Class pada power Amplifier
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  1. #1
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    Thumbs up Class pada power Amplifier

    Disini Saya mau membahas tentang class pada power amplifier, menurut info yang Saya dapat seperti ini :
    1.1 Introduction
    Di mobile environment, sekarang dikenal 4 tipe power yang paling populer :
    1. Class a/b (terpopuler)
    2. Class D (terpopuler untuk sub)
    3. Class A (terpopuler di audiophile)
    4. Class X (terpopuler di kalangan SPL mania )

    Kebanyakan power untuk mobile environment( car) menggunakan class a/b...

    1.2. Apa Dasar pemilihan kelas?
    Kelas dipilih berdasarkan topologi penempatan transistor, feedback yang dipakai dan sebagainya
    yang sebagai user ,kita gak gitu perlu tau.
    Kelas juga dipilih berdasarkan gelombang Sinus yang dibentuk (untuk class A dan B)

    2.1
    Class A
    Audison thesis HV Venti
    Overview :
    - Kelas ampli pertama, hampir semua produk HOME Audio pake kelas ini.
    - Suara yang konon "warm"
    - Salah satu dari 2 Basic Class dari amplifier.
    Amplifier yang memakai : Audison THESIS HV VENTI , TruTechnology A Class ,Sinfoni Desiderio, dst. dst. (termasuk, tenggorokan loh )

    Pro :
    1. Gelombang output (keluaran) murni gelombang sinus (seperti kita berbicara aja ), jadi amplifier ini diagung2kan oleh para sq ers yg menginginkan sinyal yang sempurna.
    2. Distorsi yang kecil.
    3. Tenaga(Power) yang cukup besar.

    cons :
    1. PANAS BOS!Karena topologi yang mengharuskan transistor dalam kondisi ON dan arus konstan mengalir ke transistor
    2. Efisiensi sangat kecil, sekitar 15% secara praktek akibat panas dan sebagainya. namun efesiensi bisa ditingkatkan oleh penggunaan heatsink dan fan yang bagus
    3. Harganya mahal euy, Hampir seluruh amplifier mobil class A berharga 2 digit
    4. Kurang cocok untuk mendrive subwoofer akibat (pada umumnya) power class A berjalan pada mode hi voltage , jadi
    untuk impedansi rendah yang butuh arus tinggi (hi current) kurang bertenaga.
    5. Mayan boros aki, akibat constant current drawing pada no.1

    2.2
    Class B
    Overview :
    - Kelas dengan efisiensi kedua tertinggi setelah kelas D
    - Tidak cocok untuk audio
    - Basic Class kedua
    - Kalau mau dipaksa untuk audio harus menggunakan teknik push-pull untuk membentuk semi a/b tetapi tidak dianjurkan untuk mendrive sub.
    Contoh Amplifier : - (tapi kalo gak salah Braxton pernah keluarin B series yang pake class B )
    Pro :
    1. Efisiensi sangat tinggi (70% an)

    Cons :
    1. Tidak cocok untuk audio operation

    2.3
    Class A/B
    push pull class B yang telah dimodifikasi sehingga jeda antara gelombang phase negatif dan positif bisa direduksi
    OVerview :
    1. "Penggabungan" antara Sine Wave Output ala Class A dan efisiensi Class B
    2. Sangat Cocok untuk penggunaan amplifier untuk car environment
    3. Kelas Amplifier yang paling populer

    Pro :
    1. Panas yang dihasilkan relatif rendah (dibanding Class A)
    2. Supply Listrik yang diperlukan tidak begitu tinggi
    3. Harganya relatif murah
    4. Semi Sine Wave mendekati Class A
    5. Efisiensi cukup tinggi (sekitar 40-50%)
    6. Suara yang terkontrol (terutama untuk drive sub)

    Cons :
    1. Gelombang mungkin sedikit rusak
    2. Sangat bergantung pada power supply untuk tenaga
    3. Sangat bergantung pada transistor
    4. Heatsink harus bisa menghantarkan panas dengan baik

    2.4
    Class D
    Orion 1200D
    Overview:
    - Amplifier dengan efisiensi tertinggi dan terhitung dingin
    - Amplifier populer untuk SPL
    - Merupakan amplifier yang menggunakan teknik PWM (pulse width modulator)
    jadi signal analog, diubah ke digital, baru dijadikan analog lagi.

    Pro :
    1. VERY RECOMMENDED FOR SUB!
    2. Efisiensi tertinggi (80-90%)
    3. Tenaga yang cukup besar walaupun watt kecil akibat efisiensi yang tinggi
    4. "dingin"
    5. Supply Listrik tidak butuh terlalu besar
    6. Transistor tidak cepat rusak karena transistor hanya ON pada saat ada sinyal, dan
    off waktu tidak ada sinyal
    7. umumnya lebih kecil dengan watt yang sama

    Cons :
    1. Tidak bisa untuk drive speaker karena adanya restriksi penggunaan filter
    (karena pada aturan untuk kelas D, Low Pass Filter digunakan untuk merubah sinyal digital
    menjadi analog, jadi penggunaan hi pass tinggi hampir tidak mungkin dilakukan)
    2. Suara Bass kurang bisa terkontrol (buat yang ehem...sq abies!)
    3. Gelombang sinus yang dihasilkan cenderung "kotak"

    2.5
    Class X
    clif designs cdx-20a
    (inget pemecahan world record no.3 di indonesia oleh Johan Gen-X?dia pake ampli ini)
    Overview :
    - Pengembangan lebih lanjut dari Class D, dimana efisiensi ditingkatkan nyaris 100%
    - Nama lainnya Digital Class D Amplifier
    - Paten Anaba Group (MA Audio, cLif Designs, Visonik, Ultra Linear, dsb.)
    Ampli : XTR 1200, XTR 3000, MA Audio HK 4000D, Visonik 4000XD, cLif Designs CDX-20A, Lightning Audio Storm X1.2000.1D (versi digital)
    www.ma-audio.com
    www.clifdesigns.com
    www.visonik.com
    //www.xtraudio.com

    Pro :
    1. Tenaga yang sangat besar akibat efisiensi yang tinggi.
    2. Hi Current, didesain untuk di "siksa" di 1 ohm secara stabil
    3. Panas yang tidak terlalu besar.
    4. Sangat dianjurkan untuk Sub2 haram jadah macem Solo X, atau MA HardKore 18"

    Cons :
    1. mahal.
    2. regulasi wattage yang hanya mengijinkan bermain di impedansi rendah
    3. Voltage dependant...

    2.6
    Class T
    Tripath Chip Amp
    Alpine MRD-F752
    phase linear OPUS2
    Overview :
    - Trademark dari TRIPATH Technologies
    - Menggunakan ADC/DAC chip amps
    - Jarang loh
    Contoh ampli : Alpine MRD-F375 (kalo gak salah, mohon bos bodapa membetulkan), MA Audio (lupa kodenya), Phase Linear OPUS series

    Pros :
    1. efisiensi kelas D, dengan gelombang kelas a/b ? who wouldn't want?
    2. dingin

    Cons :
    1. Mahal dalam hal produksi.
    2. Banyak yang kurang menganggap chip amps

    original thread by Jey "Eternity Sound"

    Trs d forum laen bos David dr Neusounds :
    class B, berkarakter kasar, dan boros listrik,ini uda hampir ga ada lagi sekarang
    class AB, berkarakter halus, tapi masih boros listrik, ini hampir semua power amp seperti ini
    class A, berkarakter halus banget, warm, tetep boros listrik, ini masih ada beberapa merk keluarin, karena ciri khas power amp class ini yg laen dari pada yg laen
    tube > ini ngerti dunk, amp tabung, arti nya amp yg transistor nya dari tabung, seperti jaman dulu, ada 2 tipe, ada full tube, ada yg hybrid alias, cuma preamp nya yg pakai tube
    class D, berkarakter kasar, tenaga gede dan efisien di listrik, nah ini biasa di ketemui untuk power amp buat angkat subwoofer
    class G, berkarakter seperti class AB, tapi lebih hemat listrik dan design lebih ramping
    class H, berkarakter galak seperti class D, bertenaga besar, tapi halus seperti class AB dan efisien di listrik dan design
    ada lagi Class T (digital) ini ga terlalu populer, karena size nya yg besar, tapi class T tenaga besar sekali, tapi efisein di listrik
    begitu sedikit ulasan newbie tentang power amp

    lanjut k monoblok
    jadi ada juga power amp monoblok class AB, contoh seperti power amp genesis DM (Dual Mono) dan DMX (Dual Mono Exterme), Gramond MLT2.1 SE
    dan banyak kan power amp monoblok class D, contoh performa 2200, venom 2000vd, dll deh
    nah yg baru ini class G/H bisa di temui di genesis DMA250 dan ARC
    jadi ga selalu power amp monoblok itu buat angkat subwoofer
    semoga membantu
    thanks

    Referensi lainnya Saya dapat dari wikipedia
    http://en.wikipedia.org/wiki/Electronic_amplifier

    Yang Saya mau tanyakan disini adalah:
    Pertama
    Apakah power amplifier yang disebut High Current termasuk power amplifier class X? Karena banyak yang bilang Power Cliff Design CDX-20A, Visonik V4000XD, MA Audio HK-4000D, Performa PC 5000D, dan lain-lain disebut sebagai power High Current, soalnya setau Saya kalau power High Current boros Accu (mohon dibetulkan kalau salah), sedangkan dari info yg Saya dapat Class X memiliki effisiensi yang sangat tinggi, bahkan lebih baik dibanding Class D

    Kedua
    Masih mengenai class X, Saya menemukan perbedaan spek disini
    http://www.onlinecarstereo.com/CarAudio/p_14753_MA_Audio_HK4000D.aspx
    tertulis
    MA Audio HK4000D
    RMS Power @ 14.4V: 50W x 1 @ 4 Ohm, 3600W x 1 @ 2 Ohm
    RMS Power @ 17.0V: 75W @ 4 Ohm, 4000W @ 2 Ohm

    dan disini
    http://ampguts.com/gallery/showgallery.php?cat=1117
    tertulis
    MA Audio HK4000D
    1 x 1800W @ 4 Ohm (14.4V)
    1 x 3600W @ 2 Ohm (14.4V)
    1 x 2000W @ 4 Ohm (17V)
    1 x 4000W @ 2 Ohm (17V)

    Sebetulnya spek mana yang betul? Karena keduanya memiliki perbedaan yang sangat signifikan pada 4 ohm dan 2 ohm.

    Disini
    http://ampguts.com/gallery/showgallery.php?cat=522
    tertulis
    Clif Designs CDX-20A
    Class X Amplifier
    1 x 25W @ 4 Ohm (14.4V)
    1 x 50W @ 4 Ohm (17V)
    1 x 3600W @ 2 Ohm (14.4V)
    1 x 4000W @ 2 Ohm (17V)

    Dan disini
    http://ampguts.com/gallery/showgallery.php?cat=2018
    Visonik V4000XD
    Rms Power @ 14.4V DC
    1 x 2500W @ 4 Ohm
    1 x 3500W @ 2 Ohm
    Rms Power @ 17V DC
    1 x 3000W @ 4 Ohm
    1 x 4000W @ 2 Ohm

    Sebetulnya mana yang menunjukkan karakter dari Class X sendiri? Karena semuanya termauk power Class. Apakah pada impedansi rendah baru menghasilkan tenaga yang besar, atau pada impedansi 4 ohm tenaga yang dikeluarkan sudah besar?

