How to reduce pop and click on simple audio circuit

[ransom peek]

I am using 6 I/O lines of a PIC processor to feed a resistor binary ladder (D to A converter), that produces a sine wave from 64 step voltages per cycle. The voltage is about 3 volts peak.

Thru a series 10 uf cap and series pot (to attenuate) headphones are driven (other side of headphones tied to ground).

When a tone starts or ends a pop sound is heard. How can it be reduced or eliminated? I have tried different values for the series cap, and tried a cap in series with the ground to headphones connection. Nothing seems to help.

Any ideas?

Ransom Peek
Fort Collins CO

[sreten]

1) crude : stop and start the the tone at a zero crossing point.

2) subtle : ramp up the values at start and ramp down the values when stopping.

sreten.

[ransom peek]

To ramp up at start - does this mean:

generate a sine wave cycle with low amplitude, then another slighty higher, then some higher, up to the standard amplitude?

Then the reverse to ramp down?

Ransom