POSITIVE FEEDBACK ONLINE - ISSUE 48
Next Class Si2 Micro Integration Line
as reviewed by Michael Wechsberg
Going for the world record for the smallest high-end audio components, Masataka Tsuda of Silicon Arts Design and Concert Fidelity has designed a set of three devices reflecting the ultimate in the "less is more" school of audio design. The philosophy at Silicon Arts Design has always been to minimize parts count and signal path length in order to realize the best sound quality. In these three fine components just about everything not germane to reproducing music is removed including the typically large and heavy chassis of most other equipment on the market. The Si2 Micro Line consists of three devices: the Si2 Line Stage preamp that copies circuitry from the famous Concert Fidelity CF-080 preamp I reviewed in PFO Issue 41; the Si2 Stereo Power Amplifier that takes after the massive ZL-120 monoblock I reviewed in PFO issue 42; and the Si2 DAC that uses a design similar to the $10,000 Concert Fidelity DAC-040 converter. All three components can fit on a single shelf as they are each less than six inches wide and two inches high, but together they pack a memorable sonic wallop similar to the big guys.
These units are made to be used together and that is the way I evaluated them. The star here may be the line stage that is almost a mini version of the CF-080 line stage. On the front it consists only of an electronic volume control and a toggle switch that electronically selects between two inputs. Electronic controls are used to avoid passing the signal through contacts.
The rear panel has three pairs of RCA jacks. One pair for the outputs and two pairs for the inputs. The rear also sports the connector for the separate DC power adapter (supplied) that plugs into the wall or power conditioner. It's an interesting choice for such high quality components to use simple wall-wart power supplies. I should mention that each of the three Si2 components has its own different power supply tailored to the current demands of the unit, so they should not be interchanged. I wondered if the sound of these units could be improved further by using a beefier power supply or batteries, but I left that test for others. I did not hear a significant difference whether the DC supplies were plugged directly into the wall or into my PS Audio Power Plant Premier power conditioner. One result of the simple circuit used in this and the other Si2 components is that they cannot drive long cables. Silicon Arts recommends a cable no longer than 1 meter between the line stage and the power amp. The line stage is non-inverting.
The Si2 Power amplifier puts out a mighty 14 W per channel into 4 ohms and 10 W in 8 ohms. The circuit uses a bridged configuration just like the much more expensive and powerful ZL-120 power amp, so the Si2 amplifier cannot be further bridged for higher power. Clearly the amp is focused on the quality of the power and not the quantity. The limited power capability was an issue for my evaluation, as you will read, and it does pose an issue for the consumer as this amplifier can only be appreciated in a system featuring either very efficient speakers, small listening rooms, or low playback volumes. The front panel has only a mute switch and a LED indicating power is on.
The rear has a pair of banana jacks for the speakers and a pair of RCA input jacks in addition to the dc power connector. I don't care for banana jacks but this is probably the right choice given the small size and weight of the amplifier. I used some pretty hefty speaker cables with the Si2, but you will probably want to use something flexible and light weight, especially if you want to install the unit off the floor. For convenience I placed all three components on the floor to keep cable runs short and to prevent them being pulled off a shelf by the weighty cables. This is something to think about if you decide to buy.
Finally, we come to the Si2 DAC. The designer has chosen to go with the simplest and oldest multi-bit chipset from Philips using no oversampling, no up-sampling, and no off-board filtering. This is the same philosophy used in the Concert Fidelity DAC-040. Kind of a throwback to 1986 but very finely executed. The front panel has only a power on LED and a second LED that only lights when there is a problem with the digital data transfer from the CD player or transport.
The rear panel has an S/PDIF digital input and a pair of RCAs for the analog output. The user manual advises that the output cables should be short, preferably 0.5m (or less).
One thing about the Si2 components is that they must reach thermal equilibrium to work at their best. I was advised to plug them in and allow them to sit for 24 hours (48 hours preferred) before listening. I found this advice to be accurate, as even powering down a short time to change cables requires another 24-hour warm up. Whenever I turned any of the units off and then turned them on again the sound lost body and the high frequencies became a bit harsh. Fortunately, they draw such a small amount of power at idle it should not be a problem to leave them turned on at all times.
I wanted to hear the Si2 Micro Line in my reference system in order to get the best sense of how good they are, but my main speakers are Marten Miles II, which are large relatively inefficient, full-range speakers in a moderate size listening room. To make matters worse, the speakers are bi-wired. It took me a while to rig up two pairs of banana plugs to attach the Kubal-Sosna Anticipation and Harmonic Technology Pro9 Reference cables to the Si2 Power Amp. I was forced to array the three components along the floor lest the weight of the speaker cables pull everything down from the shelf. I also did not have any really short interconnects, plus the way my components are arranged would not allow the three components to sit close together. Initially I used a 2m XLO Signature-3™ interconnect between the DAC and line stage and a 1m MIT Terminator2 cable between the line stage and power amp. Later I switched out the XLO interconnect in favor of a 1m length of cryogenically-treated DH Labs Silver Sonic cable. I only did a little bit of cable swapping but found the Si2 components to be more sensitive to cable length than to cable cost. They sounded good with both cheap and dear cables as long as the length was appropriate. For a digital cable between my E.A.R. Acute CD player and the Si2 DAC, I borrowed a Kimber Kable D-60 which, in my opinion, is one of the best digital cables extant. As noted previously, I plugged the wall wart power supplies for the DAC and line stage into my PS Audio Power Plant Premier conditioner, but the power cable for the power amp would not reach so it was plugged directly into the wall.