    Sekian pertanyaan Saya. Mohon maaf jika terlalu panjang, karena Saya masih merasa rancu antara Class X dan High Current, terima kasih sebelumnya

  2. Delapan Satu
  3. #2
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    Smile

    Quote Originally Posted by andyanto_wibowo View Post

    ------------------
    Yang Saya mau tanyakan disini adalah:
    Pertama
    Apakah power amplifier yang disebut High Current termasuk power amplifier class X? Karena banyak yang bilang Power Cliff Design CDX-20A, Visonik V4000XD, MA Audio HK-4000D, Performa PC 5000D, dan lain-lain disebut sebagai power High Current, soalnya setau Saya kalau power High Current boros Accu (mohon dibetulkan kalau salah), sedangkan dari info yg Saya dapat Class X memiliki effisiensi yang sangat tinggi, bahkan lebih baik dibanding Class D

    Kedua
    Masih mengenai class X, Saya menemukan perbedaan spek disini
    http://www.onlinecarstereo.com/CarAudio/p_14753_MA_Audio_HK4000D.aspx
    tertulis
    MA Audio HK4000D
    RMS Power @ 14.4V: 50W x 1 @ 4 Ohm, 3600W x 1 @ 2 Ohm
    RMS Power @ 17.0V: 75W @ 4 Ohm, 4000W @ 2 Ohm

    dan disini
    http://ampguts.com/gallery/showgallery.php?cat=1117
    tertulis
    MA Audio HK4000D
    1 x 1800W @ 4 Ohm (14.4V)
    1 x 3600W @ 2 Ohm (14.4V)
    1 x 2000W @ 4 Ohm (17V)
    1 x 4000W @ 2 Ohm (17V)

    Sebetulnya spek mana yang betul? Karena keduanya memiliki perbedaan yang sangat signifikan pada 4 ohm dan 2 ohm.

    Disini
    http://ampguts.com/gallery/showgallery.php?cat=522
    tertulis
    Clif Designs CDX-20A
    Class X Amplifier
    1 x 25W @ 4 Ohm (14.4V)
    1 x 50W @ 4 Ohm (17V)
    1 x 3600W @ 2 Ohm (14.4V)
    1 x 4000W @ 2 Ohm (17V)

    Dan disini
    http://ampguts.com/gallery/showgallery.php?cat=2018
    Visonik V4000XD
    Rms Power @ 14.4V DC
    1 x 2500W @ 4 Ohm
    1 x 3500W @ 2 Ohm
    Rms Power @ 17V DC
    1 x 3000W @ 4 Ohm
    1 x 4000W @ 2 Ohm

    Sebetulnya mana yang menunjukkan karakter dari Class X sendiri? Karena semuanya termauk power Class. Apakah pada impedansi rendah baru menghasilkan tenaga yang besar, atau pada impedansi 4 ohm tenaga yang dikeluarkan sudah besar?

    Sekian pertanyaan Saya. Mohon maaf jika terlalu panjang, karena Saya masih merasa rancu antara Class X dan High Current, terima kasih sebelumnya
    Pertanyaan bagus dengan uraian yang bagus....

    Saya jawab yang perbedaan spesifikasi yaa....

    Sebenarnya power supply amplifier ada yang regulated (constant) dan unregulated (variable) power supply

    REGULATED POWER SUPPLY AMPLIFIER


    Pada amplifier regulated, spesifikasinya mengharuskan untuk meregulasi power supply misalnya di 14,4 Volt pada 100 watt dan 4 ohm

    maka ketika musik membahana misalnya sub berbunyi kencang maka voltase cenderung mengalami dip misalnya saja turun menjadi 12 Volt,

    Nah ketika hal tersebut terjadi maka power supply akan mengeluarkan arus yang lebih besar untuk mengkompensasi hal tersebut sehingga outputnya akan tetap sama yaitu 100 watt pada 4 ohm.

    Ingat rumus




    Sehingga pada regulated power amp voltase yang lebih rendah maupun lebih tinggi tidak akan terlalu berpengaruh terhadap output yang dikeluarkannya.

    UNREGULATED POWER SUPPLY AMPLIFIER


    Pada amplifier unregulated spesifikasinya dirancang untuk menerima voltase secara variabel misalnya 10,8-16 Volt. Outputnya cenderung berubah ketika terjadi penambahan voltase maupun penurunan voltase

    Efeknya pada amplifier jenis ini dia bisa saja hanya menghasilkan 100 Watt pada 14,4 volt 4 ohm, kemudian turun menjadi hanya 50 watt pada 12 volt 4 ohm namun bisa naik menjadi 200 watt pada 16 volt 4 ohm. That's unregulated amplifier

    Dari spesifikasi di atas yaitu 17 volt adalah completely useless kecuali pakai catu daya rumah. Karena alternator mobil normal umumnya hanya menghasilkan voltase antara 13,8 volt sampai 14,4 volt dan peaknya mungkin di sekitar 16 volt itupun sangat jarang bisa terjadi tanpa treatment kelistrikan secara khusus. Accu mobil sendiri hanya menghasilkan antara 10,8-12 Volt di bawah itu sudah kesulitan menstarter mobil.

    Jadi produsen yang memasang spec 17 volt IMHO sebenarnya bukan merupakan hal yang realistis bagi customer.

