• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

SE Waveform

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mr2racer

Member
2009-07-09 12:53 am
Hey All,

I'm working on an RH84. And as I increase input the amp clips the bottom of the sine wave. In fact even before it clips the bottom of the sine wave seems rounder and more blunt than the top. (I haven't reversed the polarity of the input from the signal generator to eliminate that yet. Just thought of it.)

The more I drive it the squarer the bottom gets. But it never seems to effect the top of the waveform. Can anyone tell me is this an SE effect or an RH effect? Or is there a problem with this individual amp?

Kevin
 
Hi!

As has been mentioned: It is good practice to bias the output tube such that it clips as symmetrically as possible. With most SE amps one side of the wave will start to clip soft by just getting a bit rounded. That is the output tube driven into cut off. The other side usually clips harder, that is the output tube driven into positive region. Most drivers cannot deliver power to push the output tube into grid current. Of course it depends on the amp circuit.

Here is an example of measurements of such an amp as described above:

VinylSavor: Low Cost Single Ended 6CB5A Amplifier - Part 5

Best regards

Thomas
 
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