Learn how to understand what they are talking about when
you have a tube amp.

Tubes have a whole language of their own. "Matched" means the tubes are identical. Your amp (if it uses more than one power tube) operates in "push-pull" the tubes seesaw back and forth, delivering their half every milisecond or so. If the tubes are matched, these two signals will be the same level - and equal in power.

Matching is not new. I find references to it as far back as amps were made (1930's and earlier)

"NOS" is commonly used, it means New Old Stock. Tubes that were never sold (new) but in stock or stored for a long time. They are often Military tubes, stocked is some warehouse and forgotten

"JAN" mean Joint Army Navy. Again, military tubes made to pretty exacting standards for WWII, Korean war and peacetime uses. They may also be considered NOS.

"Bias" is the most confusing of all. To understand it you need to know (first) that the tubes we are using can do other things besides act as audio amplifiers. They can be switches, computer bytes, oscillators, voltage regulators etc.

In order for them to amplify musical signals they have to operate at the correct voltage and be able to go up and down with the incoming signal.

For this to work right the tubes, at rest, have to have a negative voltage at their "control grid" - the place the signal comes into the tube. This negative voltage is called bias and it needs to be adjusted for the type of tube in use, and since tubes vary somewhat, even within the same type, for the individual tubes used in the amplifier. Also for the "class" in which the operate. (this is the tricky Class A, class AB etc. stuff.) The real measurement of bias is how much current the tube uses, the negative voltage can be measured, but it is not as accurate as the current measurement

Bias is not a "gimmick" and it has always existed. Some amps do not have adjustments - but could use them. Some amps don't even have a negative voltage supply, they use another trick called "cathode bias" to apply the negative voltage in a different manner.

Torres Amps always have an adjustable bias, and/or a cathode bias.

The more accurate the bias, the better the amp sounds.

final notes on web page

Dan's Legendary Book "Inside Tube Amps" is now available on Amazon/Kindle

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