    Ini salah satu link penjelasannya

    http://www.diyaudio.com/forums/car-a...lated-amp.html

    CMIIW

    Best Regards

    Wendo

  4. #3
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    Quote Originally Posted by andyanto_wibowo View Post
    Sebetulnya mana yang menunjukkan karakter dari Class X sendiri? Karena semuanya termasuk power Class. Apakah pada impedansi rendah baru menghasilkan tenaga yang besar, atau pada impedansi 4 ohm tenaga yang dikeluarkan sudah besar?

    Sekian pertanyaan Saya. Mohon maaf jika terlalu panjang, karena Saya masih merasa rancu antara Class X dan High Current, terima kasih sebelumnya
    wuih.... penjelasan master suhu kumpliiid...

    Mungkin yg dimaksud dengan Class X itu adalah basically topologi yg sama seperti Class D tapi yg membedakan adalah topologi supply untuk mosfet-nya? Topologi supply-nya yg seperti digital jadi disebut class X.

    Sedangkan kalo high current seperti Orion HCCA itu mungkin hanya sebutan marketing ajah ya? Secara kalau dilihat secara topologi-nya apakah bisa dibilang termasuk class A/B yg bisa menerima impedansi sangat rendah.
    Kalo nggak salah current itu kan arus (AMPERE) yg rumus listrik-nya:
    P (WATT) = V(VOLT) x I (AMPERE)Atau kalo digabung ama Ohm's Law jadi:
    P (WATT) = V^2 / R

    Nahh... kenapa di kasus ORION HCCA kalo impedansi kecil bisa naek watt-nya jadi guede banget. Tinggal masukin rumus kaan? Mungkin mestinya Orion HCCA disebut power High Voltage yah bukan High Current? Hehehehehe..... biar nggak salah kaprah. Tapi kan namanya juga marketing jargon biar keren gitu.

    oh iya, power Class D itu termasuk high current (marketing jargon)juga kah? Kan rating-nya misal 750Watt @ 4ohm, 1500Watt @ 2ohm, 2000Watt @1ohm. makin kecil impedansi makin gede watt-nya. Hohohohoho....

    Kalo ada salah maap yee... nama-nya juga Pemula boleh copy paste dari sini nih:
    Rumus Kelistrikan
    atau
    Rumus Kelistrikan II
    Class X vs High Current

  5. #4
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    Mantap2 penjelasannya

  6. #5
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    Wah wah wah..suhu2 audio udah pada ngumpuk nih..
    makin seru aja topik nya..ijin nyimak bro

    moga2 bisa nambah ilmu nih

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    neubitol ikut memantau

    Mega Glodok Kemayoran Lt 6 Blok B2 No.9-10
    Kemayoran / Jakarta Pusat
    Tlp.021 99691521

  8. #7
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    Ini ada penjelasan bagus dari salah satu master desainer Power Amp terbaik di dunia: Robert Zeff, agak technical tapi kalau mau dipelajari dengan perlahan-lahan akan memberikan informasi yang lumayan lengkap.

    Anatomy of the Power Amplifier

    Dissecting the Modern Audio Power Amplifier and Power Supply
    By Robert Zeff

    With the Proliferation of Different Amp Types, Which is the One for You? In the past we had essentially two types of amplifiers to choose from: Class "AB" and class "A". Today we have AB, A, D, G, H, & T, in addition to some that do not have a class name. New technology brought down the size and price while improving performance and efficiency. We'll review the various topologies of the modern amplifier, spending extra time on the aspect of efficiency (as the quest for smaller, more efficient designs have spawned the class D, G, H, & T designs). We'll also try to dispel some of the misconceptions and folklore that seem to surround amp design.
    Amplifiers require circuitry for short and thermal protection, fan control, turn on delay, and over voltage protection. In the past we littered the designs with dozens of components to handle these events. Today we can use a single microprocessor to handle all of this in addition to having many more features without additional cost. The microprocessor can monitor the battery voltage, internal voltages, temperature, control volume and crossovers, and drive external displays. These embedded computer chips also allow features like compression and power limiting with little added cost. Of course, what is an amplifier without a power supply? First we'll visit the power supply designs, as every amplifier needs one.
    The Power Supply
    The purpose of the supply is to convert the auto's battery voltage to a higher voltage. For example, if an amplifier is to produce 100 watts into a 4 ohm speaker, we need 20 volts RMS. This implies that we need about +/-28 volts. (20 volts R.M.S. = 28.28 volts peak). We call that the "rail" voltage. Since the amplifier's output transistors cannot pull all the way up to this rail, we actually need a slightly higher voltage.

    The process is to convert the 12 volts DC into AC, feed it to a transformer and convert it back to DC again.
    Converting the 12 volt battery voltage to AC is simple, a PWM (pulse width modulator) IC feeds a bank of MOSFETS (MOSFETs are switching transistors perfectly suited for this task).
    The 12 volt power is switched at a very high frequency, somewhere between 40 and 150 kHz. Slower switching speeds require a larger transformer, but high speeds have more switching loss. Advanced transformer core materials, faster rectifiers, and clever winding methods have enabled us to utilize very high frequencies. Some of today's better amplifiers have very small power supplies that produce enormous amounts of power.
    Regulated Power Supplies
    Most early audio amplifiers contained unregulated power supplies. Regulated supplies require very high quality filter capacitors (called "low ESR" capacitors), output chokes, and an optically isolated voltage feedback circuit. Regulation occurs by controlling the switching pulse width from 0 - 100% to compensate for changes in the battery and rail voltage. The same action occurs when the audio level increases. As the amplifier draws more power from the supply, the rail voltage drops. Again, the regulator circuitry senses this drop and responds with an increased pulse width.

