CH Precision - A1.5 - 2 Kanal Endstufe

Modularity:

The A1.5 power amplifier has been developed with modularity in mind. It can be equipped with a single analog input board in case the A1.5 is used as a single channel but a second analog input board can also be fitted from factory for stereo operation. This modularity ensures the following operation modes:

• stereo mode
• single channel (mono) mode
• bi-amplification modes, both passive and active
• bridge mode

Changing the A1.5 operating mode is easy and can be done on-the-fly from the front panel user interface and our tablet app. Only the available options are visible depending of the hardware configuration.

Power Supply:

The central power supply is taking most of the internal space of the chassis. The huge 1'700VA transformer is mounted on silent-blocks to avoid at maximum its vibrations to be fed-back into the sensitive part of the circuitry.

It is shielded both with a magnetic screen and an electrostatic one. The transformer plate is also secured for transportation. For optimum thermal performances, the output stage diode bridges are mounted directly onto the amplifiers heatsinks and are of hyper-fast soft-recovery type.

The A1.5 features extremely low-ESR filtering capacitors ensuring tremendeous current capabilities for controlling the most demanding speakers.

Analog stages:

All analog stages inside the A1.5 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.

Gain:

A gain range of 24dB - with steps of 0.5dB - is embedded into 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 rooms with low-sensitvity loudspeakers.

This gain adjustment can also be useful with multi-amplified loudspeakers to fine-tune the various drivers level.

Output stage feedback:

The A1.5 output stage features the renown CH loudspeaker matching circuitry. The ratio between the global and local feedbacks is adjustable on-the-fly from the front panel user interface or through our tablet app. Like the A1, the A1.5 has 6 feedback ratio positions. But finer tuning is available at low global feedback, so global/local feedback ratios of 0/100, 10/90, 20/80, 40/60, 70/30 and 100/0 are available.

A different feedback ratio can be set for each channel in bi-amplification mode allowing an even finer tuning of the connected loudspeaker.

ExactBias:

Keeping the output stage bias current constant ensures the amplifier to remain as linear as possible. The bias current is highly sensitive to temperature changes. ExactBias has been designed to maintain the output stage bias current constant, by monitoring both the amplifier heatsink and output transistors temperatures, irrespectively of the musical program and room temperature.

In terms of performance, the A1.5 class-AB designed with ExactBias technology outperforms a pure class-A design with usual bias compensation.

Option board:

Control: Ethernet control board
General control board. Provides USB based firmware update and external ethernet control.
Factory built-in

Analog-Buf: 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 amplifier like the M1.1 or another A1.5.
Can be factory ordered for Left or Right channel.
Factory built-in (1x), second board is needed for stereo operation
CHF 1'700.- TTC mono

Analog inputs

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

Amplification stage	Ultra-low noise full discrete class AB design 5 pairs of complementary output transistors
Output Power	2x 150W / 8Ω, 2x 275W / 4Ω, 2x 450W / 2Ω in stereo and bi-amp modes 1x 275W / 4Ω, 1x 450W / 2Ω, 1x 700W / 1Ω in monaural mode 1x 550W / 8Ω, 1x 800W / 4Ω, 1x 1200W / 2Ω in bridge mode
Bias	Patent-pending bias circuitry for constant bias operation
Feedback	Unique user programmable local/global feedback ratio of the amplification stage
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

Analog outputs

Binding posts	Two pairs of Argento binding posts for loudspeakers connection
Monitoring	Non-intrusive DSP-based protection of the amplifier Instantaneous voltage & current values are permanently monitored for each channel
Protections	Short-circuit protected Disconnected loudspeaker detected Over-temperature of the heatsink Over-temperature of the output transistors

Power supply

Transformer	1'700VA single transformer, oversized for low-noise operation
Power capacitors	2x 82'000uF/63V capacitors with ultra-low ESR/ESL
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

General

Display	480x272 pixels, 24bits color, AMOLED
Mains operation	Selectable 100V, 115, 230V AC, 47-63Hz
Fuses value and location	Standby fuse (diameter 5mm): 250mA T (230V AC), 500mA T (100V AC, 115V AC)  Power fuse (diameter 6.3mm): 10A T (230V AC), 20A T (100V AC, 115V AC)
Power supply consumption	<1W (standby), 1800W max in operation
Remote control	Ethernet based system control via the Android CH Control App

Einige unserer Auszeichnungen

Optionale monaurale Analogeingangskarte für Hardware

• Optionskarte für Stereo- und aktive Anwendungen erforderlich (nur die benötigten Eingänge kaufen)
• XLR-, Cinch- und 75-Ohm-BNC-Eingänge
• Ausgewogener Durchgang für Verkettungsverstärker in Multi-Amp-Systemen
• Bestehende A1-Verstärker können werkseitig auf die vollständige A1.5-Spezifikation aufgerüstet werden