Spice – Montarbo 1002
Fig 1 is a simplified circuit of the Montarbo 1002. The bias for the 1st two transistors are two 1N4148 diodes and resistor. The load resistor at the collector is a 2.2k with 1.2mA standing current. The output drives the VAS. The output bias and thermal controller is in this stage. What is unique with this circuit are the two resistors, one at the op-amp output (2.2k) and the other taken from the amplifier’s output (39k). Both of them are connected to the center of the two 820 ohm resistors. This ensures the two transistors have a common reference point.
Fig 2 is the Transient analysis of the Montarco 1002. The amplifier is stable for a mirror image typology. Note the absence of any DC offset mechanism in the circuit. That’s one of the main advantages of using an op-amp at the front. Summary
The Montarbo 1002 is a high power amplifier for concert use. Their flagship loudspeaker system then was the modular W7. It consists of a horn loaded bass bin with two internal 15″ high power woofers. Sitting atop is the mid-high unit with a single 10″ and a horn loaded compression driver. I believe all drivers were by B&C. |
October 18, 2025Amplifiers, Electronics
