Type of tube the type of tube determines the power dissipation, which is required to calculate the idle current. The positive grid tonecloud is more than just a simple storage tank for your own custom amps its. If this happens to you i assure you that my tube bias calculator does nothing but calculate tube bias. Output tube biasing, an introduction wall of sound audio. In this video i show how find the zero signal bias point for any tube. How to calculate gain, bias point, and max output of a. You measure the output transformers voltage drop and. If the bias is too far the other way they wont draw enough to operate efficiently and they wont. The et pro one bias probe is also available with our custom built 9 pin head. Bias tee calculator welcome to the k6vhfs amateur radio. Remember, each time you adjust the bias control, youll have to take a new reading from both the 1ohm resistor and the plate pin three and multiply them to see what the tube is dissipating. Feb 01, 2017 the gain of a tube, also known as its amplification factor, or mu. This calculator will compute the values of the biasing resistors required to provide the maximum output voltage swing in a npn bipolar junction transistor bjt amplifier circuit.
The tube bias calculator was created using mits appinventor 2 programming environment and some antivirus programs will flag anything created with it. We will continue to offer these because in conjunction with a multimeter this is the most cost effective tool for measuring true plate current allowing you to accurately bias your amp. Tube bias calculator for android free download and. Interactive valve data sheets and amp modeling experiment with these controls to get a feel for how valve amplifiers behave. Freedom tube bias calculator for ios free download and. This app is a 3 awards winner by the vintage electronics magazine and the london university of electronics. The bias king is a simple, effective, and accurate diagnostic tool designed to read the current flowing through the tube of an amplifier bias. Please note the excel file is super easy to use but make sure you enter your figures in the blue boxes only and read the results in the green boxes. Bias tube amplifiers hot if the bias current is set too high, the valves will glow hot and will have a shorter life. Biasing an amp requires some knowledge of tube amp circuits and experience with high voltage. Bias calculator tutorial, with continuous bias formula and.
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. The formula for biasing is the plate dissipation of the tube 12 watts for standard el84s or 9 watts for the jj el844s divided by the plate voltage lets use 350 for this example times. Ftbc freedom tube bias calculator is definitely not your average tube bias calculator app. The tube will reach a stable point of equilibrium and stay there.
The best and worldwide famous beteramp tube bias calculator. A bias probe is inserted between an output tube and the amplifier. Enter the plate voltage and type of power tubes to get the bias current at various levels of plate dissipation. This technique only works with a higher impedance load. Enter values in blue and click any calculate button select the tube type from the scrolling list. In these calculations, 5% of the cathode current is assumed to be screen current. The other common type of output tube biasing is cathode bias. Bias calculator tube amp bias calculator easycalculation. I also use the 70% of maximum dissipation rule i learned from randy aikens site. Positive grid is a leading developer of component based guitar amp and effects modeling hardware, desktop plugins, and ios apps. That alone can cause premature tube failure, since one or two can become the weak link and draw more current than the others in attempting to achieve a balance. Bias amp was designed to integrate seamlessly with bias fx.
For amps with cathode bias resistors you can simply measure their voltage drop and use the tube dissipation using cathode resistor voltage drop calculator. Output tube biasing, an introduction wall of sound. 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. Given below is the tube amp bias calculator to find the bias in ampere or milliampere ma or a. It has a database of 36 tube types and will calculate the class a fixed, class ab fixed bias and cathode bias maximum safe bias settings. Tube amp bias calculator app by paco pascual youtube. The bias on an amplifier can be adjusted by a technician to allow more or less current to flow. The formula for biasing is the plate dissipation of the tube 25 watts for 6l6s, el34s, e34ls or kt77s or for 6v6s use 14 watts and for kt88s use 35 watts divided by the plate voltage lets use 480 for this example times. All software on this page is compatible with windows 95, 98, me, 2000 and nt4.
