To conclude the article a transformer suitable for an n709 ultralinear pushpull output stage, such as in the osram 912 amplifier, is described. Next, measure the voltage across the speaker taps with a. F where flux max for the particular core is in webers. It is important to note, however, that these solutions are best only for those experts who have knowledge and experience with assembly transformers. Optional rload in ohms typically the output transformer primary impedance only considered when pp pushpull is selected number of tubes. How to calculate the output amperage of transformer. There are several things that are important in getting an output transformer made. The valve supply transformer used order code xp27e can deliver a greater ht level than the design above up to 340 v unregulated and a higher regulated output is. This ensures minimal distortion and low insertion loss. Output trannys contribute most of the distortion in a valve amp and have a limited bandwidth. In most amplifiers they will be fed via resistors, the power supplies will sag and the transformer will have losses. How do you determine primary winding ohms on an unknown.
Apr 24, 2017 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. I back to back connected my two transformers so things were 8 ohm to 5kohm and back to 8 ohm. How do you determine primary winding ohms on an unknown audio transformer. This is shown in the example with 3 different circuits. Our transformer calculator will tell you the transformer capacity your led lights will use. To use it, enter the data of two of the three, amps, kva kilovolt amps, or volts. Understanding impedance in audio transformers a white paper from lundahl transformers. How to calculate the required capacity kva rating or. To design an output transformer, it is necessary to determine the output power according to the tubess characteristics, most notably the input and output. The transformers allow an ac input signal to produce a related ac output signal without the input and the output being physically connected together. It has two types, single phase and three phase transformer. The moral of this thread though is quite simple dont buy a second hand valve output transformer off an ebay seller who just rips it out of some gear, with no regard for what it is at the very least he should specify exactly what it was removed from, and what the output valves were.
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. Calculation of singe ended triode amplifier valveheart. Then i cover the different speaker combinations and. Designed for use in 12au7ecc99 low power output amplifiers. The autotransformer was no bigger than a standard output transformer and obviously much cheaper to make than a standard mains transformer. Audio transformer is the primary part of a tube amplifier which generates an electromagnetic field. Cheap output transformers classic anz valve guitar. This will result in a silent set, with a high ht voltage. We have been producing tube output transformers continuously for over 75 years, constantly improving and tweaking their performance. 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.
So i want to know, how to calculate turns, impedance and watts. Building a tube amp, how to calculate output transformer. Also the screen grid is held at the voltage specified. 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. Works for fender champ, tweed champ, blackface champ and tweed princeton 5f2a. Output transformer an overview sciencedirect topics. We wind our pushpull output transformers on two chamber bobbins which ensures full capacity and resistance balance.
Most core material saturates at a flux density a bit less than 1wbm2, so you need to find that value for the material you have. The above examples of possible combinations are to help you narrow down the choices of transformers for your favorite tube types. Lissen valve transformer trf radio 1920 rare white bathroom suite vintage valve transformer click images to enlarge description v old but in good condition needs a coat of paint. 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. An excessively low load impedance to the transformer, whilst controlling ringing and electrical resonance effects, can cause a significant drop in output from the unit. Rating of a single phase transformer in kva kva v x i rating of a three phase transformer. Modeling approximation can be used to design the microstrip trace. A valve amp using toroidal speaker output transformers. Stepup, stepdown, and isolation transformers worksheet ac. 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. Tube amp power transformer current draw calculator. M 1115 is the part number of a 100v line speaker transformer from perthaustralia based company altronics.
Audio transformer is the primary part of a tube amplifier which. Utility to calculate tube amp estimated power transformer current requirements. Transtronic produce numerous products for audio applications. I connected a 8r2 9 watt resistor aggregate made from 9 series. Audio engineering society, october 1987, ukpdf gavs.
This can sometimes be seen as a hot spiral of wire glowing inside the valve. Application of the m1115 100v line, 15w speaker transformer. The output stage of the gec bc402 set is shown here. 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. An excellent site in the netherlands, selling a good range of valve amp related components. I am going to attempt to wind my own transformer, but i need to know the how to simply calculate the output amperage. Designing your own transformer as per a specific application can be interesting, but not feasible without calculating the various parameters typically involved with them. The basis for the creation of the whole fezz audio project is a family business known as toroidy. Cheap output transformers the output transformer in a valve guitar amplifier is perhaps the most difficult component to obtain if you are building, or to replace in repair, but there may be an answer closer than you think. 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. Transformer calculator for low voltage lighting dekor.
