HeadBanger Headphone AmpAudio-taper pot, R1, adjusts ascribe akin into two LM386 amplifier chips. The LM386 is a low-voltage audio ability amplifier, advised to accomplish on 4V to 12V. It has an centralized 15K acknowledgment resistor amid pins 1 and 5 which would set the accretion at 20 (26dB). At this gain, the achievement babble is hardly audible, so R2/R4 is added, finer in parallel, to abate the accretion to 11 (21dB). Since the added acknowledgment is taken afterwards the achievement coupling cap, C3/C7, it additionally flattens the low end response. Baloney is bargain as well. The acknowledgment resistor allegation be AC accompanying to abstain advancing centralized biasing. C1/C5 decouple centralized bent networks to advance ability accumulation rejection. Since audio-induced ripple on the accumulation is nonlinear, this improves baloney achievement as able-bodied as abbreviation hum in AC operation. Achievement loading arrangement C4/C8, R3/R5 stabilizes amount impedance at aerial frequencies to anticipate oscillation.
The NiCd array is answerable through R6, which sets the charging current. Since the HeadBanger alone draws 10mA abandoned (25mA typical), the 12V AC adaptor voltage is absolutely about 14.7V. The array voltage during charging is about 8.4V. The 120mAH high-capacity NiCd needs about 196mAH of charging. [This is projected from the 60mAH low-cap NiCd which is speced to allegation in 14-hours at 7mA.] With the HeadBanger off, 20 to 25mA is supplied, so the high-cap array will allegation in about 10-hours. It ability booty alert that continued with the assemblage turned-on. The low-cap array would allegation in about 5-hours.
C10 reduces audio-induced ripple on the ability supply. C9 bypasses the accumulation at aerial frequencies, preventing oscillation. Note: Not apparent on the schematic is the break of the ascribe and achievement grounds. The arena affairs from P1 and R1 are affiliated alone from added area to a point on the amp lath abutting to pin 2 of IC1 and IC2.
