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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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SET Asylum Single Ended Triodes (SETs), the ultimate tube lovers dream. |
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In Reply to: Rule of thumb for thermistors ?? posted by rogerh113 on June 13, 2015 at 15:05:58:
I've never liked the idea of installing a thermistor in the line. The problem is, it never goes completely away. In cases where a slow start circuit is really needed (it's usually not), a relay and resistor can do the job more effectively. Below is a sketch of the basic circuit. Sorry, I don't have representative values, but someone else here or in the DIY forum might.
When power is first applied, the current draw of the power supply capacitors and cold tube filaments creates a large voltage drop across the resistor. That drop leaves insufficient voltage across the relay coil for actuation. As the circuitry in the amplifier begins to normalize, current draw decreases, the drop across the resistor also decreases, and the relay actuates. With the relay contacts closed, the resistor is completely out of the circuit.
Again, in most amplifiers, none of this is likely to be necessary or even beneficial. There's a lot of commercial tube gear out there that has stood the test of time with no surge suppression at all.
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Follow Ups
- RE: Rule of thumb for thermistors ?? - Triode_Kingdom 17:08:36 06/13/15 (1)
- I built that type of slow-start circuit into LUX MB3045s... - jeffreybehr 17:27:41 07/02/15 (0)
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