What would you buy Sub $350 Firewire/USB DAC

An iso transformer would plug into your AC supply. Then you plug your DAC's power cord into the tranny. This eliminates much of the pollution on your DAC's AC line.

The transformer accepts 120V and puts out the same voltage. No actual transformation of voltage happens. However inside the tranny there is now a physical separation between the AC circuit in your wall and the AC line which feeds your DAC. Think of it as Customs and Immigration ( OK, Homeland Security if you're that way inclined ). The barrier is not enough to stop trade but it does stop the riffraff -- the grunge and pollution on the AC line. As a side effect, it also reduces most high-voltage spikes to harmless levels ( but nothing will stop direct lightning ).

The results for digital audio are pleasing to the ear, and one of them is cleaner highs. That's why I mentioned the possibility.

Isolation transformers are used in laboratories, hospitals, server farms and sound studios to keep AC line junk from affecting the working of delicate, precise, mission-critical instrumentation; oh, and sound recording gear. They are often replaced, sold off, upgraded and so on but they don't wear out and you can frequently find suitable ones used on eBay. You'd only need a little one for your DAC, say a 125 volt-amp size ( 125 VA or about one ampere ), but bigger wouldn't hurt if that's all you could find.

My brother runs studio gear with his computer and finds he gets cleaner sound with the iMac plugged into an iso tranny.

Thank you very much for the information--it is very helpful.

I am going to do a little research to see what is available in the budget range.

The dacMagic is continuing to mellow over time. I wonder how long a typical burn in takes....

Music_prof, what Tobias says omits a very simple face, at least IMHO, isolation transformers, indeed almost all ac filtering or conditioning devices, do more harm than they than good. There is one clear exception to this, again IMHO, the Synergistic Research PowerCell. It is not cheap, however. I have no recommendations that are cheap, except nothing.

Tbg raises one of the hobby's all-but-innumerable controversies. He is on his 47th system, according to his system page, so clearly he is entitled to his opinion. There are others whose mileage varies; see posts in the archives here by Sean and Lak, among others.

My own experience is that there is no downside whatsoever to running a costly digital source from an isolation transformer of adequate size and quality, and none either to running a cheaper one from a small, cheap iso tranny. Note the word cheap. What is especially appealing about this tweak is its excellent (IMVHO) return on investment.

The power conditioning controversy has extreme positions and moderate ones, like all controversies. The extremist on the positive side uses active devices, sometimes mass-market ones with MOV surge protection, on all his gear, even power amplifiers. The purist finds no conditioner of any real help, especially not on power amplifiers where it tends to limit current supply. The isolation transformer, used on a DAC, falls pretty close to the purist position.

Too bad you did not go Blue Circle Thingee - great sound and very simple to use. I have found CA product is not a warm enough sound for my taste.

Try Frank at Signal Cable - good quality IC's and Power Cords too - for the money, Frank is hard to beat.