    The high frequency PWM waveform is rectified (converted to DC) and applied to the output filter choke and capacitors. This output of this circuit is the + and - DC rails that feed the power amplifier.
    Unregulated Power Supplies
    Unregulated power supplies are less expensive than regulated supplies. They do not require an output choke, voltage sense or isolation circuitry. Because the duty cycle is nearly 100%, capacitor ripple current is much lower in unregulated supplies. Lower ripple current requires less expensive capacitors throughout.

    Often we hear that unregulated designs have more "headroom". That means that the amplifier will produce extra power during transients. Most home audio amplifiers employ unregulated power supplies. The power supplies in these amplifiers run at 60 Hz, thus the filter capacitors must be 200-500 times larger than those used in high frequency switchers. The extra capacitance in home audio amplifiers results in extra headroom. Headroom for anything other than very short transients simply doesn't exist in the unregulated designs. The following is an example of specifications for an unregulated vs. regulated amplifiers.
    Unregulated designs have a higher supply voltage at low power, causing higher voltage on the output transistors. This reduces the amplifier's efficiency.
    Small amplifiers (less than 100 watts) cannot justify the extra cost of the regulation circuitry, so we often see unregulated supplies in these amplifiers.
    Pros and Cons of Regulated / Unregulated SuppliesSome designers try to keep their supplies regulated down to battery voltages as low as 9.5 volts. The supply compensates by increasing the current. The following table shows voltage and currents for a 500 watt over-regulated amplifier operating at full power.
    The current increases dramatically at the lower voltages. Because of higher currents at the lower voltages, the supply efficiency drops further, requiring even more current.
    At higher voltages, the pulse width reduces, causing increased ripple current. This high current creates heat in the filter capacitors and can destroy the capacitor's electrolyte. Some manufacturers do not use capacitors of sufficient quality for this range of regulation. These amplifiers may not perform up to specification just one year after installation. Also, the extra current at low voltages is extra hard on a battery that is already suffering! So, we recommend that amplifiers stay in regulation down to about 11 - 11.5 volts. Any properly working charging system can easily keep the battery voltage well above this.
    The Amplifier Section, Class AB and AClass AB and A amplifiers are similar, so we'll discuss both here. Class AB amplifiers have transistors that pull up to the positive rail and transistors that pull down to the negative rail. This corresponds to the action of pushing the speaker cone out and in.
    Class AB means that the output transistors do not always have current on them. For example, when the upper transistors are pulling up towards the positive rail (pushing the speaker out), there is no current in the lower transistors. When the output signal swings through zero, towards the negative rail, the output transistor must go through a transition from zero current to a non-zero current. The best analogy that I can think of is driving an old car with too much slop in the steering. As you go from one side of the road's crown to the other, the steering crosses a "dead" zone, and you tend to over-steer. Special temperature compensated bias circuitry reduces this dead zone, known as notch distortion. The figure below shows the output of a class AB amplifier with too little bias and the resulting distortion. Notch distortion increases at higher frequencies and low volume levels. Some modern designs have reduced this type of distortion to very low levels.
    Class A means that every transistor is always conducting current. They are very similar to class AB amplifiers, but the bias circuitry is set so that there are very high currents in the output transistors. Because these amplifiers do not have this "dead zone', less feedback is required to achieve low distortion.
    A 100 watt amplifier may dissipate nearly 100 watts internally even when there is no audio output. This type of design is impractical in the harsh auto environment. Many class A amplifiers pedaled for the automotive market are not really class A. They are huge power wasters in the home as well.
    Input and Driver Stages
    The amplifier works this way: A small audio signal is presented to the amplifier's input. Transistors are not linear, which means that the input signal will distort somewhat as it passes through the various amplifier stages. To correct this distortion, a portion of the output is compared with the input. The difference creates a correction signal reducing this distortion. The input stage is a special type, called "differential". It has a + and a - input because it must accept both the audio input and the input from the feedback circuitry. Excess feedback can lower distortion dramatically, but cause instability. Careful design rules must be followed to avoid this instability.

    The output of the input stage feeds into the driver stage. The driver stage may use one, two, or three devices. Often this circuitry is referred to "Darlington", or "Triple Darlington". The driver circuit feeds the output stage, which may have two, four, six, or more transistors. The more output transistors, the better. Multiple output devices reduce distortion (requiring less negative feedback) and improve reliability.
    Bipolar or MOSFET?
    We have seen both MOSFET (Metal Oxide Silicon Field Effect Transistor) and Bipolar transistors used in audio amplifiers. Claims have been made that each is superior. I have seen claims that MOSFETs have a tube ("Valve" for the Brits) sound. This is more folklore. The musicians and their instruments are supposed to have "the sound", not audio equipment! MOSFETs are tougher than Bipolars, and can pull closer to the supply rail. It takes more Bipolar transistors to achieve the same power as a MOSFET, therefore Bipolar amps tend to be more expensive. But, MOSFETs are very non-linear, compared to Bipolars and require much more feedback to achieve reasonable distortion numbers. They are a great choice for bass amps, as low frequency audio is not difficult for a MOSFET. The most expensive car and home amplifiers almost always use Bipolar transistors.

    Efficiency
    What makes an amplifier get hot? Both the power supply and the power amplifier generate heat. The maximum efficiency of the power supply is nearly 100%. Good power supply designs, with the highest quality components approach 85%. The class AB amplifier efficiency at full power can approach 75%. The total efficiency, including the power supply, can be about 65%. But, efficiency drops at lower power and can typically be under 20%. A class AB amplifier actually runs cooler at full power than it does at half power. Run this amplifier into clipping and it might run even cooler! Where is all this power going? The output transistor is basically a large variable resistor. If the instantaneous output voltage should be 40 volts and the power supply is 100 volts, then 60 volts must be "wasted" in the output transistors. Driving a reactive load (like a speaker) causes the efficiency to drop ever further. This brings us to the other audio classes designed to improve efficiency.

