Integrated Amplifiers

The LM-34IA offers separate '8ohm' and '4ohm' transformer taps to step-down the high voltage/high impedance output of the EL34 tubes to better match the lower impedance and higher current demand of the attached loudspeaker. In reality, precious few speakers offer a fixed 4, 6 or 8ohm impedance – instead, the load swings up and down with frequency as the various reactive components of crossover and drivers kick-in.

As the LM-34IA's output impedance is still very high indeed its response is modulated by changes in speaker load, lifting with rising speaker impedance and falling with decreasing speaker impedance. While our reference B&W 800 D3 loudspeakers [HFN Oct '16] might not be the LM-34IA's likeliest partner, they still perfectly illustrate how its response will shift and change with the impedance trend of your choice of loudspeaker. The inset Graph shows the native, unloaded response of the LM-34IA [cyan trace] versus its response driving the 800 D3s via its 8ohm tap [black trace] and 4ohm tap [red trace]. Note how the inductive upswing in the 800 D3s impedance produces a big 'lift' to the midrange/presence band, and every female vocalist... PM