[DSK]

I seem to recall aftermarket battery PS's being compared to aftermarket AC PS's on the SqueezeBoxes by ACers a year or two back and the concensus seemed to be that really good AC PS's sounded as good or better than the battery ones. Can't recall much detail but I think Zybar may have been one of those who did the comparison???

I remember thinking at the time that there was no longer any good reason to suffer the inconvenience of battery power (and sometimes poor dynamics depending upon design) and striking it off my 'to be auditioned' list.

[bhobba]

in not too technical terms what is it about the power supply that improves the Squeeze Box so much. Does it like a DC current and thus any ripple off the mains upsets its sensitive circuits?

I don't think anyone really knows.  I do however have a theory that would need experimention to substantiate.  While we can not hear above about 20K (even less if you are older) the ear is a non linear device that can quite possibly detect the absence of information above 20k rather than that information itself - due to its interaction with the information you can hear.  Power supplies may not be able to deliver current 'quick' enough to let that HF information through.  This is a 1 bit DAC, so some really HF info is present - it is not on the recording but the ear may still interpret as being more realistic. From what Hugh has written he designed the supply to be really 'quick' ie able to deliver these surges when required.  This correlates with what Wayne at Boulder found when he connected it up to his ultimate power supply - it improved it in areas differnet to his supply.  His supply helped the bass - Hugh's supply helped the musics dynamics.  That is not so say Hugh's supply is not good in the bass but Wayne uses some rather expensive and exotic components.  FWIW I believe Hugh's supply offers a better price/perforance ratio than other methods.

Thanks
Bill

[AKSA]

Yes, Darren, you are right.....!

Battery power seems ideal, but there are issues.   They are related to the chemical process of conversion;  a lead and a lead dioxide plate combine with sulphuric acid to produce a reversible reaction generating water (pulling back the SG of the acid electrolyte as it discharges) and lead sulphate (which deposits at the molecular level on the plates).

The issue is speed.  While a lead acid battery can deliver low resistance, down to tiny fractions of an ohm (it is common, for example, to fit automobiles with 1.5 hp electric starting motors, easily driven from a simple 12V, $80 lead acid battery) the conversion from chemical to electricity takes a bit of time and starts to peter out at around 10KHz.

The second issue is the inconvenience of having to disconnect the battery from its SqueezeBox, connect it to a battery charger, and charge it slowly over a long period so as to prolong its fairly short life, maybe five years if you are very lucky.

Now, 10KHz is an audio frequency, and it means you need to use a large, fast bypass cap across the battery to keep the impedance low at higher audio frequencies.  Of course, you have to do this on a standard AC supply to act as reservoir and filter the AC, too, and when you look at the inconvenience of the battery, the cost, the chemical hazard and the weight, you realise that maybe a trafo ain't so bad after all.....

The need for power supplies from AC is ubiquitous, and the large semi companies have produced very good regulator chips for years now which are getting faster and faster and delivering pure, clean DC.

They still do not have the impedance characteristics required for really good audio - my opinion only - but they are outstanding as pre-regulators.  The LM317 and the Linear Tech chips are very good, and will deliver very accurately controlled voltage with zero ripple over quite a range of currents.  Wayne exploits this very elegantly in his Ultimate power supply, which now has an Aspen Nirvana regulator in it in the premium version, and yes, Bill, I did design the supply for speed, but also for negative output impedance across the audio range.

Cheers,

Hugh