'AMP'에 해당되는 글 4건

  1. 2010.06.22 여러가지의 JLH 버전들 (2)
  2. 2010.02.08 오디오 ) 에르노보벨리
  3. 2009.08.29 JLH (John Linsley Hood) 앰프 이야기
  4. 2009.08.20 jlh evo 만들어보다.
2010.06.22 02:31

여러가지의 JLH 버전들

이상하게도 이 글은 비공개로 되어 있었다. 
별 내용은 아니지만 무언가 더 끄적거리고 공개로 바꿀 예정이었던 것 같다.

1.  DOZ를 제외한 버전으로 제작에 참고한 것은 Nob라는 일본 사람의 글이다.

JLH Class-A Ampを作成してみました。
このampは1969年にJohn Linsley HoodさんがWireless World という雑誌の4月号に発表した回路を基にしています。




  • 出力段には2SC5200を採用しました。(千石で300円と安かったので)
  • ドライバ(と言えるか)には2SC3421。(これも千石で50円と安かったので)
  • 定電流回路には2SA1538を。(2SC3421のペアでこれも50円)
  • 初段およびその他の定電流回路には2SA1015。(秋月で1000円/200個)
  • 抵抗は0.33Ω5W以外、在庫があるものは金属皮膜、なければカーボンです。
  • コンデンサですが、電解はふつーのもの。カップリングのC1は結局外しました。







2N3055 version

2N3055はTO-3型なので、後面にTO-3用のheat sinkを付けるようにしました。

2.  그런데 이 앰프는 본질적으로 2003 업데이트의 일본판이다,

JLH Class-A Update



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. 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. I am very pleased that Tim has taken the time to supplement this with his own comments. At the end of the page is a brief update on the higher power ‘JLH for ESL’ circuit.


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. Before Tim first contacted me, he had built a kit version of the 1996 design, which he had subsequently upgraded with higher quality components. 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. Each of the modifications was carried out separately so that the results could be evaluated on an individual basis.


Rather than show schematics for each stage, I will start off with the penultimate circuit and include some appropriate comments.



Fig 1 – The Penultimate Circuit


Transistor substitutions


One of the first modifications was to try alternative output transistors. The MJL3281A gave an audible indication of oscillation and was quickly rejected. The MJ21194 sounded significantly better than the 2N3055 but, in Tim’s layout, introduced a low-level hum. The MJ15003 gave a similar improvement to the MJ21194, but without the hum, and so was retained for future use. At a later stage, the BC212 and 2N1711 (Q4 and Q3) were replaced with the 2SA970 and 2SC3421.


Output dc offset control


The standard dc offset control circuitry (7815 and associated components) was replaced with a two transistor constant current source (Q5/Q6). I had various reasons for suggesting this change. 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. Also, I had received reports that certain 7815s oscillated due to the low current conditions under which they were being operated.


However, one of the main benefits of the ccs is that the output dc offset variation as the amp warms up is greatly reduced. 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). This cancellation of temperature coefficient effects can be put to further good use as will be seen later.


Quiescent current control


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. 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. As it turned out, the bootstrap circuit was a retrograde step and Tim immediately reverted to the original 1996 arrangement.


I still had some nagging doubts about the 1996 Iq control circuit and so I suggested introducing another constant current source (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. A further advantage was an increase in amplifier efficiency (or maximum output). 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.


When carrying out this modification, Tim reused the existing MJE371 for Q8. R10 has been retained to provide an easy means of measuring the quiescent current. To my relief, Tim found the second ccs to be worthwhile improvement.


Power supply


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. 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. A much greater improvement was obtained when separate regulators were provided for each amplifier, whilst retaining a common transformer, rectifier bridges and reservoir capacitors.



Fig 2 – The Final Circuit


Removal of the feedback capacitor


I had received emails from a couple of constructors reporting on the beneficial effects of removing the feedback capacitor (C4). I passed these comments on to Tim and he decided to try this modification for himself.


This modification should be treated with caution. 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. 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.


I believed that the offset variation could be reduced further by utilising the temperature coefficient of the Q5/Q6 ccs. I therefore suggested that R11 be made adjustable so that the temperature rise of Q5 could be varied. 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. With the amp at its normal operating temperature, the offset is adjusted to near zero using VR1. The offset when the amp is cold is then measured. VR3 is adjusted slightly, the amp is allowed to warm up and the offset is re-zeroed using VR1. The offset is then rechecked when the amp is cold and the process repeated until the minimum offset variation has been obtained. Tim has been able to achieve an output dc offset variation between switch-on and normal operating temperature of less than 50mV.



15/03/2003 Addendum


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. 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.


Fortunately, the cure for this problem is relatively simple. 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. Doug Self’s ‘Audio Power Amplifier Design Handbook’ indicates that this modification will improve the PSRR of the ccs by about 10dB. A capacitor value of 47uF will suffice, but higher values (within reason) can be used.


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.


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.




17/08/2003 Addendum


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. 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.


In Tim’s case, a successful solution to this problem has been to replace Q5 and Q6 with ‘slower’ transistors. The MPSA56 appears to work well in the ccs. 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).


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.



Tim’s comments on the modifications (Updated 17/08/2003)


A few years ago I built the 1996 version JLH Class-A amplifier. 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. 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. 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. The amplifier and its power supply have since been subject to extensive component substitutions and substantial circuit modifications.


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. I want to hear, with ease, the ambient signature of the recording venue, with a distinct impression of the space between its walls. 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. This is sometimes more noticeable in larger venues where the reflected sound arrives later, albeit weaker. Those delicate piano harmonics must be reproduced with the greatest accuracy, enabling subtle shadings of timbre to be noticed, again with ease. 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. 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.


Professionally, I have a very close affinity with the piano. 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. 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. This has been the case during all my listening trials. 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. 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. Only then will I look at altering the balance, perhaps with a slight adjustment to the treble. 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. 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.


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. 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. Also included are my opinions of the results of these. Each substitution has been carried out individually, this has enabled subsequent and hopefully accurate (but not always positive!) evaluation. !


