Had I used custom components, my first choice would have been a good capacitor input supply. Being a typical "cheap ham", my decision to use a choke was based on using readily available salvaged power transformers. My collection of power transformers are largely pulled from old equipment I've scrapped. Like many of us, my home project transformers are usually not specially ordered for a particular project. My transformers were mostly harvested from old gear with vacuum tube rectifiers.
You probably never heard of this or considered it, but power factor causes some very strange effects in a power supply. Regular power factor is where the current and voltage are not in phase, and so the current times voltage no longer tells us the real power of the system.
This is reactive power, and can even be called "VAR power" or volt-amperes reactive power.
Tube Power Supply
A transformer with significant flux leakage or that has a secondary loaded with an inductive or capacitive load has phase shift between voltage and current. This causes the primary to appear reactive and not resistive. This increases heating in components for a given amount of real power load. Capacitor input supplies, or supplies with inadequate filter choke inductance, have a different problem. They draw significant current only over a small portion of the AC cycle.
These systems are also known as non-linear loads. The high peak current and low average current loading, or non linear load, is why we cannot measure line voltage to determine line voltage regulation with a large capacitor input supply.
This is why normal wiring voltage-drop tables or resistance calculations do not apply with high power capacitor input supplies, like modern kilowatt-level RF amplifiers.
You can read about power factor and non-linear loads at this external link. Transformers used in vacuum tube rectification systems almost always have higher primary and secondary resistances than transformers used with solid state rectifier systems. There is a good reason for this. Vacuum tube rectifiers are much "softer" on the secondary than solid state rectifiers. With their high plate resistance, high vacuum rectifiers pull current over a fairly significant fraction of the sine wave.
This results in fairly lower harmonic levels, and a bit less apparent power factor. The softer waveform reduces transformer stress for a given load power.OuterVision Power Supply Calculator is the most accurate PC power consumption calculator available and is trusted by computer enthusiasts, PC hardware and power supply manufacturers across the Globe. Are you building a modern gaming PC, low power HTPC media server, or maybe you need to figure out power requirements for a rack in a data center?
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Note: Standard keyboard, mouse, and 8 hours of computer utilization per day already included in calculations. What power supply do I need?
Choke Input and Capacitor Input Power Supplies
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CPU Speed. CPU Vcore. Core Clock. Memory Clock. Optical Drives 0 1 2 3 4 5. PCI Express Cards 0 1 2 3 4 5. Liquid Cooling Kit 0 1 2. Liquid Cooling Pump 0 1 2.The power supply is the most important part of the amplifier because, ultimately, it is the power supply that dictates the limitations of the amplifier as a whole. Guitar amps nearly always have very simple power supplies, free from modern refinements like electronic regulators, which makes them easy to design. The Reservoir Capacitor The first capacitor after the rectifier is the reservoir capacitor.
This capacitor stores the bulk of energy for the whole amp.
Tube Amp Power Transformer Current Draw Calculator
Each rectified half-cycle charges the capacitor to the peak AC voltage with a brief-but-large pulse of current. The voltage then decays as load current is steadily drawn out by the amplifier circuit, until it can be topped up again by the rectifier during the next half cycle.
The raw DC voltage is therefore not perfeclty clean but has residual ripple voltage. The ripple voltage is often expressed as a percentage of the maximum DC voltage.
This is a somewhat conservative formula; in practice the ripple voltage will turn out a bit less than this. The greater the capacitance, the smoother the DC and the more slowly the voltage will 'sag' during loud playing.
However, greater capacitance also puts greater strain on the rectifier and transformer because it demands larger pulses of current to keep it charged up.
Most traditional amp designs use 22uF to 60uF if a valve rectifier is used, or up to uF with silicon diodes more is rarely necessary. Single-ended amps may benefit from more capacitance because they don't reject hum like push-pull amps do. Capacitors rated for V are common, but you don't see many higher than this.
If you need a higher working voltage then the usual trick is to put two capacitors in series so their voltage ratings add up. However, the total capacitance will be halved, so two uF capacitors would amount to 50uF.
Also, resistors must be added in parallel in order to encourage equal voltage sharing between the capacitors. These also act as bleeders when the amp is switched off. Smoothing Filters Most amps supply the output transformer primary directly from the reservoir capacitor. However, the reservoir capacitor alone is not enough to provide the noise-free DC needed by the screen grids and preamp stages, so further smoothing is necessary.
This is achieved with a chain of LC or RC low-pass filters, variously referred to as smoothing, bypass, or decoupling filters.Welcome, Guest. Please login or register. Home Help Search Login Register. Is there a way to calculate the size of the resistors between nodes? I built a high-gain 25 watt amp using output tubes with volts on the plate.
I put the same preamp in a 50 watt amp using EL34 output tubes with volts on the plate. On my previous build 25 wattI guessed at it and changed the resistors out until I had the right voltage in my preamp.
I eventually got there, but I would like to be able to calculate the resistor values. Loading makes the calculation much harder than using a string of resistors. Thanks for the help! Sincerely Ed Chambley.
