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Tripp Lite IS250 Review (Isolation Transformer)

Rate this product:

  • 1. Waste of money for audio use

    Votes: 118 72.0%
  • 2. Not terrible (postman panther)

    Votes: 12 7.3%
  • 3. Fine (happy panther)

    Votes: 25 15.2%
  • 4. Great (golfing panther)

    Votes: 9 5.5%

  • Total voters
    164

amirm

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This is a review and detailed measurements of the Tripp Lite IS250 Isolation Transformer in the context of audio performance. I purchased it for US $140 with kind donation from a member.
Tripp Lite IS250 Isolation Transformer Audio Review Filter.jpg


The case is utilitarian but is not meant to be something you look at. Despite the low power rating of 250 Volt-Amp, the little box is quite heavy courtesy of the transformer inside. Back panel provides two outlets which is appreciated:

Tripp Lite IS250 Isolation Transformer Back Panel Stere Audio Review Filter.jpg


Notice the UL hologram/safety certification which is quite often lacking in audio tweak products.

Despite the name, please note that the safety earth ground is NOT isolated. Let me repeat: the safety ground pin in your outlet goes right through the device and comes out the same pin in the rear outlets. This is required for safety as otherwise, if the hot wire came loose, it would not trigger your breaker to trip. The isolation therefore is only for the hot and neutral conductors which are coupled magnetically through the transformer. Since unbalanced audio gear almost always connects signal ground and chassis/safety grounds together, this box provides no isolation at all, or any cure for mains/ground loops.

Above should be enough to dissuade anyone from thinking this device helps with mains noise but let's go through our formal testing and measurements.

Tripp Lite IS250 Isolation Transformer Measurements
As usual, let's start with the dashboard of my mains AC (which I call "RAW") this evening:

AC Measurements Noise and Distortion THD.png


We have the usual harmonic distortion+noise, delivering us a SINAD of 31.7 dB. Our sine wave is visibly distorted so if this transformer can fix something, the situation is present for it to do so. Here is its dashboard:
Tripp Lite IS250 Isolation Transformer AC Measurements.png


Our SINAD remains essentially the same but there is good bit of high frequency filtering. The reason that doesn't impact SINAD is because our biggest issue are the large harmonic spikes and their noise floor which dominates. Indeed our sine wave on top left is still distorted the same way.

We can zoom into to the spectrum with wider bandwidth:
Tripp Lite IS250 Isolation Transformer AC Measurements Noise and Distortion THD.png


The light blue is raw AC and red is the trip through the transformer. We can clearly see the high frequency noise reduction but there is also some increase in distortion. The transformer is a non-linear device so it creates its own distortion. But again, at high level both waveforms are distorted.

We don't listen to AC mains so let's measure the impact on an audio device, namely the Topping A90 pre-amplifier/headphone amp which is always on my desk. Here is its dashboard with raw AC and XLR input and output:
Topping A90 Measurements Headphone Amplifier.png


Superlative performance as always with noise and distortion well below threshold of audibility. Look at what happens though when I turn on the isolation transformer but do NOT use it yet (just showing the FFT)

Topping A90 Measurements Headphone Amplifier Tripp Lite IS250 Isolation Transformer Powered On...png


The transformer is creating a strong magnetic field that is coupling into my system even though I am using XLR cabling! The transformer was about 6 inches away but moving it farther out made no difference. It may actually be leaking into the Audio Precision analyzer itself.

Now let's power the A90 via the transformer:
Topping A90 Measurements Headphone Amplifier Tripp Lite IS250 Isolation Transformer.png


General performance is identical but we are now saddled with that mains leakage. Mind you, it is harmless at -130 dB but we have caused it by using this "tweak."

For folks who complain that above test is only one frequency, let's do a full frequency sweep with much wider, 90 kHz bandwidth:
Topping A90 Measurements THD+N vs frequency Headphone Amplifier Tripp Lite IS250 Isolation Tra...png


THD+N is still below threshold of hearing and no change is seen with the isolation transformer.

