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Fidelity Research FRT-4 and Entre ET-100 step-up transformer SUT comparison

These two vintage step-up transformers are often mentioned together along with Denon AU-340 as the ones to consider if you're running multiple turntables and tonearms like myself. I have the Fidelity Research FRT-4 and Entre ET-100 and here's a quick summary of my experience between the two. I'm unaware of any current SUT offerings that allow for multiple inputs and multiple impedance selections, let me know if there's one out there.

The Fidelity Research FRT-4 boosts my LOMC signal without any negative side effects that I'm able to hear. Background noise is now almost non-existence, I'm hearing so much more air and natural extension on the top end from both of my LOMC's. Vocals just float in the air with beautiful imaging, an experience I hadn't had before adding this SUT into my system. Overall, this SUT sounds clean, clear, and punchy with just the right amount of meat on the bones for a balanced organic sound. 

The Entre ET-100 is a tad more laid-back-sounding compared to the FRT-4, the background noise is just as low with no negative side effect that I can hear. In my system, the top end doesn't sound as open and airy as the FRT-4. I love the way this SUT sounds with my jazz recordings, especially the few with a little more bite on the top end, the sound is more easygoing with this one. Build quality is just as good if not a little better than the FRT-4, and it's a little larger than FRT-4 which I was surprised by. The knobs feel smooth and sturdy with both of these units and I'm able to switch from one turntable to another without any noisy static through the speakers.

FWIW, the ET-100 allows you to use output cables of your choice, whereas FRT-4 has existing output cables. If there's a current SUT out there with all of these functions, it would garner much more than the price these two models are going for. I hope this helps someone who's considering between these two excellent SUT's.

128x128scar972
maxson
81 posts
 

How may inputs on each?

scar972's avatar
scar972 OP
231 posts
 

Both units have 3 inputs

lewm
13,142 posts
 

The mention that the FRT4 has its own leads (presumably from its outputs to the phono inputs), stimulated me to learn more about it, because the claim led me to believe the FRT4 might bear "flying leads" at its outputs. That means that the interconnect to the phono stage would be hard wired internally to the FRT4, thereby eliminating connectors at the output, which I view as a good thing.  But I found photos that show this is not the case; the FRT4 has ordinary RCA jacks at its outputs.  So what did you mean by saying it has its own leads?  Further, the review I found was very helpful in showing a schematic of the FRT4 which reveals that it places an 18K resistor in parallel with its outputs, regardless of the step up ratio chosen for use.  This would dramatically alter the impedance seen by the cartridge, compared to driving the typical 47K ohm input impedance of a typical low gain phono stage. (18K in parallel with 47K would result in a resistance of ~13K ohms.) Driving the net resistance of 13K ohms could be problematic with certain cartridges and if selecting step-up ratios higher than 1:10, even with low internal resistance LOMCs. The reviewer commented that the FRT4 sounded better (with whatever cartridge he used) when he removed the 18K resistor. Do you know whether that surgery was performed on your unit?

theflattire
198 posts
 

I think all of Fidelity Research SUT have output leads.

The one you saw maybe was modified?

I have the FRT 3 and I think the leads came straight out of the transformers.  At least they weren't any soldered connections on the outputs; I didn't dive any deeper than that.  I didn't see any resistors in mine either.

scar972's avatar
scar972 OP
231 posts
 

All of the FRT4 I’ve seen in pictures have output leads consistent with mine. I haven’t peaked under the hood to see if mine has the 18K resistor. Do you know if the 18K resistor is a mod or a part of the original design?

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