Posted on june 8, 2015 june 8, 2015 ella push pull el34kt88 amplifier schematic. The very good result got with the pp2010 and availability of a pair of old 10kohm tecnotrafo italy push pull transformers have forward me to create this new amplifier. Also included is a copy of the 20 page wireless world williamson special edition. Ella push pull el34kt88 amplifier schematic diy hifi supply. The phase inverter features arc protection the diode, and a nice big grid stopper to prevent undesirable distortion waveforms. Still most folks do not really need more than 40 to 45 watts of audio power. The 2a3 tube amplifier a tribute to simplicity and warm sound february 15 2017, 10. It is switchable between ultralinear mode and triode mode with varying degrees of feedback.
For push and pull tube amps, i always prefer 7027, kt66, 7591 and el84 over el34. It means that you will have to build it yourself using assembly manual. Ultralinear operation, also known as distributed load operation, is a term when applied to singleended or push pull vacuum tube audio amplifiers, that describes the particular output stage configuration whereby the screen grids grid 2 of tetrodes, pentodes or beam power tubes are fed from a tapping in the output transformer singleended. It really depends on which brandtype of the tube and the amp you installed them on. The signal to be amplified is first split into two identical signals 180 out of phase. Discussion in amps and cabs started by goldstrat, sep 18, 2006. There is only one tube family that has the right tone, the 6l6 family.
Williamson proposed the standard which became generally accepted as the target figure for highquality audio power amplifiers, for less than 0. Kt88 push pull project with hashimoto transformers. 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. Its exclusive screengrid radiator fins reduce a major source of. Figure 1 shows several push pull tube amplifiers only the power tubes and the output transformers primary winding. Over 90% of amplifiers are push pull, and push pull amplifier does not 2nd harmonic and off course. Kt120 push pull tube amplifier schematic oddwatt audio obho this kt120 tube amplifier is a follow on to the smaller oddwatt power amplifier. It is a good choice for those who are considering 6l6 upgrades. Now that i have built a flexible test bed for power amplifiers and purchased an assortment of output transformers i intend to do this work over again. The basic operation of a push pull amplifier is as follows. However, in the case of the screengrids in ultralinear push pull amplifier configuration this is not so, because the screengrids are located at about 43% of the lineal distance between cathode and plate. The class ab pushpull output circuit is slightly less efficient than class b because it uses a small quiescent current flowing, to bias the transistors just above cut off as shown in fig. Kt88 tube power amplifier class a single ended valve triode amplifier has not same tone with push psu amplifier.
The quality pushpull amplifier amplifier was modified from time to time to. Kt88 beam power tetrode t he svetlana kt88 is a beam power tetrode having a large standard octal base and glass envelope. A williamson amplifier is a type of vacuum tube valve amplifier whose circuit design uses the. The kt66 had less rapid acceleration, longer electron paths, and almost no kink. Circuit of a 30w ultralinear amplifier using kt66 or kt88 valves in the output stage. The drive circuitry of the control grids is not shown i assume perfect. Push pull amplifiers are commonly used in situations where low distortion, high efficiency and high output power are required. Weve covered theory and applications behind a push pull amplifier.
The original output stages used triode connected kt66 tetrodes, although a 6l6, with slightly lower output, could be used. If you have built any of these circuits, we would love to hear from you so send us your comments. It is remarkable that triode output stages still occupy an important place in highend audio amplifiers. To improve the full power efficiency of the previous class a amplifier by reducing the wasted power in the form of heat, it is possible to design the power amplifier circuit with two transistors in its output stage producing what is commonly termed as a class b amplifier also known as a push pull amplifier configuration. This amplifier, like the my other designs, can be connected directly to a cd player or to a dac without using a preamp. During the first positive half cycle of the signal, end a of the transformer winding becomes positive and end b becomes negative.
In 6l6, there is an electronic lens that focuses electron beam onto its plate. New production kt66, 6l6g, el34 or el37 is indeed available. Most of them show these audio beauties used in the pushpull configuration in order to obtain the greatest efficiency and the most power output. Because of their excellent datzsheet characteristics and overload tolerance, kt66s are preferred by some guitar players for use in guitar amps in place of 6l6gc. In the kt66 was advertised as the finest audio tube in the world. The results from testing the amplifiers are quite similar to the results from the oddwatt 225 6sl7 srpp kt77 classa push pull tube amplifier. This circuit gives a pushpull output from the two anodes of the b339, and as. In general, higherpower amps are usually push pull class ab circuits, while lowpower amps are usually pure class a.
A push pull valve amplifier almost invariably follows one of the two schemes shown in block diagrams below. Models applied to the quad ii valve amplifier vanderveen. Most of them show these audio beauties used in the push pull configuration in order to obtain the greatest efficiency and the most power output. Raphaelite 280w amplifier power transformer el34 6l6 kt66. Welcome to the most complete do it yourself guide on the d. To improve the full power efficiency of the previous class a amplifier by reducing the wasted power in the form of heat, it is possible to design the power amplifier circuit with two transistors in its output stage producing what is commonly termed as a class b amplifier also known as a push pull amplifier configuration push pull amplifiers use two complementary or matching.
