ÿþ<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns="http://www.w3.org/TR/REC-html40"> <HEAD> <base href="http://www.kennedyaudio.com/Amplifiers.htm"/> <title>Audio Full Bridge H-Bridge Amplifiers</title> <META content="audio class, buy preamp, balanced bridge, full bridge, H-bridge audio amplifier,preamplifier, slew rate, preamp prunella, archeon, sonic maximizer, buy online, DJ center, sonic maximizer, garbage in garbage out, line in, mixdown, big gig rig, amp classes, PWM, A/B, AB , quasi, transistor quadrature, sound image, vintage amplifier, impendance interface, PA studio monitor, live sound arrays, pro gear, treasury of light " name=KEYWORDS> <META content="Archaic Analog Components. Speaker and Sound Consulting, highend Systems." name=Description> <LINK REL="SHORTCUT ICON" HREF="http://site.kennedyaudio.com/favicon.ico"> <DIV> <FONT color=#909090 size=22> </HEAD> <style type="text/css">body {background-image:url(http://www.kennedyaudio.com/archeonbg.JPG);background-attachment:fixed;}.bkgspc {margin-top:10px;color:#909090;font-size:11px;font-family:Arial;}.bkgspc a {color:#909090;}</style><div class="bkgspc" align="center"> </div> <style='margin-left:0.8in;tab-stops:22.0pt'><span style='font-family: Tahoma;color:azure'> <FONT color=azure size=31> <p class=MsoNormal style="BORDER-RIGHT: 440pt; PADDING-RIGHT: 0.950in; BORDER-TOP: 0pt; MARGIN-TOP: 0.6in;PADDING-LEFT: 2.0in; PADDING-BOTTOM: 0.0in;PADDING-TOP: .0in; Margin-LEFT:0.8in"> <SPAN style="MARGIN-LEFT:-0.8in;FONT-SIZE: 31pt; width 8in; COLOR: azure; FONT-FAMILY: 'Haettenschweiler'; mso-bidi-font-size: 44.0pt;background-color:#grey"> Archeons, the human to light speed interface. </font> </span> </p> <p class=MsoNormal style="PADDING-RIGHT: 0.0in; BORDER-TOP: 0pt; MARGIN-TOP: 0.0in;PADDING-LEFT: 0.0in; PADDING-BOTTOM: -.0in;PADDING-TOP: .0in; Margin-LEFT:0.8in"> <SPAN style="MARGIN-LEFT:0.73in;FONT-SIZE: 18pt; COLOR: #AD3500; FONT-FAMILY: 'Tahoma'; mso-bidi-font-size: 12.0pt;background-color:#CCDC"> <BR> <FONT size=23 Margin-Left:0.0in> <SPAN style="MARGIN-LEFT:0.4in;FONT-SIZE: 23pt; COLOR: #22; background-color:#CCDD"> Ancient Mystical Knowledge and its Light Speed Audio Analog.<BR> </font> </span> <SPAN style="MARGIN-LEFT:0.5in;FONT-SIZE: 14pt; COLOR: #150; background-color:#CCDD"> <BR> Many folks don't need a lot of knowledge of amplification to obtain a 'hi fidelity' sounding sonic field.<BR> People do need to know a lot about sound to be sure the amplifier and preamplifiers provide quality sound.<BR> An Amplifier that uses a preamplifier is called an archeon. The Name originates from what Hollywood movies<BR> like to call 'ancient greek literature', but what is actually egyptian crypt texts about the tens years after<BR> the reserection of Jesus of Nazareth and the knowledge given during that time to his disciples. It also fits<BR> the ergonomic idea that humans interface to high speed signals most often by using this part of the audio,<BR> sometimes in the form of mixers which acts as a preamplifier. Lastly, the name archeon is associated with abstract<BR> kinds of 'bad boys' in the greco-roman-egyptian gnostic literature and all the divisions of spheres of powers.<BR> What Jesus said in cryptic gnostic terms is 'I will teach you to worship all our species' which is why a fish <BR> appears in ancient times as the symbol for the followers of Jesus who knew and understood the scope and context.<BR> It was not the same as 'I will make you all the fishers of men' as translated by the traditional Hebrew bible.<BR> Jewish scholars of that time and centuries after did not want their people to hold other non-Hebrew cultures<BR> or life forms in as high regard as their own, due to restrictive food preparation practics and other concerns.<BR> <BR> What does this all have to do with preamplification or maybe pre-emplification? People would be very surprised<BR> to hear a power amplifier all by itself and then again with a good preamplifier. The difference "goes beyond just <BR> incredible", as one television advertisement states in compressed and limited TV mix audio. It gives new meaning to<BR> the principle of the inclined plane. Sound quality takes real work too. It is very sensitive to processing. <BR><BR> Hollywood avoids any reference to real Egyptian classics like the 3rd and 4th century gnostic scrolls found<BR> in Egypt, perhaps because movies like Star Wars would appear as obvious re-writes as would many characters<BR> found in western Christian style religious mythologies and litergical traditions. Princess Leia, for instance,<BR> is a little bit like a stunt double for the character of Pistis Sophia in the gnostic (knowledge) texts.