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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: Resistors for EL34 running in triode posted by Inkasound on October 27, 2006 at 06:29:02:
Even the smallest inductance can actually make parasitics worse because they occur at very high frequencies. The risk of parasitics applies especially to high inductance tubes like the EL34. Carbon film, metal film, metal oxide and even non-inductively wire-wound resistors can all have some slight inductance, as can a long lead from the resistor to the tube's screen grid pin. It may seem insignificant, and it would be in any other part of the curcuit but, when used as a stopper, this tiny inductance can form a tank circuit in conjunction with the small capacitance between electrodes in the tube, causing ringing at very high frequency. This is well outside the audible range but it loads the tube and can make the sound "gritty".You can get away with a resistor of less than 3 watts dissipation rating but being soldered so close to the tube pin there is the risk of it being overheated, so it needs to be a sturdy device. A value of less than 150 ohm is possible but unusual for a stopper.
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Follow Ups
- Carbon comp is non-inductive - Ray Moth 17:19:46 10/27/06 (2)
- Re: Carbon comp is non-inductive - Inkasound 19:43:43 10/27/06 (1)
- Re: Carbon comp is non-inductive - Ray Moth 01:26:22 10/28/06 (0)
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