ABSTRACT
This chapter describes the level indication circuitry, the input selection system, and the power supply. The Log Law Level LED, or LLLL, was thought up to help with the correct setup of phono input with switched gain options. A single LED level driven by a comparator typically goes from fully off to fully on for less than a 2 dB change in level when measuring actual music rather than steady sinewaves. The preamplifier internal level is correct when the LED is on about 50" of the time. The input circuit boards carry the input and output connectors plus the relays that select which input is in use. The four line-level inputs can work in either unbalanced or balanced mode, though of course balanced mode is strongly recommended because it rejects electrical noise on the ground paths. The front panel board carries the input select switch, the LLLL source select switch, the three mode switches, and the power and LLL LEDs.
