I recently built my first DAC with TI's pcm2902 USB chip. I basically used the datasheet schematic example with all recommended values for resistors, caps, and voltage regulation. When using the chips digital out over Toslink to my receiver I get full and clean sound. However if I use the DAC function and go analog out to the same receiver via rca cables, the sound is fairly soft and I have to turn the amp volume up an extra 15db to get the same volume. Doing so is obviously having an effect on sound quality. The lows are overpowering with mid and high frequencies lacking. I know this is not a top of the line dac chip, but I expected a little more sound out of the chip than this. Datasheet indicates vout as .6*vcci which should be around 2.25v pp with the REG103 regulator I'm using. I see other designs using this and similar chips without opamp amplification. Any idea where I might be going wrong? Am I interpreting the datasheet correctly?
Thanks in advance.