<BR> <BR><BR> I pass this secret knowledge as a gift to the world only because I have found no mate and grow too old.<BR> My family name, which means man of (father or 'the god') Sphinx, enabled me to channel this and my experiments<BR> in achieving a better way of making cinema sound, to come from the idea stage into an actual embodiment.<BR> It was the Sphinx that gave us the Rosetta Stone, found cradled between the front paws, and thus revealed <BR> the true origins of human knowledge as well as beliefs. But Sphinx was never recognized or elevated as the <BR> God of knowledge that he was to the ancients. Today the most ancient God of man is refered to only as 'The Sphinx'<BR> as if the carving, the sunken placement which was it's genius and real 'guardian' agains invasive forces, was a <BR> mere footnote in the history of mankind rather than the one central point around which our existance revolves.<BR> The Quintessence of it's head, which may have once been the face of God himself, was defaced by an Arabic <BR> religous fanatic, in the Muslim tradition. <BR> <BR> Experiences with preamplifiers is often a little mysterious too, even for professionals. To begin with,<BR> there are newer standards for interfaces as every generation of technology makes its own revolution.<BR> Right now, a transition to +20dBu output (in Europe +18dBu) is gaining acceptance. As you might expect if you<BR> have experience, this will pretty much burn up any sensitive power amplifier designed for plus +4dBu and burn<BR> the right channel of the prolific minus 10dBV consumer grade power amplifiers, stereo surround sound or auto amplifiers.<BR><BR> The semi-pro -10dBV amplification runs out of headroom and sounds strained. The only solution is to go digital.<BR> If you have a lot of CD's recorded at older peak standards, you need digital conversion with sensitivity control.<BR> Just to begin with, the CD's signal for -10dBV is only 1/4th that of +4dBu, or about 0.447 peak volts.<BR> These new standards were intended to allow digital equipment to match the extra loundness for peak signal<BR> called headroom that is available in analog standard recordings, such as CD-R or vinyl. The result has beeen<BR> unexpectedly bad. The difference between live sound requirements and post-production was not anticipated.<BR> What is required is switchable gain structures or adjustable sensitivities, and there are no sound cards <BR> at all that have such features. These are only found on expensive studio digital mixers or KennedyAudio.com<BR> amplifiers and pre-amplifiers, or at least their analog counterparts are found there. <BR><BR> Standards for interfaces changed away from the telephone standard of <A onmouseover="ddrivetip('Open up explanatory window (/EQ)')" onclick="return opensecond()" onmouseout=hideddrivetip() href=http://www.kennedyaudio.com/Amplifiers.htm ; > 'equalized' </a>(early term for balanced)<BR> sound at 1 volt and 600 ohms (DC resistance of isolation primary coil later revised to 1000 for -10dBv<BR> to best match transistorized frequency equalization profiles and stereo systems) in the 1960's. Since then,<BR> audiophiles have been chasing the rare input impedance matching transformers at great expense and effort. <BR> Here we go again.<BR><BR> The weakness in the right channel has to do with the balancing of circuits, even though a power amplifier in<BR> solid state is rarely spoken about in terms of its balanced versus unbalanced design. The reason is that with<BR> a power amplifier that does not use an internal or an external preamp, sound is not changed so much just because<BR> of the way that the circuit works. But it needs to be changed. The typical source is unbalanced and a good <BR> example of Garbage In - Garbage Out. Think of a speaker as a motor. It can be driven forward or reverse.<BR> The source will give you only forward drive and complete the cycle on one wire, the other is neutral or ground.<BR> One way a preamplifier works is to convert the 1.4 volt unbalanced single line signal into balanced 2 lines.<BR> This restores the ability to provide more current for the power amplifier, which would lack bass tone otherwise.<BR> Often the preamplifier does more than just that. For instance the power supply it uses effects the sound quality.<BR> Tube preamplifiers have been popular where low sensitivity power amplification is used. They are tolerant to <BR> overdrive voltage distortion and can also provide underpowering distortion if wanted, but they make more noise.