Npns vpvs power voltage x current vp 240 np 100 ns 2 1002 240x 1002 50 240x 50 240 x 50 x x 12000 24012000 0. Mostly they are used as synchronously tuned filters because each stage is coupled by an active device. What i did to test some valve output transformers was rough and ready. How to calculate the required capacity kva rating or amperage capacity for single and three phase transformers. I then run the low output impedance gen into the composite 1. Since the output valve has no load on the anode, the screen grid will act as an anode and will become very hot. Output transformers transformers passive components. Features our power output transformers use the best grade m6 lowloss grain oriented silicon iron laminations. 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. Are you looking for the best transformer calculator software for your next project. Solarwinds database performance analyzer dpa benefits include granular waittime query analysis and anomaly detection powered by machine learning. Grand stack version with more iron, thus more power, more bass and finally more tone. An easily constructed highquality singleended 8w amplifier.
An online three phase transformer calculator to find the current in different power units. A combined input stage and driver drives the output valve, and a transformer matches. Stability of ultra linear pushpull output stages at high frequencies. Transformer capacity calculator three phase transformer. Working with tube amps you may need to calculate the output transformer impedance especially when we have an old transformer or a transformer with unknown values. One of the easiest way to put up a schematic for simple triode power amplifier is to open a tube manual, or some other source, containing the data of the tube and read what is written in it for the triode you have or intend to use.
I cover how to calculate the reflected impedance of the output transformer secondary onto the primary. Calculating output transformer impedance sarris custom. Unless the manufacturers say otherwise, begin with the standard phono input impedance of 47k ohms standard used for. This af output transformer calculator script is written using python and it works with most of the commonly available python interpreters. The objective of this project is to develop an output transformer for singleended tube amplifiers with. The power supply is not designed for continuous use with the output unloaded. How to safely test the output transformer on tube radio or. Dec 18, 2017 download transformer design software for free.
For valve amplifiers we make a range of mains transformers, output transformers and chokes. 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. My audio sig gen had been modded earlier with an emitter follower to test speakers. Calculate the number of turns needed in the secondary winding of a transformer to transform a primary voltage of 300.
Simulations of tube circuits with spice molecular cuisine. The output power is for the anode, and it will depend on 20db nfb to keep the thd valve circuits for quality reproduction have long been produced with no other interstage audio transformers, but an output transformer is needed to couple the relatively high impedance up to a few hundred ohms depending upon configuration of the output valve s to the low impedance of a loudspeaker. The output transformer is prone to failure, in the form of the primary going opencircuit. If you have some experience in assembling transformers, then this program is perfect for you. This is one place that the art of transformer design comes in. Output transformers for valve amps 18w push pull output transformer. Cheap output transformers the output transformer in a valve guitar amplifier is perhaps the most difficult component to obtain if you are building, or to replace in.
For any type of transformer the rms voltage from a winding is 4. This link on the schneider electric website is a transformer data calculator. Tube output 10 280 watts 16081650 series hammond mfg. You measure the output transformers voltage drop and resistance to calculate the bias current. Multi section winding for exceptional bandwidth and phase shift.
There are a number of factors in transformer design that influence the size of the core and hence set the size in one way or another. As can be seen, the design of the seamplifier is simple. Calculating output transformer impedance how to calculate the output transformer impedance of an opt with unknown values working with tube amps you may need to calculate the output transformer impedance especially when we have an old transformer or a transformer with unknown values. I am told that you get better sound quality and frequency response than a laminated core transformer. As class a single ended amplifiers are about 40% efficient, a rough calculation to determine power output can be made. Calculating output transformer impedance sarris custom tube. This current passes through the primary of the output transformer, which will drop typically 15 to 25v. How to perform a frequency response test in a tube amp output. To increasedecrease the alternating volts in electric power, transformers are used. If amplifier transformers are simply tunable inductors, usually with an integral fixed capacitor, and are typically used inside cheaper transistor radios.
Output transformer design is ultimately about maximising the number of octaves. 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. Check out the valve wizard, his site has lots of useful info. Flexible primary and secondary windings for octal power valves.