Calculating Filter Capacitor for Smoothing Ripple
There are lots of videos, this one is an air corp training video. Seems to do a good job; And they had to as training new recruits back then, you might have a full range of personnel, all walks of life to educate so the material had to be a good common denominator.
If you know your amp is similar to a published schematic, you can check that. If you're facing utter mystery, Ohm's Law is your friend. Check the tube spec charts to find the current draw for the tubes in your amp. For power tubes both the Plates and Screens draw current.
Determine what voltage you want on the downstream side of the resistor. Then recalculate Ohm's Law for the exact R value. No guesswork is required except for the standard, tentaive guesstimate of preamp current draw. You go around in circles. First observe a build that works but is not happy. Ensure you really have appropriate values throughout.
Now observe the V and I in each stage. Now you have a series string of drop-resistors and a bunch of stage-resistors hanging off. There's various network theorems to get an "exact" analysis. However if they are all low, the cave-man hack is to change an early 10K drop-resistor to 2K. That will bring-up all later voltages. Too much? Maybe take a second guess.
Or it may bring-up stage 3 good but stage 1 is low. Pick a drop-R between 3 and 1 and reduce its value. Having estimated all voltages and currents, steady power rating is easily computed.
Always double this; with fat caps going very over-Watts is wise due to start-up surge. Go through your new drop-R values and proposed decoupling caps and check each R-C works out well below the audio band.
You need to keep wall-AC buzz out of all stages, especially early stages; you need to keep late-stage power wobble from sneaking into early stages to howl-around. There's detailed calculations. At present e-cap prices, just over-sizing all caps is cheaper than hard thinking. A half-dozen such stages looks like 55K.I wasn't kidding when I said that it was simple, as the following schematic makes plain:.
In addition, the PCB requires a 5Vac winding to heat the rectifier. This power resistor can be replaced with a choke. With one tube atop another and a single heater power supply, the top and bottom heaters cannot share the same heater-to-cathode voltage relationships. The easiest way to establish this voltage relationship is to attach the heater winding's center-tap to the "Heater Ref. If the heater winding does not offer a center-tap, then place two 1k resistors in series across the winding and attach the junction between both resistors to the pad labeled "Heater Ref.
Speaking of heaters, where is the heater power supply? There isn't one—well at least not on the PCB. Many power transformers intended for use in tube audio gear are woefully weak in heater winding current. Here is an example, a 6.
When using such a transformer with a 1A load, it's best to give up on using DC and settle for AC on the heaters. In addition, I know that there is an AC-heater fan club out there, as I often get e-mail from some of its members. Well, the PS-5 is just perfect for them. On the other hand, for those who enjoy a bit less humming with their music, the other new PCB, the PS-4, offers DC regulated heater voltage. The low-voltage regulator is meant to power the tube heaters; the high-voltage power supply, the rest of the tube circuit.
Once again, the series resistor can be replaced by an external choke. It is not the equal to the Janus regulator, but then it is neither as expensive nor complex; in addition, it is much more flexible, as it can use any suitable series resistor value in its RC filter, whereas the Janus must use a ohm resistor. In other words, add a power transformer and the PS-4 PCB makes the basis of a fine tube-circuit power supply, say a tube line-stage amplifier or headphone amplifier or crossover or, even, a small power amplifier.
These amazing little power tubes are quite efficient, requiring only 15Vpp to bring them to full output.
The 6N1P is a fine little tube and about 1Vpk of input signal will bring this amplifier to full output about 8W and no feedback loop is employed. By the way, the 0. A single PS-4 power supply could easily power a stereo version of the amplifier shown above.
The power supply is shown below. Note the use of a voltage doubler in the heater circuit. The sad fact is that 6. But when 6. The voltage doubler, unlike the federal government, does not work magic; it must pay for the doubled voltage by halving the winding's potential current output.
In other words, the 6.Basic Theory - using 21st-Century technology to design vacuum tube preamps, power amps, and power supplies. System Design - a professional methodology for crafting a complete guitar amplifier.
A resistor-capacitor filter is simple and inexpensive. When it needs to supply lots of current, however, it creates a large DC voltage drop, requiring a higher input voltage to achieve the same output. In high-power guitar amplifiers the power tube screens, phase inverter, and preamps draw enough current at full power to make a choke-capacitor filter more economical at least in the early days of the Fender Bassman and the Marshall JTM An LC filter with the same amount of ripple attenuation and the same size capacitor creates much less DC voltage drop than an RC filter.
The key difference is that the inductance of the choke reacts to AC signals but presents, ideally, a short circuit to DC. A real-world choke creates a slight DC voltage drop due to internal winding resistance. Basic Theory - using 21st-Century technology to design vacuum tube preamps, power amps, and power supplies System Design - a professional methodology for crafting a complete guitar amplifier Circuit Simulation - modeling vacuum tube guitar amplifiers using SPICE.
What does this calculator do? This calculator computes ripple attenuation and DC voltage drop. About Us Legal Notice Contact.These cookies help us provide you with the best online experience, to continually improve our website and present you with offers that are tailored for you.
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