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Old 10th December 2012, 12:12 AM   #1
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Default 6H30 VA stage?

Does anyone have a link to a 6H30 as a VA stage? I am working on an amp, and I have 184V on the plates with a 28.8K anode resistor, and 11.7V on the cathode. Just wondering what is "normal" for this tube. I have a 1.5K cathode resistor.

Thanks for any information!

Blair
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Old 10th December 2012, 11:31 AM   #3
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Hi,

Thank you! I can find the tube data, but I wanted to see if anyone had a working schematic of this tube as the VA stage of their or a commercial amplifier. In my amp, I have:

Using a 28.8K plate resistor and 1.5K cathode resistor:

184V on the plate, and 11.7V on my cathodes.

I have never seen cathode voltage that high in a VA stage and wondered if it looked OK to run like this.

Thank you!

Blair
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Old 10th December 2012, 12:03 PM   #4
TheGimp is offline TheGimp  United States
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You are running 7.8mA for cathode current, which is well within the spec of the tube.

However, this is a low for best performance for this tube. Also your anode voltage is a too high. The two together will put you out of the most linear bias region.

I would suggest decreasing your cathode resistor significantly, to increase anode current and lower anode voltage.
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Old 10th December 2012, 12:13 PM   #5
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Thanks!

Looking at the tube specs, it looks like I need to also decrease the plate resistor from almost 30k to around 6-10K and change my dropping resistor in my PS to lower the plate voltage.

You think 250-560 ohms for the cathode resistor?

Ill tinker with it and post some voltages if you don't mind.

Thanks again!

Blair
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Old 10th December 2012, 12:28 PM   #6
12B4A is offline 12B4A  United States
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pRC put some 6H30Pi experimentation up on his website. AudioVidioPhilia: Mambo Foreplay
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Old 10th December 2012, 02:41 PM   #7
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I tinkered with it a bit by changing the dropping resistor, plate and cathode resistor.

Now, I have a B+ of around 150V

72V on the plates, and 3.45V on the cathodes.

Look better?

Thanks?

Blair
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Old 10th December 2012, 04:51 PM   #8
euro21 is offline euro21  Hungary
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My suggestion.
Attached Images
File Type: jpg 6H30 preamp.jpg (135.1 KB, 172 views)
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Old 10th December 2012, 07:36 PM   #9
12B4A is offline 12B4A  United States
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Is that for both sections in parallel?
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Old 10th December 2012, 07:58 PM   #10
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It was a single side. I ditched the 6H30. It acted very unstable and both that I have are fairly noisy. I had some wicked 120hz artifacts.

I swapped plate resistors, changed my cathode resistor, dropped a 6CG7 in and away went the noise and wobbly sine waves.

I got the 6H30s from a buddy, so god knows what they went through.

Thanks!
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