<BR> Still, if the signal coming in is intended to sound square wave, metalic and distorted or noise like, this is OK.<BR> With consumer grade unbalanced power amplifiers, the mismatch between 4 ohm speakers when 8 ohm is the design<BR> target is much less of a mismatch than if the power amplifier were a full bridged design. More possible <BR> variations on a basic design type of power amplifier are possible while holding constant the output matching<BR> to speaker impedances. Therefore the muliple taps for 8 ohm and 16 ohm speakers became obsolete long ago.<BR> There are so many factors related to saving either the speakers from overload or the power amplifier that <BR> the mystique of otherwise well understood solid state amplifier technology is safe for a long time to come.<BR> <BR> In almost any case - the <i>character</i> of sound is added into and enhanced or 'colored' or contoured<BR> into the signal by pre-amplification of some kind. That can be a small 1 volt internal preamplifier which makes<BR> the power amplifier into what is called an integrated amp. It can be a maxmimizer used by many DJ's to drive<BR> a Crown amp into JBL speakers, the a common match right now. It can be a mixer or digital signal<BR> processing unit <B>(DSP)</B> in either hardware or software inside a computer or sound card. Signals can be<BR> changed to sound like a musical instrument of any kind by virtual signal transforms <B>(VST)</b> or into any <BR> amplification system from mechanical pipe organ all the way through classic guitar amps with tubes or transistors<BR> to Moog synthesizers oscillators and filter waveshapers and effects. A complany called Line 6 offers a wide line<BR> to make a guitar into anything from the Mesa Boogie used in Smoke On The Water by Deep Purple to the sound of<BR> the London Symphony Orchestra's Steinway piano. All this is done with as little as a single 'LINE INPUT'.<BR> <BR> With the exception of tubes (versus solid state discreet transistors and transistor arrays; op-amps)<BR> all this sound change comes from the preamplification stage, which spans from about 1/2 volt to 1.4 volts<BR> for amplifiers under 25 watts to about 10 volts for higher power applications. Another exception is the<BR> general rule that without any preamplifier, you will get a kind of sound that ignores entirely any sub-sonic<BR> input and responds at nearly inaudible levels to any input signal below 40 hertz. But that exception applies<BR> only to solid state devices. This fact has to do with the physics of a semiconductor, which is what a solid<BR> state transistors is. It is a barrier to the passing of high power through it. The signal changes the state<BR> of the device so that power can pass through it. Amplification is achieved by allowing power to flow.<BR> <BR> A tube amplifier uses a heated wire between two plates or grids. The wire is giving off electrons as it glows<BR> and the signal is made to pass through it by the differences in the positive draw and excessive electon count<BR> push on the plates. Amplificaion is achieved more like a pump. The term valve was used for tubes so long ago<BR> that the name stuck, when really a semiconductor acts like a valve in liquid and hydraulic power transfer.<BR> <BR> We just covered a lot of technology, but what we said was that higher frequency sounds and mid-band music<BR> pass easily through any amplification system. You can plug a CD player directly into a power amplifier of<BR> any kind and its 1 volt output at a few thousandths of a ampere of power will be enough to enjoy the music's<BR> so called hi-fidelity content. <B>All that you will miss is the bass and mid-bass</b> (preamp prunella) and of course, <BR>the music will sound much less enjoyable than <B>IF</b> you had a pre-amplifier. Does it always sound better<BR> with <i>any</i> pre-amplifier? The short answer - yes. The long answer involves the unavoidable complication -<BR> that what sounds good may not actually be good. It's just like high calorie foods that taste good but are<BR> really bad or smoking a cigarette that feels good but may not be, or even like hitting your thumb with a hammer<BR> to drive a nail when it gets the job done but does more damage than the job is worth sacrificing. Signal sounds<BR> cold without some form of enhancement. It sounds even more cold in solid state than in tube ampifiers, but it<BR> also sounds chilled in tube amplifier that do not use a seperate tube pre-amplifier stage before the driver tube(s).