CH Precision I1 Integrated Amplifier Review Page 2

For all my final critical listening sessions, I opted for the CH Precision Control App and the I1’s Ethernet/Streaming input for two of the most practical reasons I could think of: It sounded spectacular and in my mind is what the bulk of buyers will be using. This is important to me because CH engineers designed the I1 as a holistic one-box solution and I want to review it on the merits of what it comes with, not what might be added as far as a USB-connected streamer/server is concerned, because there’s a lot of options out there on that front.

The I1’s alloy chassis is a work of art with fit and finish befitting of a $30,000 USD audiophile product, the included remote feels solid, weighty and just right in the hand and the unit’s settings menus are intuitive to use and navigate, as is the multi-use volume/control knob on the I1’s front panel.

The LED screen is bright and legible even from across the room and despite being a prototype, the only issue I had was that only one track would play at a time (a full album wouldn’t play through uninterrupted) via the CH Control App/Ethernet initially if my Android tablet’s screen went to sleep. After consulting with CH and then performing a full shutdown/reboot a couple of times of the I1 and then updating the OS on my Alcatel A30 Android tablet, re-installing the CH App and rebooting it, the issue resolved itself. Such is life in the digital age of music.

I decided to speak with a CH engineer who worked on the I1 directly and Raphael Pasche from CH in Switzerland was kind enough to take the time to answer a number of technical questions regarding the unit.

Here is our Q&A:

Rafe Arnott: Raphael, could you tell me about your role both at CH Precision in Switzerland and more specifically, your involvement with the the development, design and construction of the I1 Integrated?

Raphael Pasche: “I am an electronics engineer, in a team comprising electronics, software and mechanical engineers. My primary role is to design the printed circuit boards of the company's new products. Besides, my role is also to distribute our products in the United States, working alongside our US brand Ambassador Ralph Sorrentino. The design of the I1 was a team effort and my specific role was to develop the DAC and power amplifier sections of the unit.”

RA:CH Precision has been implementing modular board designs for some time in their source-chassis separates range. How was this approach initially decided upon?

RP: “CH Precision has been implementing a modular board design from the very beginning. The D1, released in 2010 was our first product and already featured slots into which option boards could be fitted. The I1, like all its predecessors, follows the same path, featuring a series of option boards. The modular approach has two major advantages:

  • It allows our customers to tailor their units to the requirements of their system. In addition, if the requirement of their system changes, then they can very easily fit new option boards at a later stage.
  • It allows us to develop new boards that feature the latest advances in technology and standards that appear on the market. This in essence makes our units future-proof and allows our customers to protect their investment.

“The CH-style modular approach also works in other ways. Our power amplifiers, the M1 and A1.5, can be reconfigured between stereo, monaural, bi-amplification and bridge mode at a touch of button. One can start with a stereo amp and then add a second amp and reconfigure it on-the-fly to be either in monaural, bi-amplification or bridge mode. Finally, units like the L1 (line preamplifier) or the P1 (phono stage) can evolve from a stereo unit to a dual monaural unit with external power supplies, going from a single chassis unit to a full blown four dual monaural system.

“With the modular approach we implemented, our customers can modify the specifications of the units to suit the changes in requirements of their system, at their own pace, whenever they want and there is no financial penalty in upgrading at a later stage compared to buying a full blown system from the start. With CH products, you don't trade in your units when you want to upgrade, you keep building on what you already have. The I1 follows the same rules and features slots into which option boards can be fitted.

“To best illustrate our modular approach, we released last summer a set of digital output and input option boards for the D1 drive and the C1 DAC called the HD board upgrade. The upgrade consists of swapping your current digital input/output board for the latest HD boards. A firmware upgrade has to be done and we provide a USB stick containing the latest firmware that you connect at the back of our units. We were very proud when the owners of the very first D1 and the very first C1 reported that the upgrade to the HD board that they both performed themselves was glitch-free and that their eight and seven-year-old units are now up to date, just like the units we produce today. “

RA: What was the design precis for the I1?  Was it to basically distill as much as the company had learned from their separates (A1, L1, C1, P1) into a one-box design to facilitate an entry-level price point into the world of CH Precision separates product range? Or was it something else entirely? A perceived gap in the CH lineup based on the company’s own observations or customer feedback?

RP: “The I1 is CH Precision's first integrated amplifier. It is based around four products; the A1 power amplifier, the C1 digital to analog converter, the L1 line preamplifier and the P1 phono stage. We combined the heart of these four products to create a unit that completes the 1-series of products. The I1 comes factory fitted with the usual digital inputs (AES, EBU, TOSLINK and CH Link HD) as well as with a set of three analog line inputs. Modular architecture is in our eyes the way forward for audio equipment. Therefore, Phono, Ethernet streaming, USB streaming and external clock synchronization option boards can be populated at the back of the unit. 

“The I1 amplification stage uses the A1 amplification circuit with a difference in the number of transistor pairs in the output stage. It therefore includes user-selectable a global vs local feedback-ratio feature, as well as the ExactBias circuit topology allowing the amplifier circuit to keep a constant-bias current in the output stage regardless of the amplifier’s internal temperature and program material. 

