M1 2-channel Reference Power Amplifier
Being able to truthfully and accurately reproduce today’s highest quality recordings has never been more challenging. Only when each element of the reproduction chain is able to precisely recreate the music’s time and level information can a genuine emotion be felt.
The M1, CH Precision 1 Series’ most powerful amplifier was developed with this in mind. The leading-edge technological advancements implemented on the A1 were further refined, among others is the ExactBias circuitry and a finer loudspeaker matching.
Specified at 200W RMS into 8Ω in monaural mode, 2x 200W RMS into 8Ω in bi-amplification / Stereo modes and 700W RMS into 8Ω in bridge mode, the M1 houses a dedicated 2200VA power transformer providing the amplifier output stage with ample energy to accurately and effortlessly drive the most demanding loudspeakers.
The M1 power amplifier was developped with modularity in mind. It can be equipped with a single analog input board in case the M1 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 Analog Input Board)
- Bridge mode
- Stereo mode (requires a second Analog Input Board)
Changing the M1 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 4-poles types, which ensures that the in-rush current flowing through the rectifiers to refill the capacitors is kept away from the central ground point.
All analog stages inside the M1 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 low-sensitvity 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 analog stages, the M1'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 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 secure the connected loudspeakers. No output relay have been used into this amplifier, its symetrical structure allows a smooth turn-on and turn-off of the power supply without noticeable noise.
Ethernet control board
General control board. Provides USB based firmware update and external ethernet control.
Monaural analog input buffer board
Three analog inputs - XLR, RCA and BNC - are provided on a single board. A pass-through XLR male connector allows a direct connection to another A1 amplifier.
Can be factory ordered for Left or Right channel.
Factory built-in (1x), second board is needed for stereo operation
|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
|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 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 100'000uF/100V 4-poles capacitors|
|Regulators||Non-regulated symetrical power supply for the power stages
Eight local regulation stages for input/driver stages
Seven local regulation stages for the logic/display
|Display||480x272 pixels, 24bits color, AMOLED|
|Mains operation||Selectable 100V, 115, 230V AC, 47-63Hz|
|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|