Review on B&H website.............
Sturdy box, wimpy transformers
By Tony the Tinkerman
from Somerset County, NJ
About Me Experienced
I got this device to reduce the annoying computer whine I experienced when I connected my desktop computer to my earth-grounded stereo setup. I had the two connected with simple unbalanced cables, but since the signal ground in the computer's sound card was the same as the main power ground, there is a lot of high frequency hash from all the digital switching going on, and it rides on the connection as a common mode signal. This noise has a very low source impedance, so it cannot be helped by further grounding. Isolation transformers seemed the only solution.
The Pureformer did the job all right--the hash was at least 10 or 15 dB lower--but I started hearing really nasty distortion on music with even moderate levels of bass. Using a signal generator and an oscilloscope, I was able to see the problem: core saturation at low frequencies. At 20 Hz, the transformers could only handle a signal of about 140 mV before distorting. Naturally, at higher frequencies the threshold was higher, reaching 570 mV at 40 Hz and a decent 2.1 V at 100 Hz. The problem is that signals with this kind of bass are very easily encountered with normal music from consumer electronics.
Opening up the metal box revealed two dinky little transformers. Truly adequate performance would require quite a bit more metal in the transformer cores. No wonder the manufacturer doesn't provide much in the way of specs!
I tamed the problem by reducing levels 10 dB, but that's not an ideal solution. At some point I'm going to have to get a couple of better transformers.
I am checking "recommended" with the caveat that you keep signal levels very low.
Yes, I would recommend this to a frien
