Push pull class b amplifiers made with bjts can be constructed using a npn transistor for one element and a pnp transistor for. A push pull amplifier is a type of amplifier that can drive current in either direction through the load. So i got my wheels turning and though it would be cool to try and make a poor mans version of the 12a seeing how 2a3s a super expensive. The aim of this project was to build a low cost valve amplifier with good quality sound output. The deciding factor here is the type of output network. Emitter follower is a case of negative current feedback circuit. All models have a secondary tapped for 4, 8 or 16 ohm outputs. Version 1 uses two 6sn7s in the input stage, and delivers full output with around 300mv input. The ultralinear or distributed load method of operating a push pull output stage in an audio amplifier has been known for some years now, and was first employed in a commercially produced amplifier just after the war. Click the image to view the full size readable annotated schematic.
Pushpull amplifier is a power amplifier which is used to supply high power to the load. Push pull amplifier circuit diagram class a, class b and. The 2a3 vacuum tube is a power triode capable of outputting 3. Utc ls55 pp audio output transformer for 2a3 6a3 we 300b.
One transistor pushes the output on positive half cycle and other pulls on negative half cycle, this is why it is known as push pull amplifier. This amp design features the 6336a power triode tube, along with push pull class a operation, no overall feedback, low distortion, approximately 20w of output power, reliability, and highperformance sound. In my book, i explain how to change an amp from pentode push pull, into an ultra linear design and even into a triode push pull design. Home tube amplifier kit power amplifier kit 2a3 pp push pull tube amplifier 15w. I used tango nc14 interstage and fx405 output transformers, which ive had around for a while. The advantage of push pull amplifier is that there is no power dissipated in output. An ac input signal is applied to the push pull circuit, with each half operating on alternate halfcycles, the load then receiving a signal for the full ac cycle.
Type 6a3 was the american answer to the british type px4 and has very similar characteristics and performance, although differing in filament voltage. This great amplifier is a classa, push pull amp using a pair of 6b4g directlyheated triodes as the output stage. Classa pushpull tube power amplifier electronics diy. Illustration of class b and class ab pushpull, inverting amplifier output current and voltage characteristics of the pushpull, inverting amplifier rl 1k.
Illustration of class b and class ab push pull, inverting amplifier output current and voltage characteristics of the push pull, inverting amplifier rl 1k. The anodes are connected to the primary winding, the cathodes to ground circuits 1, 2, and 3, and the middle of the primary to the highvoltage supply. In terms of distortion and performance, push pull amplifiers are more efficient than singleended amplifier because of its push pull arrangement. Maximum output of this amplifier is 20w that is quite enough for family use. Push pull amplifier circuit diagram class a, class b and class ab. The result is the fatboy 300b amp named as such because, like me, it is a tad overweight. The author chose the 2a3 directly heated triode power tube to implement the loftinwhite circuit. Advantages and disadvantages of a push pull amplifier.
A kennedy audio labs, and is provided with the understanding that this information is for personal use only. Figure 1 shows several pushpull tube amplifiers only the power tubes and the output transformers primary winding. This amplifier is a push pull type using lowcost irf510 power supply fets. Push pull amplifier circuit, operation, advantages and. When i started researching an amp to build, i came across this idea of using an interstage. The output power and operating voltage cannot conveniently be decided independently of each other as shown in equation 2. The end result is a solid performer with decent power, sounding unlike push pull pentode designs. The 2a3 tube amplifier a tribute to simplicity and warm.
Push pull amplifier is a power amplifier which is used to supply high power to the load. It is the amp that i designed after my popular squirrel monkey onetube amp. The 5e3 deluxe schematic with signal flow and annotations. One such amplifier is a radio frequency rf amplifier which amplifies the power of a signal carrier. This means that the two transistors are biased at the cut off point. A 40w pushpull pa for high efficiency decade bandwidth. The class b push pull amplifier is almost similar to the class a push pull amplifier and the only difference is that there is no biasing resistors for a class b push pull amplifier. Components qty device 1 2n3904 npn transistor 1 2n3906 pnp transistor 3 1n4001 diode 3. In an issue 15 of vtv article on a diy eight 45 amplifier bart brown says of push pull vs. The only thing you have to do is to replace some transformer connections.
Very few designs differing from these two have proven fit for real life, the quad ii being a notable exception you will find the diagram in the appendix together with a brief explanation. Mar 28, 2004 in an issue 15 of vtv article on a diy eight 45 amplifier bart brown says of push pull vs. Circuit diagram and working of push pull amplifier. It can be shown that the theoretical full power efficiency ac power in load compared to dc power consumed of a pushpull stage is approximately 78. The information provided is and remains the sole property of kennedy tube audio a. It consists of two transistors in which one is npn and another is pnp.
