CH Precision I1 Universal Integrated Amplifier
CH Precision was founded by Florian Cossy and Thierry Heeb, two alumni of the highly influential and innovative Swiss high-end audio firm Goldmund. Given the wide-reaching acclaim and the host of industry awards they have garnered since their founding, it is hard to believe this company is just rounding out its first decade!
For reasons that will become clearer as you get further into this evaluation, I must preface this examination by noting that my experiences with their early offerings had left me somewhat wanting. While clearly resolute and transparent, to my ears, that debut gear sounded somewhat incomplete; slight of texture and wanting of body and bloom. The editor of another journal apparently found as much truth as humor in an observation I had made aloud to him that, "You need a canteen to spend any time in their rooms," as he shared my somewhat humorous assessment in a Facebook posting back in 2017.
However, more recent listening, at AXPONA and Munich HIGH END over the past two years, and now having lived with the utterly amazing I1 for several months, it has become very clear that things have changed, and decidedly for the better. My opportunity to take a closer listen to the I1 Universal Integrated Amplifier was rather more than just enlightening, it was an absolute joy, both in terms of the user experience and the resultant sound.
As a conscientious, green-focused manufacturer, CH is quick to point out that this allows consumers to enjoy their CH purchase over a longer period of time, ultimately reducing waste and diminishing environmental impact. And every CH product consumes less than 1 Watt when in Standby mode, ensuring compliance with the latest environmental regulations.
Their technological methodology may be summarized by a handful of fundamental approaches; advanced clocking, D/A conversion enhancement, managed amplifier biasing, their unique variability between local and global feedback, as well as the systematic, comprehensive "mechanical" grounding of all components.
CH feels that both the complexity and integrity of digital signal quality is taken for granted by many other manufacturers. To this end, they do not consider clock signals as simply another digital signal, but rather, they treat them as a highly sensitive analog signal. As such these signals are given their own dedicated power supply and are galvanically isolated from all the "noisy" internal digital processing.
While there are numerous ways to synchronize a digital source and a DAC (Phase Locked Loop [PLL], asynchronous Sample Rate Converters [SRC] and First-In First-Out [FIFO] buffers, etc.), CH felt that each individual method presented its own significant drawback. This led them to conflate what they felt are the two best techniques available, a novel in-house designed VCXO-based (voltage-controlled crystal oscillator) digital PLL with a Wordclock-based source synchronization derived from the professional audio world.
Further, the digital signal processing chain in all CH gear utilizes a proprietary signal conditioning stage which they claim optimizes the signal for conversion by the numerous R-2R converters (repetitive arrangements of precise resistor networks in a ladder-like configuration) per channel. Because each converter is built with a slightly different gain and offset, an automated calibration system is employed to harmonize their operation.
To address the low-level linearity issues inherent to R-2R converters, a unique scrambling technology is applied. By sending slightly different signals to each converter through the addition of an algorithmically generated, low-level, random high-frequency noise (which is canceled out in the analog domain), they claim that low-level linearity is significantly improved.
Ideally, the amplifiers bias would remain absolutely constant, no matter how hard the amplifier was driven and/or hot it becomes over time. Even the slightest temperature variation, whether caused by changes in the local ambient temperature or by the amount of current draw demanded by the loudspeakers, will modify the characteristics of the amplifier circuit.
CH Precision has developed a patent pending electronic system called the ExactBias circuit, that automatically and linearly regulates the bias of the amplifier circuit by using real-time monitoring of the inner temperature of the power transistors. This ExactBias circuit, common to all CH amplifiers, lets them achieve what they claim is a uniformly steady bias, which in turn, keeps the amplifier acting more stably and linearly over time.
All CH amplifiers also provide a user adjustable global versus local feedback ratio, from full local to full global, with the I1 offering increments of twenty percent. Essentially, this provides a way to control the amplifier damping factor (the quotient of the speaker load impedance and the amplifier output impedance), allowing users to fine-tune the amplifier performance to any connected loudspeaker system.
