Marantz 3250B Stereo Control Console

Name: Marantz 3250b
Brand: Marantz

A preamp that separates the signal from the switchgear - a service manual written for people who actually own a distortion analyzer.

Overview

The Marantz 3250B is a stereo control console. Most people would just call it a preamplifier.

Period coverage of the 3250B is thin, but some exists. HiFI-Stereo (1979, p.53) listed the 3250B alongside the 1180 DC integrated amplifier in its equipment directory. It quoted a preamplifier input sensitivity of 2.5 mV for phono and 150 mV for aux, tuner, and monitor inputs, with a signal-to-noise ratio of 92 dB (IHF "A") on the phono stage. A year later, HiFI-Stereo (1980, p.63) ran a fuller set of measurements. Phono came in at 80 dB below 2.5 mV (IHF A), and tuner and aux at 100 dB. Input impedance was 30,000, 50,000, and 100,000 ohms on phono depending on loading, and 50,000 ohms on tuner and aux. Output impedance was 500 ohms. Crosstalk was -80 dB on phono and -95 dB elsewhere. Those are respectable numbers for a control console of the period.

Going by the documentation, the 3250B is not a power amplifier. It's a control console, the switching, equalization, and level-matching hub of a system that would have fed a separate power amp. It won't drive speakers on its own. It needs a partner.