The Amplifier


Input capacitor.

The cheap polycarbonate(?) 1uF input capacitor was replaced with a  470nF Mcap "Audiophile" polypropylene type.  This led to an improvement in both bass firmness and in detail, treble sounded less bright. Later, I replaced the Mcap 470nF with Audio Note paper-in-oil 470nF. This sounds very different, smooth, warm and open with much more textural detail and firmness in the bass. 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.  This simple modification has since proved to be one of the most effective. 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. 



All standard grade metal film resistors in both critical and semi-critical parts of the circuit were replaced with tantalum film types.

Improved smoothness and texture, with a more fluid sound. A slight "mumbling" quality has been removed.


Output transistors.

The 2N3055s were replaced with MJ21194. In comparison with these the 2N3055s sound grey and rather diffused with less sense of authority, less detail and a more prominent treble quality. In contrast, the MJ21194s have a noticeably firmer sound with more ambience in the treble and greater detail. More natural generally. Reluctantly, they were removed from the circuit due to a faint hum which was not present with the 2N3055s.

Wanting to try something else, and now with the strong impression that the 2N3055s were less than ideal, I tried some MJ15003s.

This time, a substantial improvement over the 2N3055s. The MJ15003's bass is both tauter and more authoritative, with cleaner treble and greater textural detail.


DC offset control.

Replace 7815 with constant current source.

Result...Cleaner, smoother and weightier, with what can only be described as an organic flow. It was obviously all there before, but I suppose it was masked somewhat by the noise of the regulator. The volume can be increased further without sounding "loud".  A substantial improvement in all respects.


Iq control circuit.

The Iq control circuit was replaced with a bootstrap circuit (using an Elna "Silmic"). Less clarity was the result, with less tonal variety and focus, sounding more shut-in. The bootstrap simply doesn't sound as detailed. I assume this is due to the presence of the bootstrap capacitor connected to the signal path. 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. 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. 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.  My original Iq control circuit was very quickly re-instated!


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. The initial reaction is to think that the treble detail and "air" have been diminished with a reduction of transparency. On prolonged listening things are rather different. There is actually more detail coming across, coupled with a growing sense of "rightness". Sounds are presented in a more natural light, gone is the spotlight effect with its admittedly pleasant but artificial treble detail. String harmonics are more balanced and proportioned with a sense that they now belong to the fundamental, part of the whole. The gaps between rapid piano notes are often missed by amplifiers, the JLH reproduces these well and they are even clearer now than before. Familiar recordings of woodwind and brass instruments sound remarkably smooth and natural. Differences in scale between smaller chamber music recordings and larger scale works are now more clearly conveyed. 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. Returning to the standard 1996 Iq circuit the next day was quite a relief, this time I have no plans return. I would miss the qualities that the Iq ccs circuit has brought to the amplifier. Final thought........Recommended for those who want to sit down for an evening of good music and a fine wine.


Feedback capacitor.

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). The result of this change was a more open and natural treble with an increased sense of fluidity, depth and ease. 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.   


Driver transistor (2N1711).

This was replaced with a 2SC3421. 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. 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. Timing, of course, is a musician’s greatest asset! 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.


Input transistor.

The BC212 was replaced with 2SA970 with similar improvements to those noticed with the 2SC3421.


The Power supply.


Rectifier diodes.

Having tried snubber capacitors across the original "standard" diodes with no noticeable improvement, the originals (and snubbers) were replaced with schottky types. This seemed to be beneficial with more smoothness and an improved "woody" quality with woodwind.



The LM338K regulator circuit was replaced with a capacitance multiplier. The bass now conveys more authority and the amplifier sounds a little warmer, also with more detail. 


Dual regulators.

The single capacitance multiplier was replaced with a new (adapted) dual version allowing separate regulation for each channel. 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.

It is only now that I have heard the new dual power supply, that I can identify the sonic effects of the single supply. For the first, and most important observation, I shall use a single piano note as an illustration. 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. 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. 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. A single note can therefore be followed more easily from start to finish. The tonal signature and real colour of all instruments are now better conveyed.

There is also a significant improvement in the quality of the treble where there is greater transparency. 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. This treble improvement was unexpected and is a constant pleasure!

The third improvement I have noticed is an improvement in the positioning of individual instruments. 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. 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.


Filter capacitors.

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).  A superb improvement in definition. The scale of which came as quite a surprise.



I consider the JLH in its present form, to be a very special amplifier. 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. 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 *.


* Unfortunately not the only reason - Geoff



Higher power circuit


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. 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.



Fig 3 – The Higher Power Circuit


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. 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. 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).


The peak load voltage and current can be calculated from required power and the speaker’s impedance in the normal way using:


Vpk = sqrt(2*Pwr*Rload)  and  Ipk = 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. 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. 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).


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. 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.



Voltage (Vrms)

Supply Rail

Voltage (V)


Current (A)


8ohm (W)


6ohm (W)


4ohm (W)


























3.  http://www.tinholt.eu/jlhevolution.htm 이것은 아직 분석을 안했다.

Schematic amp
4. 그런데 정말 재미있는 분석은 정작 pass 가 만든 부분이다.   (내용은 첨부 화일 참조)

The PLH Amplifier By Nelson Pass
Introduction: The JLH Amplifier
In 1969 John Linsley쵩ood wrote in Wireless World:
During the past few years a number of excellent designs have been published for
domestic audio amplifiers. However, some of these designs are now rendered
obsolescent by changes in the availability of components, and others are intended to
provide levels of power output which are in excess of the requirements of a normal living
room. Also, most designs have tended to be rather complex.
In the circumstances it seemed worth while to consider just how simple a design could be
made which would give adequate output power together with a standard of performance
which was beyond reproach, and this study has resulted in the present design.
He then described a Class A power amplifier using three gain stages of Bipolar transistors in a
topology which continues to be admired for its elegant simplicity and sound quality.
The centerpiece of this design is the middle stage, an NPN transistor used as a phase splitter,
simultaneously driving the positive half of the output stage and the negative half with symmetric
signals of opposite phase.