Right out of the box, the I1 is built to rest on O-Ring feet, ensuring scratch or mar protection as well as providing a secure, non-slip grip on any surface upon which it sits. However, as mentioned, a more advanced vibration-channeling mechanical coupling system has been provided. First you align each of the four provided polymer CH Support discs (with their matching O-Ring channels) under each corner, directly under the O-Ring footers. Next, (using all included tools) you unscrew four cleverly threaded matching caps installed over each of the chassis four corners, revealing the threaded channels for the adjustable threaded steel spikes. In a matter of minutes, the massive chassis is lifted off the surface it had been resting upon and is supported by this advanced, more secure, and greater isolating mechanical coupling technique.
If no other CH Precision units will be "stacked" on top of the I1, the covers can be reinstalled. Otherwise, the included polymer stacking caps are to be used to allow for the installation of the next unit above the I1, which will also use similar spiking.
What Makes This Swiss Device "Tick"
Next is the second factory built-in board with four digital inputs; S/PDIF, AES/EBU, TosLink, and a proprietary I2S CH Link HD digital input. The final factory built-in board offers an RG45 Ethernet port to allow for remote control via your PC, Mac, or an Android or iOS tablet or phone, but NOT streaming (more on this soon), and a USB port for firmware updates.
At this point, a user may add any combination of up to four additional optional boards, including a transimpedance MC phonostage, a network streamer, a USB input, and/or a SYNC I/O board for external clocking.
First, and of great import to an old analog hound like yours truly, there is a current-mode (transimpedance) MC phono module that allows for the connection of up to two turntables and offers RIAA, eRIAA, as well as the older EMI, Columbia, Decca, and Teldec equalization curves, and is a $4500 option. Once installed, up to two of the three existing analog inputs may be dedicated to the phono preamplifier, as this card provides phono equalization functionality and management, not another separate input.
Next up is the Roon ready Ethernet audio input board. In my estimation, this board should not even be considered an option, as it will most likely be the true workhorse and heart of any playback system being assembled today. This card enables bit-exact, low-jitter playback of high-resolution files over an Ethernet network. Compatible with Roon, UPnP local servers (Universal Plug and Play is a set of networking protocols that permit networked devices, like personal computers, printers, Internet gateways, Wi-Fi access points, and mobile devices, to seamlessly discover each other's presence on the network and establish functional network services for data sharing), and streaming services like those offered by Tidal, Qobuz, or TuneIn webradio, and is an additional $5000.
The third optional board allows for a USB audio input which enables bit-exact, low jitter playback of high-resolution audio files directly from a computer and is a $2500 option.
Finally, the Clock synchronization board, a $1500 option, allows clock slave unit synchronization when used with an external clocking device, like the $24,700 CH T1 10MHz Time Reference Clock Generator. With my current system configuration, I had no way of utilizing this option, so this board was not used in my review whatsoever.
The front panel is Spartanly appointed, and remarkably attractive to my sensibilities. The central, large, easy-to-read 480 x 272 pixel, 24-bit color, AMOLED display, with a silver I1 moniker in the lower right-hand corner, is flanked to the left by the characteristic sculpted CH Precision sweeping curve and appointed with the black and red CH Precision logo (the red being an LED), and to the right by the user control rings, a large, dual concentric rotary knob.
The user control knob on the right side of the front panel is the primary physical input device. Both the central and the external part of the knob can be rotated left or right independently, and the central part of the knob also supports dual push functionality, short or long.
The included small machined aluminum five-button remote offers Mute / Standby, Vol. Up, Vol. Down, Next Input / Polarity Inversion (long push), Previous Input/Mono-Stereo (long push), and cannot be used to configure the I1. This attractive and convenient control may be magnetically attached to the center front of the right chassis panel when not needed.
Both the front panel's dual concentric rotary knob and the slim remote are only offered as a convenience, as the preferred and intended way to configure and manage the I1 is with the CH Control app from your phone or tablet. The Control app is crucial and adjusts any and all aspects of the I1, from initial configuration through daily use, including everything from changing volume, phono EQ settings, managing display colors, to selecting and streaming files. And, it is exquisite!
CH has aimed to distill the essence of their flagship L1 Pre-Amplifier, C1 Digital Controller, P1 Phono Equalizer, and the original A1 Stereo amplifier, well over $120,000 worth of exceptional gear, into one unit. Obviously, to pull that off in a single chassis will require compromise. But, just how much, and how will it affect the sonics?