Some people think there is magic in "timing domain" so let's run an impulse response with raw AC and through isolation transformer:

Topping A90 Measurements Impulse response Headphone Amplifier Tripp Lite IS250 Isolation Trans...png


We get perfectly matching impulses. So much so that if I turn both graphs on, they land completely on top of each other (inset on the right). The ringing is due to limited sweep bandwidth of 20 kHz.

We could keep running such tests but asking the same question over and over again, just gets you the same answer.

Conclusions
An isolation transformer can be useful in blocking common mode interference. In our scenario though, people buy these boxes with seemingly no audible mains noise so that can't be the reason for purchase. Instead, buyers think something is being isolated so all the bad is left behind the transformer. As I explained, devices like this are not isolating safety ground so whatever remains on that line, gets right through them. That aside, our testing shows that no performance improvement can be had. And you can actually subject your audio system to mains noise due to strong field that the transformer generates.

While I did not show it here, there is some transformer loss as well so you will be wasting power as well.

So while this device is fine, its use for audio performance improvement is not recommended. Save your money for something else.

Edit: video review posted as well:

-----------
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/
 
Last edited:

Ralf Stocker

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Snake oil alarm again. Why does man invent a device that induces electromagnetic interference radiation in hi-fi devices??? The simplest way to filter interference is in the linear power supply.
 
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amirm

amirm

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Snake oil alarm again. Why does man invent a device that induces electromagnetic interference radiation in hi-fi devices???
To be fair to Tripp Lite, they don't make these for audiophiles. Or make any audio claims for them.
 

Vict0r

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Why would anyone buy this, thinking it will improve the sound? It's like buying a golden spoon and thinking your soup will taste better.

And yeah, Tripp doesn't mention audio in their blurb. They mention noise removal, though. I guess that's what makes some people think it'll help their system.

"Tripp Lite Isolator series isolation transformer-based power conditioners offer complete line isolation, continuous noise filtering and enhanced normal and common mode surge suppression.

Internal low-impedance isolation transformer component with Faraday Shield offers 100% isolation from the input AC line. Secondary neutral to ground bonding eliminates common mode noise, providing an isolated ground reference for sensitive equipment and an inexpensive alternative to the installation of dedicated circuits and site electrical upgrades. Removes EMI/RFI noise, utility switching transients, background spikes generated by other on-site loads and utility or related surge conditions.

Additional surge suppression components placed at both the line input and transformer output combined with full line isolation offers continuous line filtering of a full range of power line noise in all modes. Continuous transformer filtering with no wearable parts uniquely reduces surges in the worst of power environments to harmless levels. Reduces 6000V IEEE C62.41 Cat A&B ring wave and combination wave test surges to only 0.5V common mode."
 

pma

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@amirm ,the isolation transformer only makes sense for audio if the safety ground is isolated as well and then the transformer may be used to supply only one instrument, to fulfil safety standards. It really helps if there is a power ground loop issue, to remove hum.
The component that you have tested makes no sense for audio. The properly chosen transformer may reduce mains hum issue (if it exists) as much as 30-50dB, I have plenty of measurements. The tests made on improper components do not help for the amateur community to understand the possible issues and their removal.

isol_tr.JPG
 

restorer-john

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Since unbalanced audio gear almost always connects signal ground and chassis/safety grounds together, this box provides no isolation at all, or any cure for mains/ground loops.

Amir. You are missing the point (again) in relation to these products.

The isolation transformer (and I use them on my lab bench periodically) is designed to create a balanced secondary that is not referenced to your neutral/ground at the device or the breaker panel.

They can and do prevent all sorts of ground loops from antenna masthead amplifiers, cable TV and other AC injector feeds etc when multiple devices are plugged together.

Most if not all of the AVRs you have tested and are for sale are NOT safety earthed. Your ascertation of providing no isolation is wrong in all those cases. They are double insulated, so the chassis ground on the outlet of this device is unused and unconnected in any case.

