The reference power amplifier in the CH Precision 1Series. The M1.1 delivers exceptional power and drive in stereo, mono, bi-amped or bridged modes, with supreme composure and clarity. The ultimate in high-end power delivery.
M1.1 Two-channel Reference Power Amplifier
Traditionally, power amps have always been the simplest of audio components, at least on the outside: little more than a set of inputs, a set of outputs and a power switch. Until now…
The problem is that although power amps themselves might appear simple, their job is anything but straightforward. Caught in a sandwich between the output of a line-stage or DAC and the load requirements and sensitivity of any number of different loudspeakers, they must be able to accommodate the widest range of partnering equipment and interface parameters presented to any unit in the audio system. Achieving optimum results under such varied conditions demands a capable and versatile performer – yet as we’ve already established, most power amps offer a single, brute force solution to the problems they face, instead of adopting a more sophisticated response. It’s time for a change – it’s time to meet the CH Precision M1.1, a new-paradigm in power amplification.
What sets the M1.1 apart? It goes without saying that the M1.1’s sonic and musical performance challenges the state-of-the-art, an incredibly short audio signal path executed with exacting component choices and construction, a massive power supply providing absolute stability and unfettered headroom, capable of meeting both the most delicate and most massive musical demands. But what makes the M1.1 really different is its software driven housekeeping capabilities, a non-intrusive support network that does more than just keep the amplifier unconditionally stable.
For a start, it’s not just one amplifier: it’s actually four amplifiers in one – at least in conceptual terms. The sophisticated software in the M1.1 allows the owner to configure the unit in one of four different ways. So an M1.1 is a conventional stereo amplifier but it is also a high-current mono-bloc in which the entire power supply is devoted to a single output channel, a high-power, bridged-mode mono-bloc and a bi-amp mode stereo unit in which a single input can be differently configured for the two output channels. Differently configured? Yes, because the M1.1 allows owners to select gain and percentage of global feedback for each channel independently – which means that the amplifier can be adjusted for overall system gain and noise performance, as well as configuring the low-frequency damping and gain to match system topology.
That means that the M1.1 is both configurable to specific speaker loads and inherently upgradeable – as well as adaptable to upgrades elsewhere in the system. Change your speakers or line-stage and the amplifier you already own will adapt to deliver the best possible performance. Start with a stereo amp and it can grow into a pair of mono-blocs or a bi-amped system, all without having to replace existing units or even changing your interconnect cables. For once, the best sounding amplifier is also the sensible choice, because there’s finally an audio amplifier that’s got both finesse and brute force – but without the ignorance…
The M1.1 power amplifier was developed with modularity in mind. It can be equipped with a single analogue input board in case the M1.1 is used for a single channel. This modularity ensures the following operation modes:
- Single channel mode
- Passive bi-amplification mode
- Active bi-amplification mode (requires a second Analogue Input Board)
- Bridge mode
- Stereo mode (requires a second Analogue Input Board)
Changing the M1.1 operating mode has been made easy and can be done on-the-fly from the front panel user interface. Only the available options are permitted depending on the hardware configuration.
The central power supply is taking most of the internal space inside the chassis. The huge 2’200VA transformer is mounted on silent-blocks to drastically reduce vibrations transmission into sensitive parts of the circuitry. It is shielded both with a magnetic and an electrostatic screen. The transformer’s plate is also secured for transportation.
For optimum thermal performances, the output stage diode bridges are mounted on the front panel inside the chassis and are of hyper-fast soft-recovery type.
The filtering capacitors are custom-made huge capacity (2x 120’000uF), ultra-low ESR/ESL (equivalent series resistance/inductance) models, which ensures that power amplifier’s voltage rails remain almost constant.
All analogue stages inside the M1.1 are built only with discrete components, no operational amplifier have been used into these sections. This deliberate choice warranties the shortest audio signal path and allows the use of custom-made building blocks.
No capacitors have been used in the signal path, nor any output relay to ensure maximum transparency.
A gain range of 24dB – in 0.5dB steps – is embedded in each channel, for a perfect match with the loudspeakers’ sensitivity and room size. A lower gain is typically preferred for high-sensitivity speakers into a small room while a bigger gain is sometimes needed for large room with sensitivity loudspeakers.
This gain adjustment can also be useful with multi-amplified loudspeakers to adjust the level of the various drivers independently.