<BR> The amount of stereo image - that aspect that makes it sound spread out in space with different point sources -<BR> can not be achieved without both sensitive speakers as well as a 'fast' or high <A onmouseover="ddrivetip('Open up explanatory window (/slewrate)')" onclick="return openxplain()" onmouseout=hideddrivetip() href=http://www.kennedyaudio.com/Amplifiers.htm ; > 'digital slew rate' </a>amplification system.<BR> The rise time of higher speed signals often exceeds the ability of tube amplifiers to respond, as is the case<BR> if they are fed a triangle wave from an audio oscillator. But because this kind of distortion is one example<BR> of a distorted signal that sounds better than its original analog it can be used to add a seperate track or to<BR> mix with an existing signal or even to limit the rise time requirements for accurate playback on any given mixdown.<BR> Many sound enthusiasts don't care much about slew rate because they know this specification only has an impact <BR> on higher frequency sound reproduction, and their focus is mostly on bass. Dance floors just do not use much<BR> midrange and tweeter or horn drivers. They buy amplifiers with easy EQ interfaces built in for computer control<BR> and special presets for JBL speakers, which Crown has provided for a very long time for bar and DJ rig owners.<BR> The ability to be stable down to 2 ohms may not be popular either as a portable big gig rig should probably<BR> use the high power bass driver amplifiers in bridged mode rather than in stereo mode, to be fully balanced.<BR> This is why we sell the Kennedy 500 as a bass guitar instrument amplifier, in single channel, even though <BR> if someone wanted to use it in DJ rigs, a second channel could be added for another $500. This covers the cost<BR> of hand selecting and matching the extra 6 bipolar transistors, a second fan and its layout heatsink and assembly.<BR> One advantage of doing that would be to use crossovers at the speakers, which we do not usually recommend.<BR> Recently we compared out 2228h with a Fane, crossed over to 2 mids/tweets and driven in parallel with the JBL.<BR> The result was very favorable. Even though we sell crossover units for the preamplifier line level, there is <BR> an old school of thinking that likes the extra protection and access to crossover capacitors for reliability.<BR> <BR> The majority of pre-amps are made just because they add lots of distortion, carefully chosen to give a character<BR> to hardware devices. This means that a good signal going in can be changed into a 'better' one and a garbage signal<BR> in can be an acceptable signal coming out. That is the advantage of signal distorting highend pre-amplifiers.<BR> It is also the reason why it is so hard, actually impossible, to find a slew rate of a power amplifier that has<BR> a voltage slew rate matched to its own wattage output and to its target preamplifier. Only KennedyAudio.com does <BR> that. Of course digital signal processing lets users select the type of distortion added and compression in many<BR> cases, but whenever they do not, the listener is not informed that the signal coming in has been altered or in what way.<BR> <BR> It's just that tubes often do not get scrutinized because the pre-amplifier is almost always integreated into the<BR> same houseing or box as the power amplifier. The signal needs to be expanded and routed to different transducers.<BR> A DJ will always want to expand the bass into a gutt punching shock wave in addition to getting the bass section to<BR> sound louder than the midranges. Then again, a disco DJ just might not want so much emphasis on the bass or the<BR> punch, but want to allow midrange as long as it doesn't make everyone on the floor go home with a headache and<BR> bleeding ears. But some people get headaces from too much bass and don't have a problem with midrange and highs.<BR> This is the equalization and crossover network. Some form of it is almost always found in preamplification.<BR> And in addition, many vintage stereos used crossovers after the power amplifier as well. This helped in name<BR> branding and recognition. It helps give users the size of speaker boxes they want with the power they want to pay<BR> for and the speaker sensitivity that they prefer.<BR> <BR> They often prefered lower sensitivity speakers, so crossovers and dividers were common at the transducer stage.