KurtW
500+ Head-Fier
- Joined
- Jun 26, 2001
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- 13
Battery life will depend on the capacity of the battery and the power consumption of the amp. The power consumption will be a function of all of the circuitry as well as the output power used. For example, biasing the op amp into Class A takes some current, as do the output buffers and the power supply buffer.
I measured the last two META42s that I built, both with the AD8620 op amps running in Class A. One had double EL2001 buffers and measured 12.3mA and the other had triple buffers and measured 13.6mA This is a static measurement taken with a battery putting out 10.0 volts. When I listen to music at my typical levels with low impedance headphones the current goes up around 0.5 to 1 mA. The Plainview battery is rated at 170mAH, so with music I would expect to get around 13 hours from the double buffers or 12 hours from the triple buffers. Your battery may be different. This seems about right based on my experience but I've never timed it. With the AD845 you'll get a little less than half of this.
According to my calculations, the DT770 Pro would require 2 volts RMS to achieve 105dB SPL, so 7 volts should be fine with either chip. This is 4mA of current draw, so the above amp with double buffers would only last 9.5 hours with the 8620 and 5.4 hours with the 845.
I measured the last two META42s that I built, both with the AD8620 op amps running in Class A. One had double EL2001 buffers and measured 12.3mA and the other had triple buffers and measured 13.6mA This is a static measurement taken with a battery putting out 10.0 volts. When I listen to music at my typical levels with low impedance headphones the current goes up around 0.5 to 1 mA. The Plainview battery is rated at 170mAH, so with music I would expect to get around 13 hours from the double buffers or 12 hours from the triple buffers. Your battery may be different. This seems about right based on my experience but I've never timed it. With the AD845 you'll get a little less than half of this.
According to my calculations, the DT770 Pro would require 2 volts RMS to achieve 105dB SPL, so 7 volts should be fine with either chip. This is 4mA of current draw, so the above amp with double buffers would only last 9.5 hours with the 8620 and 5.4 hours with the 845.