Pasche told me that at audio shows in Hong Kong and Shanghai, where the I1 and A1.5 amplifiers were paired with Wilson Audio Alexia 2 speakers, exhibitors went with either 0% or 20% global feedback. In Nordost's room at RMAF 2018, in which YG Acoustics Sonja 2.2 speakers were biamped by driving the bass with the I1 and the mids and highs with CH's flagship M1 power amp, a combination of 0% global and 100% local feedback was used. After some experimentation, I found that, with my own Alexia 2s and Nordost Odin 2 speaker cables, 0% global and 100% local feedback delivered the fullest, most musically rewarding sound, with the most air around instruments, the best reproduction of the space around them, bass that was more believably complex and fleshed out, and treble that was less artificially forward.
Digital, Phono, Volume
The CH Precision I1's field-programmable gate array (FPGA) upsamples 16-bit/44.1kHz PCM and its multiples to 24-bit/352.8kHz, and 16/48 and its multiples to 24/384. On the DSD front, it currently handles up to DSD256 (DSDx4), and converts all DSD data to 24/352.8 before playback. The I1's volume control is designed not to lose bits and, thus, dynamic range. According to Raphael Pasche, "In a totally digital volume control, every time you reduce your level by 6dB, you lose one bit. Ours is a hybrid volume control, where the volume is controlled in coarse steps in the analog domain and fine steps in the digital domain. At the most, you lose one bit."
While the I1 uses Universal Plug and Play (UPnP) network protocols to recognize network devices, Roon uses a proprietary protocol that the I1, not yet being a Roon endpoint, doesn't recognize. This led to the first of many complications that ultimately proved solvable, if at the cost of some sleep and many FaceTime exchanges with Ralph Sorrentino, the extremely knowledgeable and helpful Brand Ambassador for CH Precision America.
Pasche said that the I1's amplifier section is "more or less a copy/paste of the A1 amplifier stage—it has the same circuitry with a different number of output transistors." Nonetheless, the I1's optional phono stage operates mostly in the digital domain—as is not the case in CH's P1 phono preamplifier ($31,000), which operates exclusively in the analog domain, and which our Michael Fremer uses with CH's X1 power supply ($17,000).
The analog gain stage that the I1 dedicates to its phono section is identical to the analog gain stage in the P1. "The I1 has a digital heart, including the phono stage," Pasche said. "The phono stage is also current-based rather than voltage-based, and is far more suitable to lower-resistance MC cartridges that deliver a lot of current." The I1's phono signal path is: input connector->analog gain stage (the most important stage of the signal path, which raises the signal from cartridge level to line level)>A-to-D conversion to 384kHz>digital signal processing via a choice of RIAA, eRIAA, EMI, Columbia , Teldec, and Decca EQ curves>DAC and power amp.
Setup Complications
Before the I1 arrived, I'd finally established an uncompromised wired Internet connection between my modem and initial router, which sit in my office on the second floor of our house, and a second router in our detached music room a considerable distance away. My goals were to be able to send to the music room Tidal and Qobuz streams with no loss of fidelity, and to use an Ethernet>optical>Ethernet scheme to completely isolate my audio system from router noise. To accomplish all this, I procured a double set of TP-Link optical-to-Ethernet converters, multiple lengths of optical interconnect, and lots of loaner AudioQuest Diamond and Wireworld Platinum Ethernet links. I also invested in hours of electrical work that included a buried conduit for the optical cable. In the music room, instead of using a computer to play music files and high-resolution streams, I customarily use a Roon-equipped NUC>second router via Ethernet>TP-Link via optical>TP-Link>system via Ethernet. To control playback, I connect my iPad to the router via WiFi, launch the Roon app, adjust volume, and listen to my heart's content. During setup I learned that inputs can be renamed easily. Given my plans for this review, I renamed my analog inputs "Analog In XLR," "Analog In RCA," and "Phono In RCA." As for other inputs, "USB" allowed me to stream music from my NUC and MacBook Pro computers using Roon, and "Streaming" to stream music already on the computer to the small router and then to the I1 via Ethernet.
The first in a series of less-than-delightful surprises surfaced soon after Pasche and I set the I1 on the top shelf of my Grand Prix Monaco equipment rack, plugged it into a PS Audio P15 PowerPlant, connected it to my Wilson Alexia 2s with Nordost Odin 2 speaker cable, and tried to set parameters and play music using CH's Control app. While all the control apps I've worked with up to now have been iOS based, the I1's app is Android based.
