Will an Isolation Transformer Help My Digital?

Hi Lowrider,

I read through the prior thread that I think you are referring to, to refresh my memory. Given that the noise was considerably less when you used the CDP’s stock power cord instead of the upgraded power cords you tried (the upgraded cords presumably having greater bandwidth than the stock cord, and therefore providing less attenuation of high frequency noise over a significant part of the spectrum), and given that the noise was eliminated when you plugged the CDP into different and more distant outlets, my guess is that the isolation transformer stands a reasonably good chance of resolving the problem. Obviously, though, I can’t say that with certainty, in part because its specs provide no indication of what frequencies its "35-65 db noise suppression" apply to. So that spec is pretty much meaningless.

Also, what was the upshot when the Sunfire tech looked at your amp, with regard to the fact that its chassis was inexplicably not connected to its safety ground?

Best regards,
-- Al

Lak makes a good point about acoustic noise being a potential concern with the Topaz isolation transformer or other comparable devices. I couldn’t find meaningful data on the Topaz model 91095-22 linked to above, but I found this datasheet covering the model 91095-32T, among others, which appears likely to be fairly similar. The spec listed for acoustic noise is "less than 50 db measured at 3 feet from the noise suppressor." Ouch, unless "less than" is actually "a lot less than."

I also note, btw, that the particular listing for the 91095-22 indicates "open box," perhaps indicating that the device was previously purchased and then returned, or was obtained by the seller from a previous user. And in fact despite the indication of "unused" in the listing the power cord pretty clearly shows signs of use, and even a bit of damage, when the photo in which it appears is expanded.

Best regards,
--Al

The ARC CD3, at least in its first version, had a specified power consumption of 40W max. I would think it very unlikely that the power consumption of the Mkii version is much higher than that. The wall wart for the QuteHD DAC is described at the Chord site as:

12v 1A 2.1mm connector. Centre point positive 100V- 240V – 50/60Hz, 1A wall adapter supplied

I seriously doubt that it actually draws anything close to 1 amp at 120V (which would be approximately 120 watts) to be able to supply 1 amp at 12V (which would be approximately 12 watts). And the 1 amp output is presumably its max output rating, and what would be drawn by the DAC is undoubtedly a good deal less than that. And correspondingly the AC current drawn by the wall wart would be considerably less than it would draw when required to supply 1 amp at its output.

So it’s probably very safe to assume that the AC drawn by the DAC + CDP is less than 100 watts. A 500W transformer would therefore provide a margin of more than 5x, which certainly seems comfortable. Intuitively I would start to feel uncomfortable at less than 3x.

If you go to a linear supply for the DAC, though, before finalizing a selection be sure to assess its current draw or power consumption, as it will most likely be a good deal more than the wall wart’s.

One thing I don’t understand is why some iso xfmr’s are rated in watts and some are rated in amps.

Just a different way of specifying things. For a resistive load watts = volts x amps. So you’ll note that it says in the description of the Tripp-Lite Isolator:

Supports combined loads up to 500 watts continuous/4.2A at 120V.

4.2 amps x 120 volts = 504 volt-amps, which for a resistive load = 504 watts.

Best regards,
-- Al