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Old 1st December 2010, 12:48 AM   #1
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Default Spect output peak to peak for 807 SE ul

Hi all, i'm building a 807 seul amplifier with 5k output transformer, my questions are as follow:

1- In my mesurements, output volts peak to peak across RL of 7.7ohm is 15 whit aproximete 5% TDH, this is good or bad, i have no reference to anhoter project because in my country valve amplifiers is not common.
2- VCC is 306v and the amblifier is biased for 390ohm catode bias, how to calculate tube power dissipation, directly 306*390?

My english is not very good i hope yuo understand, more testig my amplifier l'll have more questions, very grateful for your answers, greetings

Walter
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Old 1st December 2010, 10:48 AM   #2
DF96 is offline DF96  England
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15V pk-pk across 7.7ohm is 3.7W. I have never used the 807 but I would expect a bit more, although 306V for Vcc is maybe a bit low for that valve?

The power dissipation is current*volts. You need to measure the voltage at the cathode Vk. This is generated across the cathode resistor 390ohms. So use Ohms Law to get the cathode current Ik = Vk/390. Then the total dissipation is Ik*Vcc = Vk*Vcc/390.

OK?
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Old 1st December 2010, 11:24 AM   #3
davorin is offline davorin  Croatia
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Join Date: Aug 2005
Location: Zadar, Croatia
Quote:
Originally Posted by walter807 View Post
Hi all, i'm building a 807 seul amplifier with 5k output transformer, my questions are as follow:

1- In my mesurements, output volts peak to peak across RL of 7.7ohm is 15 whit aproximete 5% TDH, this is good or bad, i have no reference to anhoter project because in my country valve amplifiers is not common.
2- VCC is 306v and the amblifier is biased for 390ohm catode bias, how to calculate tube power dissipation, directly 306*390?

My english is not very good i hope yuo understand, more testig my amplifier l'll have more questions, very grateful for your answers, greetings

Walter
Your Ra(5kohms) and Rk(390 ohms) are to high! Try with Ra~3-3,5Kohms, and Rk~150-180 ohms, with Ua=300Vdc, Ug2=250Vdc/Rg2=470ohms.
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