Jensen PI-XX Isolation Transformer Review

[Tom C]

This kind of information is very helpful to review and refresh the basics. Thank you Amir.

 

[pma]

Where to place a volume pot then?

Into the preamp at appropriate position. Or output of the sound source + buffer. Why would you place the pot into the transformer box?? It does not make sense. You will use the transformer in between the signal cables.

 

[pma]

This kind of information is very helpful to review and refresh the basics. Thank you Amir.

If you need an info that is really helpful, then read this paper:

https://www.jensen-transformers.com/wp-content/uploads/2014/08/Audio-Transformers-Chapter.pdf

It is a must.

 

[DearSX]

So does it add Musical or warm distortion? lol, want to make sure it has good "Synergy" with my speakers and equipment.

 

[levimax]

I have the unbalanced (RCA connectors) version of this and if you have ground loop issues these work very well. Other advantages are no power or ventilation needed and great reliability. Jensen does a great job with quality and documentation and are one of the most reputable companies in audio.

 

[jmdesignz2]

PI-XX | Jensen Transformers

The design begins with an extruded aluminum case that comes standard with gold plated XLR connectors. Plug and play easy to use, this passive interface does not require any power to work. Inside is a high performance Jensen transformer that is able to withstand signal levels to +19 dBu at 20 Hz...

www.jensen-transformers.com

Typical use is at +4dBu, 1.23Vrms.

https://www.jensen-transformers.com/wp-content/uploads/2014/08/PI-XX.pdf

would it not be better to use a large isolation transformer at the mains plug? I suppose that would be far costlier?

 

[G|force]

Thanks @amirm for a very interesting review!
A variant of the same transformer from the reviewed box (Jensen JT-11P-1) is what I used to build my DIY reamp box (measured here).
Jensen transformers are pricy but they really are some of the best-performing audio transformers out there!

I have a pair here as well that I occasionally use as a stereo unbalanced>balanced line converter.

 

[G|force]

Very interesting, thanks Amir.

I wonder how much commercially available music has passed through Jensen transformers!

Under the Harman family umbrella, the higher-end dbX compressors have them inside.

 

[phoenixsong]

Twin-Iso - Radial Engineering

The Radial Twin-Iso is a two channel balanced line-level isolator that eliminates the hum and buzz caused by ground loops that is often encountered in audio systems.

www.radialeng.com

This one mentions using *Jensen transformers. Dyou think it's the same?

 

[RickS]

Yeah saw that after I posted, but it includes the spec's which usually is reserved for @RickS to post, so I just took a screenshot of the AP measurements.

Certainly fairly detailed though, which compared to some other companies is very positive.


JSmith

Pavel’s post handles for now. Amir has been doing them lately to ensure specs look good in dark mode. If he does not, will post specs later.

 

[Chilli]

Great to see this review.
Transformers can solve some problems. Be great to test lots more.

 

[Tom C]

If you need an info that is really helpful, then read this paper:

https://www.jensen-transformers.com/wp-content/uploads/2014/08/Audio-Transformers-Chapter.pdf

It is a must.

I have already

 

[ocinn]

Would love to see the Radial stereo isolator box tested

Twin-Iso - Radial Engineering

The Radial Twin-Iso is a two channel balanced line-level isolator that eliminates the hum and buzz caused by ground loops that is often encountered in audio systems.

www.radialeng.com

Transformer based devices have massive distortion products as frequency decreases.

Ex (top);

Laptop > Motu M4 > Line output > Radial DI > Digico 32Bit input card > Digico Q225 > Digico UB-Madi > Laptop


Vs (bottom)

Laptop > USB to AES converter > Digico AES input card > Digico Q225 > Digico UB-Madi > Laptop.

 

[pma]

Sure. This is a result of physical principle and core material properties. There is no “miracle” product.

 

[KSTR]

Depends on how they are designed and how they are used.
Not many people are aware of the fact that generations of Audio Precision bench test machines used transformer-coupled output and still had negligible distortion. AP engineers were of course very smart and a) used rather large transformers (no way you can trick physics once core starts to saturate) and more importantly b) designed a clever feedback scheme with additional windings to cancel the DC resistance of the primary winding (with temperature compensation) which is the main issue causing the LF distortion.

One could certainly place that circuit in a standalone box and get stellar results but the cost would be very high, actually prohibitive.

 

[pma]

Depends on how they are designed and how they are used.

Sure, but the shortcomings are just more or less pronounced.

 

[torgeirs]

Great, but couldn't they add a volume knob? It would be even better.

There are products with several output taps. So you get a crude stepped attunator.

Transformers work best with known input and output impedances. That is difficult to achieve with a potmeter passive design

 

[torgeirs]

Often there will be raised distortion with a high output impedance driving a transformer. But the headphone dongles are often ideal for driving transformers

 

[pma]

I did dozens measurements of link transformers. Even driving them from close to zero impedance does not help much.

 

[torgeirs]

Don’t get better than these measurements, but i have measured worse with higher output impedance.
Also stated here
Post in thread 'Surprising transformer harmonic distortion measurements'
https://www.diyaudio.com/community/...c-distortion-measurements.418109/post-7801745
With low impedance the attunation also gets to a minimum. Insertion loss

The drive capability of the source also come into play. But transformers are a science in itself
Dongle to transformer to PA is a little safer than dongle to PA or pc line out to PA