Jeff Rowland preamps compared – Coherence II, Synergy IIi, Concerto and Corus

Classic Rowland preamps have a their charm, but the more recent models do provide new insights

Preamps compared directly:

Coherence II series 2
Synergy IIi (with BPS and external power supply upgrade)
Concerto
Corus
Criterion

Introduction

Coherence II and Corus

This is one of those reviews where everything comes together at precisely the right time. Having been a very satisfied Coherence II owner for many years I recently decided that it was time for me to get a more recent Jeff Rowland preamp. I had already reviewed it before but as I later learned, my setup at the time was off balance and did the Corus no justice. I felt that it deserved a second try and for this reason I had a Corus on loan from Alex of A10 Audio in Amsterdam. Read the reprise here.

Concerto

The Concerto is a relatively rare preamp, it was not in production for long. When I found it second hand at a very tempting price I purchased it with the idea of it forming the heart of a new to build second audio setup. But when Devialet crossed my path, this idea was abandoned. For this reason the Concerto had been sitting idle for the longest time. I never would have thought that it could challenge the Coherence so I just never tried it in my main setup, until recently. When I finally listened to it, I was pleasantly surprised to find that it performed even better than the Coherence II in certain aspects, which warranted its inclusion in this comparison.

Synergy IIi
Synergy IIi + BPS and external power supply

The Synergy IIi belongs to my friend Jan Willem. I had also owned one many years ago but found it ultimately too smooth and lacking the midbass power and drive that I craved. The reason why the Synergy came around again was because Jan Willem had obtained a relatively rare BPS + external switching power supply. Based on the BPS-2, this BPS looks identical but has a different battery configuration inside. Unlike the BPS-2, it does not draw its power from the amp, so there is a separate very powerful switching power supply. Oddly the Synergy’s auxiliary DC output is now used as an input for the BPS power while the Synergy’s power supply remains connected so that the display and IR control still function. Naturally the Synergy’s own power supply’s IEC inlet is then no longer used. Interestingly, the BPS did not make the Synergy sound even smoother, but rather the opposite: it made it much more dynamic, with much more powerful bass and a more concincingly realistic timbre. Jan Willem brought the preamp along because he wondered how it would compare to the Coherence II and the new Corus.

I won’t dive into each preamp’s aspects too deeply here because they are all covered extensively elsewhere on this site already. Instead, I will focus on the deviating or most interesting comparative aspects.

Sound Comparisons

Coherence II series 2

It is important to note that this comparison also took place while the Coherence’s batteries had been in place for longer than recommended and needed to be renewed, and as a result as I later learned after they were replaced, it sounded slower and less dynamic than it can do when on spec.

The Coherence has been my reference for many years and during this time I have always much enjoyed its combination of transparency, timbral fulness and smooth fluidity. The bonus is in its bass, which is unusually full and rich. The Coherence is an easy preamp to live with because it tends to make most music played through it enjoyable and it is especially emotionally very appealing with its very natural timbre, while still sounding very revealing.

Synergy 2i

The Synergy 2i is a later amplifier and it is indeed slightly more refined and airy than the Coherence, but it does not have nearly as much body and substance. It is also smooth to the point of being lazy. The interesting thing about the Synergy IIi is that even though it sounds velvety rich and smooth, it is also incredibly finely resolving. In my systems the Synergy was always a little too much, with an overly smooth and slow sound as a result. The Synergy 1 however deviates from this, but has its own comparative flaws.

Concerto

The Concerto had already been sitting idle for the best part of a year, only let out occasionally to play in comparisons in the other setup, as shown above, until I started listening to it in my main setup. At this time it really surprised me with its excellent sound. Would you believe that it even surpasses the Synergy IIi and Coherence II in some aspects? The Concerto combines some of the treble air, resolution and creaminess of the Synergy IIi with the bass power, fulness and dynamic expression of the Coherence II, and has no trace of the Synergy’s soft woolyness or restraint. The Concerto also has very lifelike timbre and dynamics, in these areas even better then either the Synergy 2i or Coherence II. For a few months, the Concerto played perfectly in my setup and I wondered if I ever needed to return to the Coherence.

Synergy 2i with BPS and external power supply

Having extensive experience with the Coherence preamp and model 6 power amps, and their Battery Power Supplies, I thought I had the BPS effect figured out entirely. Imagine my surprise when it turned out that the Synergy had transformed into a much more energetic performer!

