平，功耗）。

The following table indicates the maximum power output into 8, 6 and 4ohm loads for some standard transformer secondary voltages, assuming a resistive load and without any allowance for the impedance variations mentioned above.下表显示一些标准的变压器次级电压8，6和4欧姆负载的最大输出功率，假设一个电阻负载，并没有任何上述阻抗变化的津贴。 The supply rail voltages assume a regulated supply, with the consequential volt drop, and the quiescent current has been calculated from either the maximum current into 4ohm or, in the case of the 25 and 30Vrms secondary, the transistor power dissipation limit.承担的电源电压的稳压电源，具有相应的电压下降，静态电流的最大电流从计算到4欧姆或25的情况下，30Vrms次要的，晶体管的功耗限制。

Secondary中

Voltage (Vrms)电压（Vrms的）

Supply Rail电源轨

Voltage (V)电压（V）

Quiescent静态

Current (A)电流（A）

Power电源

8ohm (W) 8欧姆（W）

Power电源

6ohm (W) 6ohm（宽）

Power电源

4ohm (W) 4欧姆（W）

18 18

18 18

2.8 2.8

16 16

21 21

32 32

22 22

23 23

3.7 3.7

28 28

37 37

56 56

25 25

28 28

3.2 3.2

42 42

56 56

42 42

30 30

33 33

2.7 2.7

60 60

45 45

30 30

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