Audio Research Reference 330M
Image source — © Audio Research
Model name
Reference 330M
Input sensitivity (mV)
N/A
Input impedance (balanced) (Ω)
N/A
Input impedance (single-ended) (Ω)
N/A
Output impedance (balanced) (Ω)
N/A
Output impedance (single-ended) (Ω)
N/A
Max current (A)
N/A
Output power (8Ω) (W)
330
Output power (4Ω) (W)
330
Gain (dBu)
N/A
Frequency response low +/- 3dB (Hz)
N/A
Frequency response high +/- 3dB (Hz)
N/A
Signal to Noise Ratio (dB)
N/A
Total Harmonic Distortion + Noise (0% global feedback) (%)
N/A
Total Harmonic Distortion + Noise (100% global feedback) (%)
N/A
Max power consumption (W)
N/A
Damping factor
N/A
Dimensions (mm)
N/A
Weight (kg)
46
Official link
The Audio Research Reference 750 SEL is a development of the well-known Reference 600 SEL model. The amplifiers use a very serious set of lamps - 16 x KT150; 1 x 6550WE; 1 x 6H30; 2 x KT150 Driver; 1 x 6H30. The company promises amazing linearity and musicality, as well as the ability to handle any loudspeaker - the claimed 750 watts (with peaks up to 850 watts) of power are provided at low speaker resistance from 4 to 16 ohms.
The amplifier circuit with automatic bias current adjustment allows you to install them instead of the KT-120 supplied with the original version, without additional modifications. In fact, it will be possible to distinguish between both versions only by the characteristic appearance of the KT-150 lamps and by the sticker on the back panel of the device. The output power also remained unchanged at 75 watts per channel.
The amplifier uses a pair of 6H30 lamps at the input and four KT150 lamps at the output. In addition to the KT 150, the amplifier can work with other lamp options, including the 6550, KT88, and KT120. A fan is built into the protective cover to cool them. The power supply unit uses a high-power power transformer with high-capacity capacitors, providing "extremely high current for transient peaks and intense dynamics, as well as amazing depth and bass power."