<BR> Capacitive filters are still used and always will be at the speaker stages because they defeat the bass signal<BR> and pass the upper range high power signal and thus enhance and protect valuable speakers. They appear on the<BR> treble transducers where the cost of the capacitor is lowered because the voltage going to the speaker,<BR> and certainly the wattage, may already be <B>buffered</B> by a midrange speaker that is in parallel with it,<BR> making the pair of mid/treble tweeter and bass driver a simple 2 way system, by subdivision into another sphere<BR> of power or into a four way matching response system. Only by doing that the <B>Treasury of Light</B> that is<BR> hidden inside the signal can be revealed in its full beauty and impressive potential.<BR> <BR> <FONT color=#568668 size=12 Margin-Left:0.0in> <SPAN style="MARGIN-LEFT:0.8in;FONT-SIZE: 23pt; COLOR: #560123; background-color:#grey"> Decisions and Choices. The more modern and the<BR> </span> <SPAN style="MARGIN-LEFT:0.8in;FONT-SIZE: 23pt; COLOR: #560123; background-color:#grey"> Vintage Name Branded Options. </span> <BR> <BR> <SPAN style="MARGIN-LEFT:0.73in;FONT-SIZE: 14pt; COLOR: #AD8550; FONT-FAMILY: 'Tahoma'; mso-bidi-font-size: 12.0pt;background-color:#CCDC"> It starts to become a little unwieldy when decisions must be made about preamplifiers. There are many factors<BR> to consider. For one concern, the power amplifier spans a <B>wide sensitivity range</b> just like speakers do, and that<BR> number can make a difference between sound that the ear can barely hear to having the windows of a house explode<BR> outward from the pressures. Some amplifiers respond down to one millivolt. These are the best and most versatile<BR> to match to any speaker, but they also pick up any noise on the incoming signal. So, it may be not be possible<BR> to use amplifiers with something like a very compact and high gain to watt ratio voltage controlled amplifier <B>VCA</B><BR> unless the signal is made to pass through a noise filter. Most informed decision makers would opt not to use a<BR> noise filter but to change the pre-amp to better match the more expensive and hard to find power amplifier.<BR> This choice is especially true because, by the time one gets up the price scale to high sensitivity amplification,<BR> there have been many other possible choices, one of which is to change out all capacitors on a vintage amplifier.<BR> <BR> Potted VCA's where the circuit is not accessable will not allow noise filters to be added to the input section.<BR> All this so far, we have said because it applies to the kind of power amplifers that Kennedy Audio designs.<BR> We feel that we like to tell our fans and customers what they need to know rather than what they want to hear,<BR> but even if we were not so concerned about them, we would need to give them some guidance anyway, just because<BR> we do not expect them to buy every component that comes between their sound source player and their ears from<BR> us, using online buying and search engine based advertising and web tool based marketing. We think that in time,<BR> many DJ's who haul around heavy amplifiers and speakers will realize that our units provide efficiency of choices.<BR> Our units weight is comparable and so is our speakers weight, but you don't need another unit for the horn set.<BR> Also, given a choice between buying and carrying 2 JBL horns or two seperate treble amps/preamps, choose horns.<BR> <BR> There are different classes of amplifiers. Are there classes of preamplifiers? No. Why not? Well its complicated<BR> and involved. How many famous guitar players use solid state amplifiers? Can any of your friends name one? No.<BR> Why not? Well, it is complicated and involved. There are almost no solid state pre-amplifiers that a guitar player<BR> can try. A few do come to mind; Marshall, Peavey, Digitech, the HH 'MA80', Traynor '/Group One'.<BR> These last two that I happen to own, but I think it unlikely that any reader of this article owns one or ever even<BR> heard of them. The most obvious reason is that to get sales and accelerate sales growth, it pays the builders of<BR> amplifiers to put a pre-amplifier into their power guitar amplifiers and just sell it as either a branded kind of<BR> sound or else some boutique model of special interest. Most are tubes or digital. When solid state, they are pedals.<BR> But solid state's compactness allows us to build a great full cabinet H-bridged 75 volt/microsecond slew preamplifier.<BR> The preamplifier is tested with Kennedy amplifiers and signal frequency splitters and works for everything, not just guitars.