Matariki amplifier

This project was built as a demonstrator. This amp can be demonstrated either in our Porirua electronics lab, or brought to your location to audition.

This amplifier can be ordered at a cost of $NZ 2200

Its features are:

  • Remote control volume, input selection and standby power
  • Tone controls
  • Phono input
  • Small footprint chassis
  • 15 wpc output

Also, this amplifier was constructed entirely on printed circuit boards, to enable easy re-use of the modules in subsequent projects.

Around the back

Inside

Everything is hand built and assembled (except for the green boards which are outsourced components for the remote control)

Specifications

Main Amplifier

Topology
Line-level amplifier, grounded cathode gain stage, DC-coupled
cathodyne phase inverter, push-pull EL84 output in class AB using fixed-bias ultralinear topology, global negative feedback. 360V Plate Voltage.
Valve complement
Gain stage: 1 X 6N2
Phase Inverter: 1 X 6N1
Output: 4 X EL84
Power Output (measured)
15W RMS both channels driven, 1kHz continuous, resistive load
Distortion (measured)
1.5% THD at rated power, 1kHz, resistive load
Output Impedance
4Ohm 8Ohm
Input Impedance
500 KOhms
Input Sensitivity
1v rms for rated power (2.8v p-p)
NFB
10dB
Frequency Response
10Hz – 24kHz ±1dB
6Hz – 32kHz ±3dB
-6dB at 50kHz
Power consumption
230v 50Hz 190w nominal

RIAA Phono Preamp

Sensitivity
4.5mV for rated power. MM-type cartridge only, 47KOhm load impedance
Gain
+42dB at 1KHz
Freq Response
RIAA Compliant ±1dB (15Hz–20KHz)
Topology
Cascaded dual-triode 6N2 implementing RIAA filter in NFB



Tone Control  

Topology
unity-gain cathode-follower driven baxandall tone stack with NFB
Valve complement
2 X 6N2
Tone adjustment
±12dB at 100Hz and 10 kHz