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Old 23rd October 2011, 10:52 PM   #21
sureshm is offline sureshm  Australia
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Ty, I agree with you. It doesn't make much sense using a thermistor on 175ma when you could just use a resistor. There is a slight benefit in that you have higher resistance on start up and then it drops but the drop is not going to be significant at 175ma. According to the data sheet the CL-90 drops to about 30 ohms @ 175ma which may not be so bad given that those who are not using a choke have 150 ohms in series with the power supply. As you say each person should choose what best suits their application.
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Old 24th October 2011, 05:10 PM   #22
rknize is offline rknize  United States
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Ty is not a fan, but I like to use a CL-140 on the center tap of most of my amps. It's gets quite toasty in most applications. I put a piece of heat-shrink tubing over it in my SSE to keep it hotter. I can't remember how much drop it has across it steady state, but it's not much. It makes B+ come up nice and softly, which makes for happy caps and rectifier!
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Old 24th October 2011, 06:37 PM   #23
sureshm is offline sureshm  Australia
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I have mistakenly bought some JJ rectifier tubes which I have heard have some issues with surge so I would be better off with something in there. Good tip on the shrink tubing to get it warmer.

So a tube rectifier brings up the B+ nice and slow already (slow start feature?), the thermistor would only dampen the initial surge right?

I dont have much experience with tube amps so this may sound like a silly question, but is there any reason why the amp doesn’t use a 4 diode full-wave rectifier such that a 185v-0-185v 200ma secondary would give you sufficient B+? Using a center tap transformer and 2 diodes seems to only use half of the transformers potential power? Am I missing something here?
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Old 24th October 2011, 09:45 PM   #24
rknize is offline rknize  United States
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The indirectly-heated tube creates a delay, but the inrush comes fairly rapidly once it reaches temp. This strains the tube more than anything. The inrush limiter softens this effect.

A bridge rectifier using tubes requires twice as many tubes and 5V windings. The SSE is designed for use with a 5AR4, but you could use a bridge if you were using solid state diodes.

Russ
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