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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: Grid choke and optimum coupling cap value posted by Deco-Doctor on July 2, 2006 at 02:07:04:
Hi,The to using gridchokes is to understand that the coupling capacitor and gridchoke form a resonant tank circuit.
The resonance frequency is calculated like this:
F = 1/(2*PI*Squareroot(L*C) with L in Henry, C in Farad, F in Hertz
Or you can be lazy and use this:
http://www.deephaven.co.uk/lc.html
It is essential to get this resonance sufficiently low that it will not be excited by any signal or you need to damp it using a resistor in parallel.
With 4,000H I have been getting away with 0.47uF coupling capacitors wich puts the resonance at around 4Hz. In your case the resonance is around 13.5Hz and I think this a bit high....
Best measure the LF response and see how things end up, if there is a significant level rise towards low frequencies your coupling capacitor is too low.
Ciao T
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Follow Ups
- Re: Grid choke and optimum coupling cap value - Thorsten 04:22:58 07/02/06 (2)
- Re: Grid choke and optimum coupling cap value - Deco-Doctor 04:42:06 07/02/06 (1)
- Re: Grid choke and optimum coupling cap value - Thorsten 07:55:24 07/02/06 (0)
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