Figure 1 shows a simplified version of the JLH topology. Signal input appears at the Base of
Q1, and is amplified and inverted to drive the Base of Q2. Q2 acts as a gain device and also a
signal splitter, driving both Q3 and Q4 simultaneously, but out of phase with each other. Q3 and
Q4 form the output transistors, Q3 operating as a Common Emitter gain device, contributing
current and voltage gain, and Q4 operating as a Common Collector device contributing only
current gain. The resistors provide bias for the system, and R1 and R2 feed the output of the
amplifier in a loop back to the emitter of Q1.
Q2 is the heart of the design, and in my opinion, it is the elegant economy with which it performs
the complementary gain to drive the output devices that gives the circuit its classic beauty.

The JLH was designed at a time when ``the tube era was in decline'' and the new generation of
designers were pulling out all the stops to create big science amplifiers ?pure voltage sources
with high power and infinitesimal distortion -- complex circuits with lots of feedback.
36 years and a little progress later, we can perhaps appreciate the simple charm of the JLH
topology as an exercise in minimalism, but if you haven't listened to one, you might be very
surprised by the quality of sound, which is extraordinarily good within it's power limitations. If
you have efficient speakers and you like to listen to two춃hannel sound at reasonable levels, the
JLH is still in the top rank.
The amplifier has reasonable specifications; nothing special that isn't wildly exceeded by a $3
chip, but it produces real music. Its flaws are not irritating and it does a wonderful job wringing
more music out of modern recordings and even MP3's. I can't think of another transistor design
from that era that works as well.
Figure 2 shows the circuit rendered more completely, but for more extensive documentation on
the versions of the JLH amplifier, I recommend The Class A Amplifier Site:
In Figure 2 additional details of setting up the DC bias for each device are shown, where
capacitors are used to separate DC values from AC values. C1 separates feedback from bias
current. C2 separates input signal from input DC bias voltage and C3 blocks the output DC of
the amplifier from the load. C4 removes supply noise from the voltage powering the front end of
the amplifier, and C5 forms a ``bootstrap'' circuit, making resistors R5 and R6 behave more like a
constant current source at audio frequencies.
The original JLH amplifier has approximately 55 dB of open loop gain divided into 22 dB of
amplifier gain and about 33 dB of feedback. As detailed in the original article, it delivered 10
watts at approximately .1% harmonic distortion or less.

The amplifier's popular longevity speaks volumes about the quality of its sound, and this is
understandable given its simplicity coupled with excellent measured performance. It has a
particularly tube춍ike quality compared to the more complex solid춖tate designs of the era and
The distortion is largely 2 nd harmonic, and is closely proportional to the output voltage. This
means that .01% distortion at .1 watts becomes 1% at 10 watts, and you can draw a pretty
straight line between the two points on a logarithmic graph. Such a curve is characteristic of a
single춅nded output topology, and there have been arguments regarding whether or not the
output stage is single춅nded Class A, push춑ull Class A or a mixture of both. We will be having
some fun with that later.
One flaw in the original JLH design was that its bias current, that idling current which flows
through the parts of the circuit, had some dependency on the power supply voltage, resulting in
altered performance for different AC line voltages. Power supply regulation solves this problem
neatly, but there were other ways this was addressed in later versions of the circuit.
Newer JLH Circuits
John Linsley쵩ood published an update to the amplifier in 1996 that addressed bias stability
issues, parts substitutions, and provided a version that had a direct춃oupled output, eliminating
the output capacitor. At the same time, it was in many ways the same amplifier, the measured
performance being very similar.
The JLH circuit continues to be interesting to the audiophile community and has been the
subject of several updates. Figures 3 and 4 show simplified schematics of later generations of
JLH amplifiers.

Figure 3 shows a simplified schematic of the 1996 version published by John Linsley쵩ood that
fixes the bias stability issue with the addition of Z1 and the Q5 portion of the circuit. This version
also direct coupled the output of the amplifier, using dual supply rails.
In 2000 someone else produced the circuit seen in Figure 4, where constant current sources are
used to bias the first two gain stages, giving good power supply rejection to the circuit. This
version also doubled up on the number of output devices. You will notice that Fig 1 -- 4 have
their feedback loop addressing the Emitter of the feedback transistor. Nowadays they have
gotten fancy and call it ``current feedback''.
Just for your entertainment, I cobbled together the circuit of Figure 5 shows an example with a
differential input. An obvious variation, but I haven't seen it used. You can drive this input stage
with a balanced signal by lifting C1 from ground and driving it as a negative input. At 100 ohms
each, R6 and R7 will give this input about the same open loop gain as the original input
transistor with the 220 ohms degeneration of the original feedback impedance.

I recently measured the performance of a working copy of the circuit of Figure 4. It had 17.5 volt
supply rails and was biased at about 2 amps per channel. The open loop gain is also about 55
dB into 8 ohms, and its measured performance is comparable to the original circuit.
Figure 6 shows the distortion versus output power. The bandwidth of the amplifier is --3 dB at
100 KHz, the damping factor is about 35, and the distortion versus frequency is fairly flat, rising
slightly at 20 KHz.
The PLH Amplifier
One of the issues that arise from adding gain stages to amplifiers is that while they increase the
open loop gain and allow more feedback correction, they themselves are the source of
additional distortion. While the extra feedback can lower the distortion numbers, usually the
additional circuitry is reflected in a more complex distortion character having higher order
harmonics and inter춎odulation components. These are generally agreed to be less musical
Michael Cunningham wrote, ``Novelists must usually decide what degree of slavish accuracy
would make their stories more alive, and what degree would make them less.'' The amplifier
designer has a similar problem to solve. It's not hard to make an amplifier that measures well --
it's comparatively hard to please audiophiles.
My own approach is to make the signal path as simple as possible, work to lower the distortion
of that basic circuit before feedback is applied, and then apply minimal (or no) feedback, largely
in agreement with the comments in Linsley쵩ood's original article. The result is not always the
best objective measurements, but the sound is often interesting.
The 3춖tage topology of the JLH amplifier routinely uses simple Class A operation and about 33
DB negative feedback to achieve this performance, and this lured me to consider what kind of
amplifier I could achieve with an even simpler circuit and less feedback. The output stage and
the intermediate phase splitter cannot be dispensed with and still resemble a JLH, but you can
certainly remove the input transistor.