The author cames no responsibility for any information provided. Normally, bias adjustment is required only for output tubes that is, the tubes in the output or power stage of the amplifier. The tube bias calculator will calculate power tube bias values of plate current, dissipation and % of max dissipation using either measured voltage drop across a cathode resistor or measured plate current. 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. In fact, go to randys site and read all the tech stuff there. The best way to understand bias is to think of it like the idle setting on a car. It the amp is like most amps that use 6l6s or kt66s, the plate voltage is around 450v. Nowadays most cars have complex computers that control the idle, however, in the end. Langfordsmith, editor, radiotron designers handbook, 4th edition, harrison. Each set of tubes you put into your amp responds differently to the bias voltage.
So we aim to adjust tube bias somewhere in the middle a compromise between long life and good tone. In order to be able to use the file, download it to your computer first. To quantify the dynamics of overdriving a guitar amplifier we can use three measures. Basic theory using 21stcentury technology to design vacuum tube preamps. The gain of a tube, also known as its amplification factor, or mu. Anode load calculator an excel 5 spreadsheet in zipped form which allows you to see the amount of stress on output valves for a given amount of standing bias current 4k bytes.
Bias is an alternating current of high frequency which is applied to the tape recorder to reduce distortion. Setting bias is not as simple as saying that 6l6 should be 35 to 40 mas, for example. The freedom tube bias calculator ftbc is definitely not your average tube bias calculator app. The power output, power dissipation and, if you wish to use cathode bias, the value of the cathode resistor is calculated. The tube bases with the wire hole already drilled and a gold sticker. The guide includes a handy reference table for all widths of bias strips from 1 to 4 inches in half inch increments and for lengths from 12 to 120 inches. Apr 11, 2017 if the bias requirements of tubes within one of those groups vary too much, that part of the power section can be very difficult, if not nearly impossible, to bias correctly. How to bias your tube guitar amplifier regis coyne. If the bias is set too low the sound will be distorted, but the tubes will last a long time. Whether you currently own or are considering exploring the wonderful world of tube amplifiers, there are a few things you should know to make sure you get as much enjoyment and life out of your valve gear as possible. Place the groove tubes tube bias tool between the output socket and the output tube to set or measure bias using the current draw method. Nobsound vacuum tube amp amplifier plate bias current probe tester 8 pin socket for el34, kt88, 6l6, 6v6, 5881, 6550, kt66, kt100, kt120, 7027 ct1p, plate current 3.
If you prefer spreadsheets you can download the excel and openoffice tube bias spreadsheets. This is my most recent program and its bias tee calculator which helps to calculate the values for a typical bias tee circuit capacitance c and inductance l. The tube bias calculator will calculate power tube bias values of plate current, dissipation and % of max dissipation using either measured voltage drop. Use bias financial calculators as tools to estimate your investment returns, your retirement income, plan your retirement and your college savings. Tube bias of an amp is used to find the optimum setting for the flow of current in the tube when the amp is idling. The 500 ohm resistor red arrow connected between the cathode and ground, controls the current flow through the tube, thereby setting the bias.
It monitors the total current flowing through the tube. Cathode current milliamps displays approximate plate current after calculation. Its ampmodeling engine captures the feel of real tube amps. The formula calculates the frequency response based on the triodes amplification factor and plate resistance. Left unchecked, we risk not only blowing a tube, but risk damaging other components of the amplifier.
Biasing tube amplifier calculator antique electronic supply. You have to put input and output impedance, frequency and impedance ratio usually value of 100. A typical bias setting is a reasonable compromise between good sound and acceptable tube life. A fixed bias pushpull amp has two advantages over a similar amp without bias adjustment. The free shipping option allows tubedepot to choose the most appropriate carrier and service.
My recommended bias measurement method is the output transformer resistance method. If the bias is incorrect your new tubes might draw too much current and burn out. This webpage offers two ways to calculate tube bias and plate dissipation. Since 2006 we have offered a single octal bias probe for use with a multimeter.