Please note that kt66 draws more heater current than 6l6. The kit includes all electronic and mechanical parts including tubes and housing required to build a ready to work, high quality tube preamplifier. When the kt66 valve was first introduced in 1937 it was given maximum anode and screen voltage ratings of 400 and 300 respectively. Feel free to send us your hifi audio schematics and we will add them here. The kt66 is a very well known audio output beam tetrode valve. Certain assumptions may be made as long as the power output of an amp is known. Kt88 matched quad introduced in 1956 the kt88 bigger brother to the lower power previously available kt66 can deliver 50 watts of audio power in push pull mode or 100 watts in parallel push pull 4 valves. These amplifier types may be modified or expanded to. Type kt66 is a high slope, indirectly beated beam tetrode designed.
The figure below gives the detailing of the construction of a push pull class b power amplifier. Oct 11, 2011 the largest difference from the transistor amplifier to the el34 tube amplifier is the bass. This amplifier, like the my other designs, can be connected directly to a cd player or to a dac without using a pre amp. The information provided is and remains the sole property of kennedy tube audio a.
Generally this splitting is done using an input coupling transformer. Our exhibit is a postwwii device, probably dating from the 1960s. It is a push pull amplifier with kt66 power tubes i love me a good kinkless tetrode. Kt66 has been used in high end audio amps in europe, as well as in the legendary marshall bluesbreaker combo amps in the 196070s. Cocking was a guru in valve electronics and wrote several authoritative texts on radio and television subjects. This great amplifier is a classa, push pull amp using a pair of 6b4g directlyheated triodes as the output stage. Its high input sensitivity is good for passive preamp systems. Quad ii valve power amplifier modernising and modifying.
Quad ii circuit there is no feedback at the screen grids. Articles from wireless world on the willamson amplifier keywords. It is not uncommon to find these valves used in parallel push pull. It uses a power transformer scavenged from a fisher 400 receiver and hammond 1645 output transformers, and produces 25 watts per channel. In a push pull amp, the input signal appears across the secondary ab of the driver transformer. For many years the kt66 valve has been regarded by many as the hallmark of a. The shape of the envelope is a mixture of the classic shape and the wide tube.
Apr 14, 2011 bob gjika playing his kt66 amp and a gjika tele. El34 pushpull tube amp kit tu8340 adopted semiautomatic bias adjustment system which allows users to adjust the bias simply by pressing buttons even if the model takes on the fixed bias method no need of manual adjustment every time of tube rolling. Thus the ac signal voltage appearing at each screengrid as a result of linear voltage gradient between the cathode and plate within each. The kt66 was essentially a 6l6 redesigned with a larger cathode and a shorter, fatter anode. It have to be experienced as a description is far from enough compared to feeling it in your chest. A push pull amplifier is an amplifier which has an output stage that can drive a current in either direction through through the load. Class b amplifier and the classb transistor amplifier. With a goldplated molybdenum alloy grid and carbon coated screen grid, the svetlana kt88 is the finest power tube of its type be ing manufactured today. The story of the williamson amplifier must begin with the wireless world quality push pull amplifier project, that commenced in 1934 and concluded in 1946 under the guidance of w.
The largest difference from the transistor amplifier to the el34 tube amplifier is the bass. It is suitable for either single or pushpull audio operation, and may be employed as a. Push pull was not a new invention, it had been used for small signal amplifiers and oscillators very early on, but we made some of the first commercial pp power amplifier s. For files in adode pdf format where indicated, if you want to download the file and view offline, click on the link with the right mouse button, then click on save link as. Taking advantage of new ratings for the kt66 valve. Download a pdf schematic of the amp wiring, the driver pcb schematic showing components for this build, and the power supply pcb schematic. Jun 27, 2016 many articles have appeared regarding projects using one of the most sturdy, versatile, and trustworthy audio tubes ever made the 6550. Pcl84 compound valve based headphone amp pentode sections connected as triodes in push pull operation 100% class a trioded push pull operation about 1wchannel po into 8 ohms due to internal dummy load, it can drive headphones from push pull amp totally in class a, then you should double the platetoplate reflected load obtained from the 1st step, because both tubes will be conducting in opposing phase all the time, and so you want each tube to see the load that it needs to function in class a without exceeding its maximum pa. I used a pushpullparallel set of 5b854m tubes, which are basically 807 tubes in a slim bottle with a loctal base.
For the most part, only two basic types, or classes, of audio amplifier are used for musical instrument, studio, hifi, and high end amplifiers. Elekit tu8340 vacuum tube pushpull amplifier diy kit. The early jtm45s used the rs deluxe output transformer which had 6. Chapter 3 describes the kt66 vacuum tubes, used in the power. The original output stages used triodeconnected kt66 tetrodes, although a 6l6, with slightly lower output, could be used. As of 2012 kt66 tubes continued to be manufactured at reflektor saratov in russia, jj electronic in slovakia, and at liuzhou in china. Atarashi originally built this amplifier as the fixed bias el34 class b push pull monaural amplifier featured on the january 2003 issue of the highfidelity audio. The kt66 was very popular in european radios and audio amplifiers.