4.  diyaudio 에 나오는 쓰레드 2003년의 글에는 여러가지 대화가 나오고 170여 페이지 뷰를 넘어간다.


그중의 하나는 없어진 웹사이트에 있던 내용이다.
Graham Maynard presented a jlh output class A amp in the september Electronics World

I뭭e abstracted the input as an ideal gm vccs and used ideal current sources to look at the output stage operation ?


suggests 2sc3281 is similar to Graham뭩 2sc5200 output devices, I was able to find onsemi spice model for mj3281 and already had fairchild bd139 model for a driver

(despite the LTSwCad file header names this is the mj3281 sim)

my question/issue is the poor current division as Vce gets within 5 V of the rail with the 200 V device, the ancient 2n3055 actually looks much better in this regard (i1 has to go up to ~150mA due to the low hfe of the 3055 model in LtSwCad) ?so is this real or modeling error?

Given that spice transistors are perfectly matched and only deviate due to differential biasing this is probably optimistically good current division so another question is how can the jlh deserve its reputation when built by diyers lacking power curve tracers to match the output devices?

And finally the sim offers an example of how to step a parameter in LtSwCad Spice for mikes

Added spice directive:

.step param A LIST .17 .35 .7 1.4

V5 input voltage source amplitude defined with {A} as parameter which is stepped from LIST in .step directive

SINE(0 {A} 2K)

see LTSpice asc file:

Trackback 2 Comment 2
2010.02.08 22:39

오디오 ) 에르노보벨리

2010.8 .15 추가:
 보벨리의 사이트는 곧 폐쇄될 것 같다. 
더글라스 셀프의 사이트가 폐쇄된 것도 오디오 자작파들의 큰 손실인데 다시 보벨리의 사이트마저 문을 닫는다. 
좋은 소리의 중요성은 줄어들지 않을 것 같은데 뛰어난 디자이너들이 점차 손을 놓고 있다. 
아마 사업성이 감소하고 관심도 줄어든 탓으로 보인다. 
사실 우리나라도 마찬가지다. 

상당히 오랜기간 존경을 받아온 회로 디자이너다. 특별히 욕심을 부린 적도 없고 오랜 동안 오픈소스에 가깝게 활동한 분이다. 
만약  오디오 특히 fet 회로에 대해 배우고 싶다면 이  사이트의 글글을 읽어 보면 아마 많은 것을 배우게 될 것으로 안다. 
사진은 전형적인 오디오 작업 세팅이다. 공간만 더 있다면 이렇게 했으면 좋겠다고 항상 부러워하고 있다. 
그보다는 시간이 더 절박하지만 ... 아무튼 사진이 분위기는 정말 멋지지 않은가?


BORBELY AUDIO�s primary objective is to develop and sell high quality kits for DIY audio amateurs. We started 25 years ago by offering hard-to-find components to Mr. Borbely�s amplifier designs, which were published in the AUDIO AMATEUR in the USA and the HIGH FIDELITY in Denmark. Today we are offering high quality kits and audiophile components to the audio amateur community and to OEM customers.

Mr. Borbely at his workbench, testing a custom-made ALL-FET lineamp.
About Mr. Borbely...
Mr. Borbely received an MSc Degree in Electronic Engineering from the Norwegian Institute of Technology, University of Trondheim. He worked seven years as a design engineer at the Norwegian Broadcasting Corp., developing studio equipment, both in tube and in semiconductor technology. In 1969 he moved to the US and worked for David Hafler at DYNACO. Mr. Borbely was named Director of Engineering for DYNACO in 1972. He developed the Cascode output stage for the Stereo 400 power amplifier, and the DYNATUNE circuit for the FM5 FM tuner, for which he received a US patent. In the 70s he worked at Motorola Semiconductor, developing power amplifiers, low-noise preamplifiers and FM-tuners. Some of this work was put to good use, when he joined The David Hafler Company as Director of Engineering. Mr. Borbely developed the DH101 preamplifier and the DH200 power amplifier, which was the first one to use MOSFETs in the US. From 1980 until 1997 he worked for National Semiconductor in Germany as its Technical Training Manager. In 1984 Mr. Borbely and his wife Irene started BORBELY AUDIO, which is selling high quality Kits to end-users. Since 1982 he has been publishing his designs in the Audio Amateur Publications (Audio Amateur/Audio Electronics, Speaker Builder, Glass Audio and now in AudioXpress). In the last several years Mr. Borbely has developed a line of ALL-FET audio amplifiers. Besides the kit business, Mr. Borbely is designing audio products for OEM customers. 

