Difference between revisions of "AudioAmp380"
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** The impedance of a line input is typically around 10 kΩ | ** The impedance of a line input is typically around 10 kΩ | ||
** R1 = 10 kΩ | ** R1 = 10 kΩ | ||
| − | ** RV2 = | + | ** RV2 = 50 kΩ pot |
* RCA jack | * RCA jack | ||
Latest revision as of 20:36, 29 March 2022
Contents
Design Features
- Pre-amp plus power amp
- 50 Ohm input impedance matches Product Detector outputs
- 0-10x Gain trimmer potentiometer on preamp
- External mount gain potentiometer
- NE5534 Pre-amplifier
- LM380 2.5W Audio Power Amplifier
- 12V nominal power
- 10-22V
- Fits into standard 80x50x20mm extruded aluminum enclosure
Pre-Amplifier (NE5534)
- Low-Noise Operational Amplifiers
- Internally fixed gain of 50 (34 dB)
- Equivalent Input Noise Voltage 3.5 nV/√Hz Typ
- Unity-Gain Bandwidth 10 MHz Typ
- Common-Mode Rejection Ratio 100 dB Typ
- Wide Supply-Voltage Range ±3 V to ±20 V
- Used as single supply
Audio Power Amplifier (LM380)
- Wide Supply Voltage Range: 10V-22V
- Low Quiescent Power Drain: 0.13W (VS= 18V)
- Voltage Gain Fixed at 50 (34 dB)
- High Peak Current Capability: 1.3A
- Input Referenced to GND
- High Input Impedance: 150kΩ
- Low Distortion
- Quiescent Output Voltage is at One-Half of the Supply Voltage
Controls
- RV1 - trade-off gain/bandwidth - Tune for best sound
- RV2 - volume control (after preamp and before LM380 Amp). 1x5 header wire to external pot
Jacks
J1 - Audio In
- 50 Ohms input impedance for radio applications
- Output of Product Detector stage
- R1 = 51 Ω
- RV2 = 500 Ω pot
- Optional Line Level Input
- The impedance of a line input is typically around 10 kΩ
- R1 = 10 kΩ
- RV2 = 50 kΩ pot
- RCA jack
J2 - Audio Out
- 8 Ohm speakers
- RCA
J3 - Power
- 10V-22VDC
- 5.5mmx2.5mm DC jack
Measurements
- MHS-5200A Signal Generator
- 200 mV
- 100-10KHz
- Drives 50 Ohms
- Adjust Trimmer CCW for full gain
- With adj screw to the right side
- Benchtop Power Supply DPS3005
- 12V
- 20mA with volume control fully down
- 300mA with volume control fully up (3.6W)
Rev 2/3 Schematic
Revision History
Rev 1 Rework
Rev 1 Schematic
- (Before rework)
LM380 Equivalent Schematic
- Issues
- Pre-amp opamp has + and - reversed
- Also hooked up the feedback to the wrong input
- Replace R1 with wire jumper
- Replace C9 with wire jumper
- Remove C2
- 5 Cuts
- 4 on front
- 1 on back
- 5 jumper segments on back
- 2 nodes
- Jumpers on rear side
Rev 2
- Schematic C5 was 100uF, should be 100nF
- Fixed on prototype
- Footprint wrong on C2 (older rev 2 was ordered)
- 10uF can be fit onto the card
- Didn't have any 100uF cap to use at C9
- Used 47uF - power bypass = OK value
Rev 3
- Fixed C3 footprint already
- Fixed C5 footprint back to 0.1" small cap footprint
- Card works
Videos
- Charlie Morris ZL2CTM design
Panel Cutouts
- Panel cutout (PDF File)
