If you find the tube in North America, assume the European code is correct. So if Gm is matched to, south get matched Mu the important characteristic in this circuit Rp must be matched also and Rp is almost never measured. Email tubeaudiostore gmail.
Pentodes Pentodes are an entirely different matter. Since electrons have a negative charge, the plate is given a positive voltage to attract them. This means the tube on the right will wear out quicker than the tube on the left, leading to an earlier loss of clarity and definition. Transconductance is related to the amount of amplification the tube provides at a particular bias setting. For some reason, it's quite common to find Soviet era Russian tubes marked made in Germany, England, Holland etc.
They will allow for more playing time with rich, well defined tube tone. Once you know where it was made, that narrows down the possible manufacturers by a lot. Depending on where it was made, you there are different clues to look for. Since Mu is what controls voltage gain, and voltage gain is what we listen to, hook it up then lets measure that directly.
Tube Matching Demystified
- Only in rare cases will this not be true.
- There is no assurance that these tubes will have equal voltage gain.
- Only Sylvania and National Union had the equipment to make them.
- Because most testers only measure Gm!
This is not true, many companies used it. It was in the interest of companies like DuMont, Admiral, Emerson etc to have their own logos on the tubes that they supplied in their equipment. Transconductance is a measurement of how much the plate current changes as a result of a corresponding change in the control grid voltage.
These were no small efforts. Nudist picnic and blind date with JotaDe. They did this in hopes that when a tube failed the customer would order a tube with the same brand as their equipment at a markup so the company would profit. To avoid a situation where the idle plate current is matched at one bias setting, but unmatched at another. If the bias pot is set too cold, the sound will be lacking in warmth.
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Here is a list of European factory codes courtasy of audiotubes. Once you've seen this type of paint it's easy to spot. Here, Mu voltage gain is the more important parameter to measure and most directly affects what you hear.
Triodes and pentodes both possess the characteristics Gm transconductance and Mu voltage gain. Why then do most vendors measure Gm and Gm alone? Hot geeky broad Yunnox proves herself as a real slut. Triodes are most widely used for voltage amplification in our preamps.
When in doubt, these code should be given the most weight in your determination. Not only must Gm be matched, but it must stay matched over the range of bias currents typically found in amps. If the grid is made more negative, the number of electrons passing through the grid is reduced. This is important for two reasons. Norma likes the first date sex!
Henessy is busy updating her dating profile. Vacuum tubes were simply a commodity that everyone needed like batteries or light bulbs are today. The manufacturer sold in bulk to a wholesaler or distributor that marketed the tubes differently for a profit. Many tubes have a printed country of origin on them.
Written by world-renowned amplifier, Roger Modjeski, this article, will look at what each of these characteristics mean, how they are measured and what each of them means to the sound of a component. Why does this difference in idle plate current matter? Typically, European codes are printed a chalky, easily rubbed off type of paint towards the bottom of the tube near the pins. Often, the printed brand or printed country is incorrect. Despite what a tube has printed, they were made by one of the two companies only.
If the vendor measuring Gm would give you the Rp then you could calculate the Mu by simple multiplication. It puts you in control of your tone. Rp or plate resistance is the second most important parameter as it directly affects the output impedance of the preamp.
All you need to do is monitor the condition on the cathode coating, which is easily measured via emission. If you're familiar with Ohm's Law, you'll know that voltage V divided by current I is equal to resistance R and resistance is measured in ohms. So if a tube was properly made and tested when new, dating among christian youth all one needs to assess its current state is a simple emission tester. There were a few different reasons a given company would re-brand or write the wrong country of origin on a tube.
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There were many trade sanctions due to the various wars that went on while tubes were still being produced in bulk. All we are concerned with here is the Manufacturer code. Gm is the thing to measure here but the Hickok does not measure anywhere near the real world operating voltages and currents found in a typical circuit. No commercial tester ever measured Mu either.
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For a more technical explanation of why we match tubes, click here. The tube with more plate current will be dissipating more power and getting hotter than the tube with less plate current. How these measurements are applied and their relevance differs for triodes and pentodes. Matching the plate current and transconductance allows you to set the bias with maximum precision for that optimal sweet spot where the tubes will sound their best and won't burn out early. There is much confusion in the audiophile community about these factors as they affect tubes and their performance in components.
Given that, all we need to measure is the emission to know the tube is still good. Plate dissipation is calculated by multiplying the plate current by the plate voltage. If two tubes are biased for the same amount of idle plate current, but provide different amounts of amplification, are they truly matched? The reason you don't get the Rp data is that it is hard to measure and no commercial tube tester ever measured it.
Plate current matching makes sense. If the bias pot is set too hot, the tube will be overheating and the sound can be lacking in definition. Akward tinder date with russian blondie finishes pretty good Lets go to russia. In many cases this is incorrect. They want everything to be matched, though they rarely know what it should be matched for.
- Therefore, gain is Gm times the load impedance presented to the tube through the output transformer.
- They had a contract with a large company to print their logos on the tubes.
- We will also look at tube testing, tube matching and which characteristics are most important when matching tubes for a given circuit.