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    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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    With respect to audio, distortion refers to any kind of deformation of an output waveform compared to its input, usually clipping, harmonic distortion, or intermodulation distortion (mixing phenomena) caused by non-linear behavior of electronic components and power supply limitations.[3] Terms for specific types of nonlinear audio distortion include: crossover distortion and slew-induced distortion (SID).
    Other forms of audio distortion are non-flat frequency response, compression, modulation, aliasing, quantization noise, wow and flutter from analog media such as vinyl records and magnetic tape. The human ear cannot hear phase distortion, except that it may affect the stereo imaging.
    https://en.wikipedia.org/wiki/Distor...dio_distortion

    Cancellation of even-order harmonic distortion
    Many symmetrical electronic circuits reduce the magnitude of even harmonics generated by the non-linearities of the amplifier's components, by combining two signals from opposite halves of the circuit where distortion components that are roughly the same magnitude but out of phase. Examples include push-pull amplifiers and long-tailed pairs (differential amplifiers).
    https://en.wikipedia.org/wiki/Distor...nic_distortion

    Symmetrical push–pull
    Each half of the output pair "mirror" the other, in that an NPN (or N-Channel FET) device in one half will be matched by a PNP (or P-Channel FET) in the other. This type of arrangement tends to give lower distortion than quasi-symmetric stages because even harmonics are cancelled more effectively with greater symmetry.

    Square-law push–pull
    The output devices, usually MOSFETs or vacuum tubes, are configured so that their square-law transfer characteristics (that generate second-harmonic distortion if used in a single-ended circuit) cancel distortion to a large extent. That is, as one transistor's gate-source voltage increases, the drive to the other device is reduced by the same amount and the drain (or plate) current change in the second device approximately corrects for the non-linearity in the increase of the first.[9]

    Super-symmetric output stages
    Employing some duplication in the whole driver circuit, to allow symmetrical drive circuits can improve matching further, although driver asymmetry is a small fraction of the distortion generating process. Using a bridge-tied load arrangement allows a much greater degree of matching between positive and negative halves, compensating for the inevitable small differences between NPN and PNP devices.

    Push–pull tube (valve) output stages See also: Valve audio amplifier – technical The push–pull power amplifier

    Vacuum tubes (valves) are not available in complementary types (as are pnp/npn transistors), so the tube push–pull amplifier has a pair of identical output tubes or groups of tubes with the control grids driven in antiphase. These tubes drive current through the two halves of the primary winding of a center-tapped output transformer. Signal currents add, while the distortion signals due to the non-linear characteristic curves of the tubes subtract. These amplifiers were first designed long before the development of solid-state electronic devices; they are still in use by both audiophiles and musicians who consider them to sound better.

    Vacuum tube push–pull amplifiers usually use an output transformer, although Output-transformerless (OTL) tube stages exist (such as the SEPP/SRPP and the White Cathode Follower below).[citation needed] The phase-splitter stage is usually another vacuum tube but a transformer with a center-tapped secondary winding was occasionally used in some designs. Because these are essentially square-law devices, the comments regarding distortion cancellation mentioned above apply to most push–pull tube designs when operated in class A (i.e. neither device is driven to its non-conducting state).

    A Single Ended Push–Pull (SEPP, SRPP or mu-follower[10]) output stage, originally called the Series-Balanced amplifier (US patent 2,310,342, Feb 1943). is similar to a totem-pole arrangement for transistors in that two devices are in series between the power supply rails, but the input drive goes only to one of the devices, the bottom one of the pair; hence the (seemingly contradictory) Single-Ended description. The output is taken from the cathode of the top (not directly driven) device, which acts part way between a constant current source and a cathode follower but receiving some drive from the plate (anode) circuit of the bottom device. The drive to each tube therefore might not be equal, but the circuit tends to keep the current through the bottom device somewhat constant throughout the signal, increasing the power gain and reducing distortion compared with a true single-tube single-ended output stage.

