The ART T8 mounted in one of the six slots of the Raxx Starter Kit.
The ART T8 is a simple 1U rackmount box containing eight transformers which you can use to break ground loops. As there is no active support circuitry required, there is no need for a power supply. Each of the channels is identical, and all inputs and outputs are available on balanced XLRs and TRS jacks, plus unbalanced RCA phonos. As supplied, the XLRs are on the rear panel, while the jacks and phonos are on the front, but you can undo four screws to reverse the rack ears if you want, bringing the XLRs to the front.
Technically, the signal path has a 10Hz-50kHz response, flat within ±0.5dB (measured with a +4dBu signal). Distortion is typically 0.01 percent at 1kHz, with an operating level of +18dBu and a crosstalk figure better than 90dB. How much signal is lost through the transformer depends on the load that each transformer is driving, and ranges from less than half a decibel into 100kΩ to 5.5dB when driving 600Ω — I found insertion losses for typical studio line-level inputs to be mostly unnoticeable. A CMRR (Common Mode Rejection Ratio) of 60dB is quoted for the balanced inputs. The balanced connections of the T8 can be used with unbalanced connectors where required, but it is invariably better to use balanced connections where possible. In a typical setup, unbalanced electronic instruments will feed the jack inputs, while balanced jack or XLR cables carry the outputs of the T8 to the mixer or audio interface.
In practice the T8 sounded surprisingly transparent, and the only very very subtle difference that I could detect was that the bass end actually seemed slightly more solid via the T8! I find it remarkable that such a low-cost transformer-isolation system can work so effectively while retaining a commendably high degree of audio transparency. I have no doubt that more sophisticated transformers can provide a better technical specification, but I'm equally convinced that any audio deterioration produced here will be far less of a concern than the quality of the output electronics in much budget studio gear.
Pros
- Clean audio path.
- Full transformer isolation.
- Choice of connectors.
Cons
- None at the price.
Summary
Eight channels of effective and clean-sounding transformer isolation at an affordable UK price. A very practical solution to ground-loop problems with unbalanced equipment.