A selection of Erno Borbely�s articles from the Audio Amateur Publications:
  • 60W MOSFET Power Amplifier, Audio Amateur, 2/82
  • Third Generation MOSFETs: The Servo 100 (Part I), Audio Amateur, 1/84
  • Third Generation MOSFETs: The DC 100 (Part II), Audio Amateur, 2/84
  • The Borbely Preamp, Part I, Audio Amateur, 4/85
  • The Borbely Preamp, Part II, Audio Amateur, 1/86
  • A Moving Coil Preamp, Part I, Audio Amateur, 4/86
  • A Moving Coil Preamp, Part II, Audio Amateur, 1/87
  • A Simple Curve Tracer, Part I, Audio Amateur, 4/90
  • A Simple Curve Tracer, Part II, Audio Amateur, 1/91
  • Balanced Audio Amplifiers, Audio Amateur, 1/91
  • The New Borbely Preamp: The Modules, Audio Amateur, 2/91
  • The Gaertner-Borbely Line-Level Preamp, Part I, Audio Amateur, 1/93
  • The Gaertner-Borbely Line-Level Preamp, Part II, Audio Amateur, 2/93
  • New Power Amp Modules, Part I, Audio Amateur, 3/93
  • New Power Amp Modules, Part II, Audio Amateur, 4/93
  • Modular Active Crossovers, Speaker Builder, 1/94
  • A 15W SE Power Amp With 6C33C-B, Glass Audio, 5/96
  • A Differential Line Amp with Tubes, Glass Audio, 1/97
  • An MC/MM Preamplifier with Tubes, Glass Audio, 2/97
  • Class-A Power Modules, Audio Electronics, 4/97
  • Low-Voltage Tube/MOSFET Line Amplifier, Glass Audio, 1/98
  • JFETS: The New Frontier, Part 1, Audio Electronics, 5/99
  • JFETS: The New Frontier, Part 2, Audio Electronics, 6/99
  • The ALL-FET Line Amp, AudioXpress, 5/02
  • Starter Kits Part 1: EB-604/410 All-JFET Line Amp, AudioXpress, 3/05
  • A Hybrid TUBE/MOSFET Headphone Amplifier, AudioXpress, 4/05 

  • 저작자 표시
    Trackback 0 Comment 0
    2009.08.29 17:43

    JLH (John Linsley Hood) 앰프 이야기

    마소에 실렸던 내용입니다. 
    그러니 저작권은 마소에 있습니다. 

    읽을거리 > 디벨로퍼 플러스

    텡구 클론 비슷한 것 만들어 보기

    텡구의 클론을 만들기로 하고 정작 세운상가에서 구입한 것은 5×7 LED 하나뿐이다. 나머지는 이미 갖고 있거나 비슷한 것을 찾을 수 있었기 때문이다. 이 LED 매트릭스로 간단한 숫자나 문자 표시기를 만드는 것과 텡구 비슷한 장난감을 만드는 것은 전혀 다른 일이다. 문화장난감과 산업용품의 차이라고 할 수 있다. 물론 제품이라면 둘의 부가가치 역시 매우 다르다.

    안윤호 mindengine@freechal.com|필자는 현재 xray21의 기술담당 이사로 근무하고 있다. 오픈 소스와 운영체제에 많은 관심을 기울여 왔다. IT 기술을 바탕으로 사회, 문화현상에 대한 학구적인 토대를 갖추기 위해 노력하고 있다.

    제품이나 부품이 흔해져버린 세상에서 물건의 존재가치를 찾기는 쉽지 않다. 먹고사는 필수적인 생필품이 아니라 설계되고 만들어지는 제품 가치는 재미있거나 꼭 필요한 이유가 있어야 한다. 현실 세계에서 보자면 많은 부품이 쉽게 구해지지만 이들의 성능이 예상보다 훨씬 좋으며, 일부는 마구 버려지기 때문에 필자는 버려지거나 주변에서 사용되지 않는 많은 물건들이 독자들 상상력의 재료라고 말했다. 문제는 이 상상력을 훈련시키는 것이다. 억압받고는 있지만 상상력과 창의력은 본질적인 부분이다. 이들을 억압하는 편이 산업을 돌리는데 유리하던 시절이 있었고 사람들은 많은 시간을 일했다. 일을 많이 하는 시절이 있었지만 그 시절이 가고나니 사람들을 TV나 인터넷에 붙잡아 놓는 일이 생산자에서 소비자로 붙잡아 놓는 편이 더 산업에 유리하게 보이던 시절이 되었다. 이는 현재도 진행 중이다. 그러나 본능적으로 상당히 많은 사람들은 자기가 만들어 보고 DIY의 즐거움을 누리고 싶어 한다.

    DIY의 즐거움
    말은 거창하지만 사실은 별것 없다. 기술적인 재료들이 많이 널려 있으니 만들고 싶은 것을 만들어 보는 것이다. 오타쿠적인 요소와 만들기의 욕구, 이들을 뒷받침하는 기술과 이론이 있으면 되는 것이다. 그러면 아트도 할 수 있고 필요한 물건을 만들어 볼 수 도 있다. 요즘같이 세상이 시끄러울 때는 세상을 잠시 잊는 진지한 놀이를 할 수도 있는 것이다.

    사실 세상에 토이는 이미 많다고 볼 수 있다. 흔해져 버린 컴퓨터도 토이라고 볼 수 있으며 컴퓨터로 프로그래밍을 배우는 과정은 정말 진지한 토이다. 프로그램의 기본을 배우는 단계를 지나면 프로그래머는 나름대로의 실험과 관찰을 통해 발전한다. 교과서에는 나와 있지 않거나 실감하기 어려운 부분이다. 이런 과정을 거치지 않고는 프로그램 실력이 잘 늘지 않는다. 예전에 필자는 피터노빅(Peter Norvig)의 에세이 『10년 동안 프로그램 배우기(teach yourself programming in 10 years)』를 소개할 때 피터노빅이 how to들을 버리라고 말한 구절도 언급했다.

    how to는 일종의 작은 교과서들이다. 피터 노빅은 다양한 경력을 가진 구글의 연구책임자이다. 노빅은 한때 자신만큼 Howto의 글들을 많이 읽은 사람은 없었을 것이라고 적으면서 HowTo만 읽을 때는 아무 것도 제대로 할 수 없었다고 한다. HowTo를 무시하고 자신만의 방법으로 일을 시작하면서야 제대로 무엇을 할 수 있었다고 적었다.

    비슷한 일은 필자에게도 항상 있었다. 프로그램 역시 실제로 돌려보지 않는 한 깊은 이해는 불가능했다. 시스템이 손에 잡힐 것 같은 느낌이 들지 않으면 개선이 불가능했다. 아무리 작은 코드나 시스템이라도 머리보다는 손으로 이해하는 편이 더 실감이 난다. 해크(Hack)라는 것은 그런 것이다. 몇 줄짜리 코드라도 하나씩 테스트해 봐야만 전체를 이해할 수 있다. 책이나 문서로 제공하는 지식은 밀착도가 떨어진다.

