This is a review and detailed measurements of the Blue Jeans Cable SWT1 Isolation Transformer meant for removal of ground loops. It was kindly sent to me by a member and costs US$50.
As you can see, the box is small which does not bode well for good performance when we think of transformers and low frequencies. The enclosure is plastic which I guess is OK for consumer applications.
Blue Jeans Cable SWT1 Measurements
Even though this is meant for subwoofer use, I thought I start with a 1 kHz tone as to make the results comparable to general purpose isolation transformers:
As expected, we get fair bit of distortion, knocking 50 dB from the performance of my audio analyzer by itself. There is also an 8% drop in level. Before doing more, let's look at the frequency response:
What the heck is this? Built-in high pass filter?
Edit: This is likely caused by the transformer saturating at lower frequencies. If the drive voltage is lower, then it will do less of this.
Ironically response is flat from 100 Hz up so it is better for your main speakers than subwoofer!
Back to our dashboard, let's put in 40 Hz:
Wow! We have nothing left of our sine wave. Our poor SINAD as a result has dropped to just 5 dB! No wonder there are reports of this box severely distorting subwoofer output. Before you say 2 volts is too much, let's sweep our voltage and frequencies and see what picture emerges:
This could pose as the poster for a horror movie!
We see the classic rise of distortion inversely proportional to frequency which for subwoofer application, is really bad. The little transformer is saturating and saturating bad. Even at 100 Hz we have clipping at about 1.5 volts out. Optimal output voltage is just 0.1 volt!
No sense in testing more. We know what is going on.
Conclusions
This is a major miss for a company like Blue Jeans Cable which produces very good cables at very reasonable prices. Whoever thought of this product clearly had no understanding of what transformers do to signals other than isolation they provide. It takes a lot to make audible distortion in a subwoofer but the SWT1 gets there with ease. I guess if you have bad hum and you keep levels low the trade off may be worth it. Otherwise I can't figure out a good use for this box.
I can't recommend the Blue Jeans Cable SWT1 Isolation Transformer.
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As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
As you can see, the box is small which does not bode well for good performance when we think of transformers and low frequencies. The enclosure is plastic which I guess is OK for consumer applications.
Blue Jeans Cable SWT1 Measurements
Even though this is meant for subwoofer use, I thought I start with a 1 kHz tone as to make the results comparable to general purpose isolation transformers:
As expected, we get fair bit of distortion, knocking 50 dB from the performance of my audio analyzer by itself. There is also an 8% drop in level. Before doing more, let's look at the frequency response:
What the heck is this? Built-in high pass filter?
Edit: This is likely caused by the transformer saturating at lower frequencies. If the drive voltage is lower, then it will do less of this.
Ironically response is flat from 100 Hz up so it is better for your main speakers than subwoofer!
Back to our dashboard, let's put in 40 Hz:
Wow! We have nothing left of our sine wave. Our poor SINAD as a result has dropped to just 5 dB! No wonder there are reports of this box severely distorting subwoofer output. Before you say 2 volts is too much, let's sweep our voltage and frequencies and see what picture emerges:
This could pose as the poster for a horror movie!
We see the classic rise of distortion inversely proportional to frequency which for subwoofer application, is really bad. The little transformer is saturating and saturating bad. Even at 100 Hz we have clipping at about 1.5 volts out. Optimal output voltage is just 0.1 volt!No sense in testing more. We know what is going on.
Conclusions
This is a major miss for a company like Blue Jeans Cable which produces very good cables at very reasonable prices. Whoever thought of this product clearly had no understanding of what transformers do to signals other than isolation they provide. It takes a lot to make audible distortion in a subwoofer but the SWT1 gets there with ease. I guess if you have bad hum and you keep levels low the trade off may be worth it. Otherwise I can't figure out a good use for this box.
I can't recommend the Blue Jeans Cable SWT1 Isolation Transformer.
----------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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