Interview discussing microphony and other design choices. The important takeaway is that some designers choose to tackle power supply and microphony issues and others ignore them. If you buy a DAC that is not designed to eliminate these issues then of course you can spend far more than you spent on the DAC itself trying to fix power supply and microphony issues.
http://www.stereo-now.co.uk/interviews-Benchmark.html"In a well-designed system the DAC chip is the limitation. Anyone who is building “high-end” products that are limited by power supply performance should find a different “d**n” business."
"Before any product is released to market, we subject it to very high levels of vibration while listening to the noise floor and while viewing the noise spectrum on a high-resolution audio analyser. Any disturbance in the noise floor is an indication that a microphony problem exists. We also tap each component with a ceramic probe while listening to the noise floor. Benchmark products are not microphonic and can be used in high sound pressure and/or high vibration environments without isolation accessories."
On the DAC2 and DAC3 the power supply is switched Mode and this new form of power supply running at very high frequency has eliminated all the 60Hz hiss and hum issues that come with a linear power supply.
Benchmark is not the only maker of excellent sounding DACs but I present their design philosophy here to show that not all designers ignore the problems of power supply and microphony - so choose your products wisely or else you face the challenge of trying to get them to work properly through the use of band-aids!