    전자 장치의 시스템도 사정은 같았다. 요즘에 빠져 있는 간단한 오디오의 세계 역시 실제로 만들어 보고 파형을 봐야 이해할 수 있었다. 여담이지만 지난번의 Gainclone 칩 앰프 이후 필자가 오랫동안 빠져 있던 오디오는 JLH class A라는 앰프였는데 1969년에 발표한 John Linsley Hood의 채널당 네 개의 트랜지스터를 사용하는 10W짜리 앰프다. 40년이 된 회로다. 회로를 보면 전자공학을 공부한 사람에게는 아주 간단한 회로일 것으로 보이고 이 회로를 이해하는 것은 어렵지 않아 보인다. 조립의 난이도 역시 간단한 전자키트보다 쉬워 보인다. 아주 쉬워 보이는 회로처럼 보이지만 그렇지도 않다. 40년 가까운 시간동안 DIY 오디오의 중요한 레퍼런스, 그리고 모든 오디오 앰프 교과서의 중요한 레퍼런스로 남아 있었고 앰프 디자이너들의 해석은 모두 달랐다(http://www.tcaas.btinternet.co.uk/index-1.htm).

    강력한 pspice 같은 도구로 시뮬레이션 해석을 하는 것은 실제 트랜지스터의 복잡기괴함을 모두 반영하지도 못할 뿐 아니라 pspice가 소리를 내주는 것도 아니다. Nelson Pass 같이 유명한 앰프 디자이너도 이 앰프의 워킹 카피를 만들고 나중에 PLH(Pass Linsley Hood)라는 자신의 MOSFET 버전을 만들었다. 시간이 한참 지난 2005년도의 일이었다. 그 전에 많은 시간을 내어 이 앰프의 회로를 벤치마크 했다. Douglas Self 라는 또 다른 유명한 디자이너의 해석도 달랐으며 정작 설계자 본인의 아이디어는 또 달랐다. 대중적인 DIY 오디오 사이트로 유명한 Rod Elliott의 Death of Zen이라는 앰프는 이 앰프를 자신의 해석으로 다시 만들어 본 것이다. 그러니 모두 한 번씩은 이 앰프를 만들어 보거나 진지하게 생각한 것이니 필자 역시 그냥 지나칠 수는 없었다.

    CPU의 트랜지스터가 코어당 천만 개 레벨을 넘는 세상에서 트랜지스터 네 개짜리 앰프가 아직도 오디오 디자인 영감의 원천이 된다는 것이 신기하기만 했지만 커다란 방열기를 뜨겁게 달구며 깊은 바이어스가 걸리는 회로들은 실제로 만들고 재봐야 이해할 수 있다. 회로의 트랜지스터들은 단종 된 탓에 구할 수 없지만 요즘은 훨씬 더 좋은 소자들이 나오며 가격도 싸기 때문에 필자는 조금 동작이 이상한 인켈의 앰프를 뜯어서 호기심을 참지 못하고 만들어 보았다. 하우투는 아니지만 Death of Zen(http:// sound.westhost.com/project36.htm) 앰프를 참조하기는 했다. 이 회로 역시 30년이 넘어서 JLH를 재해석한 워킹카피를 만든 것이다. 필자가 할 수 있는 일은 이들을 모두 검증해보는 일이었고 사실상 재설계했다. 

    필자가 트랜지스터 네 개를 가지고 진지한 놀이를 10여일 정도 하고 난 후의 결과는? 전자 기초 공부를 오랜만에 다시 했다고 볼 수 있다. 오디오 앰프  회로의 이해 역시 증가되었다. 악어클립을 물리고 전압과 전류를 재던 예전의 시절로 잠시 돌아갔다. 전원전압은 17볼트에서 40볼트까지 바꾸어 볼 수 있었고 회로의 이해는 점차 새로운 측면으로 접어들었다. 오실로스코프에 물려 파형과도 씨름했다. 전자쟁이로써는 아주 소중한 경험이었다. 그야말로 간단한 회로를 갖고 이리저리 해킹한 느낌이었다. 어떻게 보면 10줄짜리의 심오한 리다이렉션 셀(shell) 프로그래밍의 이해와 비슷한 순간이었다. 간단한 것이 반드시 쉬운 것은 아니다. 물리적으로는 소리가 아주 좋은 앰프를 하나 갖게 되었다. 해보지 않으면 알 수 없었을 것이다.

    필자는 이런 통찰력 있는 장난감을 망라하는 키트들이 있으면 좋겠다는 생각이 들었다. 어떻게 보면 진지한 장난과 실제의 개발은 종이 한 장 차이라고 볼 수 있다. 그런 면에서 전자 키트는 예전의 학생과학키트 같은 것이 없어지거나 존재가치가 줄어든 이후에 적당한 대체품들이 나오지 않고 있다고 볼 수 있다. 실제로 팔리는 키트들은 재미가 없다. 이들의 재편이 새로운 재해석이 필요하다는 생각이다. 예전에 Art of Electronics, TTL cookbook 같은 책이 나왔다면 요즘 버전의 새로운 종합 텍스트가 나올 만도 한데 아직은 아니다. 디지털 세계를 잘 반영한 토이들을 위한 교과서로 마땅한 교재가 없다. 필자가 실력이 좋으면 한번 써보고 싶을 정도다.

    그런 면에서 볼 때 『Fab』라는 책의 내용들은 일리가 있다. 개인적인 제작은 앞에서 적은 아날로그 앰프보다는 디지털 세계에서 더 잘 먹혀 들어간다. 워킹카피는 디지털적으로 반복될 수 있다. 같은 소스를 갖는 하드웨어나 소프트웨어의 공동 작업에 의한 개발도 가능하다. 몇 년이 지나면 제작자의 블로그나 웹사이트는 제작 자료와 개발의 교과서로 충분한 정보와 복잡성을 갖게 될 수 있다. 아두이노는 그런 소재 중의 하나다. 필자는 지금 아두이노의 이야기를 적고 있지만 조금 더 높은 수준의 프로젝트도 더 많다는 것을 잘 안다. 시간을 낼 수 있다면 자료가 공개되는 구글폰을 재료로 삼거나 조금 높은 수준의 다른 프로젝트들도 많이 있다. 그러나 토이수준의 성찰에서는 아두이노의 수준이 잘 맞는다는 것을 안다. 제일 간단한 레벨의 어플라이언스들은 복잡해져서는 안 된다. 그것은 집의 전등과 스위치가 복잡하지 않은 이유와 같을 것이다. 아주 쉽게 무엇인가를 마음 편하게 만들 수 있는 가위와 풀처럼 남아있을 충분한 이유가 있다.