<BR> <BR> Pre-amplifier classes would likely be split into op-amps and discreet transistor classes, the second of which could<BR> be very small and fit on the head of a pin, or the tip of the pin of you don't need much wattage. You could make a<BR> quick third class with tubes. If you get creative you could say that voltage controlled amplifiers are a class because<BR> they offer a new way to interface and control the signal, but then you are really not talking about HOW they amplify<BR> but how you as a person act. And that makes the discussion turn into one about Archeon classes.<BR> <BR> It is easier and less unwieldy to use the idea of Archeon classes instead of power amplifier's class. Just to begin<BR> a discussion of why this is better, I could ask the reader what class that they would guess that a MOSFET power<BR> amplifier would most often be? Would you guess class-A? Perhaps one that could switch at about 680 milliampes or<BR> say 60 watts from pure class-A into class B mode where it can supply more power - just like the Kennedy Audio 500<BR> used to be built?<BR> <BR> What is class A/B? Hint - the Kennedy 500 was not MOSFET but bipolar transistor based. You already know<BR> it was at that time a class A/B, but now stays in A-class with better control of the offset bias. So are there any<BR> class-A MOSFET amps? The MOSFET is the lowest distortion transistor type and very powerful. Another hint- they<BR> have a tendency to get very hot. So are they usually not class-D which most car amplifiers are. Who wants a hot<BR> amplifier in their trunk. Ok, then consider that they have a tendency to actually blow up in a little explosion<BR> of sorts. You are right, they are never used as class-D. Stereo enthusiasts love them and use them a lot.<BR> Sterophiles almost always end up buying class A. You are right, again, MOSFETs are NOT class-A. The industry gives<BR> them a number of other classes : F, H, or often they avoid the term class and just say it is 'good'; a 'workhorse'.<BR> <BR> They take the power that the transistors are capable of switching and say that this is how may watts of power the<BR> amplifier has, and, what can match that in your 'class' kinds of amplifiers? If we did that, Kennedy audio's 500<BR> watt amplifier in bi-polars would them become an instant 1600 watt and we would not have to change anything but to<BR> add 1600 watts to a decal sticker or front bezel or foil hotstamp. This is why efforts by the Federal Trade Commission<BR> and to get amplifier manufacturers to rate their wattages in some intelligent and consistent way have all failed.<BR> Auto amplifiers that do not use the transistor power often rate their amplifiers at 0.5 percent distortion. <BR> The Kennedy amplifier is rated at 500 watts which is essentially its distortionless output or at about .05 percent.<BR> Of course, to be fair, any amplifier used in a noisy enviroment like an auto interior does not need to be rated<BR> at its clipping onset, but that depends on how it sounds when clipped. Some clipping is good to listen to for a while,<BR> but long term exposure can be a bad idea. So, an amplifier used in a Mac truck rated this way may be OK while the<BR> same amplifier installed in a Kenworth Texas large car cruiser would be a very poor choice of applications.<BR> <BR> It depends too much on the characteristics of the power amplifier that you make and sell the most of, and to whom.<BR> If that happens to be MOSFET, it would be a very bad idea to go along with the crowd and use the terminology of amp<BR> class rather than wattages because that would favor the competition. If purely signal PRE-amplifiers, which we<BR> have just explained, are the important factor concerning tayloring sound character to what you need or would<BR> like to even explore, then how bad is it going to get when we start talking the talk and walking the walk of the<BR> general amplifier classes? What we need to understand is the entire Archeon spheres of power contouring, their <BR> interface standards and versatility. We need a way of speaking about them in generalizations, not power alone or<BR> their circuitry's quadrature controls.<BR> <BR> We could classify archeons as microphone pre-amps and guitar pre-amps or music and movie playback pre-amps. <BR> All three of these have a wide enough range of prices, types, styles, output volts and milliamps.