I got off on a tangent a while back and was looking at how ESR is measured, and simple test sets for measuring it.
I built a 100KHz pulse measurement unit and was measuring some capacitors and was quite surprised at the variation in ESR.
Some new caps (Al electrolytic) measure as high as 10 ohms and others were less than 0.5 Ohms (resistors used as reference for calibration).
Since the ps caps are in the audio path it seems they would matter, and this may be in part why film caps sound better (less than 0.1 ohm ESR).
I measured a bunch of film caps for comparison and can't even measure the ESR as it is close to a short on the test set.
I built a 100KHz pulse measurement unit and was measuring some capacitors and was quite surprised at the variation in ESR.
Some new caps (Al electrolytic) measure as high as 10 ohms and others were less than 0.5 Ohms (resistors used as reference for calibration).
Since the ps caps are in the audio path it seems they would matter, and this may be in part why film caps sound better (less than 0.1 ohm ESR).
I measured a bunch of film caps for comparison and can't even measure the ESR as it is close to a short on the test set.
The first step for a better understanding is to appreciate what variation the ESR would introduce in a valve amp. Include some example values of the anticipated variation at max signal level in an amp you have, based on your worst measured value of ESR. Then rationalise what aspect of the variation is going to be most noticable (mains ripple or rectification noise or signal ripple).
If you have golden ears then you can do a blind test by switching in and out a 10 ohm series resistor.
If you have golden ears then you can do a blind test by switching in and out a 10 ohm series resistor.
Hi
Both Eli Duttman and trobbins have made valid comments. I normally bypass my power supply electro's with good quality low ESR non polar capacitors, one can at least have very low ESR at higher frequencies. Running the amp at various power levels and frequencies into a dummy load while observing the power supply rails with an oscilloscope can also be of some merit.
Regards
Ken
Both Eli Duttman and trobbins have made valid comments. I normally bypass my power supply electro's with good quality low ESR non polar capacitors, one can at least have very low ESR at higher frequencies. Running the amp at various power levels and frequencies into a dummy load while observing the power supply rails with an oscilloscope can also be of some merit.
Regards
Ken
If you are adding bypass caps then you may need highish ESR in the main electrolytics, or a series resistor, or a snubber. This damps out the HF resonance you may introduce.
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