    Class D
    First, let's dispel another myth: Class D does not stand for digital. The input is converted to a two-state (binary) representation of the audio waveform. That's where the similarity ends. This distinction is important because class D doesn't provide the benefits normally associated with digital components.

    That being said, class D designs dramatically improve efficiency. Instead of wasting power in the output transistor, the output is switched at a very high frequency between the positive and negative supply rails. If the output is to be zero, then the waveform is at a 50% duty cycle. If the output is to be a positive voltage, then the duty cycle would be greater than 50%. Because the output devices are either completely turned on (no wasted voltage) or completely turned off, theoretically efficiency is 100%. So the audio input must be converted to a pulse width modulated waveform (PWM). The yellow trace below is the output of the amplifier; the blue trace is the PWM waveform. The blue waveform is fed to an output filter, which results in the yellow output waveform. Notice that the output looks somewhat distorted. All of the switching noise and distortion cannot be removed and the result can be seen here. Because of this process of converting the input signal to PWM and converting back to analog, a good deal of distortion is introduced. Conventional feedback like that used in class AB designs is used in these amplifiers to reduce distortion.
    MOSFETs are the only choice for class D designs. Most class D designs are useful only for bass amps as they can not switch fast enough to reproduce high frequencies. Some high quality, full range class D designs exist for pro audio, but they are complex with multi-phased outputs.
    Class T
    Class T (Tripath) is similar to class D with these exceptions: This class does not use analog feed back like its class D cousin. The feedback is digital and is taken ahead of the output filter, avoiding the phase shift of this filter. Because class D or T amplifier distortion arises from timing errors, the class T amplifier feeds back timing information. The other distinction is that this amplifier uses a digital signal processor to convert the analog input to a PWM signal and process the feedback information. The processor looks at the feedback information and makes timing adjustments. Because the feedback loop does not include the output filter, the class T amplifier is inherently more stable and can operate over the full audio band. Most listeners can not hear the difference between class T and good class AB designs. Both class D and T designs share one problem: they consume extra power at idle. Because the high frequency waveform is present at all times, even when there is no audio present, the amplifiers generate some residual heat. Some of these amplifiers actually turn off in the absence of music, and can be annoying if there is too much delay turning back on.

    Class G
    Class G improves efficiency in another way: an ordinary class AB amplifier is driven by a multi-rail power supply. A 500 watt amplifier might have three positive rails and three negative rails. The rail voltages might be 70 volts, 50 volts, and 25 volts. As the output of the amplifier moves close to 25 volts, the supply is switched the 50 volt rail. As the output moves close to the 50 volt rail, the supply is switched to the 70 volt rail. These designs are sometimes called "Rail Switchers". This design improves efficiency by reducing the "wasted" voltage on the output transistors. This voltage is the difference between the positive (red) supply and the audio output (blue). Class G can be as efficient as class D or T. While a class G design is more complex, it is based on a class AB amplifier and can have the same clean characteristics as well.

    Class H
    Class H is similar to class G, except the rail voltage is modulated by the input signal. The power supply rail is always just a bit higher than the output signal, keeping the voltage across the transistors small and the output transistors cool. The modulating power supply rail voltage is created by similar circuitry that you would find in a class D amplifier. In terms of complexity, this type of amplifier could be thought of as a class D amplifier driving a class AB amplifier and is therefore fairly complex.

    How to Choose?
    Regulated or unregulated? Class AB, D, or T?If you're really into a lot of bass, the class D or T may be for you as these amplifiers will produce the highest SPL with the smallest size. If you just want to wake the neighbors, blur your vision, or make a big splash in SPL contests, maybe you just need one of the inexpensive, powerful, & dirty class D designs. Want the cleanest high frequencies? Maybe a good class AB amp would be your selection. Whatever you choose, I hope this information helps you achieve the sound you're looking for!
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    Quote Originally Posted by UnSCAC View Post
    Ini ada penjelasan bagus dari salah satu master desainer Power Amp terbaik di dunia: Robert Zeff, agak technical tapi kalau mau dipelajari dengan perlahan-lahan akan memberikan informasi yang lumayan lengkap.

    Anatomy of the Power Amplifier

    Dissecting the Modern Audio Power Amplifier and Power Supply
    By Robert Zeff

    With the Proliferation of Different Amp Types, Which is the One for You? In the past we had essentially two types of amplifiers to choose from: Class "AB" and class "A". Today we have AB, A, D, G, H, & T, in addition to some that do not have a class name. New technology brought down the size and price while improving performance and efficiency. We'll review the various topologies of the modern amplifier, spending extra time on the aspect of efficiency (as the quest for smaller, more efficient designs have spawned the class D, G, H, & T designs). We'll also try to dispel some of the misconceptions and folklore that seem to surround amp design.
    Amplifiers require circuitry for short and thermal protection, fan control, turn on delay, and over voltage protection. In the past we littered the designs with dozens of components to handle these events. Today we can use a single microprocessor to handle all of this in addition to having many more features without additional cost. The microprocessor can monitor the battery voltage, internal voltages, temperature, control volume and crossovers, and drive external displays. These embedded computer chips also allow features like compression and power limiting with little added cost. Of course, what is an amplifier without a power supply? First we'll visit the power supply designs, as every amplifier needs one.
    The Power Supply
    The purpose of the supply is to convert the auto's battery voltage to a higher voltage. For example, if an amplifier is to produce 100 watts into a 4 ohm speaker, we need 20 volts RMS. This implies that we need about +/-28 volts. (20 volts R.M.S. = 28.28 volts peak). We call that the "rail" voltage. Since the amplifier's output transistors cannot pull all the way up to this rail, we actually need a slightly higher voltage.