First, the amplification stage features a pure Class A ultra-low noise driver and class AB follower power stage using their patented exactBias circuitry, employing no output relay. Where the original stand-alone A1 stereo amplifier used a 1,200 VA transformer, the I1 power supply uses a shielded 1,000 VA power transformer. Small enough compromise, given the hyper-fast, soft recovery diode bridge rectifiers and the total filtering capacitance of 100,000uF, assuring that the output stages will have more than merely ample energy to accurately and effortlessly drive any loudspeakers.
Given the physical constraints imposed by the choice of a single chassis for the I1, there simply wasn't the space to use something like the highly celebrated but massive analog volume control of the L1 Pre-Amplifier. In fact, a large part of the secret to the I1s successful distillation is that at the core of its versatility, at its very heart, the 1 is a highly specialized and powerful computer, with everything done in the digital domain.
To maximize space, yet still maintain the CH Precision sound, the design team built a remarkable volume control, an amalgam of the L1 Pre-Amplifier's analog regulation with the substance of the C1 Reference Digital to Analog Controller's digital volume capability. The result applies course scale gradation change (6dB steps) in the analog domain, with finer scale changes (0.5dB steps) applied in the digital domain. Aside from reducing the amount of hardware needed, and subsequently, the extra volume of space needed to house it, another major advantage realized is that bits of resolution are not lost every time the volume is decreased by 6dB. This subsequent hybrid digital and analog volume control, using tight tolerance high-grade metal film resistors, provides a range of 120dB variation, in 0.5dB steps. Sweet!
Use of this hybrid volume control mandated that all sources would need to be digital, including the analog inputs! To deal with this, all analog sources are directly converted to DXD 24 bit/384kHz, using a low-pass filter above 30kHz to suppress modular HF noise, which is managed by its impressive and dedicated computing power.
The use of a transimpedance phono amplifier obviates the load resistor section, the space it would occupy, and affords a shorter signal path. Another benefit here, one of both versatility and space savings is that all equalization in this phono stage is done in the digital domain, as the different RIAA, eRIAA, EMI, Columbia, Teldec, and Decca curves are all managed digitally.
There are so many more technical aspects to cover that I could fill dozens more paragraphs, but I'll let you go to their website if you crave more of that kind of technical detail. Now it's time to give it a test-drive and take a listen.
True enough, you can acquire some mighty fine integrated's for well under half the I1's asking price with names like Aesthetix, Constellation, Esoteric, Hegel, MBL, or Pass Labs. Yet none of them really offer anything more than analog source connectivity; even the few with a digital port don't really support digital in any real manner, do they?
This CH contender can readily handle line-level analog inputs, but it can also be a phono preamplifier, a file based music streamer from multiple sources, and a DAC that can be fed from computers, optical players, or other sources using its USB, S/PDIF, AES/EBU, TosLink, or custom CH Link. This is a level of versatility and degree of expandability that you simply won't find among even the finest of other integrated amplifier offerings today.
All these installable options offer another advantage, that of the reduction of space necessary for your system. With the wide selection of other integrated's available, you will still likely use a host of external devices like phono stages and DACs, as well as all the required ancillaries (interconnects, power cables, isolation shelves / devices, etc.).
Further, if you want to talk about real versatility and the ability to grow into rather than out of a product, the I1 can be expanded beyond belief when paired seamlessly with other CH products. Need (or want) to bi-amplify your speakers? Add the CH Precision A1.5 stereo amplifier and you are set; you can use the A1.5 to drive the woofer inputs and the I1 to drive the Mid / Tweeter inputs. Or let's say you decide you want to elevate your phono performance. No worries, you can add the CH Precision P1 Phono Equalizer and use the I1 in analog bypass mode. Wait, you say you want to use the remarkable CH Precision L1 Dual Monaural linestage? No worries, just connect it to one of the I1's analog inputs, set the I1 to bypass mode, connect your sources to the LI, and you are set. I could go on, but I'm sure you get the picture. The Universal appellation here is an exceptionally appropriate choice of descriptor for the I1.
Living With The CH Precision Sound
My listening was evenly split between my source libraries, a variety of digital files (from 16-Bit/44.1kHZ to DSD128) and LPs. Digital flowed either directly via USB (using the superb new Audience frontRow USB cable) or by using the I1's optional Streaming Board, JRiver MC25 (MC26 has just been released), and the CH Control app on my Samsung Galaxy S10. Vinyl was transcribed by my Kronos Sparta 'table ($24,000), its Helena tonearm ($8,550), and the Etsuro Gold MC cartridge ($20,995).