    텡구의 간단한 클론
    디지털의 세계 역시 아날로그와 크게 다르지 않다. 가지고 놀면서 장난을 치는 것이 해크의 세계다. 텡구 클론을 만드는 것이 오리지널 텡구를 다시 복원하는 것이 아니기 때문에 가능성은 널려 있다고 볼 수 있다. 원래의 목표가 디지털 레벨 미터를 만드는 것이었기 때문에 소리의 레벨에 따라 표정을 바꾸는 정도로 만족할 수 있고 소스코드도 간단하다(이 달의 디스켓 참조).

    표정은 열 개도 안 된다. 그나마 있던 표정 데이터는 도용해 오다시피 한 것이고 LED를 5×8에서 5×7로 잘못사서 표정의 한 줄이 빠진 것이다. 그러니 독자들이 필자의 소스코드에서 참조할 것은 극소수다. 소스 코드를 보면 알겠지만 코드는 유치하기 그지없다. 발전형이 있다면 소리의 진폭의 강약에 따라 조금 표정의 변화를 바꾸어주는 것인데 이 과정은 개인마다 다를 것이고 지난번에 말한 것처럼 표정을 만드는 일이 바로 실제의 프로그래밍이다. 제품의 하드웨어와 펌웨어가 아니라 어플리케이션의 어플라이언스가 더 중요한 일이 될 것이다. 그러니 아두이노의 스케치 개발환경으로 프로그램을 만드는 것 자체를 어려워 할 개발자는 독자 중에 거의 없다고 봐야한다.

    <화면 1>처럼 아두이노는 브레드보드라고 하는 빵판 위에 조립되었다. 만약 조금 오래 만지작거리고 싶다면 만능기판에 조립해야 한다. 실제로 오래 장난치고 싶다면 아크릴이나 플라스틱 케이스에 넣은 편이 나을 것이다.

    마이크는 버려지는 헤드셋에서 뽑은 것이고 지난번과 바뀐 것이 있다면 마이크의 회로도다. 트랜지스터는 범용 NPN 트랜지스터면 아무 것이나 써도 된다. 이 회로가 싫다면 지난번에 사용된 lm386을 사용해도 된다.

    지난번의 adc 입력 테스트의 가변 저항이 이번에는 마이크 앰프로 대체 되었다, 물론 너무 입력 값이 크거나 작으면 값들을 대체해야 하지만 이것으로도 잘 동작한다. 
    그리고 LED가 변경되었다. 추석 전에 문을 닫기 전의 LED 집에서 구입한 것이지만 마침 5×8을 구할 수가 없었다. 그러니 그냥 이것으로 만들 수밖에 없다. 5×8의 매트릭스를 쓰는 편이 빠르다. 디바이스마트에서도 판다. 아마 온라인으로 비슷한 것을 구하는데 아무런 지장이 없을 것이다. 설명이 너무 단순해서 정보가 너무 적기는 하지만 테스트해보니 숫자가 적히지 않은 쪽이 1번이었다.

    그럼 코딩과 조립에 같이 돌입해보자. <그림 3>에서 열(column)에 해당하는 핀은 13, 3, 4, 10, 6 번이고 행에 해당하는 핀은 9, 14, 8, 5, 1, 7, 2가 된다. 이 행에 해당하는 핀에 1(high)값을 주고 열에 해당하는 값에 0 (low)을 주면 LED 매트릭스는 표정을 갖게 된다. 그 값의 데이터는 소스코드에 있으며 지난번에 소개했다. LCD 매트릭스는 워낙 화소가 많기 때문에 시리얼로 데이터를 보내지만 그 방법 역시 이번에 소개하는 방법의 확장판이다. 간단하고 좋은 LCD 예제는 아두이노 사이트에 소개되어 있다(http://arduino.cc/en/Tutorial/LCD8Bits).

    그러면 연습 삼아서 지난번의 코드를 가지고 테스트를 해보자. 우선 일목요연하게 정리된 보두이노의 핀을 보면 디지털과 아날로그 입출력의 핀을 볼 수 있다(http://www.ladyada.net/ images/boarduino/boarduinosch.png). 이 그림으로 본다면 디지털 입출력은 여유가 없이 매우 빡빡한 편이다. 이번 방법은 아두이노 예제의 LED의 구동(http://arduino.cc/en/Tutorial/ Loop)을 2차원 매트릭스로 확장하는 방법이다. 

    그러면 핵심적인 루틴만 정리해보자.  아주 간단하게 생각한다면 메인에 해당하는 루틴은 다음과 같다.

    void loop() {
      val = analogRead(potPin);
      amp = (val >= 512) ? val - 512 : 512 - val;
      if (amp < 100) {
      else if (amp <200 ) {
      else if (amp < 300)  {
      else if (amp < 400)  {
      else if (amp <= 512)  {
      face (6);
        delay (100); // 이 부분은 마음대로 변할 수 있다. 
       face(0) // 모든 표정을 지운다. 여기에 딜레이를 줄 수 있다.

    그렇다면 face라는 함수를 정의하면 될 것이다. face는 이해를 쉽게 하기 위해서 표정번호를 받으면 디지털 입출력으로 매트릭스를 표현한다. 우선 지난번의 코드를 보자.