There are perfectly valid reasons for isolation transformers and they do go a long way to preventing hums, buzzes, front panel nuisance shocks etc.
 

digicidal

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It would be interesting to see how valuable such isolation would be on something for which it was designed... like seeing if it improved (even slightly) the performance of a 10G network switch fully saturated.

My guess is that if you have significant noise into the MHz or GHz range it might cause some errors egregious enough to cause minor packet loss - which in an enterprise environment could easily justify the cost. On the other hand, it would bring into question the regulation on the switch itself however - since your average 10G and higher switch costs several times as much as a Topping DAC does. ;)
 

fordiebianco

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Another myth bites the dust.
 

pma

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Another myth bites the dust.

No. The test posted in this thread reflects misunderstanding of the issue.

It was explained here>


index.php


and in such case a properly chosen isolation transformer, without interconnected safety ground, really helps.
 
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amirm

amirm

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Most if not all of the AVRs you have tested and are for sale are NOT safety earthed.
Pretty sure the people who buy power tweaks in general are not AVR users.
 
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amirm

amirm

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It would be interesting to see how valuable such isolation would be on something for which it was designed... like seeing if it improved (even slightly) the performance of a 10G network switch fully saturated.

My guess is that if you have significant noise into the MHz or GHz range it might cause some errors egregious enough to cause minor packet loss - which in an enterprise environment could easily justify the cost. On the other hand, it would bring into question the regulation on the switch itself however - since your average 10G and higher switch costs several times as much as a Topping DAC does. ;)
As I have shown in other tests, mains noise is filtered by the power supply in the device already. So there is nothing to be gained here.
 
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amirm

amirm

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Amir. You are missing the point (again) in relation to these products.

The isolation transformer (and I use them on my lab bench periodically) is designed to create a balanced secondary that is not referenced to your neutral/ground at the device or the breaker panel.
Not missing a thing. You didn't read the review. This product is 100% mains referenced as I wrote. I reviewed what is sold. Not whatever you have on your bench which won't pass certification.
 
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amirm

amirm

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The only thing 'biting the dust' is ASR's credibility.
Tell that to this Amazon buyer of this product:

"Tripp Lite IS-250 250W I got this to clean up some ac noise in my audio setup with turntable. Didn't do much."

It is clear that neither you nor PMA have any idea of who buys these to tweak their audio systems and confusing them with others used for safety reasons on a workbench.
 

nyxnyxnyx

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This is not directly connected to the reviewed product, but is there a clear difference between consumer-grade isolation transformer and medical-grade isolation transformer? is one made of higher quality components while the other isn't?
A quick surf on the internet shows me various pricing of those products, some are considerably more expensive than others while having identical specs.
 

Ralf Stocker

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No. The test posted in this thread reflects misunderstanding of the issue.

It was explained here>


index.php


and in such case a properly chosen isolation transformer, without interconnected safety ground, really helps.
You have still a ground loop wihout safety ground thru transformer capacitance. Furthermore, you have a reserved place in heaven.
 

syzygetic

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Happy owner of the 1000VA version of this, and I used it on my audio system to filter out electrical interference from my dishwasher, which was causing display flickers on my Meridian DSP speakers’ displays.

This made no audible or measurable change to audio performance, it was literally some kind of noise triggering a flicker, perhaps because the Meridian display is especially sensitive, I don’t know, and it was driving me crazy to watch (visually) so I fixed it with the IS1000.

Anyway, there are indeed reasons this could be useful, though I agree they aren’t audio reasons for almost all practical applications.
 

theREALdotnet

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And you would get UL certification how?

The iso-transformer device as such needs to be safety-earthed or double-insulated (earthing is easier), but the earth must not be carried through to the output receptacle. That would defeat the device’s purpose.

Also, you will not get electrocuted if you touch either of the output leads (one at a time, of course) while standing on the ground.
 
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