Rather than sounding even smoother or thicker, it had much more solid and powerful bass and its dips in the upper bass and lower midrange filled in completely. Dynamics were now very impressive as was its newfound transparency. Its timbre was now also much more natural and closer to that of the Coherence II. Speaking of the Coherence, it still had bigger, beefier bass, and an overall fuller tonality, but it now had to bow to the Synergy in terms of dynamics and overall liveliness, in addition to its already better transparency and resolution.

Coherence II series 2 with old / new batteries and combined with the Synergy’s BPS power supply

Now that we had all the puzzle pieces available we started thinking: if the Synergy can be so obviously transformed this way, then its standard power supply may have been insufficient in the first place. And what would happen to the Coherence if we used this switched + BPS power supply with it rather than its own linear + BPS supply? The units are compatible so this was easily tested.

Yup: again we heard a much more open sound across the entire frequency spectrum as well as tighter, more articulate bass, a more detailed and more communicative midrange and a more open treble. The bass was less voluptuous though, and for better or for worse, did not carry the weight that it did with its own linear power supply. After having heard this performance, we stepped back to the Concerto once again and this time around we could not help being underwhelmed.

As part of this group, the Concerto was revealed as sounding comparatively a bit flat and gray, as well as being bested by the Synergy’s resolution and refinement. Even if its timbre is much more lifelike and its bass so much more solid, there’s a free-flowing naturalness about the Synergy IIi that the Concerto simply lacks. It is just a more sober sounding preamp, which is no criticism in itself because it is absolutely not dry and still possesses the typical classic Rowland sound. I would say that the Concerto exhibits precisely the kind of sound that you would expect from a component smack in the middle of a transition between the classic and current JRDG sound signature.

The whole power supply thing however got me thinking: obviously the Coherence is an excellent preamp, but when was the last time that I replaced the Coherence batteries? Way too long ago! I now had a strong suspicion that the Coherence wasn’t performing its best. Even though it was always used in AC mode with the batteries just standing by, I was now sure that they still influenced the sound. The batteries were replaced and when the preamp was listened to again my suspicions were confirmed: the Coherence still sounded lush and richly colourful as always but much more energetic and upbeat. So, it is really important to change the batteries at least every 5 years.

What I think is most important to take away from all this, apart from the differences in character, is the evident importance of a component’s power supply. It really forms the heart of the music signal.

Corus

The Corus is extremely finely detailed and articulate across the board. Interestingly, its treble is superbly refined, but also airy and fluid – no dryness there! Bass is superbly well-defined and articulate, and there is an overwhelming feeling of utter coherence and openness across the entire frequency band. Because the Corus is so very neutral and has such sublime control across the board, some recordings can sound a little clean or lacking colour and the preamp also has a tendency to be very revealing of the quality of the other components that make up the system. For me this was the second time around with the Corus and while I had gotten used to its cleaner, more modern presentation and actually had fallen in love with it, my guests at this time were having mixed feelings. Even though they admired the Corus’ incredible resolving power, transparency and finesse, and like me, were impressed with its nible and articulate bass performance, with some music they were more emotionally moved when listening to the Coherence or Synergy.

In Summary

Ultimately it was felt by majority of the group that the Coherence II and the Synergy IIi, both with the BPS + external switching power supply, sounded best. While I shared some of this sentiment, I felt that none of the other amps could match the enormously impressive levels of transparency and resolution of the Corus, and its superb bass sealed the deal for me. I have been on a quest for more neutrality for some time now and for me, the Corus was the winner, even if it marked the start of a different sound signature for the Jeff Rowland brand.

Postscript

The outcome of this very interesting comparison, plus the fact that I could not afford a new Corus, brought me to buy a second hand Jeff Rowland Criterion preamp, which is basically a Corus + Battery power supply. This preamp arrived later and was not included in the comparison described above.

The Criterion most definitely delivered on its promise by sounding much like a mix between the best aspects of the Corus and the Coherence/Synergy. When over for another listening session, the very same group of guests were now smitten with the sound, as was I. There was no doubt in anyone’s mind that any of the other preamps could match the Criterion’s combined qualities.

As these things go (agum, with me at least), eventually I still caved in, got a loan and spent it on a brand new Corus + PSU. All this is detailed in separate reviews on this site, so I won’t repeat myself here. Suffice to say that the Corus + PSU do everything the Criterion does, and then some. The Criterion’s sound is also described extensively in the Corus + PSU review.

Associated Equipment

More Jeff Rowland

Jeff Rowland Company Special Main Page
Jeff Rowland Company Special Preamplifiers
Synergy  IIi + Coherence II Extensive Review
Corus Extensive Review
Corus + PSU Extensive Review

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