Bear in mind that the 5f6a was intended to be used clean as a bass amp rather than an overdriven guitar amp. There are hundreds of pages of tube amp information on my library page. This is necessary to get an efficient transfer of the audio signal to the speaker. I just got this response when i asked someone about swapping 6v6 and 6l6 power tubes. System design a professional methodology for crafting a complete guitar amplifier. Optional rload in ohms typically the output transformer primary impedance only considered when pp pushpull is selected number of tubes power tubes pre amp tubes. Output trannys contribute most of the distortion in a valve amp and have a limited bandwidth. The halfprimaries of the output transformer should have identical voltages on them. Nov 18, 20 the sense of a tube amp opening up and producing a singing overdriven note is certainly a function of the transformer compressing and putting its signature on things.
Audio transformer is the primary part of a tube amplifier which generates an electromagnetic field. Running at full power and no load will create very high voltages across the output transformer primary. Generally speaking the larger the output transformer the more low end and clean headroom in the power stage the amp will have. 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. Single ended output transformer calculating spreadsheet. Optional rload in ohms typically the output transformer primary impedance. Output transformer primary impedance the gear page. Wide band output transformers with third winding for nfb exclusive use, which can make stabilized nfb. Hammond puts a century of experience into manufacturing high quality magnetics for tube applications like hifi audio and guitar amplifiers. If you would like to simply calculate number of turns and other aspects of your output transformer for a single ended tube guitar amp or a hifi home tube amp, dont miss out on this tried and tested method which is an easy to use excel spreadsheet which automatically calculates a transformer according to your needs.
Output transformerless otl is a type of vacuum tube audio power amplifier, which omits an output transformer for the purpose of greater linearity and fidelity. Instead, otls use one of two primary methods for output stage coupling. The more modern approach is to use a direct coupled cathode follower to drive the output tube grid so it allowed triode to make a similar of power in class a2 as a pentode or tetrode with the same idle power. My recommended bias measurement method is the output transformer resistance method. Ttgcfb4000pp tube output cfb transformer 4kohm cathode feedback pushpull. I volunteered to put a 4 ohm load on my amplifier and re run the tests. If you would like to simply calculate number of turns and other aspects of your output transformer for a pushpull tube guitar amp or a home hifi tube amp, dont miss out on this tried and tested method which is an easy to use excel spreadsheet that automatically calculates the transformer windings according to your needs. Realtime audio transformer emulation for virtual tube amplifiers. Tube bias calculator rob robinettes car and tube amp. It is important to note, however, that these solutions are best only for those experts who have knowledge and experience with assembly transformers. Its a simple enough question, but the answer is a little complex. Please visit my tube amplifier forum heres the place you can go to ask tube amplifier questions. To separate the high voltage and match the speaker impendance with the tube impendance we. More than 80% of our transformers manufactured is for this market and bring over 70 years transformer manufacturing expertise to our product.
Vacuum tube calculators basic theory using 21stcentury technology to design vacuum tube preamps, power amps, and power supplies system design a professional methodology for crafting a complete guitar amplifier. Vacuum tube calculators basic theory using 21stcentury technology to design vacuum tube preamps, power amps, and power supplies system design a professional methodology for crafting a. Conventional vacuum tube amplifier designs rely upon an output transformer to couple the amplifiers output stage to the loudspeaker. But since the output transformer was designed to load the current put out by 4 power tubes we need to make an adjustment on the speaker end to load 2 tubes properly. The cathode resistor in a typical triode preamp is bypassed with a large capacitor to eliminate a form of negative. Calculating output transformer impedance sarris custom tube. This means that, with the transformer in question having a 25 turns ratio, the load presented to the tube would be 252 x 50 31. Topics such as winding ratio, output voltage, current limitations, and mounting. To get rid of flub, coupling caps are best reduced in value. When you adjust these you see the voltages change on the schematic.
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 set up for 8 ohms and will run. The tube amp library of information click the link above for tube amp info, schematics, board building information. Audio transformer and impedance matching transformer. Utility to calculate tube amp estimated power transformer current requirements. Tube bias calculator rob robinettes car and tube amp website. Tube output transformer 5kohm 2x6as7g 2x6ns pushpull or similar. This method is more dangerous because when your meter probe. Secondaries should have multiples of the voltage youre putting on the tap you chose. Jun 08, 2014 the way i understand things is that the transformer doesnt have an own impedance, rather it reflects the load impedance based on the square of its turns ratio and presents that to the tube. Tubes do not affect impenitence, speaker load does.
The output transformer is the heart of a valve amplifier. In a nutshell, this program is a virtual workbench for singleended tube amplifier output stage design. The way i understand things is that the transformer doesnt have an own impedance, rather it reflects the load impedance based on the square of its turns ratio and presents that to the tube. Amp diy adventures in amplification gear diy amps howtos. Pushpull output transformer spreadsheet calculator with pdf. Transformer calculator kva calculator full load amps calculator. If a tube arcs internally, it can create a high voltage. Prices are generally extortionate, though they do sell a good 25w output transformer online. Calculate the nominal impedance of the loudspeaker required for maximum. Those of us who are in search of perfection in audio amplifiers must often have looked askance at the output transformer.
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. Testing an unknown output transformer on a speaker i recently acquired. 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. I am often asked how upgrading an amplifiers transformers will improve tone. 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. Feb 02, 2017 testing an unknown output transformer on a speaker i recently acquired. Tube amp power transformer current draw calculator javascript must be enabled in order for the calculations to work. 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. Assembly manual schematic parts list tubes and applications design simulations. By trying out several different sets of operating conditions in the computer i could eliminate hundreds of possibilities without playing with electricity. Some folks will judge an amp by the size of the output transformer but this is matter of taste. Circuit of tube amplifier device the output transformer is an important part of the amplifier requiring a thorough parameter determination. How amps work rob robinettes car and tube amp website.
