First One M and First One L  mosfet power amplifier module
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Hi guys :wave2:
Finally the First One mosfet amplifier module is ready to go to travel the world. It has been a long testing and measuring period, just to make me sure the module is good enough to meet your expectations. First One Medium and First One Large are plug & play class AB, current feedback type mosfet amplifier modules, ready made to the last detail, calibrated and tested. Technical specifications First One Medium (Large) module: Maximal power (20 Hz  20 kHz, THD 0,1 %) 160 (300) Wrms/8 Ohm 250 (600) Wrms/4 Ohm Maximal power (20 Hz  20 kHz, THD 0,05 %) 150 (280) Wrms/8 Ohm 230 (560) Wrms/4 Ohm THD (100 Wrms/4 Ohm, 10 kHz) 0,004 % THD (100 Wrms/4 Ohm, 100 Hz) 0,0034 % IMD (80 Vpp/4 Ohm, 19+20 kHz) 0,003 % THD (1 Wrms/8 Ohm, 1 kHz) < 0,0016 % Frequency response (3 dB) DC  1 MHz Slewrate 240 (300) V/us Signal to noise ratio > 110 dB Voltage gain +27,5 dB Input impedance 10 kOhm Output impedance (20 Hz  20 kHz) < 10 mOhm Damping factor (100 Wrms/4 Ohm, 20 kHz) > 2000, measured on PCB output terminals Output DC offset < +/10 mV Supply voltage +/40 V to +/63 V (+/45 to +/85 V) Size  dimensions (W x D x H) 100 (160) mm x 50 mm x 40 (50) mm First One Medium module price: 110,00 EUR First One Large module price: 220,00 EUR Orders & Support welcome: First One Shop esl@siol.net First One User Manual Best regards, Lazy Cat :cheers: https://scontent.flju21.fna.fbcdn.n...43&oe=5917536D https://scontent.flju21.fna.fbcdn.n...a8&oe=5906868A 
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Plots of the First One amplifier, 40 ppm THD 10 kHz at 100 Wrms/4 Ohm
1. Input signal 10 kHz 2. Output signal 20 Vrms, no load 3. Output signal 20 Vrms on 4 Ohm 
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Plots of the First One amplifier, 34 ppm THD 100Hz at 100 Wrms/4 Ohm
1. Input signal 100 Hz 2. Output signal 20 Vrms, no load 3. Output signal 20 Vrms on 4 Ohm 
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Few square waves and rise time measurements of the First One amplifier module.
1. 50 kHz 2. 200 kHz 3. mid signal level rise time 4. high signal level rise time Calculation from picture 4, 60 V (90% Vpp) in 250 ns results in: Slew Rate of 240 V/us 
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Measurement showing the First One's behaviour at 2,77 MHz sine signal.
We can see 0,9 Vpp input sine signal present on CH2 and 14,3 Vpp output signal on CH1 Calculations from the plot: 1. Voltage gain is x15,89 or +24 dB at 2,77 MHz 2. Linear voltage gain of the First One is +27 dB, meaning that 2,77 MHz is exactly 3 dB gain point 3. Phase shift at 2,77 MHz is 76° 4. 10 Ohm zobel load (Zr+Zc) dissipates 2,4 Wrms at 2,77 MHz 
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The task was to find a proper output inductor and test the amp to all possible values of capacitance as a load, to be sure there are no chances for the amp to oscillate, no matter what kind of speaker cable is connected to its output terminals.
Lowest possible output serial inductance to fulfill upper demands is 0,2 uH, very practical small size still to be located on PCB. Few pictures attached as follows: 1. Plot of 10 kHz/20 Vpp square waves on 6 Ohm +1 uF load. Upper trace amp's output in front of inductor, lower trace behind the 0,2 uH inductor. 2. 32 ppm THD10k spectrum 20 Vrms on 6 Ohm load (60 Wrms/6 Ohm) 3. 24 ppm THD10k spectrum 20 Vrms on 6 Ohm + 1 uF (90 Wrms/4,3 Ohm impedance). We can see that 1 uF loading capacitor completely filtered out third harmonic and elevated the second for 5 dB. The whole THD droped for 8 ppm but since third harmonic is also present in the input signal, this THD reduction is actually bad, not preserving the input signal integrity. 4. 0,2 uH output inductor and 1 uF loading capacitor in series with on/off switch 5. Complete measuring assembly 
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As a conclusion of the measurements here's 19+20 kHz intermodulation distortion measurement
1. 30 ppm THD19+20k 80 Vpp on 4 Ohm load 2. Setup 
Hi LC,
Interested for a pair. Thanks, James 
Thanks chunek, you're the first one ;)

Class AB/D?

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