Tube DIY Asylum: Profiling harmonic distortion for different Driver Stages.... by Thorsten Do It Yourself (DIY) paradise for tube and SET project builders.

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Posted by Thorsten (M ) on January 18, 2002 at 02:22:04

In Reply to: Re: Distortions and operating points and ... posted by Thorsten on January 17, 2002 at 16:36:24:

Hi all,

Now that Fortunecity is back on line I can show these:

Some comments on the Data presented in these graphs, please note the perspective and look for relative hight "above ground". The 300B Output Stage was run fixed Bias, 400V/80mA and was a Svetlana, Output Transformer an SJS 2K6 unit loaded with an 8 Ohm 20W "Dummy" load. PSU was very simple, 240V mains isolation transformer with solid state rectifier and around 1,000uF Filter Capacitance, plus a choke and another around 1,000uF, supplying both Output and driver with around 400V +B.

Finally, in the pictures for the lower power one can see on some curves a peak around the 5th Harmonics. I'm not sure if this is a phenomenae of the 300B or of my testsetup (PC with Wavetools and soundcard), but it is NOT present in the Driverstage alone.

And before someone complains that the 6SN7 is better because it does not show this rise (someone already did), please note that it is not visible because the 6SN7 cascade already generates so much mush that it swamps this effect....

I wish I had access to the fancy Tek gear Lynn and Matt used with their tests, but alas, I ain't, so this crude but illustrative stuff is all I can manage....

Ciao T

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