INNERSOUND LINE STAGE PREAMPLIFIER Frank Alles, reviewer

Stereo Times Magazine, June 2001, Frank Alles, reviewer                  

Not Just a Speaker Manufacturer:  When audiophiles mention the brand name InnerSound, usually what springs to mind is their fine line of electrostatic hybrid loudspeakers. However, lately the Georgia-based firm has been gaining recognition for its line of high-quality electronics.
Yours truly was most impressed with the excellent performance of the InnerSound ESL amp, as mentioned in my joint review of that product with Martin Appel, last year. Having heard the InnerSound preamp in a friend's system prior to the arrival of the review unit, I was hoping to hear the same positive musical attributes that were apparent during that enjoyable session. As it turned out, I wasn't to be disappointed  but more about that later.

Physically, the InnerSound preamp is a modern slim-profile design, available with either a black or silver faceplate that matches the cosmetics of the company's amplifiers. The vivid blue digital volume display shows the volume setting in 1 dB increments, from 00 to 99 and is large enough to be read from a reasonable distance. 

The knob that controls the volume also provides precise balance control with LED readout to confirm the settings. Another nice feature that I haven't seen in other preamps is the ability to set the total system gain to a predetermined maximum, so that the volume cannot be inadvertently set to excessive and potentially damaging levels. Owners of this preamp who have teenagers or young children running about will immediately grasp the significance of this feature. 

Users can also equalize the volume levels for each respective source, ensuring that they will produce the same apparent volume level at any given numerical setting. All functions are operable via a row of micro-touch electronic switches on the front panel and from the SL-9000 Home Theater Master learning remote. The remote can also be programmed to operate your TV, CD player, VCR, DVD  most sources, really. Great idea! 

An ample array of RCA-type inputs and outputs is provided on the rear panel, including 2 processor loops, as well as one pair of balanced ins/outs via XLR connectors, and a female IEC connector allows the use of after-market power cords. All outputs may be operated simultaneously.Due to the narrow profile this preamp presents, the unit's many rear panel jacks are positioned horizontally and fairly close together. The manufacturer suggests that the slender unit can be stacked atop other equipment to conserve shelf space. However, those of you with "fat" interconnect connectors may find, as I did, that the fit can be very tight between adjacent jacks. If the connectors on my Full Spectrum Signature interconnects were any wider, I couldn't have crammed them into the input jacks  in which case I may have had to use less familiar wires to conduct my listening tests. Luckily, with a little digital finesse on my part, they just made it. 

Additionally, I found the setup instructions in the preamp's owners manual a bit difficult to follow. I know that I found myself wishing for a couple of instructive diagrams to help clarify and support the text. I think that the major area of confusion for me appeared under the BALANCE heading. The last sentence in the first paragraph cries out for clarification, Simultaneously, the number display will show 00, which means zero attenuation (or maximum volume).  Skimming through as I and other folks tend to do, I automatically (and erroneously) inferred from reading this line that 99 must then represent maximum attenuation (or minimum volume). Just imagine my shock if I had set the preamp volume to 99 (thinking I had set it for 99 dB attenuation), put on my favorite CD, and let 'er rip! I could have damaged my system, and even worse, my ears. Yikes! In contrast, the separate manual that came with the Home Theater Master learning remote was well written and easy to understand. 

The volume control knob rotates continuously in either direction and has fairly fine detents that each correspond to a 1-dB change in volume. InnerSound circumvents the usual channel balance problems and the transient switching pops and noises that sometimes plague conventional volume controls by using the volume control knob to drive an optical-comparitor circuit. The optical circuit operates a micro-processor-controlled electronic gain system. This permits control of the overall level using one hundred, 1-dB steps, reducing channel tracking errors to less than 0.1%. Switching transients are eliminated because the microprocessor waits for the musical signal to cross the zero point before switching to the next step. 

The preamp's entire chassis is anodized, and constructed from CNC-machined aluminum. Goldplated printed circuit boards and high-quality components are used throughout the unit. The audio circuitry is minimal, and employs very low-noise FETs (field effect transistors), which are claimed to diminish noise, distortion, and crosstalk to vanishingly-low levels.

Setup:  I initially installed the InnerSound line stage in place of my custom AHT tube preamp, in my Plateau equipment rack. My source was the Parasound C/BD-2000 transport coupled to the Perpetual Technologies P-1A/P-3A digital gear via a Harmonic Technology silver coaxial digital cable. As previously mentioned, I used Full Spectrum Audio Signature interconnects (good, but out of production) to connect the ModWright PT P-3A to the CD input of the line stage. The RCA outputs of the InnerSound line stage fed my InnerSound active crossover/bass amp, and the Monarchy Audio SE-160 hybrid monoblock amplifiers were used to drive the electrostatic panels of my InnerSound Eros speakers. 

Normally I use the Eros with a subwoofer, but I lacked the right cable connectors (XLR to RCA) to use the InnerSound's balanced outputs for that purpose. I suppose I could have used the tape outputs, but that would have necessitated resetting the subwoofer level every time I changed the preamp's volume setting, so I let it fly sans sub.For some obscure reason, I couldn't get the preamp to play when I first installed it in my reference system. I could switch sources and make balance and gain adjustments via the front panel controls, and the readout showed the gain setting alright, yet no sound was forthcoming. Later in the evening, for whatever reason, the preamp began working properly without me making any further changes. 

Roger Sanders explained that the preamp's micro-processor may have failed to boot-up initially because I may have inadvertently jiggled the AC plug when I originally powered it up. The usual cure for this, he said, is to unplug the preamp for about 10 seconds and then to re-power the unit, so that the micro-processor can reboot.  He intimated that a momentary lapse in AC power could have the same effect. 