    The White Cathode Follower (Patent 2,358,428, Sep 1944 by E. L. C. White) is similar to the SEPP design above, but the signal input is to the top tube, acting as a cathode follower, but one where the bottom tube (in common cathode configuration) if fed (usually via a step-up transformer) from the current in the plate (anode) of the top device. It essentially reverses the roles of the two devices in SEPP. The bottom tube acts part way between a constant current sink and an equal partner in the push–pull workload. Again, the drive to each tube therefore might not be equal.

    Transistor versions of the SEPP and White follower do exist, but are rare.
    https://en.wikipedia.org/wiki/Push%E...h%E2%80%93pull

    A bridge-tied load (BTL), also known as bridged transformerless and bridged mono, is an output configuration for audio amplifiers, a form of impedance bridging used mainly in professional audio & car applications.[1] The two channels of a stereo amplifier are fed the same monaural audio signal, with one channel's electrical polarity reversed. A loudspeaker is connected between the two amplifier outputs, bridging the output terminals. This doubles the available voltage swing at the load compared with the same amplifier used without bridging. The configuration is most often used for subwoofers.[2]
    https://en.wikipedia.org/wiki/Bridge...dged_amplifier


    With two inputs and two outputs, this forms a differential amplifier stage (Figure 2). The two bases (or grids or gates) are inputs which are differentially amplified (subtracted and multiplied) by the transistor pair; they can be fed with a differential (balanced) input signal, or one input could be grounded to form a phase splitter circuit. An amplifier with differential output can drive a floating load or another stage with differential input.
    https://en.wikipedia.org/wiki/Differ...ng-tailed_pair



    Some hobbyists who prefer class-A amplifiers also prefer the use of thermionic valve (tube) designs instead of transistors, for several reasons:
    Single-ended output stages have an asymmetrical transfer function, meaning that even-order harmonics in the created distortion tend to not cancel out (as they do in push–pull output stages). For tubes, or FETs, most distortion is second-order harmonics, from the square law transfer characteristic, which to some produces a "warmer" and more pleasant sound.[7][8]
    For those who prefer low distortion figures, the use of tubes with class A (generating little odd-harmonic distortion, as mentioned above) together with symmetrical circuits (such as push–pull output stages, or balanced low-level stages) results in the cancellation of most of the even distortion harmonics, hence the removal of most of the distortion.

    Historically, valve amplifiers were often used as a class-A power amplifier simply because valves are large and expensive; many class-A designs use only a single device.* Transistors are much less expensive than tubes so more elaborate designs that use more parts are still less expensive to manufacture than tube designs. A classic application for a pair of class-A devices is the long-tailed pair (differential amplifiers), which is exceptionally linear, and forms the basis of many more complex circuits, including many audio amplifiers and almost all op-amps.
    https://en.wikipedia.org/wiki/Power_...s-A_amplifiers

    * ( SE 8 ) ( ) symmetrical circuit to drive a floating load or another stage crossover distortion lower distortion because even harmonics are cancelled more effectively with greater symmetry as with symmetrical circuits (such as push–pull output stages, or balanced low-level stages) results in the cancellation of most of the even distortion harmonics, hence the removal of most of the distortion.
    2 mosfet floating ( ) slew rate induced distortion – …)
    Last edited by Vassilis; 03-15-2021 at 04:18 PM.
    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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    internet site forum co co page . .

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    , crossover (DSP) ( - , PWM, class D , , 30) ( ) software .

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    Last edited by Vassilis; 03-19-2021 at 12:02 AM.
    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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    Quote Originally Posted by Vassilis View Post
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    internet site forum co co page . .

    . , .

    , crossover (DSP) ( - , PWM, class D , , 30) ( ) software .

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    ....
    In the high country of the mind one has to become adjusted to the thinner air of uncertainty...
    Robert M. Pirsig

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    Quote Originally Posted by Ornithorhynchus Anatinus View Post
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    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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    In the high country of the mind one has to become adjusted to the thinner air of uncertainty...
    Robert M. Pirsig

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    Quote Originally Posted by Ornithorhynchus Anatinus View Post



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    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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    "It is certainly preferable to grow vegetables" as "Class A amplifiers sound better than the alternatives"

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