Owner`s manual
Owner's Manual 444
A word on impedances
When it comes to impedances and matching of valve amplifiers and speaker cabinets, there have been
written a lot of words and there have been told many opinions, myths and beliefs. And as it is so often
in our world, all of them are in between the truth and the untruth. Some more, some less. Don't expect
mine to be the only truth! But I give you some arguments on hand, why it is not necessary to match
your amp and cabinet and why your amplifier will not get damaged when the load does not match the
impedance switch setting.
Let's start with one of the most often heard opinions. Some claim that a mismatch between amplifier
and cabinet causes the valves to wear out quicker or can cause damage to the output transformer
and/or valves while at the same time advertising their amplifiers to work with any kind of valves,
doesn't matter if EL34, 6L6, KT66, KT88 etc.
Don't get me wrong that this is not possible, but the matching between amplifier and cabinet isn't
isolated on the secondary winding of the output transformer and the speaker. It's an interaction
between valves, primary winding of the output transformer, secondary winding of the output
transformer and speaker. It starts with a certain impedance each valve type has and which would
require (if we go on with the argumentation) a specific primary winding and thus again an impedance
of the output transformer to be 'matched'. The output transformer itself not only transforms the
voltage, it also transforms the impedance. It continues to the output transformers secondary winding
(with another you know what) and ends with the speaker (sorry, but yes...).
As mentioned above, this is not a one way street, it's an interaction, which means the speaker
influences the power amplifier and the power amplifier influences the speaker. Surely this is not a linear
process, it is dependend on frequency, power or wattage, electric and even mechanic speaker
specifications.
And if this wouldn't be enough, remember that it's called impedance because it alters with the
frequency... if you have ever seen the impedance curves of a speaker you know what that means.
There are several ways to 'mismatch', using different speaker impedances is only one possibility.
Different valve types or 2 instead of 4 valves are others. But none of them causes the power amp,
valves or output transformers to fail.
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