My recommended bias measurement method is the output transformer resistance method. It also determines the turns ratio and type of transformer. It is important to understand the output transformer is in the signal path, and not only matches the impedance of the load to the amp, it also helps shape the sound of the music created. How to calculate the required capacity kva rating or amperage.
When current passes through the primary coil, it creates a magnetic field which then. If you need assistance with circuit protection devices such as fuses or breakers, or wire sizing, please consult a licensed electrical contractor or electrician in your area who will be familiar with state and local codes. Also the screen grid is held at the voltage specified. If you have some experience in assembling transformers, then this program is perfect for you. Practical winding sequence equivalent to the simplified circuit above. I just got this response when i asked someone about swapping 6v6 and 6l6 power tubes. Iif you would like to calculate and wind your own single ended and push pull output transformers for guitar amps and home hifi amplifiers, ive.
V5 is the output valve, driving output transformer t1. Using a 75 kva three phase transformer as a starting. Afaik, there is no available output transformer calculator program available anywhere so that you enter tube type, mode of operation, output power maximum, and after clicking calculate, all the winding details appear on a sheet. It is important to note, however, that these solutions are best only for those experts who have knowledge and experience with assembly transformers. Brainstock video production our diy amp, studio, gear blog. Turns ratio v in to the primary v out measured in the secondary e. Enter the transformer rating and select the appropriate unit. The specification of a high quality valveamplifier output transformer is given in figure. Audio transformer and impedance matching transformer. In most amplifiers they will be fed via resistors, the power supplies will sag and the transformer will have losses. Prices are generally extortionate, though they do sell a good 25w output transformer. Transformers part 2 beginners guide to electronics. The output transformer in a singleended tube amplifier is the device which matches the high output impedance of the tube to the low input impedance of the speaker load 4, 8 or 16 ohm. Then take the other black wire from the output transformer primary and stretch it the other way across the chassis.
As an example, you might want to design an output transformer for a single pair of 6l6 output tubes. The output power is for the anode, and it will depend on 20db nfb to keep the thd output transformer valve save output transformer valve to get email alerts and updates on your ebay feed. Output trannys contribute most of the distortion in a valve amp and have a limited bandwidth. You know you would like to match this impedance to loads of 8 and 4 ohms, and this will be used for. Stepup, stepdown, and isolation transformers worksheet. It is a 15w 100v line speaker transformer with multitapped primary and secondary to suit 8 ohm speakers. To separate the high voltage and match the speaker impendance with the tube impendance we need audio grade output transformer. Finding a 1v ac source is difficult unless you have access to a variac, small transformer or similar device.
The one thing im stuck on is the output transformer, according to the datasheet i need to get a 35004000 ohm transformer with a 4 ohm output to power a car speaker i have. Application of the m1115 100v line, 15w speaker transformer. Drain valves, threeway valves, ball valves and gate valves for oilimmersed transformers valves for oilimmersed transformers the ambitious climate targets of the energy revolution are a great challenge for all involved. This is practically the determination of the output impedance of a circuit by means of the dc transfer function. If you have an 8 ohm output transformer hooked up to an 8 ohm speaker, the transformer is seeing what it is looking for, if you hook the same transformer to a 16 ohm speaker it will have a 16 ohms load, the transformer is. Apr 30, 2010 the output transformer is the heart of a valve amplifier. Checking an unknown output transformer we can now use this knowledge to determine the impedance of any unknown output transformer. The quiescent anode current is generally between 25 and 60ma 50ma in this case. Professionals with experience in transformer assemblies use the computer program to calculate the number of coils and wire thickness. Using a 75 kva three phase transformer as a starting point. The output transformer is the heart of a valve amplifier. Next, measure the voltage across the speaker taps with a.
This webpage offers two ways to calculate tube bias and plate dissipation. Download transformer calculator coils and wire thickness at. The output transformer in a singleended tube amplifier is the device which matches the highoutput impedance of the tube to the low input impedance of the speaker load 4, 8 or 16 ohm. For example, a transformer with a 12v, 2a output at 120 v input would be. Transformer turns ratio calculator electrical classroom. There are several things that are important in getting an output transformer made. Calculation of output transformers the output transformer is probably the most expensive part in the amplifier and something you have to live with if you like classic tube amplification. From the tube data books, you determine that a pair of 6l6s will put 4050w in class ab push pull into a 4400 ohm plate to plate impedance. If you used an 8 ohm tap, a 4 ohm tap will have about 2. Transformer losses and different types copper iron stray dielectric. A good output transformer should only loose power, not quality.
M 1115 is the part number of a 100v line speaker transformer from perthaustralia based company altronics. So we apply an ac voltage to the primary of the transformer and we measure the output voltage to the secondary. Calculating output transformer impedance sarris custom tube. Hence for an ideal transformer, the output current varies as the inversely proportional to the voltage. Below that are the sliders that let you play with the parameters.
