Sonic Impact 5066 Amplifier Upgrade - Page 3 of 10The stock amp is great (especially for the extremely inexpensive price!) but it can be improved through several modifications. CaseThe stock amplifier is housed in a cool modern, but cheap-feeling, light plastic case. Since most digital amplifiers are susceptible to RFI & EMI, mounting it in a metal case will help. Mounting the amp in a nice-looking metal enclosure will also make it look "high-end". The "si 5" logo looked cool on the case but one may also want to add one's own logo for the new case's exterior. Volume Control & Power SwitchThe stock amp uses a very cheap combination potentiometer/switch combination wired to the amplifier board with a suspect "ribbon cable". The on/off power functions and the volume control should be handled by two separate devices; an SPST switch for the power and a better quality potentiometer for the volume control. To keep the "high-end" theme going, a nice knob should be installed on the volume control. Source InputThe SI 5066 board only accepts analog inputs. (I wish it accepted digital inputs to avoid a A/D conversion.) These are received via a 3.5 mm female PCB-mounted stereo jack on the stock unit. This should be replaced with separate female, panel-mounted, RCA jacks to accept the more common interconnects found on most audio equipment. Theses RCA connectors should also be wired directly to the potentiometer. Both the jacks and the connecting wire should be of higher quality. Power inputThe SI 5066 has two modes of power; (8) AA 1.5 VDC batteries in series (for 12 VDC) or a 2.5 mm female PCB-mounted jack (center tip-positive) to accept a DC source from a 120 VAC-to-12 VDC wall wart or 12 VDC power supply. IMPORTANT NOTE: I quit using my existing Radio Shack wall wart (#273-1779) after I measured the actual voltage output at 15 VDC instead of 12 VDC! The Tripath TA2024 datasheet says the maximum rated supply voltage should not exceed 13.2 VDC. This AC/DC converter is unregulated and not very accurate. Make sure that the 12 VDC power supply you use actually is 12 VDC output! Of course, the ideal power supply (cleanest supply and least induced noise) is a sealed lead acid (SLA) 12 VDC battery. So, I also chose to add a 2.5 mm locking, female, panel-mounted 12 VDC jack to the amp. This allows me to connect to a 12 VDC SLA battery via a cable with appropriate connectors for the battery's + and - terminals on one end and the 2.5 mm male locking plug on the other end. Hint: It's nice to use a small trickle charger on the battery to keep it at maximum playing power. I kept the main power switch connected to the I 5066, but I also added a separate power switch the either supplies 12 VDC from the SLA battery or lets the charger trickle charge the SLA battery in the "off" position. Speaker OutputThe stock amp uses horribly cheap (and small!) spring clips for the speaker outputs. These should be upgraded with high quality panel-mounted binding posts. Power IndicatorThe existing power indicator is a red LED that is mounted closely to the amp's PC board. In order to panel mount the indicator it must be relocated or, better yet, replaced by other LEDs! I chose to mount a green LED to show when the amp has power. I also installed a green LED on the main power switch to show when the battery is supplying power and an orange LED to show when the battery is being charged. Mounting FeetThe stock amp uses tiny rubber dots as its mounting feet. For vibration isolation these should be replaced with isolation pods or spikes. I modified some rubber door stop tips for use as feet.
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