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. 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. Uk vintage radio repair and restoration audio output stages. Use the following instructions to determine the load resistance of an unknown audio output transformer. Ive made a simple automatic calculation spreadsheet along with a short pdf tutorial to help. This is practically the determination of the output impedance of a circuit by means of the dc transfer function. The output transformer on a tube radio or amp is a crucial part of the design of the circuit, so a restorations viability may depend on whether it is functioning or not. Professionals with experience in transformer assemblies use the computer program to calculate the number of coils and wire thickness. The advantages afforded by the ultralinear circuit for pushpull output stages have now been well established, but the necessary conditions to be met when designing the associated output transformer have not always been given the attention they deserve. All we have to do is to calculate the turns ratio of the transformer. To separate the high voltage and match the speaker impendance with the tube impendance we need audio grade output transformer. The transformers allow an ac input signal to produce a related ac output signal without the input and the output.
The majority of output trannys were the minimum size, made from the least expensive materials. I want to make an audio output transformer for tube amplifier. Fezz audio are based in poland and make the fezz audio silver luna valve amplifier. Valve amplifiers with output transformers may sing audibly when operated at. 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. It is a 15w 100v line speaker transformer with multitapped primary and secondary to suit 8 ohm speakers. I am building a valve guitar amp, i have been advised that i should get a toroidal output transformer made rather than a laminated steel core like most amps use. Oct 10, 2009 i am building a valve guitar amp, i have been advised that i should get a toroidal output transformer made rather than a laminated steel core like most amps use. Ultra linear output transformers the national valve museum. How to calculate audio output transformer load resistance. I therefore dont recommend toroidal type output transformers unless the tubes are carefully matched both static and dynamic and also that there is a dc balance control included in the circuit. Below are two simple formulas to find the rating of single phase and three phase transformers. The dropper resistor is often positioned close to the rectifier and output valves, both of which also run hot, so the localised heat buildup can be considerable.
For homebrew projects, the best option is to construct those transformers by ourselves and this script helps to calculate winding parameters for those transformers. Only a few hiend valve amps had output trannys that were made with the best quality materials. Unfollow output transformer valve to stop getting updates on your ebay feed. Transformer calculation software electronic circuits. The two main modes of oscillation in a pushpull ul stage can be classified as.
How do you determine primary winding ohms on an unknown audio. Finally we can calculate the value of the cathode resistors bypass capacitor. The above amplifier wattage ratings are approximates only for categorizing purposes. Universal system and output transformer for valve amplifiers. Audio note valve output transformers are arranged into three categories in order to offer the best possible outputs at different price points, fall into the following. Application of the m1115 100v line, 15w speaker transformer to valve pushpull output transformer application. Design of a single ended 2a3 valve amplifier part 1. My ios calculator app for power and output transformers. If youre serious about this, consult flanagans transformer design books for charts and graphs or other transformer references. Apr 30, 2010 the output transformer is the heart of a valve amplifier. Feb 02, 2017 the peavey butcher has 4 speaker jacks. The wattage output in an amplifier may vary from application to application due to many variables such as tube types, solid state vs. How to calculate the output transformer impedance of an opt with unknown values.
V5 is the output valve, driving output transformer t1. Uk vintage radio repair and restoration power supply stages. Sorry for no narration in this one, i am in the process of upgrading my pc so i had to do all the editing on ipad. I brought the tubes over to a friend that had a tube tester and they work as they should. Oscillation involving crosscoupling between the valves in the output circuit. This method is more dangerous because when your meter probe. 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 you can take to a person who. Then, also select if the service is three phase or single phase. Audio transformers are transformers designed to be used in the amplifiers and highfrequency audio and voice circuits, for coupling ad impendence matching applications. Output transformer in the fm receiver is a 240 to 6. How to calculate electrical transformer output sciencing.
I just needed to drill a few more holes to accommodate different output transformers, chokes and a volume pot. Experience or comparison works best, though, and is what the pros do in practice. How to calculatefind the rating of transformer in kva. Get a low voltage ac transformer about 10v or less and place it across the speaker taps of the output transformer ot. Used, lissen valve transformer trf radio 1920 rare. This calculator provides the missing variable in the three transformer characteristics. Economy range, where the pricequality relationship is carefully calculated to ensure audio quality in a compact package.
590 1339 684 297 1194 839 1286 87 558 71 941 1315 1206 850 1181 404 359 633 592 1314 150 1194 491 588 702 142 128 1145 643