Batteries

As we wound up our series on power supplies several of you mentioned what would seem to be the best power supply of them all: a battery. Indeed, a battery delivers perfect DC without any ripple or noise and is completely independent on the quality of the incoming AC. It would seem to be the perfect solution - one the AC power supply could only hope to emulate. Ahh, were it so simple. Like every solution out there, a battery supply itself is plagued with issues as well. Chief amongst them is DCR - meaning the ability of the battery to deliver as much current as needed when it's needed - unrestricted by the built in resistor every battery has. If we look at a simple battery solution - one that's almost practical - it would be a low current draw preamplifier or DAC. We know that these low power devices would make an easy target for a battery supply because they wouldn't drain the batteries too much and thus give you some decent playing times without a recharge. We also know that the source impedance of the supply plays a critical role in the way these sound - hence the need for oversize power transformers, lots of capacitance (energy storage) in a conventional supply. As an example, take a look at our entry level DAC the NuWave. Inside this low power source we use a power transformer that's half the size of the entire chassis and is capable of supplying adequate power to 20 or 30 such DACS - and we do this because there's a clear sonic advantage of the oversized transformer. So if we were to take that supply out of the NuWave and add a battery supply instead, what would happen? Much of that answer depends on the size and type of battery used. If we want to better the sonics of what we already have, we'd need a battery capable of delivering many amps of power so it had low DCR. Because the NuWave needs about 40 volts to operate, we could take three or four 12 volt car batteries and place them in series so we get the appropriate voltage. My guess would be we'd have improved the sound of the DAC rather dramatically if we did this. We'd also be thrown out of our homes by our loving wives - who just wouldn't understand the price that needs to be paid for great sound. Aside from the fact having this much stored energy hanging about in the home is dangerous, there's also the out gassing, charging and so forth that wouldn't be all that practical. So instead of the holy grail, we would naturally want something a bit more practical like a group of lithium ion or NiCad batteries instead - unfortunately, these have higher DCR than our oversize transformer and in the end, we've accomplished nothing except making our DAC sound worse - wimpier, thinner and more threadbare. So, when it comes to a practical solution that sounds best, we stick with our conventional supplies or go for a newer SMPS design that gives us everything we want and then some. Take a lok inside of your DAC or preamp and note the size of the transformer - if it's typical it'll be small - and one could have an immediate improvement if the size of that transformer were a lot larger. 'Tis a shame so many designers in high end still do not understand what's going on here. I'll keep plugging away at it through these posts. Batteries, however, aren't the path that's going to get us where we want to go - that is if we wish to have peace in the home.