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In the Forum: Melquiades Amplifier
In the Thread: A different breed of 6C33C amplifier.
Post Subject: 6C33C clipping @ 20WPosted by KOTriode on: 9/11/2011
I ran the tube conservatively at 40W, because it is still breaking in, and I do not want to push it too much power to damage it (then I will have to break-in a new tube all over again). This amp can give max power  at 20.35W (12.76Vrms into 8 ohm) with 9.65% distortion, but this is not the kind of power you are "proud" of driving any speaker with (see photo below). At 40W plate dissipation, the amp put out about 10W at 5% distortion, which is a good point to test the amp "real" bandwidth which numbers are more meaningful to me, coincidentally this is what class A is all about, 25% efficiency. My output transformer is rated 30W and 350mA at the primary, so, I still have room to push it for more power, but my 200VA power transformer is inadequate to get more power out of the amp due to power loss for the rectifier/regulation.

"The adjustable current on the tube from 100ma-300ma and 160-220V? Why do you need it? 

7) Using voltage and current on the output tube try to make the clipping symmetrical from top and bottom of the sinusoid. The top way is voltage, the bottom wave is current (or vice versa, I do not remember already). As the symmetrical will be find try to play with operation point more in order to get lessen symmetrical clipping at higher power.

8) If change of voltage and current will get rid of clipping then add more input voltage to drive the amp into clipping again


This is one reason I felt regulator is so convenient with this 6C33C tube, like you mention, I can set the amp to a level I like and adjust the voltage/current for a symmetrical clipping. I can get few more watts by pushing the tube to 250ma, but the voltage now sag close to the point that B+ start loosing regulation. 
Below is the photo why I dont rate this amp as 20W
1Khz Sine wave @ 10W


20.35W 1Khz Sine Wave 12.76 Vrms at %10% Distortion



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