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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: CCS study in depth, what do you think this approach posted by Paul Joppa on April 30, 2024 at 06:49:35:
I have got the reply from NAZ，saying to use big R as much as possible, but I intend to use as driver, swinging 100V p to p needed, so what appropriate value the R should be, if it is plate stopper, normally 100 ohm can do
"Hi Eric,
It depends on the operating points you use but only in as much as I would use as high a value as you can that still allows your chosen operating points. Eg, if you were operating the tube at say 300V B+ and wanted a plate voltage of say 120V at say 15mA you could use a 10K plate resistor. This would drop 150V, leaving a 30V drop across the CCS. Of course, this would only be OK for max AC swings of around 20V on the plate but if this needed to be higher, say for a driver stage then you would use a lower value plate resistor to allow greater head room for the CCS..
As I mentioned, the plate resistor is not technically required at all with a suitable CCS but IME it definitely sounded better with the FETs I have tried. The way I look at it this gives you the best of both worlds in that the CCS provides the high impedance load that tubes want for the lowest possible distortion and the resistor shields against the often harsh traits of FETs
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Follow Ups
- RE: CCS study in depth, what do you think this approach - Eric Chan 07:52:18 04/30/24 (1)
- RE: CCS study in depth, what do you think this approach - Paul Joppa 12:06:20 04/30/24 (0)
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