    The process is to convert the 12 volts DC into AC, feed it to a transformer and convert it back to DC again.
    Converting the 12 volt battery voltage to AC is simple, a PWM (pulse width modulator) IC feeds a bank of MOSFETS (MOSFETs are switching transistors perfectly suited for this task).
    The 12 volt power is switched at a very high frequency, somewhere between 40 and 150 kHz. Slower switching speeds require a larger transformer, but high speeds have more switching loss. Advanced transformer core materials, faster rectifiers, and clever winding methods have enabled us to utilize very high frequencies. Some of today's better amplifiers have very small power supplies that produce enormous amounts of power.
    Regulated Power Supplies
    Most early audio amplifiers contained unregulated power supplies. Regulated supplies require very high quality filter capacitors (called "low ESR" capacitors), output chokes, and an optically isolated voltage feedback circuit. Regulation occurs by controlling the switching pulse width from 0 - 100% to compensate for changes in the battery and rail voltage. The same action occurs when the audio level increases. As the amplifier draws more power from the supply, the rail voltage drops. Again, the regulator circuitry senses this drop and responds with an increased pulse width.

    The high frequency PWM waveform is rectified (converted to DC) and applied to the output filter choke and capacitors. This output of this circuit is the + and - DC rails that feed the power amplifier.
    Unregulated Power Supplies
    Unregulated power supplies are less expensive than regulated supplies. They do not require an output choke, voltage sense or isolation circuitry. Because the duty cycle is nearly 100%, capacitor ripple current is much lower in unregulated supplies. Lower ripple current requires less expensive capacitors throughout.

    Often we hear that unregulated designs have more "headroom". That means that the amplifier will produce extra power during transients. Most home audio amplifiers employ unregulated power supplies. The power supplies in these amplifiers run at 60 Hz, thus the filter capacitors must be 200-500 times larger than those used in high frequency switchers. The extra capacitance in home audio amplifiers results in extra headroom. Headroom for anything other than very short transients simply doesn't exist in the unregulated designs. The following is an example of specifications for an unregulated vs. regulated amplifiers.
    Unregulated designs have a higher supply voltage at low power, causing higher voltage on the output transistors. This reduces the amplifier's efficiency.
    Small amplifiers (less than 100 watts) cannot justify the extra cost of the regulation circuitry, so we often see unregulated supplies in these amplifiers.
    Pros and Cons of Regulated / Unregulated SuppliesSome designers try to keep their supplies regulated down to battery voltages as low as 9.5 volts. The supply compensates by increasing the current. The following table shows voltage and currents for a 500 watt over-regulated amplifier operating at full power.
    The current increases dramatically at the lower voltages. Because of higher currents at the lower voltages, the supply efficiency drops further, requiring even more current.
    At higher voltages, the pulse width reduces, causing increased ripple current. This high current creates heat in the filter capacitors and can destroy the capacitor's electrolyte. Some manufacturers do not use capacitors of sufficient quality for this range of regulation. These amplifiers may not perform up to specification just one year after installation. Also, the extra current at low voltages is extra hard on a battery that is already suffering! So, we recommend that amplifiers stay in regulation down to about 11 - 11.5 volts. Any properly working charging system can easily keep the battery voltage well above this.
    The Amplifier Section, Class AB and AClass AB and A amplifiers are similar, so we'll discuss both here. Class AB amplifiers have transistors that pull up to the positive rail and transistors that pull down to the negative rail. This corresponds to the action of pushing the speaker cone out and in.
    Class AB means that the output transistors do not always have current on them. For example, when the upper transistors are pulling up towards the positive rail (pushing the speaker out), there is no current in the lower transistors. When the output signal swings through zero, towards the negative rail, the output transistor must go through a transition from zero current to a non-zero current. The best analogy that I can think of is driving an old car with too much slop in the steering. As you go from one side of the road's crown to the other, the steering crosses a "dead" zone, and you tend to over-steer. Special temperature compensated bias circuitry reduces this dead zone, known as notch distortion. The figure below shows the output of a class AB amplifier with too little bias and the resulting distortion. Notch distortion increases at higher frequencies and low volume levels. Some modern designs have reduced this type of distortion to very low levels.
    Class A means that every transistor is always conducting current. They are very similar to class AB amplifiers, but the bias circuitry is set so that there are very high currents in the output transistors. Because these amplifiers do not have this "dead zone', less feedback is required to achieve low distortion.
    A 100 watt amplifier may dissipate nearly 100 watts internally even when there is no audio output. This type of design is impractical in the harsh auto environment. Many class A amplifiers pedaled for the automotive market are not really class A. They are huge power wasters in the home as well.
    Input and Driver Stages
    The amplifier works this way: A small audio signal is presented to the amplifier's input. Transistors are not linear, which means that the input signal will distort somewhat as it passes through the various amplifier stages. To correct this distortion, a portion of the output is compared with the input. The difference creates a correction signal reducing this distortion. The input stage is a special type, called "differential". It has a + and a - input because it must accept both the audio input and the input from the feedback circuitry. Excess feedback can lower distortion dramatically, but cause instability. Careful design rules must be followed to avoid this instability.