    #define MAX_FACES 6

    byte faces[MAX_FACES][8] = {
      { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // empty
        0x00, // ----- 
        0x0A,  // -x-x-
        0x00,  // -----
        0x0E,  // -xxx- 
        0x00,  // -----
        0x00,  // -----
        0x00,  // -----
        0x00  // -----

    이 데이터를 디지털 IO 핀으로 출력한다. 여러 가지 정교한 출력 방법이 있지만 가장 간단한 방법으로 생각해보자. 다행히 매트릭스는 하나뿐이니 복잡한 방법이 필요한 것은 아니다. 매트릭스를 여러 개 사용한다면 래치를 사용하거나 일정시간 On이 되도록 스캔하는 방법이 있다. 이런 자료는 인터넷에 널려 있으니 가장 직관적인 방법만을 사용해 보자.

    우선 행을 스캔한다. 그러려면 void face(int face_no)처럼 정의되는 함수 face()의 동작을 생각해보자. 이를테면 face(0)는 첫 번째 데이터 어레이를 다룬다. 우선 데이터의 행을 스캔한다.  

    아두이노와 그 클론들에는 많은 유희의 요소가 들어있다. 우선 간단하게 줄일 수 있고 빠르게 만들기 가능하며 바꾸면서 놀기도 가능하고 문턱이 낮다. 문턱을 낮추기 위해 AVR의 능력과 C의 인터페이스를 간단하게 만들었다. 그러나 미니멀리즘은 간단하다는 강력한 장점이 있다. 아무런 부담 없이 놀이에 몰입할 수 있다. 그리고 얼마 이상 복잡한 일은 다른 개발도구를 써야 한다는 사실을 잘 안다. 그러나 실생활의 전기배선이 복잡하지 않은 요소로 많은 것들을 하는 것과 마찬가지로 독자들은 사실상 무엇이든지 만들 수 있다.

    매트릭스에 숫자를 표시하는 예제를 만들 수도 있다. 이를테면 100원대의 온도 센서 lm35같은 것으로 1도 증가하면 센서의 출력은 10mv 씩 올라간다. 필자는 이 센서로 앰프 방열기의 온도를 재었다. 아무런 부가 설비도 불필요하다. 방안의 온도도 알 수 있다. 그리고 숫자의 매트릭스를 만들어 +35C 같이 천천히 표시되는 장치를 만들 수도 있고 온도에 따라 표정이 변하는 텡구 클론 비슷한 것을 만들 수도 있다. 마이크에서 센서만 바뀐 것이다. 필요에 따라 릴레이를 달아 온도가 더 올라가면 전원을 꺼버리도록 만들 수도 있다. 몇 개의 센서 예제가 아두이노 사이트에 올라와 있다. 이들을 더 합치고 인터액션을 강화하면 이것은 정말로 다른 무엇으로 변한다. 이런 것들을 산업 교육받듯이 재미가 없는 기계로 만드는 것이 아니라 진지하기도 하고 장난감 같은 아두이노로 바로 만들어 볼 수 있다. 생각이 나면 바로 만들어 볼 수 있는 것이다. 달리 이만한 장난을 칠 수 있는 기계도 없을 것이다. 그냥 만지작거리고 있으면 할 수 있는 일들이 늘어난다. 그 다음에는 인터페이스라는 것이 별다른 것이 없다는 것을 알게 되고 AVR Studio 나 다른 개발 툴에 대해서도 문턱이 없어진다. 

    만약 아두이노를 벗어날 정도의 실력이 되면 다른 AVR 변종을 이용할 수 있다. 훨씬 작은 타이니 계열의 AVR들이 많이 있다. 이들은 기계어 코딩이 필요하지만 작은 사이즈로 다양한 일을 할 수 있다.  더 작은 패키징을 이용하면 AVR 이 부품인지 주 제어기인지 헛갈릴 정도다. 표현력의 자유는 극적으로 증가한다. LED와 배터리 그리고 전지를 포함하여 단추 속에 넣을 수 있을 정도다.


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    2009.08.20 02:12

    jlh evo 만들어보다.

    대단히 중요한 클래스 A 앰프의 자료의 보고인 
    에 보면 이 앰프의 변형에 대한 두가지 변형이 있다고 적고 있다,

    이 앰프는 40년동안 별로 변화없이 지겹도록 만들어지는 앰프인데 이만큼 많이 언급되면서 실제로 만들어지지 않은 앰프는 별로 없을 것이지만 많은 디자이너들에게는 영감의 원천이자 컴플렉스의 시작이었다. 

    개인적으로는 모든 변종을 다 만들어 보았다, 머리가 좋지 않으니 손으로 생각할 수 밖에 없다. 
    옵션 2를 만든 사람은 적어도 한명이 있다는데 내가 아는 한 한명 더 있다. (http://www.tinholt.eu/jlhevolution.htm)

    그리고 한명이 더 추가 되었으니 바로 나다. 
    대단한 일은 아니지만 역시 묘한 사람이라는 것을 입증한 셈이다. 

    For those who prefer the greater simplicity of the 1969 version, but wish to avoid the output capacitor (C2), the circuit can be modified to operate off dual supply rails. Figures 1 and 2 illustrate two methods of achieving this. It must be stressed that Option 1 has yet to be verified in practice (so far as I am aware), but Option 2 has been successfully implemented by at least one constructor.



    Figure 1. 1969 design with dual supply rails (Option 1)




    Figure 2. 1969 design with dual supply rails (Option 2)

    이 앰프의 두번째 버전은 Rudy Van Stratum 이 만들겠다고 하고 결국 몇년동안 변형을 가한 것인데  몇년동안 듣다보니 음질을 개선하겠다고 만든 것이다. 유럽 사람들의 질긴 면은 알아주어야 한다. 캐패시터를 바꾼는데 한참 세월이 걸린다.   이 사람은 네델란드에서는 유명한 오디오 평론가라고 한다.  이들이 쓰는 평론이 가볍지 않은 것은 다 이유가 있다. 

    아무튼 열이 펄펄나는 이 앰프를 나도 하나 갖게 되었다,  지금까지 만들거나 사본 앰프중에서는 최고였다. 

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