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. As an example, you might want to design an output transformer for a single pair of 6l6 output tubes. The output transformer as an impedance matching device, works on the principal of reflected load. Calculating output transformer impedance sarris custom. It was suggested that you could put an 8 ohm load on a 16 ohm 5k primary transformer to get a 2. The wattage output in an amplifier may vary from application to application due to many variables such as tube types, solid state vs. The following guidelines should be taken into account.
The next two are the dc resistance of the output transformer, followed by the impedance. Pushpull output transformer spreadsheet calculator with. This might give you some interesting ideas for your own projects. 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. The tube bias calculator will calculate power tube bias values of plate current, dissipation and % of max dissipation using either measured voltage drop. Basic theory using 21stcentury technology to design vacuum tube preamps, power amps, and power supplies.
Audio transformers are designed for use in audio amplifier applications for. Next select the type of bias fixed or cathode and power supply dc or ac. Tube amp transformers tube amp parts, guitar amp parts. 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. Amplifiers without the output transformer therefore produce cleaner, less distorted sound.
If you want to see tube amplifiers built by customers, visit our customer tube amp gallery. You measure the output transformers voltage drop and resistance to calculate the bias current. Output transformers in tube amplifier designs are typically used to lower the amplifiers output impedance and to make them more universally compatible with many headphones. Because of this, the cost of the output transformer often accounts for a very big part of the total cost of a tube amplifier. We offer transformer covers for the output and mains transformers and chokes of your diy tube amp. Professionals with experience in transformer assemblies use the computer program to calculate the number of coils and wire thickness. A trio of software programs for the intrepid tubephile.
For amps with cathode bias resistors you can simply measure their voltage drop and use the tube dissipation using cathode resistor voltage drop calculator. Jan 31, 2014 in this video, i discuss the design and function of power transformers pt, primarily those utilized in amplifiers. So we apply an ac voltage to the primary of the transformer and we measure the output voltage to the secondary. Apr 30, 2010 the output transformer is the heart of a valve amplifier. Many pushpull amps designed to run 4 power tubes can be run with 2 power tubes to cut the output power in half. The function of the audio output transformer is to transform the high impedance of the output tube to match the much lower impedance of the speaker. That can cause arcing inside the output tubes and, of course insulation breakdown in the transformer. Building a tube amp, how to calculate output transformer. Finally, test for the resistance from primary to secondary.
Are you looking for the best transformer calculator software for your next project. Projects, mods, transformer diagrams, photos, sound clips. An excellent site in the netherlands, selling a good range of valve amp related components. First off, lets examine what an output transformer is and why someone would inquire about replacing it. There is really one circuit this thing was made for that is a cathode follower. Select an output transformer and a power tube from the builtin libraries. We have been producing tube output transformers continuously for over 75 years, constantly improving and tweaking their performance. Single ended output transformer calculating spreadsheet with. Sep 27, 2014 tcj pushpull calculator has but a single purpose. Understanding your output transformer part one by mark baier. 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. You can change the tube current, and the cathode resistor will change, or change the cathode resistor and the tube current will change.
I brought the tubes over to a friend that had a tube tester and they work as they should. Importantly output transformers have different primary impedances. The free shipping option allows tubedepot to choose the most appropriate carrier and service. There are several things that are important in getting an output transformer made. A low reading here indicates a short to the transformer core again, dead transformer. 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. Understanding your output transformer part one by mark. Some designs sound better with a small output transformer.
The sense of a tube amp opening up and producing a singing overdriven note is certainly a function of the transformer compressing and putting its signature on things. To separate the high voltage and match the speaker impendance with the tube impendance we need audio grade output transformer. Audio output transformers are heavily used in a vacuum tube and some. Moreover, it is extremely difficult and therefore very expensive to make a good output transformer. The crack has no output transformers and as a result of its particular design, it has a high output impedance 120 ohm. All covers are made in germany and sold ex factory. The cost of a tube amplifier mostly consists of the cost of an output transformer and tubes that is usually a factor limiting the sound quality.
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. Tamura corporation audio transformers for tube amp. Turns ratio v in to the primary v out measured in the secondary e. Usually tube arcing does not cause permanent damage to the tube, but it is possible. Do a similar test on the secondaries look for open windings, or shorts to the core.
The objective of this project is to develop an output transformer for singleended tube amplifiers with. Hammond manufactures direct replacement transformers for popular tube amps from fender, marshall, vox, ampeg, orange, and yorkville traynor. Brainstock video production our diy amp, studio, gear blog. Why and how to replace your amplifiers output transformer. A low value, under a few k indicates an internal short, and a dead transformer.
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. You measure the output transformer s voltage drop and resistance to calculate the bias current. But since the output transformer was designed to load the current put out by 4 power tubes we need to. In general it would be possible to reduce the nonlinearities in an amplifier below any desired value by the application of a sufficient amount of feedback. Output amplifier consists of a 6p1p output tube and output transformer fig. In this video, i discuss the design and function of power transformers pt, primarily those utilized in amplifiers. Here you will find three example for typical operation of the 6l6gc tube they were provided by ge to make it easier for amp designers to use their tubesand gives us good info, too the 9th line effective load resistance, plate to plate gives the plate to plate load resistance or primary impedance of the ot for each of the three examples. First off, lets examine what an output transformer is and. How to calculate the output transformer impedance of an opt with unknown values. If you used an 8 ohm tap, a 4 ohm tap will have about 2. The 50s amps that are most renowned for having this smaller ot are the tweed 5e5 pro, 5f4 super, and 5e7 bandmaster prior to this, the ots used for two 6l6s were.
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