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AR9 caps ESR values???


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Does anyone know what the "like new" ESR values are for the caps in the AR9, especially the woofer section (2500uF and 470uF)?

Thanks, KKC.

People with good ears who have replaced the old Callins and Sprague NPE capacitors say that the sound is quite good after new caps are installed.

No one knows what the precise values of ESR and C were in the capacitors when they were new in 1976. What we do know is what we measure today. Several new and one NOS unit--all built in the mid 1970s--measure very close in 2008.

First how are you defining ESR? as the metal resistance, the constant (high frequency) part of the loss? or are you including the frequency dependent low frequency dielectric loss? I define ESR as the total of dielectric plus metal loss. Here are some representative measurements made this spring.

2500 uF: (about six units) fell in the following range:

From 10 Hz to 100 Hz, the loss = A/f Ohms, where A is a constant in the range 1.5-to-2 and f is the frequency in Hz.

From 100 Hz to 4, 000 Hz, the loss is a constant in the range 0.015-to-0.02 Ohms

470 uF (a few units) average as follows:

From 10 to 200 Hz, loss = 10/f Ohms where f is the frequency in Hz

From 200 Hz to 10,000 Hz, the loss is a constant = 0.05 Ohms

Some people call ESR the high frequency metal resistance, but strictly speaking it includes the whole enchilada.

These numbers will not tell you much about what the devices were like 30 plus years ago. Other effects that we don't understand likely did change in thirty years. Bottom line: new devices with simlar ESR as these old units are reported to produce much improved sound.

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