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Re: Voltage rating for Tone stack Capacitors

10/5/2005 4:29 PM
R.G.	Re: Voltage rating for Tone stack Capacitors ... or tie the point between the DC blocking cap and the tone caps to ground with a 4.7M resistor, just enough to eat any leakage from the DC blocking cap. The DC voltages do split between the two caps, but they split in the inverse of the ratio of the leakage currents of the caps, not their capacitance. Well, OK, they split by capacitance during the power up/down cycle and that could be a problem, but with different dielectrics in the caps, estimating the DC split is very hard without using a sledgehammer resistor to force the DC to ground. With the resistor, you just need the tone caps to have a voltage rating big enough for the signal. 33V is pretty low, but I bet 100V would handle it nicely.

10/5/2005 4:29 PM

R.G.

Re: Voltage rating for Tone stack Capacitors

... or tie the point between the DC blocking cap and the tone caps to ground with a 4.7M resistor, just enough to eat any leakage from the DC blocking cap.

The DC voltages do split between the two caps, but they split in the inverse of the ratio of the leakage currents of the caps, not their capacitance. Well, OK, they split by capacitance during the power up/down cycle and that could be a problem, but with different dielectrics in the caps, estimating the DC split is very hard without using a sledgehammer resistor to force the DC to ground.

With the resistor, you just need the tone caps to have a voltage rating big enough for the signal. 33V is pretty low, but I bet 100V would handle it nicely.