Isolating Transformer (Cinch)

Differences in ground potential between devices play a major role in shaping the sound of any HiFi system. When mains ground potentials are not exactly the same on two or more HiFi units connected via cinch/RCA, this results in a homogenisation of potentials via the chinch/RCA interconnects. The effects may range from a 50/60 Hz hum to a leaning of the resulting sound towards bright, harsh, and unpleasant.

Ground potentials often vary when HiFi devices are plugged into power strips that have not been designed for use with HiFi gear, when power plug polarity has not been optimised, when individual devices are connected to an outside grid, such as the cable or radio network, or are connected to a wall outlet far from the main system. While small differences in ground potential may stay unnoticed for some time, any HiFi system’s delicate audio signals will benefit from near perfect grounding.

When I first set up our system consisting of Martin Logan SL-3 electrostatic speakers, Hafler XL-280 power amplifier, DB Systems DB-1 preamp, Nikko FAM 600 radio tuner, Rega Pant 2000 CD player, Sansui SR-525 turntable, and Apple TV with HDMI to cinch/RCA audio extractor, I understood that I had found some worthwhile components, but what I did not know was that I had also produced serious grounding issues.

The result was an unpleasant humming from the speakers that I was unable to eliminate by optimising power plug polarity. It took my some weeks of tests and listening to to understand that the power supplies for the Martin Logan’s high voltage needed to be plugged into the same outlet as the other units of our system. By doing so, humming was reduced by roughly 33%. The other humming factor was the house antenna connected to our Nikko radio tuner. I purchased a device for the physical decoupling of the antenna. This reduced audible humming on our system by a further 33%. At this stage it was only when I held my ears directly on the speakers that I could still hear a slight hissing which I thought was normal for our HiFi units. 

It was not until a few days ago, when I was changing the tubes on our PAS-4, that I had one hand on the Dynaco preamplifier and the other on the chinch connector leading to the audio extractor of our Apple TV and suddenly felt a strong tingling in my hand. I did not measure it, but, from the feeling alone, I would guess it to have been at around 100 volts. I could not believe it and touched it again to the same result. There were about 12 meters of cinch/RCA cable running from the position of the Apple TV to our HiFi system, as I had always viewed the ability to play movie audio little more than a necessary evil.

Without the Apple TV, audio extractor, and Acer DLP projector attached, our HIFi system was dead silent, despite our Hafler XL-280 amplifier being set at full 145 watts gain. With all our video gear connected to the cinch/RCA input of our Dynaco preamplifier, the remaining 33% of humming noise returned and remained the same regardless of the music source. Given the scope of my blog and my knowledge regarding the importance of ground potentials, I was starting to wonder how it was possible that I had missed this noise factor for so long. It must have had to do with the little care I have been willing to devote to video.

In search for a solution, I came across ground loop isolators that could be placed directly in the path of a cinch connection. As I learned, the isolator is a transformer of two equal coils of which the primary acts as the inductor and the secondary as the receiver. Having gathered some experience with XLR and optical connections and converters, I was sceptical if any affordable device would be able to solve my issue without audibly diluting the sound or sacrificing the joy of music and therefore decided to first try a budget device with acceptable ratings.

I ended up with a Ground Loop Isolator branded “Sinus Live” that was sold by the German profihifi Vertriebsgesellschaft m.b.H. in Kaltenkirchen, an importer of HiFi gear to Germany. I enjoyed the fact that the device came in an unpretentious-looking housing that was not labelled as High-End. The cables seemed to be of decent quality, and the plugs were bare metal with a split centre prong and a split outer ring. While gold-plating usually has a negative effect on sound due to additional material transitions, a split prong and split ring do make some sense. I also liked the low-mass design of the plugs.

Having listened to the Sinus Live Ground Loop Isolator for a few days, I must say that I was very happy with the result. Not only was the small and inexpensive device able to instantly stop the humming on our system, it also did not take away any of the familiar charm of listening to music or watching movies via our Apple TV. I would have liked to present more proper specifications with the device, but so far have found none. If profihifi is able to provide me with specifications, I will later add them below this article.

Specifications:

• Type: ground isolation for chinch/RCA connections
• Principle: two isolating transformers 
• Number of channels: two (stereo)
• Transmission: induction
• Frequency range (-3 dB): 2 - 20,000 Hz (?)
• Line input: 2x cinch/RCA (female)
• Line output: 2x cinch/RCA (male)
• Dimensions: (L) 70mm, (W) 50mm, (H) 34mm
• Country of manufacture: China
• Year(s): approx. 2000 - 2023

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