CH Precision I1 Universal integrated amplifier John Atkinson August 2023

John Atkinson wrote about the CH Precision I1 Universal in August 2023 (Vol.46 No.8):

When my wife and I got engaged, we each bought each other a “bubble-back” Rolex watch from an antique shop in San Francisco. Mine was a 1939, hers was a 1940; both watches still run fine, though I am not sure for how much longer, as Rolex no longer services watches that old. My respect for Swiss engineering is based in part on my experience with the Rolexes. So I readily agreed when Editor-in-Chief Jim Austin proposed that I spend some time with the current version of the I1 Universal integrated amplifier from Swiss company CH Precision.

Jason Victor Serinus reviewed the modular, class-AB I1 Universal, which is currently priced at $38,000–$53,000, depending on options, and offers an output power of 100Wpc into 8 ohms, in February 2019. The basic version has one balanced pair and two single-ended pairs of analog inputs, all of which are converted to hi-rez digital and fed to a D/A section capable of handling sample rates up to 384kHz. The volume control is a hybrid type, adjusting the level in both the analog and digital domains. Four optional modules provide additional inputs: a current-mode MC phono input module; a digital input module with AES3, coaxial, and optical S/PDIF inputs, and a CH Link port for use with CH Precision’s D1.5 CD/SACD transport; an Ethernet port, which can be used with CH Precision’s CH Control Android app; and an asynchronous USB port, to allow hi-rez streaming from a computer. There is also a SYNC-IO module that allows synchronization with an external digital word clock and a USB port for firmware upgrades.

My sample (serial number 0Z0F0904, running firmware v2.1) was fitted with the Ethernet and USB modules. These both accept 24-bit PCM data with sample rates up to 384kHz and DSD data up to DSD256. (DSD data is converted to 24/352.8 PCM before conversion to analog.) A bypass mode disables the A/D conversion and volume control and configures the I1 as a two-channel, all-analog power amplifier.

There has been a major firmware upgrade since JVS’s review. Version 2.0 updated the time-domain-optimized “PEtER” spline-filter algorithms with fixed-point processing, reflecting those introduced on the C1.2 D/A processor that Jim Austin reviewed in February 2023. With the new firmware, the I1 is also now fully MQA-compatible, whether replaying streamed music or MQA-CDs from the D1.5 transport.

Most significantly for this Roon user, the amplifier now supports Roon’s audio distribution technology (RAAT). At the time of the original review, the I1 wasn’t a Roon endpoint. I connected the review sample’s Ethernet port to my NetGear NightHawk router with an AudioQuest CAT-6 cable, and the Roon 2.0 app recognized the updated I1 as an MQA decoder and renderer. When a file is played with Roon, the I1 automatically switches its input to the Ethernet port, and “Roon Ready” appears on the front-panel display, with the sample rate shown top left. With an MQA file, the display shows “ORFS” with the unwrapped sample rate (footnote 2); with DSD data, even though the data are converted to hi-rez PCM (this confirmed by Roon’s Signal Path window), the display shows, for example, “DSD64.” The display also shows the internal heatsink temperature in degrees Celsius and the amount of negative feedback selected (see later). The display can be set to show just the volume.

Once the I1 Universal had arrived, Kevin Wolff, CH Precision’s US rep, visited to run through the amplifier’s features and lend me an Android tablet with which to run the CH app (footnote 1). As Wolff unpacked the I1 Universal, I was impressed not just by the amplifier’s physical appearance but by the attention to detail with which it had been constructed.

For example, in addition to that sculpted front panel with the large, four-color display in its center, the chassis’s aluminum-alloy panels join seamlessly with no visible screws. Circular aluminum plates at the four corners of the top panel conceal height adjustment shafts for the feet tipped with hardened aluminum (footnote 3). Height adjustment is performed with a supplied CH-branded screwdriver once the circular plates have been unscrewed with the supplied suction cup. The feet are each fitted with an elastomer ring for when the amplifier rests on a delicate surface, but these can be removed to allow the spikes to dissipate vibration. The small remote control can be attached to the right-hand side panel, which has an internal magnet, a felt pad on the remote’s base protecting the panel’s finish. The overall impression is of Rolex-like quality.

For my auditioning, I sent network audio data to the I1 from my Roon Nucleus+ server. I also connected an MBL N31 DAC’s balanced analog outputs to the CH Precision’s balanced analog inputs with Ayre/ Cardas Signature interconnects. (The I1’s input gain was set to “0dB.”) Loudspeakers were my usual KEF LS50s, these connected with AudioQuest Robin Hood speaker cables. The KEFs sat on 24″ Celestion stands that had their central pillars filled with a mixture of sand and lead shot and were spiked to the wooden floor beneath the carpet; the speakers were mounted with pads of Blu Tack. In addition, the stands’ base plates were weighted down with bags of lead shot. Though the KEFs are minimonitors, I use Roon’s parametric digital equalizer to flatten and extend their in-room low-frequency response to 42Hz, the frequency of the open E string of the double bass and bass guitar. As long as I keep the SPL at the listening position below 85dB(C), the little KEFs offer effective low-frequency performance without noticeable distortion.

