CH Precision M1.1 power amplifier
- May 27, 2020
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CH Precision’s massive, versatile, technologically sophisticated, 165 lb M1.1 power amplifier ($54,000 configured for stereo) can easily crush your foot if you’re not careful when installing it. But the more important consideration is this: Can this cool gray techno-square sing and dance without stepping on its own feet?
Unlike their playfully mischievous neighbor darTZeel, whose corporate sense of humor runs so deep that the LCD readout on their NHB-18NS preamp displays the messages foreplay and climaxed when working its on/off switch, Swiss manufacturer CH Precision is all business. Founded by Florian Cossy and Thierry Heeb (hence the company namealthough, coincidentally, CH also stands for Confoederatio Helvetica, the Latin abbreviation for Swiss Confederation), CH Precision is a relatively young company, though the founders have a long history in high-performance audio beginning in the 1990s with their work for Goldmund. The two left that company to form OEM Anagram Technologies, which quickly established a fine reputation for its DACs, among other products. In 2009, with the encouragement of a group of distributors, the partners founded CH Precision.
Like all CH Precision products, the M1.1 is an unusually flexible designso much so that, although you wouldn’t know it from the headline, I reviewed two of them, as monoblocks. Each M1.1 contains two power amplifiers and can be configured in any of five different modes. The simplest of theseand the only one that requires just a single M1.1is stereo mode, in which the M1.1 outputs 350Wpc into 4 ohms. But because each M1.1 is shipped with only a single input card, stereo mode requires the purchase of a second card ($2000).
After that, there are four different ways of using a pair of M1.1s:
Monaural mode, which uses only one output section per amp, yet which diverts to that board the entire output of the amp’s massive power transformer. In this mode, the M1.1 can deliver up to 350W into 4 ohms.
Bridged mode, in which both output sections per chassis operate together as a single balanced amplifier, outputting up to 1200W into 4 ohms.
Passive bi-amplification mode, in which the two output sections per chassis separately drive the two pairs of input terminals on a bi-amplifiable speaker. Interestingly, in this mode, feedback and gain can be independently adjusted for each pair of terminals, to more precisely match the individual speaker segment’s efficiency and sonic characteristics.
Active bi-amplification mode, which also requires the purchase of an additional input boardfor each ampand allows the use of an external crossover. As in passive bi-amplification mode, feedback and gain can be independently adjusted for each pair of speaker terminals.
The modular design allows end users to order an M1.1 with a single analog input board for both monaural and passive bi-amplification use, and later add a second analog input board for active bi-amplification mode or, if times get tough, sell one amp and add the second input card to create a stereo amplifier. Speaking of tough times, a pair of M1.1s configured as monoblocks (with a single input board each) costs $104,000.
The M1.1 was created in June of 2018, as an upgrade from their M1 power amp. For the new model, the single 100,000µF power capacitor of the original was replace by a pair of “monstrous” (according to the CH website) 120,000µF ultralow-ESR/ESL capacitors, for a total storage capacity of 240,000µF per chassis. This upgrade brought about a $3000 price increase from the old model to the new; for the same $3000, CH will ship the upgraded parts to the customer’s home and, for no additional charge, send a technician to perform the install. The manner in which a company handles their “legacy” customers tells you a great deal.
The power supply, occupying most of the chassis interior, features a massive 2200VA transformer that’s magnetically and electrostatically shielded and mounted on vibration-reducing blocks. The analog stages feature discrete components only and the shortest possible signal paths. No capacitors are in the signal path, nor does the circuit use output relays.
The JFET-based, fully differential input stage runs in class-A, while each output stage, featuring six pairs of complementary output devices, is biased for class-AB. CH Precision uses OnSemiconductor’s ThermalTrak devices, which make possible the precise monitoring of the operating temperature of each transistor’s circuit or silicon die, in order to keep output-stage bias as constant as possibleindependent of ambient temperature or the demands placed on the circuit by varying music signals. CH claims that the M1.1’s class-AB design, using their patent-pending circuitry, outperforms a typical class-A biased amplifier. Claimed frequency response is wideband: DC450kHz (3dB) at 1Wwhich in the words of the old British comedy duo Flanders and Swan, in their “Song of Reproduction,” “should please any passing bat!”
A DSP-based protection system, operating at a sampling rate of approximately 100kHz, monitors output voltage and current. An abnormal condition immediately shuts down the amplifier to protect the loudspeakers in the event of a short circuit, or a disconnected speaker, or an over-temperature heatsink or over-temperature output transistorsall accomplished without relays.
Built using pin assembly, the M1.1’s chassis of high-grade aluminum alloy conceals the front-, top-, and side-panel fastening screws, producing smooth joints between metal parts, while the solid steel baseplate provides a firm mechanical foundation and effective magnetic shielding. Despite its high mass, the M1.1 can, if necessary, be spiked and vertically stacked using an ingenious engineered-in system similar to that in other CH products.
Though at first glance the M1.1’s industrial design appears square and austere, a closer examination reveals a satiny finish that’s luxurious to the touch and visually quite pleasing, in an understated way. Again, the look is quite the opposite of the fanciful industrial design of my even-more-costly reference amps, the darTZeel NHB-458 monoblock (170,000 Swiss francs/pair).
Complex yet user-friendly setup
Each M1.1 requires two AC cords: A 20A IEC jack supplies power to the aforementioned 2200VA toroidal transformer, while a 15A jack connects to a second toroidal transformer, which powers the small-signal stages as well as the amp’s digital functions (front panel display, microcontroller, and DSP features). (A third toroidal transformer that draws only 1W insures “green” operation when the amp is in standby mode.)
Once the amps are in placehopefully accomplished without injuryan ingenious footer/spike system is used to level the chassis and help draw away mechanical vibrations. The M1.1’s rear panel includes the above-mentioned two AC sockets plus two pairs of Argento Audio speaker terminals. The input board features two single-ended jacksone RCA, one BNCand an XLR socket for balanced input, as well as an XLR balanced “pass through” output in case the user wishes to “daisy chain” multiple M1.1s. The rear panel also includes separate grounding jacks for analog and digital circuitrytwo for the former, one for the latter, all banana socketsin addition to a USB port for software updates and an Ethernet port to facilitate network operating system control via the CH app.