A novel apparatus for and method of upstream power control for multiple transmit channels. The invention is particularly useful in environments that include two level amplification, wherein the first level corresponds to each channel separately and the second level corresponds to the joint sum of all the channels. When working with two-level amplification, changing the joint sum amplification is permitted during specific time periods known as “CMTS re-configuration time” in the DOCSIS specification. The mechanism functions to maintain an optimal transmit power operating point of the PGA using self-configuration without any need to receive permission from an exterior control entity such as the cable head-end thus bypassing the prior art requirement of waiting for a global reconfiguration time from the CMTS (i.e. when the specification assures that there is sufficient time to change the PGA gain). This can be achieved with high confidence if there is sufficient quiet time (which is calculated) to perform the self-configuration of the PGA within a specific period of time.