The first cat I'll let out of the bag here is that there was virtually no indication or artifact that the analog output from my superb LP front end was being converted to digital, where its gain and equalization were managed, then reconverted to analog for amplification. I don't mind admitting that I had been highly concerned about this possibility. Further, the inherent ease, body, and tonal bloom, attributes typical of current-based phono stages like the one in the I1, was quite engaging overall.
The second is that the CH Control app is the BOMB! "Driving" the I1 from my Android tablet or phone was one of the most intuitive, easy, and powerful remote experiences I've yet had with any digitally controlled device. I could manage volume, select my source, or change any setting (mute, phase polarity, balance, mono/stereo, global feedback, even phono stage EQ settings) on the fly from my listening chair. Virtually anything is possible from the CH Control app. I could even set the display color to be different for analog (I chose white), PCM (I chose blue), or DSD (I chose green) sources! Just to give you a sense of how powerful it is, I had to use thirteen screen captures to show all the options and settings available.
Now, I'm not going to tell you that the Phonostage board in the I1 was the equal of my reference $13,500 DSA Phono II phonostage. It wasn't. World class phonostages like the Phono II offer a level of transparency, texture, clarity, quietness, definition, body, bloom, tonal accuracy, and engagement that allow LP playback to still be sonically superior to digital sound, even as we move into this new decade. But what it did, at one-third the cost, was afford the lion's share of what makes good analog so desirable, offering rich tonality, fine texture, a wonderfully spacious sense of body, and exceptional bloom.
However, with the I1, it was the digital music experience that was the most remarkable, closely approaching the sound I associate with DACs in the $10,000-$15,000 range. And the ease of access and completeness of functionality made that experience that much more enjoyable and rewarding.
Bass was not only well extended, remarkably accurately pitched, and wonderfully detailed and resolute, it was powerful, with remarkable slam and seismic impact when using my full-range floor-standing VR-55 Aktive's.
Yet it was the deepest octave-and-a-half, from roughly 60 or 65Hz down, that was the most surprising to me. The I1 exhibited a much firmer, more effectual grip on the deepest bass than any 100-watt stereo amplifier in my experience, reproducing this region with an amazing essence of graceful power.
Early in "Three Wishes," from Roger Waters' 1992 masterwork Amused to Death [CBS/Sony — Netherlands], as the track picks up momentum, the QSound voice of a Genie fills the room — surrounding and engulfing you. And it goes deep! The envelopment effect here was much more complete than with even the Constellation Inspiration gear, easily extending behind my listening chair down both left and right side walls of my large listening room. And the weight of the voice was monumental, convincingly so, enough to make me shudder, as this track does when the system is up to the challenge. This recording can evoke a visceral reaction, one that the CH Precision I1 easily produced.
With the organ work from the second movement of Saint-Saëns Symphony No. 3 [Reference Recordings], the I1 had the authority to convincingly create the power that loads the room with the lowest, sustained organ notes. Though slightly limited in comparison with more powerful amplifiers, the lowest bass here, into the mid-teens at some points, was nonetheless very well extended and articulate, showing remarkable transient capability and excellent pitch definition. This slight limitation I noted was more clearly a result of the slight mismatch between the 100 Wpc output power of the I1 and my rather large room, which is 45 feet by 13 feet.
I was treated to some of the most tonally and texturally convincing lower midrange to mid-treble performance I've experienced from any all-in-one or integrated design to date. Performance here bordered on extraordinary, possessing a purity, texture, and bloom that was somewhat redolent of the best valve designs; alive with luminous instrumental color and genuineness of texture. Midrange was rendered vibrantly with almost reach-out-and-touch texture, rich tone color, copious bloom, and an unerringly faithful sense of dimensionality and space.
Uppermost octaves were well refined, conveying a natural sense of air, delicately recreated, with exquisitely rich and shimmering timbre. Listening to the diversity of cymbal work by drummer Duncan Moore on Dmitri Matheny's 2014 Sagebrush Rebellion [Papillion/Blueport] bordered on revelatory. It may help that I've seen Duncan live many times, at Dizzy's Jazz Club in San Diego, and the Soka Performing Arts Center in Alisa Viejo, California, but Moore's touch here is masterful, all revealed with nearly unsurpassed resolution, with accurate spatial and tonal characteristics, in an exceptionally lifelike manner.