    The output of the input stage feeds into the driver stage. The driver stage may use one, two, or three devices. Often this circuitry is referred to "Darlington", or "Triple Darlington". The driver circuit feeds the output stage, which may have two, four, six, or more transistors. The more output transistors, the better. Multiple output devices reduce distortion (requiring less negative feedback) and improve reliability.
    Bipolar or MOSFET?
    We have seen both MOSFET (Metal Oxide Silicon Field Effect Transistor) and Bipolar transistors used in audio amplifiers. Claims have been made that each is superior. I have seen claims that MOSFETs have a tube ("Valve" for the Brits) sound. This is more folklore. The musicians and their instruments are supposed to have "the sound", not audio equipment! MOSFETs are tougher than Bipolars, and can pull closer to the supply rail. It takes more Bipolar transistors to achieve the same power as a MOSFET, therefore Bipolar amps tend to be more expensive. But, MOSFETs are very non-linear, compared to Bipolars and require much more feedback to achieve reasonable distortion numbers. They are a great choice for bass amps, as low frequency audio is not difficult for a MOSFET. The most expensive car and home amplifiers almost always use Bipolar transistors.

    Efficiency
    What makes an amplifier get hot? Both the power supply and the power amplifier generate heat. The maximum efficiency of the power supply is nearly 100%. Good power supply designs, with the highest quality components approach 85%. The class AB amplifier efficiency at full power can approach 75%. The total efficiency, including the power supply, can be about 65%. But, efficiency drops at lower power and can typically be under 20%. A class AB amplifier actually runs cooler at full power than it does at half power. Run this amplifier into clipping and it might run even cooler! Where is all this power going? The output transistor is basically a large variable resistor. If the instantaneous output voltage should be 40 volts and the power supply is 100 volts, then 60 volts must be "wasted" in the output transistors. Driving a reactive load (like a speaker) causes the efficiency to drop ever further. This brings us to the other audio classes designed to improve efficiency.

    Class D
    First, let's dispel another myth: Class D does not stand for digital. The input is converted to a two-state (binary) representation of the audio waveform. That's where the similarity ends. This distinction is important because class D doesn't provide the benefits normally associated with digital components.

    That being said, class D designs dramatically improve efficiency. Instead of wasting power in the output transistor, the output is switched at a very high frequency between the positive and negative supply rails. If the output is to be zero, then the waveform is at a 50% duty cycle. If the output is to be a positive voltage, then the duty cycle would be greater than 50%. Because the output devices are either completely turned on (no wasted voltage) or completely turned off, theoretically efficiency is 100%. So the audio input must be converted to a pulse width modulated waveform (PWM). The yellow trace below is the output of the amplifier; the blue trace is the PWM waveform. The blue waveform is fed to an output filter, which results in the yellow output waveform. Notice that the output looks somewhat distorted. All of the switching noise and distortion cannot be removed and the result can be seen here. Because of this process of converting the input signal to PWM and converting back to analog, a good deal of distortion is introduced. Conventional feedback like that used in class AB designs is used in these amplifiers to reduce distortion.
    MOSFETs are the only choice for class D designs. Most class D designs are useful only for bass amps as they can not switch fast enough to reproduce high frequencies. Some high quality, full range class D designs exist for pro audio, but they are complex with multi-phased outputs.
    Class T
    Class T (Tripath) is similar to class D with these exceptions: This class does not use analog feed back like its class D cousin. The feedback is digital and is taken ahead of the output filter, avoiding the phase shift of this filter. Because class D or T amplifier distortion arises from timing errors, the class T amplifier feeds back timing information. The other distinction is that this amplifier uses a digital signal processor to convert the analog input to a PWM signal and process the feedback information. The processor looks at the feedback information and makes timing adjustments. Because the feedback loop does not include the output filter, the class T amplifier is inherently more stable and can operate over the full audio band. Most listeners can not hear the difference between class T and good class AB designs. Both class D and T designs share one problem: they consume extra power at idle. Because the high frequency waveform is present at all times, even when there is no audio present, the amplifiers generate some residual heat. Some of these amplifiers actually turn off in the absence of music, and can be annoying if there is too much delay turning back on.

    Class G
    Class G improves efficiency in another way: an ordinary class AB amplifier is driven by a multi-rail power supply. A 500 watt amplifier might have three positive rails and three negative rails. The rail voltages might be 70 volts, 50 volts, and 25 volts. As the output of the amplifier moves close to 25 volts, the supply is switched the 50 volt rail. As the output moves close to the 50 volt rail, the supply is switched to the 70 volt rail. These designs are sometimes called "Rail Switchers". This design improves efficiency by reducing the "wasted" voltage on the output transistors. This voltage is the difference between the positive (red) supply and the audio output (blue). Class G can be as efficient as class D or T. While a class G design is more complex, it is based on a class AB amplifier and can have the same clean characteristics as well.

    Class H
    Class H is similar to class G, except the rail voltage is modulated by the input signal. The power supply rail is always just a bit higher than the output signal, keeping the voltage across the transistors small and the output transistors cool. The modulating power supply rail voltage is created by similar circuitry that you would find in a class D amplifier. In terms of complexity, this type of amplifier could be thought of as a class D amplifier driving a class AB amplifier and is therefore fairly complex.

    How to Choose?
    Regulated or unregulated? Class AB, D, or T?If you're really into a lot of bass, the class D or T may be for you as these amplifiers will produce the highest SPL with the smallest size. If you just want to wake the neighbors, blur your vision, or make a big splash in SPL contests, maybe you just need one of the inexpensive, powerful, & dirty class D designs. Want the cleanest high frequencies? Maybe a good class AB amp would be your selection. Whatever you choose, I hope this information helps you achieve the sound you're looking for!
    Mantabs

 

 
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