Introduction in a wireless communication, a signal amplifier is required in order to deliver signal over a long distance cripps, 2006. Pushpull class b and class ab amplifiers analog devices. The push pull amplifier which was just discussed improves efficiency but the usage of centertapped transformers makes the circuit bulky, heavy and costly. Class b amplifier and the classb transistor amplifier. Emitter follower and darlington amplifier are the most common examples for feedback amplifiers. The circuit shown in figure 129 is a class a transistor push pull amplifier, but class ab or class b operations can be used. The push pull amplifier in figure 1625 has ivcni ivcni 30 v and ri.
When the screen grids are connected to the high voltage supply you have a standard push pull pentode amplifier circuit 1. Modification to a broadband hf amplifier using lowcost power mosfets i decided to build a amplifier for my softrock rxtx6. Construction of push pull class a power amplifier the construction of the class a power amplifier circuit in push pull configuration is shown as in the figure below. In case of the circlotron the two tubes works in parallel, meaning half the load of a single tube or 25% that of the load for a traditional push pull series arrangement. The class b amplifier circuit above uses complimentary transistors for each half of the waveform and while class b amplifiers have a much high gain than the class a types, one of the main disadvantages of class b type push pull amplifiers is that they suffer from an effect known commonly as crossover distortion hopefully we remember from our tutorials about transistors that it takes. Its a slightly more complex push pull amp but its surprisingly similar to the little champ. This paper presents a push pull classe power amplifier based on a simple load network using the impedance matched transformer. Modification to a broadband hf amplifier using lowcost.
Like the classa amplifier circuit, one way to greatly boost the current gain ai of a class b push pull amplifier is to use darlington transistors pairs instead of single transistors in its output circuitry. Easy to build pushpull amplifier using plitron output and. Push pull transistors semelab plc produces a wide range of push pull mosfets and this application note is intended as a guide to some circuit design principles which are particularlyappropriate when using these devices. Regardless whether the amplifier is single ended or push pull, solidstate or vacuum tube, classa or classabto achieve the best performanceall power amplifiers require a precisely set idle current for their output stages. I would probably build more 2a3 amps if they did not need 2. Pdf 1650f 1650h 1650k 6146b, 6550b 6l6gc 5881 tube kt88 kt88 tube kt88 6a3 tube el34 tube 807 tube el34 6l6gc tube. This project is related to the other tube amplifier projects i have posted. A perfectly balanced push pull stage will cancel all even harmonic distortion and sum odd harmonic distortion generated within the power stage. This made it necessary to carefully tune the feedback loop for stability.
Vintage 1960s rca 2a3 double gray plate oo getter amplifier tube. Two examples of semelab push pull mosfets are shown in figure 1. Electraprint is your finest source for analog amplifiers and high quality handmade audio transformers. Consider this type of amplifier as a more advanced version of singleended amplifiers. These are the mostly used ones with a number of applications. Pushpull a2 6a3300b amplifier and power supply electraprint. Cripps centre for high frequency engineering, cardiff university, cardiff, cf24 3aa, u. Ece 3274 power amplifier project push pull qty device. This arrangement mainly reduces the harmonic distortion introduced by the nonlinearity of the transfer characteristics of a single transistor amplifier. Amplifier design the design of a high power push pull amplifier operating from 150 volts requires several decisions. The drive circuitry of the control grids is not shown i assume perfect. The ultra linear arrangement applied to both a singleended and a push pull stage. Pushpull amplifier article about pushpull amplifier by. Claus byrith l an approach and a practical circuit.
A pushpull amplifier is a type of electronic circuit that uses a pair of active devices that alternately supply current to, or absorb current from, a connected load. It has more than a casual similarity to the first push pull el84 6bq5 oddwatt project from nearly two years ago. An amplifier that uses two amplifying elements in this type of arrangement is often referred to as a push pull class b amplifier because one device pushes current into the load and the other pulls current from the load. This section introduces one example using r core audio interstage and output transformer. When the need for longdistance audio communication increased, it created the need to. These transformers were as always heavy, bulky, expensive, and nonlinear, and added insult to injury as their lf and hf phaseshifts severely. E many people today think that push pull tube amps are no different qualitatively than transistor amps. The proposed load network consists of an impedance matched transformer and series lc filter. Both tube amplifier projects use el84 6bq5 tubes and the earlier one used a ecc802s driver while this one uses 5751 driver tubes. The class of operation has been specified as class c. They form mirrors with the quiescent current set by r. Ece 3274 power amplifier project push pull richard cooper 1.
With the screen grids connected to taps on the primaries at 33 or 40% in general the amplifier is in an ultralinear configuration circuit 2. But you will need to decide which power transformer to use, both have identical performance but one runs cooler than the other because of the laminations. A class b pushpull amplifier is more efficient than a classa power amplifier because each output device amplifies only half the output waveform and is cut off during the opposite half. In this arrangement, one transistor amplifies the positive half cycle whereas another.