<BR> The sound of a microphone is said to be highly corelated to the speaker or singer's voice, making it<BR> a very personal preference to many professionals. That would leave out the automotive crowd, which may not<BR> be such a bad thing, unless we started with the typical speaker sensitivity, which in automotive would be<BR> the very lowest sensitivity. Why don't we try that. We can keep class D for them, make class miCrophones<BR> and class B archeons for Bass and other guitars. Class A, which is obsolete in this digital age could then be<BR> reserved for the mostly digital and DSP intensive pre-processed and compressed sphere of power which<BR> is the movie, 2 inch standard tape mastered sound. A reel to reel tape has on it at least 10 times more<BR> information that is captured by 24 bit sound samples taken at a rate of 96 kilohertz per second.<BR> This is why any recording studio from Nashville to Hollywood is making their first recording of any artist<BR> group using the good old reel to reel magnet tape.<BR> <BR> Of course the method of capturing, whether magnetic or digital, has nothing directly to do with what output<BR> impendance or input resistances are used on the inputs of any device. A tube will use resistances on the<BR> inputs of 240 KilaOhms to match it with what signal is coming in, and requires an output transformer to go<BR> out in almost all cases with some special long cable exceptions, but they use a transformer at the input end<BR> of the receiving device anyway. The tube power amplifier doesn't know if the input will be balanced or unbalanced.<BR> It can provide for both in a simple way, or by adding a center tap transformer, for which Jensens are well known,<BR> to make an ideal match for either type of input. The same holds true as we go down the line from high impendance<BR> tubes to the highly eclectic +20dB equipment with lower input matching to plus 4 so called Pro audio to the<BR> consumer grade minus 10dBV. <BR> <BR> </span> <BR> <FONT color=#560123 size=23 Margin-Left:0.0in> <SPAN style="MARGIN-LEFT:0.8in;FONT-SIZE: 23pt; COLOR: #560; background-color:#grey"> The more modern Archeon Amplifier Classes terms.<BR> </span> <SPAN style="MARGIN-LEFT:0.73in;FONT-SIZE: 14pt; COLOR: #C55; FONT-FAMILY: 'Tahoma'; mso-bidi-font-size: 12.0pt;background-color:#ADCOFF"> <BR> It will become aparent that efforts to link archeon to classes results in what is really a span of classes that<BR> any given archeon would work well for. A microphone pre-amp (class C) could be used as a guitar pre-amplifier,<BR> which would be a class B. Likewise a class-A pre-amplifier is often so close to a bass guitar amplifier, that<BR> it becomes a sticky wicket to differentiate a class A archeon from class B archeon. <BR> <BR> The best solution if we stick with common sense and commonly used terms of a more modern age of here and now<BR> is to discuss interfaces that change sound as <B>class A/B</b> and <B>class C/D</b> and then class <B>E/D</b>, the E for<BR> and others that are too compact, weak, noisy or insensitive to be used class A power/preamped system amplifier, <BR> or if the would unlikely be biamped into a splitter circuit application. We want to use the term Class-A to relate<BR> to accessability of the inputs to the preamplifier section, both to assure the ability to interface a wider range of<BR> devices and to eliminate noise. A classic example is a guitar foot pedal, which acts as a pre-amplifier but is usually <BR> easy to bypass.<BR><BR> Then, if we would wish to talk only about power amplifiers, a Pure Class-A means one with a slew rate that <BR> is high enough for the .05 percent distortion output sine wave supplied either integrated or seperately <BR> with a matching slew rate preamplifier, both having more than one possible input impedance or balancing.<BR> Class B would be NOT <B>B</b>ridgable, but otherwise highly sensitive amplification and high wattage hi-S Speakers.<BR> The wattage requirement should depend on slew rate, but there is no good standard for amplifier wattages.<BR> Because transistors are widely available at 50 Million Volts/Second this should be used as A-1 typical. <BR> Keeping the quality control meaning of the word typical, it means everywhere, then both amp and preamp<BR> are A1 and if not it is Archeon A-2. Again, A for access, number following for higher slew, broad band.<BR> <BR> The D would indicate an amplifier built to digital circuit standards. These are not repairable at the<BR> component level. Even a small spot of solder would add too much capacitance to the delicate connection<BR> for the signal to remain acceptable. Auto already uses class-D so this is not confusing. Class A/B would<BR> now be used wherever high sensitivity speakers AND high sensitivity amplifiers are used, but only along<BR> with an open, transparent 'above board' preamplifier. Thus the preamplifier, if built in, should have some kind<BR> of controls beyond just bass boost, which is normally added by preamplification or even a 1 to 1 buffer stage<BR> with no amplification at all.