"flipper" wrote in message
...
On Thu, 29 May 2008 09:01:52 +1000, "Trevor Wilson"
wrote:
"Ian Thompson-Bell" wrote in message
...
wrote:
"In a word: YES...
"The answer is rooted in the harmonic content that the device can pass
or generate..."
Continued: http://easyurl.net/TubesTubes
There is a lot missing from this article. First, it is triodes alone
that
generate pleasing 2nd harmonic distortion. Pentodes generate odd
harmonics
just as much as transistors do.
**So much nonsense, so little time to correct it. Why this myth continues
to
be perpetrated is a complete mystery. The TOPOLOGY dictates what type of
harmonics are generated, not the devices.
Well, you're half right. They both dictate the harmonics.
**I am 100% correct. Topology is the factor. Not the devices. Of course,
various devices DO contribute different distortion amounts. For instance:
* At low bias currents, pentodes add large amounts of distortion.
* At low bias current, triodes add smaller amounts of distortion.
* At low bias currents, MOSFETs add very large amounts of distortion.
* At low bias currents, BJTs add smaller amounts of distortion.
Push pull eliminates even order
distortion products. Valve or solid state.
But does nothing for the odd orders, which are dictated by the
devices.
**Sure. ALL amplifiying devices add odd order distortion. At moderate bias
currents, the approximate order is (from best to worst):
BJTs
Triodes
Pentodes
MOSFETs
At high bias currents, the order shifts somewhat to:
BJTs
MOSFETs
Triodes
Pentodes
It is the TOPOLOGY which dominates the issue of distortion production,
however. Depending on the amount of feedback employed, the devices used
makes little difference.
--
Trevor Wilson
www.rageaudio.com.au