Dating vacuum tubes
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Dating vacuum tubes

So what's transconductance? However what is important in triodes is Mu and what is important in pentodes is Gm as these parameters are the dominant characteristics affecting performance when each is used in a typical circuit. Typically, European codes are printed a chalky, online dating no easily rubbed off type of paint towards the bottom of the tube near the pins. Plate dissipation is calculated by multiplying the plate current by the plate voltage. Only Sylvania and National Union had the equipment to make them.

This is a dangerous situation as many of you are buying because the vendor says it is matched, though it may or may not be matched for something unimportant while something important is not matched. Plate current matching makes sense. The manufacturer sold in bulk to a wholesaler or distributor that marketed the tubes differently for a profit.

In pentodes, Rp is very large and is swamped out by the load impedance. Email tubeaudiostore gmail. 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. Often, the printed brand or printed country is incorrect. The filament is used to provide the heat necessary to release electrons from the cathode.

Apex Tube Matching

They are simple to use, stable, accurate and relate well to the life remaining in your tubes. Akward tinder date with russian blondie finishes pretty good Lets go to russia. For some reason, it's quite common to find Soviet era Russian tubes marked made in Germany, England, Holland etc.

Dating vacuum tubes

If the bias pot is set too hot, the tube will be overheating and the sound can be lacking in definition. The Manufacturer code is always the first symbol on the second line. Why does this difference in idle plate current matter? This is not true, many companies used it.

Dating vacuum tubes

Identifying Vintage NOS Vacuum Tubes by Brand Country and EIA Code

There is much confusion in the audiophile community about these factors as they affect tubes and their performance in components. Rp or plate resistance is the second most important parameter as it directly affects the output impedance of the preamp. If you find the tube in North America, assume the European code is correct. This is actually more common today with New Production tubes.

Once you've seen this type of paint it's easy to spot. These parameters are locked into a relationship so that knowing any two will yield the third. If you see this type of getter, there is no doubt it's a less valuable Russian tube even if it's a Telefunken labeled West Germany.

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All we are concerned with here is the Manufacturer code. So if a tube was properly made and tested when new, all one needs to assess its current state is a simple emission tester. 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. No commercial tester ever measured Mu either. Much can be deciphered from these codes but that's for another article.

Tube Matching Demystified

Why Should I Match My Tubes

  1. If two tubes are biased for the same amount of idle plate current, but provide different amounts of amplification, are they truly matched?
  2. How these measurements are applied and their relevance differs for triodes and pentodes.
  3. Therefore, gain is Gm times the load impedance presented to the tube through the output transformer.

Why Should I Match My Tubes

Vacuum tubes

Only in rare cases will this not be true. Which is part of the reason it can be so hard to figure out today. Written by world-renowned amplifier, Roger Modjeski, this article, will look at what each of these characteristics mean, i am so done with how they are measured and what each of them means to the sound of a component. Transconductance is a measurement of how much the plate current changes as a result of a corresponding change in the control grid voltage.

Apex Tube Matching

Dating vacuum tubes
  • Since Mu is what controls voltage gain, and voltage gain is what we listen to, then lets measure that directly.
  • Those specs are built into the tube and will remain constant as the tube ages.
  • Depending on where it was made, you there are different clues to look for.

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. The control grid is placed between the cathode and plate and is given a negative voltage to repel electrons and restrict their flow to the plate. Transconductance is related to the amount of amplification the tube provides at a particular bias setting.

It puts you in control of your tone. When in doubt, these code should be given the most weight in your determination. Setting the bias involves finding a bias point where the amp sounds the best and the tubes are not overheating.

For Pentodes, as used in our power amp output stages, Gm does indeed matter and must be matched for good performance. Here is a list of European factory codes courtasy of audiotubes. Once you know where it was made, that narrows down the possible manufacturers by a lot. If the grid is made more negative, the number of electrons passing through the grid is reduced. They ran out of stock of one particular type and contracted another company to make them to fulfill an order.

They had a contract with a large company to print their logos on the tubes. Here, Mu voltage gain is the more important parameter to measure and most directly affects what you hear. If the bias pot is set too cold, the sound will be lacking in warmth. For a more technical explanation of why we match tubes, click here. Buy your tubes from someone who certifies their specs to be proper when new.

Triodes and pentodes both possess the characteristics Gm transconductance and Mu voltage gain. These were no small efforts. All you need to do is monitor the condition on the cathode coating, which is easily measured via emission. Triodes Triodes have an interesting relationship where two parameters relate to make a third. Triodes are most widely used for voltage amplification in our preamps.

So as you can see although the famous Hickock tube testers are sought for their ability to measure Gm, this was more of a marketing ploy and less useful for real-world testing. Given that, all we need to measure is the emission to know the tube is still good. Because most testers only measure Gm! There were a few different reasons a given company would re-brand or write the wrong country of origin on a tube. The tube with more plate current will be dissipating more power and getting hotter than the tube with less plate current.

Of course we had to build our own tester to do that. Norma likes the first date sex! In many cases this is incorrect. This is important for two reasons.

Henessy is busy updating her dating profile. Vacuum tubes were simply a commodity that everyone needed like batteries or light bulbs are today. Many tubes have a printed country of origin on them. We will also look at tube testing, tube matching and which characteristics are most important when matching tubes for a given circuit.

In that case, the next best thing is to identify where the tubes was made. If they could source the tubes cheaper than they could manufacture them. If Gm, Rp and Mu are right and matched when new, they will stay right and matched through the usable life.

Identifying Vintage NOS Vacuum Tubes by Brand Country and EIA Code

If the grid is made less negative, the number of electrons passing through the grid increases. To avoid a situation where the idle plate current is matched at one bias setting, bios but unmatched at another. When trying to identify a tube it makes the most sense to first determine where it was made. Nudist picnic and blind date with JotaDe.

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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. There were many trade sanctions due to the various wars that went on while tubes were still being produced in bulk. While the codes are usually at the bottom, we have seen these codes in other places like the bottom of the base.

Identifying Vintage NOS Vacuum Tubes by Brand Country and EIA Code
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