This means that the load must be twice that of a single tube. D1 and d2 are diodeconnected transistors identical to qn and qp, respectively. The amplifier stage is based on the compact hifi power amplifier. Application notes 2a3 push pull 20w monaural power amplifier. In a conventional push pull configuration the tubes works in series from a signal point of view. The class b configuration can provide better power output and has higher efficiencyup to 78. This push pull amplifier is used where high power output and good fidelity are needed. A push pull valve amplifier almost invariably follows one of the two schemes shown in block diagrams below. Nov 12, 20 this design is a close copy of a design in the acrosound catalog, and in this case, the hammond transformers have a somewhat lower bandwidth. Diy 500 watts mono high power amplifier using transistors 2sc5200 and 2sa1943 v1 duration. The main features are excellent performances low distortion, wide. A singleended amplifier is a vacuum tube which has 3 electrodes in it. Even if the phase inverter is perfectly balanced it will inevitably go out of balance when the power. Raysonic sp10 2a3 class a push pull integrated tube amplifier factory box remote.
I like klipsch speakers and noticed a while ago that pk recommended in the klipschorn brochure to pair the speaker with the brook 12a amplifier, which is a push pull 2a3 amp. I think an amplifier builder should consult with himself and his amplifier before asking the reference books and authorities. Objective this project will introduce two common power amplifier topologies, and illustrate the difference between a classb and a classab amplifier. Enclosed shielded, 4 slot, above chassis type x mounting. This classa push pull tube power amplifier uses a pair of push pull class a, ultra linear mono block tube amplifiers that can be used with several different vacuum tubes including kt77 6l6gc kt88 with a 12sl7 driver and 6no30 tubes. Complementary symmetry push pull class b amplifier. Pdf pushpull classe power amplifier with a simple load. Since the center tap passes rf when used as a balun or transformer, it will also pass rf to the dc supply. Class b amplifiers are greatly preferred over class a designs for highpower applications such as audio power amplifiers and pa systems. Anyone building this circuit should spare no expense on the output transformers.
It has a ton of power, especially in comparison to the flea powered set amps i own, but this amplifier also projects a sense of space and life to the music that is hard to match. One device pushes current out into the load, while the other pulls current from it when necessary. From this level up the tubes start to saturate, and the current through the control grids forces the polarization level more negatively, out from classab. This spiffy little amplifier uses a push pull design featuring a pair of 6aq5 beam power tubes driven by a 6j6 dual triode, all of which are 7 pin miniature tubes. However, guitar amps rarely use matched valves and usually have a lessthanperfect phase inverter. A push pull amplifier offers greater power gain and better efficiency than does a single ended amplifier. This amp has great specs, produces twice the power from your favorite tube and is simple to build. A push pull amplifier is an electronic circuit which delivers currents and absorbs currents from loads. The last few amplifiers that ive designed used pentodes and lots of nfb to get low distortion.
Coates 2007 2012 power amplifiers introduction to power amplifiers power amplifiers amplifier circuits form the basis of most electronic systems, many of which need to produce high power to drive some output device. Chokeloaded triode direct coupled to dht driver, transformer coupled to the push pull 300b output tubes. Figure 10 shows the excellent third order linearity performance of the push pull amplifiers. The amplifier changes smoothly from classab to classf as the plate voltage rises following the input signal envelope.
In push pull circuits the center tap is connected to the power supply. Pushpull amplifier an electronic circuit in which two transistors or vacuum tubes are used, one as a source of current and one as a sink, to amplify a signal. The cost of such an amplifier is determined mainly by the transformers and the audio output valves. Note that the coax center conductor in the diagrams below are connected to the center tap of the coil as is the power supply in a push pull amp. Class ab amplifier biasing a straightforward biasing approach. Pushpull amplifier circuit diagram, working and application. The principal difference is that whereas the px4 is based on a twosided planar construction the 6a3 is based on two conventional electrode assemblies wired directly in parallel in order to obtain a very low ra value 800 ohms.
I built this amp because i wanted that sweet directly heated triode sound but with more dynamics and punch for modern electronic, rock, etc and classical orchestra music. Its high input sensitivity is good for passive preamp systems. With mirrors, the device temperature for all transistors needs to be matched. The circuit is called a pushpull because one transistor pushes in one direction while the other pulls in another direction.
I think an amplifier builder should consult with himself and his amplifier. Class operations were discussed in an earlier topic. Electronics tutorial about class b amplifier and class b power amplifiers including its pushpull configuration and crossover distortion. Units are designed to provide ample headroom at bass frequencies note the weight of each transformer. The howler monkey push pull 6aq5 guitar amp c 2012, g. A 40w pushpull power amplifier for high efficiency, decade bandwidth applications at microwave frequencies r. This pcb makes all those changes extremely easy, just some minutes soldering and the job is done. The above examples of possible combinations are to help you narrow down the choices of transformers for your favorite tube types. It consists of two transistors in which one is npn and. Some of the 6a3 and 2a3 tubes were not strictly made to original design, they were made as mono plates. This super industrial, scratch built 6bg6 amplifier by jim nichols is one of the finest sounding amplifiers i have owned. The idea for the amplifier started from the authors discovery of the loftinwhite circuit. Emitter follower circuit has a prominent place in feedback amplifiers.
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