This refined extension provides for a more convincing sense of air and shimmer on cymbals, upper-octave strings, and winds, clearly noticeable on classical pieces like the Bach Violin Concertos and Double Concertos [Philips].
Spatial recreation is exceptional, especially with recordings offering an enormous and/or clearly delineated acoustic, like Falla's The Three-Cornered Hat or the blues harmonica feast, Harp Attack [Alligator LCD 4790]. The soundscape on The Three-Cornered Hat is enormous, with expansive and detailed sonic queues, cavernously deep and wider than your room when your system is up to the challenge. Harp Attack features the voices of veteran bluesmen Carey Bell, Billy Branch, James Cotton, and Junior Wells, each playing a different keyed harp (harmonica). In the opening cut, "Down Home Blues," the four men are lined up left to right, and as they take turns soloing, both their location within the soundstage and the resultant sounds of their voices and harps were vibrant and lifelike. This was recreated with remarkably nuanced pitch and so well recreated in space that, with eyes closed, you might credibly believe the four were standing in your room!
Soundstaging was finely and accurately layered, with stable and rock-solid image locations. Listening to "Peggy's Kitchen Wall" from Bruce Cockburn's Stealing Fire [True North TN 57], you hear the background singers as an assemblage of discrete individual voices, behind Bruce and slightly elevated, not as a single conglomerate "massed" voice.
Overall transparency was astonishingly see-through, and the I1s ability to render fine detail was more than merely convincing. Key-fingering on instruments like sax or clarinet was revealed cleanly and accurately. While you might be tempted to assume that such sounds would routinely be unmistakably and honestly rendered, such micro-detail is not always this finely presented.
As I mentioned in my opening comments, this was not the sound that I'd come to associate with earlier CH Precision gear, products I had heard many, many times since their introduction. With the I1 in play driving my VSA VR-55 Aktives, there was no vestige of the leanness and dryness I had routinely noted with CH Precision electronics in play. It was so curious to me, in fact, that I put the question to Ralph Sorrentino.
This was his response. "I've discussed this with our engineering staff and can provide the following explanation. First, The I1 design has taken advantage of many of the design innovations that we have developed in our 1-Series separate components. For example, take the upsampling and digital filter that has been implemented in the I1. We've taken this filter design from the C1 HD upgrade and adapted it to the I1. The big difference is that this filter fits a polynomial curve between the data points when upsampling rather than padding the data stream with zeroes. This filtering algorithm improved our digital presentation across the board. It's more open, warm, and natural.
Also, the power supply in the I1 has been optimized for its purpose. Many enhancements were added to the regulation stages of the I1 power supply that feed digital and analog circuits since the I1 power amp is only used in stereo configuration.
Finally, the modular design principal that we carry throughout our 1-Series products allows us to plug the same option cards in our separate components as well as the I1. USB streaming, Ethernet_HD streaming, Digital input card HD, and clock synch card, are all examples of option cards that are used in our separate components and the I1 again allowing the I1 to take advantage of the innovations we make."
Regardless of what specifically may have made the significant sonic improvements I had noted, this sound was more full-bodied and fleshed out, much more real sounding, than any other prior experience I can recall with CH Precision electronics. In fact, the sound of this remarkable single-chassis device has me on a quest to hear more of the entire CH Precision line. With their cooperation, I hope to bring you more articles about their discerning lineup of exceptional gear in the future.
But such an exceptionally versatile and remarkable sounding solution as the I1 will also be very desirable for the audio maniacs (like me!) among our ranks, those with a dedicated music room housing a system that represents a lager investment than their home. It will make a splendid core system for a vacation home or condo, or an unrivaled music system for a library, den, or even a bedroom or family room of a primary residence.
I absolutely loved my time with this splendid device. The CH Precision I1 offers a level of performance from a single package that is completely unsurpassed in my experience. It represents a dazzling and exhilarating execution of a product in a relatively new device category; a category I will venture to suggest will only grow to occupy a larger and larger share of the high-end audio market. While I could never call the I1 an "affordable" all-in-one solution, the level of resolve, refinement, grace, sophistication, and engagement this device offers make it an absolute steal, an overachieving value, a true bargain at its lofty price point. Most highly recommended.
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