Battery power

[Vincent Kars]

There is a lot of talk about using a linear PSU to power your dedicated audio PC.
Will sound quality really improve?
I tried a simple test using my laptop.
Measure it using the AC adapter in place and do the same when running on battery only.

Running on AC

Running on battery

Obvious running on battery creates a lot of distortions
This is the power saving schema.
Better put it off.

 

[microstrip]

Interesting.
But I fail to see what is the connection between a PC powered by a linear PSU and and a battery powered laptop.

In instrumentation, sometimes we prefer to use the laptops to get data and/or control systems powered by the batteries just to avoid ground loops.

 

[Vincent Kars]

Just a little experiment.
If a linear psu would improve sound quality compared with a switched, a battery powered one might do the same as a linear one (no switching).
So I used battery power to check if there was a difference.
There was.
The advice to disable power saving schemas does make sense.

 

[DonH50]

Interesting that on battery the fundamental acquired significant skirts but the 3 & 5 HD went down significantly (by about 10 dB)... Makes me wonder if the clocking scheme changed.

 

[Vincent Kars]

The clocking scheme might be changed indeed: http://en.wikipedia.org/wiki/SpeedStep

 

[DonH50]

The fundamental frequency and sampling rate, sample record etc. were exactly the same in both cases? And, are both cases repeatable?

 

[Vincent Kars]

The procedure was a very straight forward one.
Run RMAA with AC in place.
Remove AC and run RMAA with the same parameters.
Switched a couple of times between AC and battery with the same results.

 

[DonH50]

OK, thanks. The processor clock speed-stepping should not affect the DAC's clock, in theory, but obviously something has changed. I suppose it is possible the rails on the DAC were changed when running on batteries, but I would expect the on-board regulators to handle that. I wonder if RT operation is not as clean on batteries; more latency causing clock jitter? Or maybe the processing is simplified to save power, resulting in those lare signal skirts (though the harmonics appear clean). I wonder if the power supply is causing more noise/jitter when running on batteries (extra converters, etc. and more noise spikes nearer the audio band). Strange... - Don