Lets Talk Power Supplies
Since the topic of changing the power supply of the SB is such a bone of contention to some, I thought I'd explain the basic of differences between the typical switching power supply and a linear power supply. If you remember, I mentioned back in the first article that there was a dramatic difference in sound between the two.
As you can see from the waveforms from the typical 5 volt switching and linear power supplies, the switch-mode power supply generates pulses of power due to its switching (or pulse width modulation PWM) design. The linear power supply generates a nice, smooth voltage output.
Quoting the Lambda technical papers, linear power supplies can be up to 10,000 times quieter than their switching counterparts. That's pretty significant especially when it comes to high resolution audio.
"If the output load quickly changes from say full load to half load, the output voltage of the power supply will rise (overshoot) before the internal control circuit has time to compensate, and then undershoot a little less as the circuit over compensates. The length of time is takes from the instant of the load change to the time the output voltage settles back into the load regulation limits can be critical to some loads. Here the linear again outperforms the switch-mode.
For a 50% change in load the switch-mode will often take 3000us* to recover. A linear supply will recover in 50us."
The linear power supply provides a pretty dramatic improvement in recovery times from heavy load conditions.
Output Ripple and Transient Recovery. These are the two biggies as far as I'm concerned. The heavy output ripple of a switching power supply translates directly into noise, high frequency hash, and generally a hard, grainy sound. Throw in poor transient response recovery time and now you have power supply that likely won't be able to respond well to the heavy transients found everywhere in music. Those crisp leading edges of transients and the trailing decay of the sounds will be minimized as a result. Will it be horrible? No, but it sure could be better with a nice, properly sized linear power supply.
Since I've just (essentially) slammed the switching power supply, I feel the need to point out the obvious. 99% of the populous won't be able to hear the difference between the switching and the linear power supplies because their systems don't have sufficient resolution for the switching power supplies artifacts to be heard. It's only when you get into the high end realm of audio do the differences become clearly audible. This is no different than when you get into the high end realm of anything, Wines, Furs, High Definition Home Theatre, Jewelry or any market where true premium' goods can be found. The differences are there but you have to develop your skills to see, hear, smell or taste a discernable difference.