“Just like in the C1, the hub of the I1 is digital. Using the CH-HiD synchronous data over-sampling processing, digital streams and analog inputs are up-sampled before being processed and converted to the analog domain for amplification. The volume control uses a hybrid technology based on the C1 digital software processing and the L1 analog circuit, where coarse 6dB steps are done in the analog domain (post DA conversion) while fine 0.5dB steps are done in the digital domain (pre DA conversion). This method of applying volume control retains the maximum number of significant digital bits and therefore retains the highest signal-to-noise ratio. 

“The optional phono input is a current-sensing input and is dedicated to MC cartridges. It uses the technology developed in the P1 , in particular its current-sensing analog amplifier stage. This type of input harvests the information from the cartridge by reading the current generated by the cartridge (in opposition to reading its voltage often found in more traditional phono stages). The more current a cartridge can create, the higher the gain of the first stage. The generated current is proportional to the cartridge’s internal resistance (the lower the resistance, the higher the current it can generate). This focuses the I1 phono input to MC cartridges because of their low internal impedance.

“The Ethernet and USB inputs are the same ones as the ones used in the C1. A variety of digital formats can be read from a NAS or a computer. The I1 was developed with multiple audiences in mind. In this day and age of minimalistic interior designs and fashion, the Swiss Army knife of hi-fi finds its place easily. It also serves as a secondary system, used in parallel with the main system, making the secondary system's sonic characteristics in the same vein as the main system as well as sharing the same controls and features. Secondary homes and chalets are also places where you find an I1. But the I1 is also the gateway to the CH world. By combining four units into one, we open the door to the CH gear.

“The unit can be used as a single unit, but the features of the unit allows the user to upscale his system at any time. Upscaling can go in a lot of directions; the modular architecture allows to fit new types of inputs to the I1. The I1 features a preamp outputs (analog signal post-volume control, pre-amplification stage) that allows for connection to an M1 or A1.5 and therefore provide bi-amplification (for example I1 for trebles and M1/A1.5 for bass). The Sync board allows an external clock like the T1 to be connected to the I1. Finally, the next step in refining your system is to take the digital-to-analog conversion out of the I1 and to use the C1 for conversion. The I1 becomes a pure analog power amplifier and the C1 is connected to the I1 analog input. The analog inputs feature a Bypass path allowing for a bypass of the digital hub of the unit and access the analog-amplifier stage directly. All the digital input option boards can simply be taken out of the I1 and fitted at the back of the C1.”

RA: I noticed from the front-panel display on the I1 that regardless of file type that I was streaming to it, it appeared that there was up-sampling taking place. For example, 44.1k streaming files looked as if they were being converted to 352.8k. is my assumption correct? Is there  on-the-fly upsampling taking place?

RP: “Yes, that's absolutely correct. All the digital inputs are up-sampled to 384kHz (resp 352.8kHz). Besides, as the hub of the I1 is in the digital domain, the analog line and phono inputs are converted to the digital domain at 384kHz. The upsampling process is done on-the-fly by DSP processors inside the unit. We use our own in-house development procedure of upsampling processing, implementing Spline filters. This technology has also been implemented in the C1 thanks to the introduction of the DIG IN HD board which populate both the I1 and C1.  Why upsampling? Upsampling allows us to present data to the DAC in a way that makes it work at its best performance.”

RA: Can you talk about the DAC that is used in the I1 and the digital-to-analog resolution architecture which the company employed in its design? Is it FPGA, multi-bit, R2R or Delta-Sigma based and why?

RP: “In the I1, we use a Delta-Sigma chipset. The DAC receives the upsampled 384kHz digital stream and converts it to the analog domain. We have already used this chipset in our D1 Drive on the analog outputs with great results. Crucially important, the power supply for the voltage reference of the DAC is using our Shunt-regulation technology. It provides a regulated DC reference with a noise floor that is barely measurable by our in-house measurement apparatus. This allows the highest signal-to-noise ratio, ie; the highest dynamics to the signal.”

RA: To me the I1 does everything but one for my specific needs and that’s an USB-A input capable of reading music files off dedicated external USB drives or USB sticks. In it’s current guise, the USB-A input is for firmware upgrades only. Will we see a USB-A board made available for those who don’t want to implement noisy NAS-based drive system for local file access?

RP: “This is a very interesting point. We do listen to our customers and welcome ideas, feedback and comments about our products. The USB drive directly connected to the back of our units has been mentioned on various occasions and we have had a look at solutions that could work with our units. Nothing is set in stone at this moment in time, but who knows, maybe one day you will see a Hard Drive USB port at the back of our units.” 

RA: Where does CH officially stand on MQA? Will we see an MQA-certified CH DAC any time soon?

RP: “We are talking to the MQA folks in order to become MQA certified. There is no set date to when you'll see MQA certified CH units, but this is a work in progress.”

CH Precision Sàrl
ZI Le Trési 6D 1028 Préverenges Switzerland
+41 (0)21 701 9040

Everclear's picture

Pass Labs INT-250 integrated amp weighs 105 pounds and puts out 250 WPC/8 Ohms :-) ..........

volvic's picture

If I am correct, and forgive me but going by memory, that for the asking price there are fewer inputs than my Linn Kairn. At that price there should be a few more, or am I just an old curmudgeon.