Using the Marten speakers gave me a good reference, but it was obvious they were not a good fit for the Si2 gear. So, for the second half of my listening tests I borrowed the rear speakers from my home theater system, the NHT SuperOnes. These are small 2-way speakers with a 6.5-inch long-throw woofer and 1-inch fluid-cooled soft dome tweeter in an acoustic suspension enclosure. I set them up in my listening room on some VPI stands and moved them out into the room for a more nearfield listening experience. The SuperOnes are not very efficient, but by sitting closer I was able to achieve satisfying listening levels without distortion. I used the excellent XLO Signature-3™ speaker cables I reviewed in PFO Issue 45 with the SuperOnes. Now it should be noted that the Marten speakers cost about $12K new whereas the SuperOnes cost only about $350 when they were last available several years ago. However, as you will read below, I was able to get a pretty clear handle on the sound of the Si2 components despite the low cost of the drivers.
Alas, the Si2 power amp could not do much to drive the Marten speakers in my room. I had to scale back the volume quite a bit to well below my normal listening level to avoid distortion. However, for a few hours of listening I got a clear hint of the excellent sound offered by the Micro Line components. I especially appreciated the clarity and whip-snap-speed I remembered from my reviews of the much more expensive CF-080 and ZL-120. The midrange was very smooth; best appreciated on piano music (just about any piano I tried sounded great) and female vocals. I was amazed at how low in frequency the Si2 power amp extended. The Marten speakers go down to about 30Hz in my room and I was able to sample notes that low on selected cuts, but the poor 10-watt amp could not fully control the woofers on the Marten speakers so the bass sounded slower and less distinct than the rest of the frequency range.
I was also amazed by the wide and deep soundstage rendered by the Micro Line gear. This was truly impressive on some classical pieces as well as selected jazz recordings. On the other hand the presentation was more forward than I am used to and the images were less detailed than I remembered hearing with the full size Silicon Arts and Concert Fidelity components (these were reviewed with a different set of speakers). Also, the Micro Line gear did not give as good a rendering of the recording space as my reference system. Low level details and microdynamics were obscured, although this perception may be due to the low listening level I was forced to use. High frequencies were clean and clear but lacking in fine detail and transparency; this was a sound I associated with older CD players. More on this later.
My overall impression of the Micro Line through the Martens was very, very positive, but also frustrating in that I could not listen at sound levels I was used to. So, I switched over to the NHT speakers, hoping the lower quality of the drivers would not jeopardize my ability to hear through to the electronics. Well, my fear was unfounded as the Micro Line components made by $350 speakers sound like $3000 speakers! I heard a wide and detailed sound stage with good bass (not as good as with the Martens of course), a terrific midrange, and very clean highs. Voices and solo instruments were reproduced with excellent timbral accuracy and coherency—and with the same transient speed and dynamic range I remembered from listening to the full size components from the same company. On more complicated music with many players going at the same time the clarity was not as good, but, based on what I heard through the Marten speakers, I attribute this mostly to the small speakers and not to the electronics. At the higher listening levels I was able to hear more room sound and micro dynamics, but with this combination of speakers, electronics, and cables I would say the quality was only average. The overall spatial perspective was recording dependent, but tended to be more forward than I usually hear on the same recordings over my reference system. High frequencies again were the weakest link; they were good, just not great.
The last thing I tried before sitting down to write this review was to bypass the Micro Line DAC and to insert the analog outputs of my CD player directly into the line stage using the second analog input. I was then able to switch quickly between the DAC and the analog CD inputs by toggling the input switch on the front of the line stage. Listening to the Acute analog output made a significant difference. It resulted in a wider, deeper, and more detailed soundstage. The spatial perspective was further back with more detailed depth layering. The midrange was fuller and more robust and the highs took on more character and transparency. I was surprised what the simple dome tweeter on the NHT speakers could do. Now, I don't want to be unfair to the Micro Line DAC. I was not using it as intended with a very short interconnect cable, plus the E.A.R. Acute costs around $6000 which is more than the DAC, line stage, and power amp combined. On the other hand, this experiment revealed how very good the Micro Line line stage and power amp could be in allowing the full quality of the E.A.R. CD player to be heard.
Silicon Arts has successfully brought the sound of their top-of-the line components down to a price point an order of magnitude lower. This feat is amazing! The additional "price" to be paid for this is the need to use the correct cables and efficient high-quality speakers in a room that is not too big. The Silicon Arts/Concert Fidelity house sound is clear, fast, dynamic, and transparent with outstanding timbral accuracy and spatial perspective.
That being said, I have to ponder as to where this set of diminutive audio gear will find a market in this country. I believe the motivation for the design was twofold. One to extend Tsuda's philosophy of short signal paths and minimum parts to realize the best sound quality, and second to make the Silicon Arts sound more accessible to the public through lower cost. From an ergonomic standpoint I'm not sure what to say. The small size of the Micro Line products would make them ideal for a desktop computer-based audio system, but $4260 is a bit much to spend for most people, plus the Si2 DAC doesn't have the right inputs for a computer-based system (meaning like USB). Some users may find the small size of the components convenient, but given the egos I observe among audiophiles, not many would be willing to boast about spending so much for such modest looking gear. Ultimately the Si2 Micro Line will have to sell itself on sound quality. If you like highly efficient speakers of any size, the Micro Line should be able to get the best out of them. Not for everyone, but I recommend these three pieces highly to those with the right speakers, room, and cables. Michael Wechsberg
Next Class Si2 Preamplifier
Si2 Power Amp