But John pointed out that, unless the transformer is designed for low capacitance, as with these obsolete Topaz Ultra-Isolator transformers, common-mode noise that comes in from your mains will not be attenuated very well above 400 Hz. Prior to reading John Swenson's posts about the need for a low inter-winding capacitance, I had been very content with the lowering of my noise floor, as had with a modern Tripp-Lite is500 isolation transformer. John Swenson (of Uptone Audio) attributes their ability to remove power line noise from the higher audio frequencies to the very low inter-winding capacitance of these "30 Series" Ultra-Isolator transformers (per several posts he has made at This first chart shows that below 20 kHz, the attenuation of common-mode noise is even greater than -146 dB, going below -150 dB, at audio frequencies as high as 8000 Hz. They also provide 65 dB (1780:1) reduction of normal-mode noise. Greater than 146 dB (attenuation) throughout the audible spectrum, up to 20kHz, equates to a 20,000,000-to-1 reduction of common-mode noise. The following page, shows additional specs and some interesting performance curves, for the exact same transformers, re-branded under the Daitron logo. They are unique in that, unlike many other Isolation Transformers, including the Tripp-Lite is500, is1000, or is1800, which are still in production, the Topaz Ultra-Isolator -31 and -32 transformers have extremely low inter-winding capacitance, which equates to being far superior at removing common-mode noise from the treble frequencies.
#TOPAZ CLEAN REVIEW PDF#
Though long obsolete, the Topaz Ultra-Isolator "-31" and "-32" models ("30 Series") are readily available on the used market, at various VA ratings, as shown in the PDF at the link, above. Here's my Topaz Ultra-Isolator 91095-32, rated at 120V, 50/60 Hz, 500VA, with a low inter-winding capacitance of only 0.0005 pF (recently purchased used, on eBay): Other "Ultra-Isolator" models have higher capacitance ratings, with less noise attenuation.
Note that only the "Series 30"models offer a 0.0005 pF inter-winding capacitance, which yields -146 dB attenuation of common-mode noise. Several Head-Fi members are already aware of some other forums where people have done a lot of trailblazing with the use of "Series 30" Topaz Ultra-Isolator Isolation Transformers, such as those shown in the following PDF.
Have you been looking for a very effective, yet affordable solution for removing common-mode and normal-mode noise from your AC mains? How about a way to prevent noise from being injected back into the mains from your audio components' power supplies? How about a way to prevent ground loops between components and to discourage leakage currents? How about a way to remove any DC offset that might be coming in from the mains? And how about surge protection?
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