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Old 1st December 2016, 07:28 PM   #1
aldovan is offline aldovan  Brazil
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Default Questions about tetrodes for specialists

Friends

I found a type 36 tetrode and built the above circuit to test it as a preamplifier. However, I observed that from 20Hz to 15KHz the circuit provides 35Vpp at the output, but this voltage goes down to 27Vpp at 20KHz.
What can cause this loss of gain? The capacitances on the tube look ok.

Thanks

Aldovan
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Old 1st December 2016, 07:31 PM   #2
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Probably the design and characteristics of the valve.
A pentode, by the way, has 5 electrodes.
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Old 1st December 2016, 07:44 PM   #3
Matt BH is offline Matt BH  United Kingdom
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Take a good look at how you are feeding G2.

Cheers
Matt
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Old 1st December 2016, 07:59 PM   #4
hpeter is offline hpeter  Slovakia
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Click the image to open in full size.
oh no, the kinky one
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Old 1st December 2016, 08:10 PM   #5
aldovan is offline aldovan  Brazil
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Originally Posted by Matt BH View Post
Take a good look at how you are feeding G2.

Cheers
Matt
Matt

What is the problem on g2 ?

Aldovan
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Old 1st December 2016, 09:10 PM   #6
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Quote:
Originally Posted by aldovan View Post
What can cause this loss of gain?
Have you verified that your test setup has not such capacitance that it could load the signal at 20 kHz ?

How did you measure the output voltage ?
What is the impedance of that test device ?
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Old 1st December 2016, 09:16 PM   #7
aldovan is offline aldovan  Brazil
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Originally Posted by artosalo View Post
Have you verified that your test setup has not such capacitance that it could load the signal at 20 kHz ?

How did you measure the output voltage ?
What is the impedance of that test device ?
I use a Šudio generator with 800 ohms impedance and a oscilloscope for mesure the wave.
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Old 1st December 2016, 09:39 PM   #8
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Quote:
Originally Posted by aldovan View Post
I use a Šudio generator with 800 ohms impedance and a oscilloscope for mesure the wave.
10x probe?
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Old 2nd December 2016, 12:04 AM   #9
kevinkr is offline kevinkr  United States
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What Artosalo and Spreadspectrum said.
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Old 2nd December 2016, 12:06 AM   #10
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Quote:
Originally Posted by aldovan View Post
Matt

What is the problem on g2 ?

Aldovan
You only have half of a voltage divider
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