You measure the output transformer s voltage drop and resistance to calculate the bias current. How to calculate electrical transformer output sciencing. This second formula does not look at the plate to plate impedance. Select the number of phases from the dropdown menu. Electronics tutorial about the audio transformer which can be used as a line. Class a insulation is the most common for output transformers, as no great. Whether you are into the clean, free spirited single ended tube output or high efficiency, high power, pushpull audio, we have the output transformer for you. Minimum inductance of the primary winding of output transformer. Calculate the nominal impedance of the loudspeaker required for maximum power transfer. Looking through all of my scavenged transformers i cant find a single one in the thousands of ohms, most are a few hundred and lower. The output stage of the gec bc402 set is shown here. All we need to do is determine the turns ratio of the transformer, and with that information we can calculate what impedance will be reflected back to the primary with a given load on the secondary. Calculate the voltage output by the secondary winding of a transformer if the primary voltage is 35 volts, the secondary winding has 4500 turns, and the primary winding has 355 turns. Are you looking for the best transformer calculator software for your next project.
Tube amp power transformer current draw calculator javascript must be enabled in order for the calculations to work. Finding unknown values for output transformers a little math is required if you have an output transformer with unknown values and want to find the intended speaker impedance for a given tube type there are several things to consider. You must then divide the answer by the number of volts you applied to the secondary. The next two are the dc resistance of the output transformer, followed by the impedance. Application of the m1115 100v line, 15w speaker transformer to valve pushpull output transformer application. A transformer is essentially a pair of coils wrapped around iron cores, which are called primary windings and secondary windings for input and output, respectively. Building a tube amp, how to calculate output transformer. You can use a 5v rectifier winding from an existing pt or the 6. Output transformer efficiency usually in the range from 0. The halfprimaries of the output transformer should have identical voltages on them. Design for ultra linear output transformer for n709 valves in pushpull. Secondaries should have multiples of the voltage youre putting on the tap you chose.
To design an output transformer, it is necessary to determine the output power according to the tubess characteristics, most notably the input and output. How to calculate audio output transformer load resistance. Oct 10, 2009 first time ive heard that valve amps are low quality, i have only heard that they can be low quality if you have a poor quality output transformer. How to calculate the required capacity kva rating or. There is actually a wide range of valves that fit the bill, but the most common for guitar use are the el34 25w, 6l6gc 30w, or a pair of parallel el84s 24w. You can also measure the actual plate current by shunting the output transformer with a multimeter in the dc milliamps mode and use the tube dissipation using plate current calculator. When you begin the calculation you have to select the respective. Use the following instructions to determine the load resistance of an unknown audio output transformer. The formula calculates the frequency response based on the triodes amplification factor and plate resistance. The two output trannys are rotated 90deg to the power mains tranny to avoid picking up induced hum from the mains tranny external magnetic field. A classic example of this is the lt700 audio transformer which can be used in the output stage of an amplifier to drive a loudspeaker. Transformer valves, product range safety valve and.
Download silvio klaics neat little transformer calculator from his website. Transformer calculation software electronic circuits. If your students are not strong in their ratio skills, this question provides an. Determination of power and energy losses in power transformers. K 1,000 the full value in va, 50,000 is then divided by the voltage 240v 208 amperes. Economy range, where the pricequality relationship is carefully calculated to ensure audio quality in a compact package. Transformer winding turns and voltage ratio calculator v1, n1, v2, n2. Langfordsmith, editor, radiotron designers handbook, 4th edition, harrison.
Using a 50 kva single phase transformer as a starting point. Variable prices, although the transformer shields are truly excellent and. Calculating output transformer impedance sarris custom. The transformers allow an ac input signal to produce a related ac output signal without the input and the output being physically connected together. Uk vintage radio repair and restoration audio output stages.
We know that for a transformer, the ratio between the number of coil turns on the primary winding n p to the number of coil turns on the secondary winding n s is called the turns ratio. Transformer calculator kva calculator full load amps. In this guided applications exercise well examine, install, and test a control transformer. This current passes through the primary of the output transformer, which will drop typically 15 to 25v. When current passes through the primary coil, it creates a magnetic field which then acts as an inductor to create voltage in the second coil. Get a low voltage ac transformer about 10v or less and place it across the speaker taps of the output transformer ot. An excellent site in the netherlands, selling a good range of valve amp related components. The wattage output in an amplifier may vary from application to application due to many variables such as tube types, solid state vs. For amps with cathode bias resistors you can simply measure their voltage drop and use the tube dissipation using cathode resistor voltage drop calculator. As far as hifi goes, yes you would build it totally different than a guitar amp, using pentodes such as the ef86 for example. Maximum leakage inductance of the primary winding of output transformer. Earlier research 17 about toroidal output transformers has shown that the toroidal transformer is very well suited to function as the impedance converter between. Interactive valve data sheets black magic amplifiers.
This transformer calculator helps you to quickly and easily calculate the primary and secondary fullload currents of the transformer. We have been producing tube output transformers continuously for over 75 years, constantly improving and tweaking their performance. Tubes do not affect impenitence, speaker load does. Valve amp manufacturers purchase trannys from transformer winding companies. Transformer winding calculations are simply an exercise in mathematical ratios. For a 100volt supply such as might be used with a mosfet amplifier and output powers between 10 and 100 watts, rl varies between 500 and 50 ohm. For a simple primaryoversecondary winding, you can calculate the leakage. Details of a transformer for use with n709 valves in ul pushpull are given in tabular form below. Output transformer primary connections with the filaments installed lets now install the output transformer wires these are the primaries the red wire as shown will connect to pin 2 of the 300b. Unfollow output transformer valve to stop getting updates on your ebay feed. Knowing the regulation and voltage, we can calculate the effective winding resistance. Audio transformers are transformers designed to be used in the amplifiers and highfrequency audio and voice circuits, for coupling ad impendence matching applications.
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