Before we talk about different types of biasing found in tube amps, it is probably a good idea to explain what exactly the bias is. May 17, 20 this video shows a way to calculate transistor bias and the values of the actual circuit. Superb resistor calculator from morgan jones and mark lovell. Use this calculator to determine the bias current for an amplifiers power tubes. The first, mentioned earlier, is the opportunity to adjust the tubes for the best compromise between sound quality and longevity. If we set the bias so the tubes are at their upper limit, the sound quality might be lovely, but the tubes wont last very long. Tentlabs negative bias supply designed in cooperation with menno vanderveen, we are proud to announce a new module when using fixed bias in your amps, the currents need constant readjustment to compensate for mains variations and tube aging. Treble boost can be introduced by using a lower capacitor value, one that acts as a short circuit for high. If your tube isnt listed then pick one with the same max dissipation rate which is shown to the right in the tube list. With multiple tubes sharing the same cathode resistor, this calculator assumes the tubes.
The tool allows bias checking, setting, and adjustment in the field or anywhere with a minimum of tools. Tube bias calculator for android free download and software. A good analogy from the automotive world is the idle speed of a motor. Theres nothing worse than running out of bias binding before you get to the end of your project, so make sure you always have enough with this handy continuous bias binding guide and calculator. Output tube biasing, an introduction part 2 wall of. All you need is a simple meter sold separately and a screwdriver.
By owning a bias probe youre not at the mercy of a tech anymore and you are now in control of your tone. How to assemble the hoffman amps bias current checkers note that mojo musical supply also sells my bias checker use these instructions to assemble the mojo version also click on the images below for a larger image. Ftbc lite freedom tube bias calculator lite is definitely not your average tube bias calculator app. How to calculate gain, bias point, and max output of a vacuum. Current is read on a digital voltmeter dvm and may then be easily adjusted to the required settings. The bias controls the current that flows through the tube and defines the quiescent point of the tube, so that the tube reacts immediately to an input signal and so that it amplifies that signal accurately. I can see that there is a middle normal column on the charts but cant read the green or yellow or whatever unless i highlight the chart. All of the custom amps you create with bias amp 2 are automatically available in your bias fx, providing a foundation for your ideal finished tone.
It has been designed to give you the freedom to set it. The tube bias calculator will calculate power tube bias values of plate current, dissipation and % of max dissipation using either measured voltage drop across a cathode resistor or measured plate. Bias amp 2the ultimate guitar amp designerpositive grid. As the name suggests, these amplifiers are essentially plugandplay and will not need to be tinkered with if tubes are being replaced.
The second is that distortion is minimised when both tubes in the pushpull pair are adjusted for identical current draw. I am of course referring to tube bias an important part of amp care that will increase tube life a. This page contains details of software available from this site, to assist with the design of amplifiers and related equipment. If its as low as 400 or high as 500 thats only a 10% difference and wont make or break a bias calculation.
If you are uncertain that you are experienced enough to work on a live high voltage amp, please take your amp to a professional to get it biased. Antique electronic supply makes no claims, promises, or guarantees about the accuracy, completeness, or. The et pro one bias probe is calibrated at 180 milliamps to plus or minus one tenth of one milliamp at 700 volts dc, so unlike other probes on the market the et pro one can be used on amps that exceed plate volts. You can play your guitar through the amp each time you adjust the bias, and see how you like it. Bias settings for safe plate dissipation class ab 70% class a 90%. Biasing is important because there is a lot of variation from one tube to the next. In electronics, cathode bias is a technique used with vacuum tubes to make the direct current. Bias amp is an accurate guitaramp modeler and designer. However, just as different tubes from different manufacturers will draw varying amounts of current in a fixedbias amplifier, the same is true of a cathodebiased amplifier. The algorithm makes use of ac and dc load line theory and formulas and is one of the most accurate you will find online. When we bias were setting the working condition of our tubes. The following guidelines should be taken into account.
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