The combination of tubes and amplifier needs always some attention

Part 1. What to do in problem cases.

Part 2. Amplifiers which need special attention


Actually, problems with Emission Labs tubes are very rare. For the few cases we had, it seemed seldom a direct quality problem of the tubes, or the amplifier itself, but more a problem of the way the combination, or the tubes were replaced. However if any defects occur, it is likely a tube heater failure, because the amplifier can be electronically against too high plate current, this protecting tube and amplifier, but with tubes we can do little against errors with the amplifier heater voltage. In this previous sentence, the whole nature of the issue is described.

If any problem occurs, it can be one of those:
  1. Emission problems, due to wrong heater voltage
  2. Spark effects inside, due to in-rush current too high
  3. Loss of power output, due to thermal overload of the anode
  4. Spark effects inside, due to in-rush current too high

In the following pages, we want to gives some background about how to prevent problems, by correct installation.

If a problem happens, it is useually such that the tubes that stopped working after relatively short time. For such problems, we must not cure the symptoms, but we must find the root cause. The EML tubes are really a high quality products, and just replacing non working tubes, will logically repeat the problem, if the root cause is to be found in the amplifier. Even when the problem is in the amplfier, sometime tube replacement can solve it. Yet, it should be clear, without knowing the root cause, this is not the ideal way.

We do not build ECC83 tubes at EML, so we give neutrally this example: Some amplifiers are build with this tube at a position in the circuit, where signal is extremely low. Any tube, no matter what age or brand, will show some noise, but with good circuit concept, it can be eliminated. Though this is diffcult, and it is the art of the circuit design. If the designer failed to do so, logically the user will observe some noise, and this will be tube brand dependant, but also randomly tube dependant. So at replacement of this tube, there may be dissatisfaction with noise, and yet exchanging the new bought tube with another one of the same brand, may indeed solve the problem by coincdence.

With power tubes, such as EML builds, any complications is rather loss of function, and once the tube has stopped working, the root cause can not be found easily. Yet if the root cause is indeed the amplifier, replacing the tubes will only repeat the problem. Even so, replace the tubes may seem to solve such a problem, though of course amplifier problems are not solved that way, just become not visible.

For instance, somebody has broken tubes in a 220V amplifier, which was connected to 240V mains, and he did now know this, and never look at the mains voltage, because there never was a problem. Until he replaced the tubes. Logically he will say, 220V or 240V, was never a problem, so why is it now?

When we analyze this, it means he expects tubes to work fine in a 220V amplifier, which he connects to 240V. He feels this should be possible because it never went wrong. At this moment, already the conclusion is wrong. The users says it never went wrong, but it fact it did go wrong, because that is what we were talking about.

In short, users expect from the tube Lifetime and Quality. If plug&play appears to be possible, does not mean this was a right thing to do. You would find out only after a defect, but it is too late then.

These pages just try to give some assistance. Good users manuals are rare. So at EML we try to help you out, when manufacturers play a hide and seek game with manuals, but it is assistance only. We do not have responsibility for the amplifiers.