All the amplifier’s functions can be adjusted by either the CH app on the Android tablet or the large multifunction control knob on the front right of the I1’s faceplate. I controlled playback with the Roon app on my iPad mini rather than with the CH app. The volume control setting applied by the amplifier’s front-panel knob or the remote control was echoed in Roon’s volume window.

The I1 is unique in that its global feedback level can be set between 0% (the default setting) and 100% in 20% increments without altering the amplifier’s overall gain. With his preferred setting of 0% global feedback and using Wilson Alexia 2 loudspeakers, JVS found the CH Precision’s sound to be “clean, strong, and direct,” yet it did not “filter out those intangibles that allow the music to elicit a powerfully emotional response.”

Using Roon via my network, I investigated the effect of the feedback settings using a familiar recording, the 24/96 version of Molto Molto, Sasha Matson’s recent project for jazz orchestra on the Stereophile label, streamed from Qobuz.

With 0% feedback, the presentation was involving, but the low frequencies sounded somewhat loose. The double bass on Matson’s Symphony No.3, for example, lacked some of the control I had been used to. I had found that without global negative feedback, the original sample’s output impedance was a fairly high 0.4 ohm in the midrange and bass. With the feedback set to 100%, the output impedance had dropped to 0.11 ohm, and with that setting, the amplifier’s low-frequency articulation improved. However, the presentation of high-frequency detail on instruments like cymbals and trumpets started to sound a touch exaggerated. Too much of a good thing too much of the time, I decided.

I ended up with 40% global negative feedback, which, I judged, provided the best balance between low-frequency definition and the unfatiguing presentation of high-frequency detail. (With Jason’s sample, I found that with 40% feedback, the output impedance was 0.3 ohm.)

Once I had settled on that feedback level, I embarked on critical listening, first using the CH Precision as a digital processor.

Without a doubt, this amplifier features a first-rate D/A section. Imaging was precise, the soundstage deep when appropriate, the midrange uncolored, the high frequencies clean and unfatiguing. Low-level recorded detail was present in abundance but without the feeling that it was being unnaturally emphasized.

This was the case with both hi-rez PCM like Molto Molto and with DSD-encoded music like The Dave Brubeck Quartet’s Time Out (DSD64, Analogue Productions). The reverb surrounding Joe Morello’s drums at the start of “Take Five,” for example, was well and tangibly decoded by the CH Precision. I intended to listen to just this one track but ended up playing the rest of the album.

As the firmware update enables the amplifier to behave as a full MQA decoder and renderer, I streamed several MQA-encoded albums from Tidal and played some MQA files from local storage. Given the current uncertainty of MQA’s future—the MQA company’s South Africa–based main investor was looking for an exit and the company went into administration in April 2023; see Industry Update in the June 2023 Stereophile, p.13—there might have been little point in my doing so. Even so, the CH Precision I1 did well with MQA files. Despite the naysaying on the interwebs about MQA, in level-matched comparisons with recordings of known provenance, I felt that the MQA versions offered more palpable imaging when unfolded with the I1. One exception was “Take Five,” where even with the level of the drums and piano at the beginning of the Tidal version matched to that of the DSD file, Paul Desmond’s alto sax sounded a touch more strident and more forward in the soundstage. (The same master must have been used for both the MQA and DSD albums, as Desmond’s familiar clam at 51 seconds into “Blue Rondo à la Turk” was present in both.)

I then tested the CH Precision’s analog inputs. I used Roon to send network data to the MBL D/A processor, so that the parametric equalization I used with the I1’s Ethernet port would still be applied. The MBL’s volume control was set to its maximum.

Hmm. I am well familiar with the presentation of the MBL processor with its minimum-phase reconstruction filter: an excellent sense of drive and low-frequency impact coupled with easy-on-the-ears high frequencies. Fed to the CH Precision’s analog inputs, the low-frequency character seemed unchanged, but the upper frequencies sounded slightly thinner and somewhat less involving. Perhaps this was the result of the I1 digitizing its analog inputs?

Only one way to find out: I used the app to turn off the balanced analog inputs’ A/D conversion and bypass the volume control. Again, I sent data from the MBL N31, but as the I1 was now operating with a fixed output level, I controlled volume with the processor. That did the trick. The N31’s familiar sonic signature returned, but with slightly greater clarity than I remembered experiencing with the Parasound monoblocks that usually drive the KEFs.

JVS’s verdict on the original sample CH Precision I1 Universal: “one of the most complete, most neutral sounding, most carefully conceived components I’ve reviewed.” My auditioning of the updated version, even using speakers that cost a small fraction of the amplifier’s price, supports what JVS wrote back then. The I1 Universal marries a state-of-the-art, superb-sounding, solid state integrated amplifier with a superb-performing, streaming D/A processor.

This comes at a price, but as with Rolex watches, it appears that is what you have to pay for Swiss precision.—John Atkinson

Footnote 1: The Android app appears power-hungry. If the user doesn’t exit the app when they are finished using it, the tablet’s battery rapidly runs down.

Footnote 2: Apparently, “ORFS” stands for “original sampling frequency.”

Footnote 3: Paired with rods that CH Precision can supply, this system also allows two or more CH Precision components to be stacked while limiting vibration that could impact sound quality—although CH Precision recommends avoiding stacking components for optimal results.