Hello, I have to check my old Parasound A23.
I measure THD and this is how it looks like. To 5R load
It is issue with electrolytic capacitors, What do you think?
I measure THD and this is how it looks like. To 5R load
It is issue with electrolytic capacitors, What do you think?
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That 100 hz distortion looks like hum. Minus 95 db is not a lot. My industrial grade Peavey MMA-875t claims 95 db with the volume minimum, 77 volume max. A consumer grade M-2600 claims -95 db hum & noise below 130 W.
ESR is the best test of electrolytic rail caps. You have to remove them to check it. There has been a recent cost reduction in ESR meters. Some senior person here recommended the longruner multifuction meter, which is $35 from ebay here. I've had the Peak ESR meter, which was $96 last week.
Alternate rail capacitor test, run the amp just below clipping into load resistors of suitable resistance & wattage. I buy mine from surplus houses. I series connect 4 one ohm 200 w or series parallel connect 10 ohm 225 w to get 10 ohm 450 w or whatever is required for your amp rating. A $40 DVM produces random numbers on music. I use a $20 analog VOM with a 20 vac & 50 vac scale. I use pocket FM radio for signal source, out the earphone jack, about 1/3 volume or less. P=(v^2)/Z where Z is speaker impedance at rated power. Power < rating, your rail caps are dried up usually. Especially if amp is over 15 years old, 20 years on industrial grade equipment. Equipment with competent original capacitors that has been lightly used can exceed the year rating. Advantage of watts test, you don't have to take the cover off the amp & remove a capacitor. If speaker power rating exceeds the amp rating (like organ speakers do usually) you can use them as a load instead of load resistors.
ESR is the best test of electrolytic rail caps. You have to remove them to check it. There has been a recent cost reduction in ESR meters. Some senior person here recommended the longruner multifuction meter, which is $35 from ebay here. I've had the Peak ESR meter, which was $96 last week.
Alternate rail capacitor test, run the amp just below clipping into load resistors of suitable resistance & wattage. I buy mine from surplus houses. I series connect 4 one ohm 200 w or series parallel connect 10 ohm 225 w to get 10 ohm 450 w or whatever is required for your amp rating. A $40 DVM produces random numbers on music. I use a $20 analog VOM with a 20 vac & 50 vac scale. I use pocket FM radio for signal source, out the earphone jack, about 1/3 volume or less. P=(v^2)/Z where Z is speaker impedance at rated power. Power < rating, your rail caps are dried up usually. Especially if amp is over 15 years old, 20 years on industrial grade equipment. Equipment with competent original capacitors that has been lightly used can exceed the year rating. Advantage of watts test, you don't have to take the cover off the amp & remove a capacitor. If speaker power rating exceeds the amp rating (like organ speakers do usually) you can use them as a load instead of load resistors.
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