Tube Amp Archive

Attaached is a schematic I made of the driver and concertina splitter from an old Lectrolab amp that was given to me after the last tech gave up. There is no available schematic of the amp, model S 950. The 47K resistor at the bottom was unconnected at one end, as shown. Can any one tell me: - What ...

The pot below the mid pot increases resistance to ground for the entire tone stack, thereby decreasing both its tonal effect AND the attenuation normally created by the tone stack, thus increasing signal to the volume wiper. So yes, it's a variable preamp boost. It also "flattens" the effect of the ...

In the 1960's tapped volume pots were used in many hifi circuits for the "Loudness" function, which increased bass and treble at low volume. This was/is done because humans perceive low and hi frequencies as lower intensity (vs. mids) at lower sound pressures. Google "Fletcher-Munson Curve", and "Lo...