PS Capacitor Voltage Rating

dsavitsk · 15th January 2006, 07:40 PM

I am building a R(100R) C(220uF) L(7H) C(220uF) R(120R) C(56uF) power supply for a line stage using a 5V4G. The transformer will be 300 - 0 - 300, and the B+ is about 290V.

What voltage rating is reasonable for the caps? I assume 450V is fine, but is 350 pushing it? I ran a Duncan Amps simulation, and the voltages are all reasonable, except at D where the program shows -800V. The V at C1 (loaded) is about 320V.

Tweeker · 15th January 2006, 08:39 PM

400VDC or 240VAC would be fine, I think that 350VDC is pushing it. Since its not difficult to have a >10% margin here, I dont see why you wouldnt. Higher voltage caps often have lower ESR too. Your also depending on your load to drop voltage, what if it goes open?

Im not sure how your using a 300-0-300 xfmr here to get 800V peak inverse voltage (piv, the -D value), to use the center tap in full wave rectifier, youd have 600V of winding (and piv would be ~1600). Using a bridge across 0-300V piv would be around 400V, and if there arent other loads your transformer would be unevenly loaded and unhappy. The only way I can come up with 800V piv is using a half wave rectifier across 0-300V?

rdf · 16th January 2006, 01:13 AM

Don't forget startup conditions. I did.

My 6c45 spud headphone amp runs at a nominal ~125 VDC on plates but (I'm working on it) will see 300+ on turn-on before the tubes begin to conduct. Fortunately the prototype was assembled with 600 volt oils caps pending a final circuit. Still pounds the tubes though.

tubelab.com · 16th January 2006, 03:37 AM

A 300 - 0 - 300 transformer can deliver over 400 volts of DC with no load. The 5V4 will heat up quicker than your other tubes. For a few seconds there will be no load. I would use 450 volt caps.

15th January 2006, 07:40 PM	#1
dsavitsk Crusher diyAudio Member Join Date: Jan 2005 Location: Chicago	PS Capacitor Voltage Rating I am building a R(100R) C(220uF) L(7H) C(220uF) R(120R) C(56uF) power supply for a line stage using a 5V4G. The transformer will be 300 - 0 - 300, and the B+ is about 290V. What voltage rating is reasonable for the caps? I assume 450V is fine, but is 350 pushing it? I ran a Duncan Amps simulation, and the voltages are all reasonable, except at D where the program shows -800V. The V at C1 (loaded) is about 320V.

15th January 2006, 08:39 PM	#2
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	400VDC or 240VAC would be fine, I think that 350VDC is pushing it. Since its not difficult to have a >10% margin here, I dont see why you wouldnt. Higher voltage caps often have lower ESR too. Your also depending on your load to drop voltage, what if it goes open? Im not sure how your using a 300-0-300 xfmr here to get 800V peak inverse voltage (piv, the -D value), to use the center tap in full wave rectifier, youd have 600V of winding (and piv would be ~1600). Using a bridge across 0-300V piv would be around 400V, and if there arent other loads your transformer would be unevenly loaded and unhappy. The only way I can come up with 800V piv is using a half wave rectifier across 0-300V? __________________ Be sure your foil hat has a good low impedance ground.

16th January 2006, 03:37 AM	#4
tubelab.com diyAudio Member Join Date: Jul 2005 Location: South Florida	A 300 - 0 - 300 transformer can deliver over 400 volts of DC with no load. The 5V4 will heat up quicker than your other tubes. For a few seconds there will be no load. I would use 450 volt caps. __________________ Too much power is almost enough! Turn it up till it explodes - then back up just a little.

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16th January 2006, 01:13 AM	#3
rdf diyAudio Member Join Date: Jun 2004 Location: the thermionic past	Don't forget startup conditions. I did. My 6c45 spud headphone amp runs at a nominal ~125 VDC on plates but (I'm working on it) will see 300+ on turn-on before the tubes begin to conduct. Fortunately the prototype was assembled with 600 volt oils caps pending a final circuit. Still pounds the tubes though.

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