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Grid choke as I/V?
Grid choke as I/V?
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Old 8th April 2008, 07:05 PM   #1
dsavitsk is offline dsavitsk  United States
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Default Grid choke as I/V?

I have a DAC that uses a resistor (~200R) as the I/V. This resistor doubles as a grid leak and the signal is fed to the grid of a tube. Overall, this works surprisingly well.

But, it occurs to me that it might work better with a grid choke instead -- high Z, low DCR. Anyone have any thoughts? All of the grid chokes I have seen have much too high DCR, so I think it would need to be a custom part of some sort, or maybe just a low H hammond. Also, the particular DAC chip (AD1865N-K) has no DC on the Iout if that changes what will work well.

Attached is what I am thinking. If you replace the choke with a resistor, it is what I am currently using.
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File Type: jpg chokeiv.jpg (20.3 KB, 176 views)
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Old 8th April 2008, 07:44 PM   #2
DougL is offline DougL  United States
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For a current output Dac, the load must have a much lower Z than the source.

An inductor has a very high Z, and would create extra distortion.

What I have seen people do is use a step up transformer to lower the effective load resistance while maintaining output.

I like the way you think. Keep at it.

Doug
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