Many posters ask about the correct capacitors for use in audio.and various parameters are brought up. I have high precision testing equipment but I wanted one I could use that could stand up to being dropped/leaned on etc. Most modern testers that show a lot of data seem to be made out of plastic and have to be used gingerly. There is on the web a Chinese all singing dancing tester at around $200 but on checking the replies to people that bought it it was condemned for breaking down after a month or two .One poster had it replaced and the replacement broke down -they wouldn't change it blaming the wall-wart. Other posters complain of old but reliable ones don't have a ESR test. Looking at the same ex government supplier that I bought an old Bradley CT471 high impedance MM I bought a Wayne Kerr -B424/N -LCR meter . It has an accuracy of-0.2% and will test from-0.1PF to 20000 UF and it did so accurately . But I was surprised to find it also tested ESR . Granted its written in very technical terms that you would need to know to realize it had that feature. But I tested various high value electrolytic caps and yes it did. After displaying the cap value you push the resistance button and after a second or two it displays the ESR . I went through many different caps just to make sure but yes it worked okay.
The price was approx $80[£50] ex-shipping which was cheaper as someone was selling on EBay- £80-ex shipping. Granted it only has 2 test frequencies-100HZ-for high value caps and 1000HZ on lower values. But for those changing caps on this website it is certainly good enough [ higher frequency testing is used for testing prototypes ] I would like to add that film caps paralleled up to 10UF or more produced a very low ESR nil or-nearly nil Those testers giving out a test frequency of 100KHZ and testing ceramic and other types of caps are really a relevant case for using in RF circuits as audio covers say -20HZ to 20KHZ. If you have a high frequency oscillation in your amp you have a big problem with stability and maybe your comp. cap needs adjusting. unless it is coming from the PS which I have found to be not more than 10% of the cases. That's why I stick to linear PS-old fashioned but less chance of HF interference.
Edited by duncan1 - 6/15/13 at 5:04am