While I can't actually recall any power line problems on that particular evening, we are speculating that this may have been the cause. At any rate, the preamp has worked fine ever since.

Up and Running!Right off the bat, it was clear that the performance of the InnerSound preamp is extraordinary. It is very neutral in its tonal balance, the bass is excellent, deep and superbly delineated; the mids are transparent and detailed, and the highs are very well focused and extended, yet have no discernible harshness or edginess. Soundstaging is expansive and precise, and low-level detailing is superb. Lyric comprehension of the lead and backing vocals is possibly in a class by itself. 

The clarity and articulation that this unit preserves is amazing. This was evident when listening to lead vocals, while the backing vocalists were singing or speaking different lyrics simultaneously in the background. Even so, I'm not going to tell you I could make out every word on every recording  that would be impossible  but I can say that I could hear more of the words more clearly than with any other preamp I have used in my system. This is no small feat. 

The following is an excerpt from an e-mail I received from Roger Sanders:  I did the final testing on it (the InnerSound preamp) using doubleblind, ABX testing using a short, straight piece of wire as a  reference standard. None of the listeners could hear any difference between the preamp and the wire, so I figured we had done our homework well enough! 

Normally, I'd be inclined to attribute such a comment to a designer's inability to be highly critical and objective regarding the performance of his own product. However, after using the Inner-Sound preamp in my own familiar system with my own recordings, my feeling is that the InnerSound folks have done their homework very well, indeed. If any product has ever sounded completely neutral and transparent in my experience, this has got to be the one. 

Recently I received a new high-quality test CD, the Manger CD Sampler, soon to be available from Manger's US distributor (www.mangerusa.com). The recording encompasses a unique assortment of musical instruments and genres, such as classical violin and piano works from Vivaldi and Beethoven, a jazz trio, a couple of vocal cuts from Livingston Taylor, some heavy clanging church bells, and a rambling jazz drumfest from the O-zone Percussion Group. The recording is firstrate, displaying lightning-quick transients, wide dynamic swings, coherent well-balanced sonics and expansive imaging with a superb sense of depth. Using the InnerSound line stage helped to showcase the superior sound of this interesting CD. 

One of the best recordings of classical violin that I've heard is on track 5, Vivaldi's Der Winter and Die 4 Jahreszeiten, 3. Satz, performed by the Sonatori De La Gioiosa Marca. The violins' sound was lively, distinct, and natural, without any sense of hardness, stridency, or general distress. At the same time, the energetic performance was quite riveting and effectively held me captive. 

The intense chiming and rich harmonic overtones of the church bells on the first cut of the Manger Sampler, Volles Gelaut, were dimensional, weighty, and quite majestic. And the percussive joy ride embodied in the last cut "Jazz Variants," was very convincing. The assorted drum whacks & rolls and cymbal work made for a potent and volatile musical mix. It verified the preamp's ability to handle extremely quick transients and wide dynamic swings, while at the same time maintaining superior imaging and localization of the various instruments. 

Compared to What? In this somewhat competitive hobby, comparisons to other gear are as inevitable as they are essential. I've recently had a good cross-section of high-quality preamps in my system, including the Adcom GFP-750, Krell KAV-250p, Rogue Audio 99, and my own custombuilt, minimalist, tube line stage from American Hybrid Technology (AHT). Of all these fine units, I believe the InnerSound to be the most neutral and transparent. 

If memory serves, the InnerSound sounds a bit more musical and coherent than the Krell, while being equal in detail retrieval and all other performance aspects, including transient speed (the Krell's forte). The Adcom unit is very detailed and not really harsh to any significant degree, but the InnerSound seems somehow more relaxed in its presentation and possibly a little smoother throughout the audible range.  As for comparisons to the Rogue and AHT preamps, I would say that these excellent tube units impart a slight softening to the overall presentation, and along with it, a slight smearing or blurring of images, which is mainly perceptible only in direct comparison to the precisely-focused, always-composed InnerSound. Also, the bass of the InnerSound was quite a bit tighter than that of the Rogue and actually quite similar to that of the AHT. 

In terms of freedom from the deleterious and insidious effects of noise, kudos must go to the InnerSound, although the Adcom was also very quiet. I'm not certain if the reason for the apparent improvements in inner detailing or lyric comprehension were due to lower levels of noise, crosstalk, or distortion, but what is crystal clear is the InnerSound's delivery of the music. The usual tiny vestiges of interstitial noise were simply not intrinsic to the fabric of the InnerSound's persona.

Conclusion:  Three thousand dollars is a lot of money to spend for a component that some audiophiles consider superfluous since the advent of digital volume control. That said, the InnerSound line stage preamp is a lot of preamp for the money. Its features and control layout are very well thought out, and the learning remote worked well and was simple to operate. Its clean modern styling should compliment any decor. 

If this device has any sonic flaws, they are very minor and well concealed. As I have said earlier on, this is the most transparent preamp I have had the pleasure to use and until another preamp comes along and does something (anything) appreciably better, I have only praise and no real quibbles with its performance. It may not be perfect, but I had an unusually difficult time trying to find any area at which to point the critical finger. If pressed very hard, I might admit that the unit's macro-dynamic envelope may be very slightly compressed when compared to the very best units I've auditioned. However, I'm not even entirely certain of that one criticism  its unflappable demeanor may just make it appear that way with a few of my recordings. 

Generally, I am very pleased with the wide range of dynamic gradations the unit provides. The InnerSound preamp is a solid-state device, yet to my ears it doesn't sound like solid-state  nor does it sound like tubes. Truth be told, it doesn't sound like anything  but it sure does let the music play! I have a strong suspicion that many who audition this line stage will find that its unique user-friendly features and considerable sonic virtues will make it virtually indispensable.




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