Better recording quality if Mac on battery power?

With the ?latest Audacity (?2.0.3) installed from the dmg file under the latest Mac OSX Mountain Lion on a MacBook Pro, I have recently been recording (at 24/192 resolution, via an Apogee Duet 2 USB audio interface) with the laptop on battery power, in order to minimize any possible adverse effect on sound quality from the low level noise potentially associated with mains power. So far, I have not noticed any difference in sound quality when compared with previous recordings made with the laptop connected to its “magsafe” charging connector (and thence to the mains). Has anyone else tried this experiment? If so, I would be very interested in their results…

While it’s a safe bet the further you can get from the mains the better, I noticed that all my top important recordings were made on mains power and it didn’t make any noticeable difference at all. Those Mac adapters are pretty good at filtering out noise. You can still get into trouble on a stage with high power lighting or in an industrial setting with computer controlled heavy machinery.

I think once thousands of years ago on a PowerBook, I noticed that I had some noise in my headphones that responded to reversing the power supply in the wall socket.

Just because I’m never shy about going to extremes, I have an install with two MacBook Pros and a mains-powered sound mixer that does hum with both Macs lugged into their adapters, but it’s only in the mixer headphone connection and it doesn’t appear to make it to the recording. And it goes away if I touch either Mac or the mixer with my finger or unplug both Macs from the wall. No, I don’t understand what’s happening there, but I know we’re all going to laugh about it later when I figure out where that’s coming from.


Since typing that, I have had a good listen (via naim amps and Quad ESL 57s) to some recordings I made both ways, and I thought all the recordings made on battery power sounded slightly clearer and more musical. However, it wasn’t a double blind test, so I may have been imagining it. Meanwhile, I’ve switched to recording on battery power always (I can record three LPs on one charge, and that’s about my patience limit per day anyway).

Many thanks for your reply. Incidentally, regarding the snip above, would it be worth trying an earth connection to the mixer or one of the Macs? It sounds as if you might be earthing them (albeit via a high resistance) by touching them.

ASIDE: @Gordon, which Naim amps are you using, do they drive the ESLs well?

The reason I ask is that I run ESL 57s currently with a QUAD 33/303 and the 33 is beginning to show its age and plays up occasionally (the volume on/off control - which apparently are no longer available as a spare) so I my need a replacement strategy up my sleeve.


Hi WC, I’m currently using a NAC 202 pre-amp, a NAP 200 power amp, a NAPSC-2 PSU (for the control circuitry and panel lights of the 202) and a FlatCap 2 PSU (one half for the 202 and the other half for a Stageline phono stage). This combination drives my ESL 57s (which have the Otto Major/Christian Feillafe Mark 2 mid-treble panels, so they can take about twice as much power as the original panels) beautifully.

Previously I used a NAC 112 / NAP 150, again with the FlatCap 2 and Stageline, for eight years, which also drove them very well. I also tried a Supernait for a couple of years, which sounded better than the 112 / 150, but not as good as the 202 / 200. However, the Supernait had unbelievably disastrous control electronics, which would frequently freeze but (far worse) would occasionally wind the volume up autonomously - and the third or fourth time this happened (despite the control circuit board having been replaced under warranty by my naim dealer) the protection circuitry in the power stage mysteriously failed to prevent it from blowing up my Quads, requiring two new mid-treble diaphragms (so they would match, though only one had failed) and one new PSU, both repairs done expertly by Christian Feillafe, long may he stay in business …which is why I traded in the Supernait for the 202 / 200!!

Incidentally, if you happen to be in Sydney, I can recommend Christian Feillafe for any repairs you ever need for your ESL 57s, and I can also recommend my long-time naim dealer, Harry York of Audio Genesis Hi-Fi in Pyrmont, for any new purchases of naim or Quad equipment. (Talking of the latter, he now keeps a new version of the Quad II valve power amp and a matching Quad pre-amp in stock, both now made in China. I haven’t heard them, but they might be well worth checking out.)

Meanwhile, happy listening…

Thanks for the detailed reply Gordon - much appreciated.

And Sydney is a bit far away from the UK for me to get to use your dealers :wink:


I am reasonably sure the power level coming from the battery and charger were designed to be identically the same, since the computer is supposed to perform the same operations regardless of the power source.

It is very possible the difference was in your head; I had similar problems with absolutely identical audio files in the past.

Quite likely - but in the absence of super-powers, and until or unless I get around to organizing a double-blind trial, my head seems to be enjoying the “difference” quite a lot - so I’ll probably let it continue on in ignorant bliss :wink: