icOn PRO 4 Balanced Preamp

George Sallit


icOn 4 PRO Unbalanced


icOn 4 PRO Balanced (Taller Preamp)​

Earlier this year I wrote a review about the icOn4 control unit https://www.hifiwigwam.com/blog/icon-4-passive-preamplifier.30/ and right at the end I mentioned there would be a further development with a new icOn control unit the icOn4PRO and a special balanced version available soon, and here it is.

This version is adjustable in 1 dB volume steps, which allows a smooth control of volume, having a range of 75 dB with 68 steps as opposed to the 40 steps of the previous version. And the PRO version comes either unbalanced or “true” balanced (with 2 pairs of autoformers) with flexible input/output configurations. Yes, the balanced version has 4 David Slagle autoformers and that is the version I received. Other autoformer control units only use 2 transformers and ‘other means’ to derive a balanced signal.

When I asked Pal Nagy about getting this version, he questioned whether I had a true balanced power amplifier as a lot are single-ended and use either a simple connection, an op-amp or better still a transformer to generate a balanced signal. In my case, the Bryston 4B3 is a true balanced power amplifier, so the balanced version of the icOn4 PRO was sent.


This balanced version had XLRs in and out (surprise, surprise). The balanced version of the icOn4 PRO is taller than the single-ended version with two autoformers per channel with one autoformer on top of the other. Similar to the single-ended version, the balanced version is controlled by an Apple remote. You will have noticed the icOn4PRO has a volume range of 75dB but only 68 steps, some steps are actually 2 dB. The display jumps 2dB on those steps with all others being 1 dB, which is fine enough unless you are using ultra-sensitive power amplifiers or speakers.

I will not repeat what I said in my previous review about the background to this control unit and if you want more details have a look at that review.

So how did it sound?

Well, very much the same as the single-ended version except that I believe (it was earlier this year after all) the balanced version gives a larger 3D soundstage and it is more open and detailed. The detail is not thrown at you but it is easy and relaxing to hear. I could listen to this control unit all day without any listening fatigue and I often did so. It also has even better dynamics. Overall, the differences were not huge but in my view, they were well worthwhile.

I could list all the music I listened to, but the overall improvement was consistent across all tracks with the better-recorded tracks showing larger differences. Please remember, that this is based on my memory of the sound of the single-ended version. But it especially shone with powerful orchestral music such as Beethoven's 9th Finale or big rock music such as Roger Waters Us and Them, which allowed the music to flow unhindered, even when the volume levels became really high, >90dB.

So where does the icOn 4PRO fit in the overall market then? I compared it to a few more expensive active preamplifiers I have here and in all cases, the icOn PRO4 set the benchmark. The icOn 4PRO was more detailed, with a larger 3D soundstage and better dynamics than all of them. You need a really good active preamplifier to match them. The previous weakness of some passives, particularly the resistor type, a lack of power and drive, is not here and the dynamics were better with the Icon4PRO. The other bugbear of previous passives (but not the Icon4) was usability. The icOn control units are modern and easy to use. So, I would put the Icon4PRO in the top bracket of control units. In fact, its biggest competitor is probably itself. If your power amplifier is NOT a true balanced power amplifier, then I would suggest you use the icon 4PRO unbalanced control unit. If you have a choice of using XLRs and RCA inputs on your power amplifier I would seriously question the power amplifier manufacturer and if it is not a true balanced amplifier then go for the RCA input.

Another reason for that choice would be cost, with the RCA input version costing £2880 and the balanced version £4,560. If you think that is high, remember you will have to pay a lot to equal the IcOn4 PRO with an active preamplifier and another Autoformer control unit with XLR inputs that only uses 2 autoformers costs £12k.

A superb control unit that is very easy to use and gives superb audio results that deserves all the success it gets. Try it against active preamplifiers up to £13K, and save yourself a lot of money.

icOn Passive Preamps