Hum Adjustment


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Some H.H. Scott amplifiers and tuners have a Hum Adjustment control that is designed to minimize 50/60 Hz noise on the tube heaters. The factory adjustment procedure follows:

"...This control is set to minimize hum output and has been adjusted at the factory for the tubes supplied with the amplifier. When tubes are replaced or aging occurs, readjustment may be required if noticeable hum develops. Turn this control carefully until hum is minimized. For the laboratory, use the following procedure:

A. Turn the (input) level control to zero and put a resistive load across the output terminal. Connect an oscilloscope in parallel with the load.

B. Adjust the hum control for minimum output on the oscilloscope."

You can also perform the Hum adjustment using your hears: 

Remove all input cables and leave only the speakers connected. On an integrated amp, set the Input Selector switch to phono and turn up the bass while turning down the treble.

Use the Stereo Selector switch to choose the channel under adjustment, i.e.., LEFT INPUT. Adjust that channel's HUM Adjustment for the faintest hum. Repeat for RIGHT Channel.


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