<BR> <BR> Class B/C would be less sensitive, for more line noise, poorer shielding or tubes, but still capable of capturing<BR> tiny currents. Guitar output and microphone output, phonograph preamplifiers and amplifiers would fit there. <BR> This category rarely uses such ear output combined sensitivity levels like 116dB JBL 2 inch horns or the 103dB Kennedy<BR> reproduction of the JBL 2228 wide range transducer, they do not fit into class A/B. They may fit into class B or C<BR> if such an equipment upgrade was being considered. Theaters and arenas with loud sound could easily fit into<BR> class B such as a public address systems that rarely need digital processing but nevertheless need noise guarding<BR> and feedback controls that restricts it from a class-A rated system. A good guitar rig could become class-A if <BR> it were open to either multiple signal level input or modification of existing jacks and impedance matchings.<BR> <BR> We admit, this is all pretty simple and basic. If you want to talk to a sales person intelligently about buying<BR> a McIntosh higher end 6550 tube amplifier and you know you want a silky sounding midrange and sweeter sounding<BR> square waves with lots of compression, a very flat and accurate profile to reproduce the original, even to the point<BR> of monitoring the signal for a decision on which your reputation as an agent of the final approval of a mixdown rests,<BR> this information will leave you a little short of the required pre-requisite course in H-bridged power output with<BR> and without the intents of the designer to allow a stereo two channel amp to be bridged into one channel, and the<BR> speed or slew rates of the preamplifier to power amplifier ratio, the signal to noise and minimal required filtering<BR> for the full balanced Jensen +4dBu input section with humbucker lifting of the center tap as an option and DC offset<BR> digital readout and fine adjust with negative fee-dB-ack phase control both front panel mounted for quick adjust and<BR> maybe a few other goodies you will need to survive in your job as an artist's audio approval quality consultant.<BR> <BR> So, you may ask, how could your reputation ever be at stake if you have good ears, listen a lot and test for noise?<BR> Well for one thing, the idea of a 'flat' sound profile is not the same thing as the idea of an equally damped flat profile.<BR> That is to say, just a scan of frequencys showing equal input is resulting in equal sound output does not tell you IF<BR> and this is a BIG if, the same equality holds when the input is only loud treble versus the level of loudness when<BR> for purposes of explanation, the input is only soft low sound pressure bass notes. Digital has a problem with that ratio<BR> due to what has now, in the digital age, become known as 'headroom'. In the old school days, headroom meant that, if a<BR> boosting circuit or a specialized note of music needed to include extra harmonics beyond the usually highest 3rd or 4th,<BR> up to the 7th or 9th harmonic of instuments like Tuba, the system would not attenuate it, which is why vinyl records<BR> with high hi (impedance) sensitive needles was considered to be a fine source for recorded music playback.<BR> This in spite of the obvious intrusion of having to reset the needle manually for many record changes.<BR> For tape media, headroom meant the highest frequency that tape, and later metalized tape, could retain magnetically. <BR> The emphasis was, clearly, on distribution of concept, not on satisfaction, and not on wise buying or administrating.<BR> <BR> But at least now you know enough to understand why so much jargon gets tossed around so fast, and why we decided<BR> to build a pre-amplifier as a seperate unit to match as best as possible the timeless Kennedy 500 single channel<BR> voltage and current drive power amplifier; and, of course, why we built the preamplifier in stereo.<BR> <BR> For reference,<BR> <A href="http://www.kennedyaudio.com/OldAmplifiers.htm"> here is an article on power amplifiers we have been using for 5 years now </a><BR> and plan to phase out as we add more information about the Kennedy Audio Dark Arts / Quintessence pre-amplifier itself<BR> and as an Archeon for other forms of audio control.<BR> </pre> <br> <BR> article by KA webmaster : John R. 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