Output stage feedback
Unlike all other CH Precision’s analogue stages, the M1.1’s output stage can be configured to have some global feedback. The global versus local feedback ratio is adjustable on-the-fly from the front panel user interface, only a few relays are switched during this operation. Ranging from 0% – local feedback only – to 100% – global feedback only, in 10% steps.
Independent feedback ratios can be set in bi-amplification modes.
Output Stage Bias
In order to keep the output stage distortion constant over time, the output stage’s bias must be kept as constant as possible. The bias is highly dependent on the output stage internal temperature – the transistor die – which can be known thanks to ThermalTrak devices from OnSemiconductor.
A very special circuit was built around the output stage which is taking into account both the temperatures of the heatsink and the transistors’ dies. It allows the amplifier’s output stage to keep its bias constant independently of the musical program and the room temperature.
In term of performances, the M1.1 class-AB design is outperforming a pure class-A design with usual bias compensation. This schematic is patent-pending.
Each channel’s output signal is permanently monitored – both in voltage and current – processed by a DSP, which computes in real-time the effective channel’s output power.
If an abnormal situation arises, the amplifier is immediately turned off to protect the connected loudspeakers. No output relay have been used into this amplifier, its symmetrical structure allows a smooth turn-on and turn-off of the power supply without noticeable noise.
“The M1.1 power amp is simply the most musically accomplished, high-powered solid-state piece it has been my pleasure to use. I love its configurable nature and I love the idea of adding additional amps along the way.” – ROY GREGORY, THEAUDIOBEAT.COM (read in full here)
“The M1.1 amps are so relaxed at signal peaks they make you relax.” – MARSHALL NACK, POSITIVE FEEDBACK (read in full here)
|Inputs type||Balanced (XLR), one connector per board
Single-Ended (RCA & BNC), one connector per board
|Input impedance||Balanced: 94kΩ
Single-Ended: 47kΩ or 300Ω
|Input stage||JFET input stage
Ultra-low noise, discrete fully differential stage
24dB range adjustable gain in 0.5dB steps
|Amplification stage||Ultra-low noise full discrete class AB design
6 pairs of complementary output transistors
|Output power||2x 200W / 8Ω, 2x 350W / 4Ω, 2x 600W / 2Ω in stereo and bi-amp modes
1x 350W / 4Ω, 1x 600W / 2Ω, 1x 1100W / 1Ω in monaural mode
1x 700W / 8Ω, 1x 1200W / 4Ω, 1x 1600W / 2Ω in bridge mode
|Bias||Patent-pending bias circuitry for constant bias operation|
|Feedback||User-adjustable local vs. global feedback ratio, from 0% to 100% in 10% steps|
|Bandwidth||DC to 450kHz (-3dB) at 1W into an 8Ω resistive load|
|Signal to Noise Ratio||Better than 115dB in stereo and bi-amp modes
Better than 118dB in bridge mode
|Total Harmonic Distortion + Noise||Less than 0.1% with 0% global feedback
Less than 0.01% with 100% global feedback
|Binding posts||Two pairs of customised Argento binding posts for loudspeakers connection|
|Monitoring||Non-intrusive DSP-based protection of the amplifier and connected loudspeakers
Instantaneous voltage & current values are permanently monitored on each channel
Disconnected loudspeaker detected
Over-temperature of the heatsink
Over-temperature of the output transistors
|Transformer||2’200VA toroidal transformer for output stages, oversized for low-noise operation
100VA separate toroidal transformer for input stages
|Power capacitors||2x 120’000uF/100V ultra-low ESR/ESL capacitors|
|Regulators||Non-regulated symmetrical power supply for the power stages
Eight local regulation stages for input/driver stages
Seven local regulation stages for the logic/display
|Display||480×272 pixels, 24bits colour, AMOLED|
|Mains operation||Selectable 100V, 115, 230V AC, 47-63Hz|
|Fuses value and location||Standby fuse (white holder): 250mA T (230V AC), 500mA T (100V AC, 115V AC)
Audio (mid power) fuse (black holder): 1.6A T (230V AC), 3.15A T (100V AC, 115V AC)
Power fuse (IEC20 holder): 16A T (230V AC), 32A T (100V AC, 115V AC)
|Power supply consumption||<1W (standby), 2200W max in operation|
|Dimensions/Weight||440 x 440 x 266mm (W x D x H), 75kg|
|Remote control||Ethernet based system control via the Android CH Control App|