Pasche explained: "At the time we started to design our app, we realized that Apple was changing things in the heart of the OS very quickly without notice, and could have life-and-death implications to the functioning of the unit. Since we couldn't afford to keep updating our app, we went with Android because it's a more stable platform. We want our customers to have the most exhilarating experience, which won't happen if, all of a sudden, the app won't work."
While this reasoning is indisputable, it mandated that Pasche loan me an Android tablet loaded with the I1 Control app, plus a separate little router that we could use to set up a closed network between the tablet and the I1. Once my Roon-equipped NUC was connected to the little router and the little router was connected to the I1, both with Wireworld Ethernet links, we expected that I'd be able to play music with ease using the Control app on the Android tablet.
Wishful thinking. Since the I1 won't be able to be used as a Roon endpoint before summer 2019, it refused to recognize music sent from the Roon-equipped NUC via Ethernet. Nor, because the I1 uses the 10/100 ethernet protocol, would it even accept a wired Ethernet>optical>ethernet connection transmitted through my optical TP-Link Gigabit Multi-Mode Media Converters, since they are not backwards compatible with the 10/100 ethernet protocol. As a workaround, we downloaded to my MacBook Pro the free Roon Bridge application, with which an Apple computer can be used as a Roon-compatible network bridge, and placed the MacBook atop the I1. (There was no room for it in the rack.) Because the I1 puts out significant heat in use, I erected, in a procedure fraught with peril, a double stack of equipment supports to create enough space between I1 and computer to allow that heat to escape. To reach the keyboard, I had to crane my neck and stand on tiptoe. Thanks to my regular gym workouts, I managed to type with steady hands and never once tip the whole thing over.
Next, we connected my Roon-equipped NUC to the MacBook Pro via Ethernet, and the MacBook Pro to the I1 via a Nordost Valhalla II USB link. Playback was controlled by the Roon app on my iPad Pro rather than by the CH app. All other I1 functions could be controlled and adjusted by either via the I1 app on the Android tablet, or by the large multifunction control knob on the front right of the I1's faceplate.
The CH Precision I1's field-programmable gate array (FPGA) upsamples 16-bit/44.1kHz PCM and its multiples to 24-bit/352.8kHz, and 16/48 and its multiples to 24/384. On the DSD front, it currently handles up to DSD256 (DSDx4), and converts all DSD data to 24/352.8 before playback. The I1's volume control is designed not to lose bits and, thus, dynamic range. According to Raphael Pasche, "In a totally digital volume control, every time you reduce your level by 6dB, you lose one bit. Ours is a hybrid volume control, where the volume is controlled in coarse steps in the analog domain and fine steps in the digital domain. At the most, you lose one bit."
The analog gain stage that the I1 dedicates to its phono section is identical to the analog gain stage in the P1. "The I1 has a digital heart, including the phono stage," Pasche said. "The phono stage is also current-based rather than voltage-based, and is far more suitable to lower-resistance MC cartridges that deliver a lot of current." The I1's phono signal path is: input connector->analog gain stage (the most important stage of the signal path, which raises the signal from cartridge level to line level)>A-to-D conversion to 384kHz>digital signal processing via a choice of RIAA, eRIAA, EMI, Columbia , Teldec, and Decca EQ curves>DAC and power amp.
Before the I1 arrived, I'd finally established an uncompromised wired Internet connection between my modem and initial router, which sit in my office on the second floor of our house, and a second router in our detached music room a considerable distance away. My goals were to be able to send to the music room Tidal and Qobuz streams with no loss of fidelity, and to use an Ethernet>optical>Ethernet scheme to completely isolate my audio system from router noise. To accomplish all this, I procured a double set of TP-Link optical-to-Ethernet converters, multiple lengths of optical interconnect, and lots of loaner AudioQuest Diamond and Wireworld Platinum Ethernet links. I also invested in hours of electrical work that included a buried conduit for the optical cable. In the music room, instead of using a computer to play music files and high-resolution streams, I customarily use a Roon-equipped NUC>second router via Ethernet>TP-Link via optical>TP-Link>system via Ethernet. To control playback, I connect my iPad to the router via WiFi, launch the Roon app, adjust volume, and listen to my heart's content. During setup I learned that inputs can be renamed easily. Given my plans for this review, I renamed my analog inputs "Analog In XLR," "Analog In RCA," and "Phono In RCA." As for other inputs, "USB" allowed me to stream music from my NUC and MacBook Pro computers using Roon, and "Streaming" to stream music already on the computer to the small router and then to the I1 via Ethernet.
