Team #3 presented their pre-amp and power amp project. The team encountered issues with bad connections that were resolved. Oscillation was observed and resolved by adding capacitors. Current draw was out of phase and resolved by adjusting a potentiometer. Testing of the power amp showed a gain of approximately 23 with a maximum undistorted voltage of 22.5 volts and loaded power of 5.5 watts. Meetings were held throughout the process and the power amp was built and tested as a group effort.

1. Team #3 Pre Amp and Power Amp Presentation

2. Team Members Faizan Mian (Pre-amp builder) Oscar Guillen (Pre-amp tester) Adam Zermane (Power Amp builder) Chris Straniero (Power Amp builder) Steve Grobelny (Power Amp tester)

3. Pre-Amp connected to Power Amplifier

4. Issues Pre-Amp Bad connection at +12 V bus. Resolved with reconnecting power Power Amp Bad connection at MJE 2955. (Clipping observed at negative region of sinusoidal function only) Resolved with reconnecting base Mutual Oscillation was observed having sausage-like appearance. Resolved by connection of 1 uF capacitor across the voltage follower in the pre amp phase Power Amp Currents drawn from +12 V and -12 V branch were out of phase Addition of 10k potentiometer in series with 5.1k ohm resistor resolved this issue by adjusting pot until equal potential was achieved Power Amp Oscillation was observed having sausage-like appearance on negative cycle of sinusoidal wave. Resolved by connection of 1 uF capacitor from +12 V (closest to source) to ground. Power Amp When voltage was increased to 18 V(in) in order to increase gain, currents again went out of phase Additional adjustments to 10k pot were necessary to adjust DC offset to 0

5. Narrative Steve, Chris, and Adam approached the power amplifier building and testing as a group effort Faizan and Oscar followed a similar approach Meetings were held: 40 for pre amp build and testing 45 for power amp build and testing 49 for joining of amps and troubleshooting 44 for discussions for presentation Chris drew up presentation with input from group

6. Pre-Amp

7. Pre-Amp Building Voltage follower was used to provide isolation. That is high input impedance and low output impedance was implemented An inverting op amp was cascaded with our voltage follower in order to provide adequate frequencies more suitable for the human ear

8. Pre-Amp Testing

9. Power Amplifier

10. Power Amp Building To simplify, we utilized a positive and negative 12 V power bus Steve was allowed to build freely as Chris stood by to feed components. Adam and Chris provided feedback as Steve designed.

11. Power Amp Testing Testing Base-Collector-Emitter configuration MJE 2955 Yellow-Red-Green wires are Base-Collector-Emitter respectively MJE 3055 Yellow-Red-Green wires are Base-Collector-Emitter respectively BD 139 Black side toward observer from left to right Emitter-Collector-Base BD 559 Flat side toward observer from left to right Collector-Base-Emitter BD 140 Black side toward observer from left to right Emitter-Collector-Base Gain Testing performed at 1000 Hz using sinusoidal function Voltage in (peak to peak) was observed to be 260 mV Voltage out (peak to peak) was observed to be 6 V Gain (Av) was calculated (Vout / Vin) to be approximately 23 Frequency Response Our power amplifier achieved a Vmax of 22.5 V undistorted with no load applied Vmax w/ (250W 10ohm) load achieved 21 V undistorted Loaded, Vrms was found to be 7.4 V . . . Power modeled was 5.5W

12. Frequency response for combined circuitry