PSU capacitors: 30uF film ok instead of 100uF electrolytic? - diyAudio
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Old 12th September 2008, 05:59 PM   #1
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Default PSU capacitors: 30uF film ok instead of 100uF electrolytic?

I'm about to build the Hawthorne Audio 6CL6 Spud amp (2.5Wpc).

The schematic suggests that two 100uF electrolytic caps are used in a CLC arrangement for the B+ supply.

Would 30uF motor run caps be suitable replacements for the 100uF electrolytics?

The ESR of a typical 30uF motor run cap is lower than a 100uF 'lytic (at 100Hz) and the ripple current is much higher (more than double that of the 'lytic)....

Any advice would be appreciated :-)
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Old 12th September 2008, 06:54 PM   #2
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It will work but you will see drastically reduced filtering ability due to less series resistance and massively less capacitance.
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Old 12th September 2008, 07:01 PM   #3
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Yes, if the voltage rating is adequate and you use 4 in parallel for each 100u.


Oh, advice. Use the electrolytics.
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Old 13th September 2008, 08:49 AM   #4
Tweeker is offline Tweeker  United States
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High ESR makes a cap less effective, not more.

Either way the ripple performance (if not HF impedance) should still be overwhelmed by the difference in capacitance with modern elcos. A compromise would be to parallel the final cap with a film/oil cap.
Be sure your foil hat has a good low impedance ground.
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