Resolution Audio Opus 21 s30 Integrated Amplifier

Category: Amplifiers

This review concerns the Resolution Audio s30 integrated amplifier. This unit mates directly with the infamous Opus 21 CD player and is based on DNM technology from England (see their web site for all the design details). The power output is rated at 35 watts. The s30 has one balanced and two unbalanced inputs in addition to the CD input. It comes standard with banana plug speaker connections but can also include optional Cardas spade connections (these are very nice and easy to use). The s30 is powered by the same power supply as the Opus 21 CD player, but with a separate cable (therefore only one powercord is required!). The remote is shared with the Opus 21. I was using the Opus 21 in a small system in a second bedroom (doubles as home office) where I wanted a quality system that was also simple and unobtrusive. The rest of this system as reviewed includes a TG Audio 688 powercord, Au24 speaker cable, JM Reynaud Trente speakers (it easily drives the Trenete speakers) and a Blue Circle Music Ring. In my current setup I’m not using any isolation, though I have used a Neuance platform with the Opus 21 in the past.

I’ve had the Resolution Audio Opus 21 CD player for a while now, used initially in a headphone system and since then in my home office where I spend quite a bit of time both day and night. The Opus 21 is a product that has impressed me from the day I picked it up from the factory, such as it is. The industrial design and its usability are well executed with the one exception that when the CD drawer is open it’s hard to see the control buttons if the unit is located low to the ground (but this does not bother me at all frankly). The unit has operated flawlessly. The built-in volume control has been handy when I’ve used it and it does not appear to degrade performance.

I cannot separate the s30 from the CD player for this review so consider the comments to reflect both components used in tandem. They are cohesive components in my system. Having been curious about the s30 for a while I finally contacted Jeff Kalt at Resolution Audio to ask how I could demo the amplifier. The s30 requires that two additional toroid transformers be added to the power supply. Since I live close by Jeff offered to build an amp and bring over a separate power supply to replace my current one and thus power the s30 as well. He held my original power center hostage while I demo’ed the s30. Of course I purchased it and have been enjoying it.

Now for the ergonomics. The CD player sits on top of the s30 and plugs in through a direct SCSI connection on the top of the unit. The power supply, a separate box, powers the CD player and s30 integrated through separate and differently shaped umbilical cords, one a SCSI for the CD player and the other an XLR cord for the s30. This is another user-friendly idea since you can’t mess it up. The CD player and s30 should be located next to or on a different shelf from the power center; they should not be fully stacked. Obviously no interconnect is needed to connect the CD player and only one power cord is needed for the system. Ah, simplicity!

I won’t comment much on the Opus 21 CD player except to say that it is smooth, detailed and dynamic (the opus 21 is well documented in many other reviews). The DIN out is an improvement over using the RCA outs (through the built-in volume control) (and the direction connection to the s30 even better). I have a custom Au24 DIN-RCA cable that I no longer need. The Opus 21 is clearly improved through the direction connection with the s30. My main system includes an Audio Note DAC that is better at portraying the specific ambiance of a recording than the Opus 21. I would say that adding the s30 mostly corrects this issue with the Opus 21. With the s30 the stereo image is clear and solid, both left to right and front to back. With the AN DAC I could probably identify the music hall should I be familiar with it; the Opus 21 is not that specific but it does give more ambiance through its direct connection with the s30. The s30 is also more detailed yet also smoother.

Again, it’s hard to separate the amp and CD player so please keep that in mind. There are two characteristics that stand out to me the most about the s30. The first was quite shocking. The decay is as good as I’ve heard in tube components. Instruments come and go naturally, and hang around, as the musician played them. The other characteristic is that the low volume listening is excellent. It retains the life and presence of music. Even the stereo image remains nicely balanced. This reminds me of hearing SETs at a local dealer through his perfected setup. I have not expected this from an SS amp. The listening room where the RA components are located is also my home office so low volume listening is important (for late at night too). At low volume I don’t feel like I’m missing anything at all; what more is there to say on this topic. But mostly, the s30 is just fun to listen to. One thing I’ve realized is that with the addition of the s30 I now look forward to listening to music not because it sounds good through the system (but it does!) but because I feel like I get a better perspective of the performance and a better portrayal of the intent of the musician (emotional intent, technical intent, whatever). It makes it all about the music.

Overall I would describe the s30 as fast and agile, meaning it keeps up with the music well. It is highly musical in the cohesive nature of SET amps. Treble performance from the s30 is very smooth and clear and not bright at all. Acoustic guitar sounds perfectly natural. Bass performance is tight and fast. It appears to control the speakers well in this regard. Midrange is excellent and very natural. The stereo image is clear and rock solid. Instruments appear to float openly between the speakers. It’s very compelling. The soundstage is not huge but I attribute this to the room setup and not being able to space the speakers as far apart as I’d like. But as I listen to a Michael Hedges CD I can virtually hear him move from string to string. On another album I can hear the layout of a drum kit. Sometimes I look up wondering if someone is actually there playing live for me. This is amazing.

In the realm of music, I listen mostly to acoustic guitar, classical, jazz, space music, bluegrass, world music, and a smattering of rock like Wilco, Los Lobos, Widespread Panic and R&B like Keb Mo. Acoustic guitar in the style of Michael Hedges really appeals to me and the s30 absolutely portrays the fantastic finger play accurately, keeping up with all the moves and realistically conveying the sound of the guitar. Kaki King is another favorite. Listen to track no. 7 on Kaki King’s first release and you’ll see how an amp can keep up with fingers. Native American flute is another staple that plays extremely well through the s30. I also listen often to space music like Steve Roach, Robert Rich and many others and this music through the s30 completely draws me in and feeds my creativity.

I have not tried other CD players with the s30. Why bother.

The s30 has been a great surprise because it’s nice to find a great sounding system in a simple, small (and clearly well-thought-out) package. The system appears to be extremely well designed with lots of forethought built in for planned future additions. Resolution Audio is a small company led by a friendly, energetic, intelligent designer who bodes well for the industry. I spoke with him briefly when I picked up my updated power supply and it was interesting to hear about the design of CD players in general and the specific design of the s30/Opus 21 system. With the Opus 21/s30 pair (and the Trentes) I feel settled with no need to look around. I thought I might consider a more efficient pair of speakers, but frankly this system works as is. The s30 has really brought the Trentes to life.

The s30 is more popular in Europe according to Jeff, but I hope it gains more exposure in the US because it is a beautiful overachiever that deserves more exposure. With the 30 day trial it’s easy to demo. This system is excellent in its own right, but is also perfect for those seeking a small quality system, those looking for simplicity, and those simply tired of the audio carousel. I hope this review has been useful because there is little info out there on the s30; I have tried to be detailed but please ask any questions you have.

Thanks for this informative review. I've been curious about the s30. I owned a RA Opus 21 for a while, but I sold it. It was one of only a few audio regrets as I had purchased it used for a really good price from another local audiophile! Live and learn!!!

So, a couple of questions:

Is the Opus 21/s30 combo a 3 piece deal?

What is your main rig (for comparision).

What is the total list price for Opus 21 and s30 if purchased together?

Thanks again for the great review.


Reubent, I don't know if there is a package deal. I purchased them seperately and about a year apart. You can ask a dealer or contact Jeff at RA. Most dealers will offer you a deal when you buy a whole system. My system is listed in the "System" link under my moniker.
Did you noticed a distortion coming from the amplifier when the volume is over 80 and there are musical peaks?

I have been noticing it with my Opus 21/S-30 and i keep wondering if that could be a malfunction or if it is the limit of the amplifier...