Thus safe and simple bias adjustment is realized a dream feature for tube lovers. The value of the quiescent point and its adjustment is dependent on the amplifier type. A williamson amplifier is a type of vacuum tube valve amplifier whose circuit design uses the same principles as a design published by d. Push pull amplifier circuit, operation, advantages and. While these tubes have the same pinout and minimum tolerances required of a kt66 tube, they do not have the performance characteristics of a true kinkless tetrode kt66. From the 1970s kt66s lacked the internal carbon dust coating of the glass bulb. And with that out of the way, here is the schematic it is a push pull amplifier with kt66 power tubes i love me a good kinkless tetrode. Pdf 1650e 1650g pushpull 6l6gc el34 schematics 6bq5 el34 6aq5 tube tube 6v6 6550b el84 tube 807 tube. Pushpull 58816l6 amplifier this was the second amplifier i built for myself and was completed in september 2006. In general, kt66s tends to have a bit warmer sound with more low end.
Classa amplifiersingleended classab amplifierpush pull. Mar 21, 2015 kt88 tube power amplifier class a single ended valve triode amplifier has not same tone with push psu amplifier. But then it turns from williamson to futterman in that the output configuration are the so called single end push pull. 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. A class ab amplifier can be made from a standard class b pushpull stage by biasing both switching transistors into slight conduction, even when no input signal is present. This small biasing arrangement ensures that both transistors conduct simultaneously during a very small part of the input waveform by more than 50 per cent of the input. Version 1 uses two 6sn7s in the input stage, and delivers full output with around 300mv input. This is our collection of diy and hifi audio schematics. Kt120 pushpull tube amplifier schematic oddwatt audio obho. Weve also demonstrated different types of push pull amplifiers, like class a, class b and class ab push pull amplifier models.
I have begun to have doubts about the results presented in this article. Practical implementation of the pushpull, common source amplifier method 1 c lr vin vout iout. Lecture 060 pushpull output stages 11104 page 0601. The kt66 had less rapid kt6, longer electron paths, and almost no kink. It was the standard output tube in the classic quad ii 1952, a version of which is still being manufactured today and in the leak type 15 1945 and tl12 1948, both among the earliest british hifi amplifiers. The 2a3 tube amplifier a tribute to simplicity and warm. Here each single valve of the push pull pair is replaced with two valves connected in parallel. In the 1950s the production used black base caps and prewwii had the classic envelope shape. Jun 08, 2015 home schematics ella push pull el34kt88 amplifier schematic. In this article, the 6550 is used in a clean, sweetsounding, singleended design. El34 push pull tube amp kit tu8340 adopted semiautomatic bias adjustment system which allows users to adjust the bias simply by pressing buttons even if the model takes on the fixed bias method no need of manual adjustment every time of tube rolling. The circuit arrangement of class b push pull amplifier, is same as that of class a push pull amplifier except that the transistors are biased at cut off, instead of using the biasing resistors.
A kennedy audio labs, and is provided with the understanding that this information is for personal use only. Also included is a copy of the 20 page wireless world williamson special. Class a and class ab also known as push pull amplifiers. Vatasheet each single valve of the push pull pair is replaced with two valves connected in parallel.
Many articles have appeared regarding projects using one of the most sturdy, versatile, and trustworthy audio tubes ever made the 6550. Atarashi modified the amplifier to fit for kt88 ab1 push pull ultralinear operation. When the circuit design reached the mainland years later constructors reacted. Its deep as the internal hell, clear like tuned piano and makes a world of difference to enjoying music. 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. The williamson amplifier was of symmetric pushpull design and used negative feedback and a. Nov 02, 20 pushpull 58816l6 amplifier this was the second amplifier i built for myself and was completed in september 2006.
Complete circuit diagram of 50 watt amplifier using kt66 valves with fixed bias. Figure 1 shows several pushpull tube amplifiers only the power tubes and the output transformers primary winding. Gec also manufactured kt66 tubes under the name of genalex. The design presented here is based on a combination of optimal quality and reasonable construction cost. The kt61 is not that hard to find, but any of the similar pentodes. Measurements pushpull kt88 tube amplifier 12sl7 driver measurements were made using a hp 331a distortion analyzer, tenma low distortion signal generator 0. It has a cathodyne phase inverter that only uses one triode, so it leaves 3 triodes for the preamp for a total of 2 12ax7s. Always prefer the nos tubes over the modern chinese and russians. Kt88 tube power amplifier class a circuit wiring diagrams. This is a quick run through of the williamson 1947 circuit. A 50 watt amp with two 6l6 or el34 tubes, or a 100 watt amp with four 6l6 or el34s, is a push pull amp. From a dc point of view the two output tubes actually made of 2 x 3 6lf6s in parallel are in series. Oddblocks classa pushpull kt88 tube amplifier 12sl7.