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Class D Switching Power Amplifiers and Power D/A conversion 

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10th September 2014, 10:12 PM  #1 
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Join Date: Sep 2011

LJM Gain L25D Gain Help
Just noticed the gain on L25D modules is 40 volt. My Rotel units are 27.2db. Calculating that is:
Rotel:22.908677 Voltage Ratio Gain 27.2db Gain L25D: 40 Voltage Ratio Gain 32db Gain. LJM lists the L15D as a 36db gain. This seems to be a problem causing full power draw of my 1000w Power Supply at 15db from full power. Is there a method to change the gain on L25D's? Hopefully I can make it adjustable for my different pre/pro's. Thank you! Last edited by mstang1988; 10th September 2014 at 10:51 PM. 
11th September 2014, 01:25 AM  #2  
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Quote:
determines the voltage gain of IRAUDAMP7S. ( see MY DESIGN L20D IRS2092+IRFI4020H 200W8R for resistor numbers ) Cheers , Rens
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11th September 2014, 03:41 AM  #3  
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Parameters: Supply Voltage: DC +60V to +80V, the recommended voltage +70V Output power: 250W 8ohm, 350W 4ohm Voltage Gain: 40 Input sensitivity: 1.6V Output current = 14A of the (25C), 10A (85C) Noise Residual Noise: 200 μV (22 Hz  20kHz, AES17 the filter Selfregime of the oscillating frequency) THD + N, 100W: 0.008% 1kHz, Singlechannel driven Total Idle Power Consumption 7W No input the signal The Channel Efficiency 90% Singlechannel driven Power=Voltage^2/Load Resistance from what I can find So if the ramp does the rated 350 watt RMS at 4 ohm and 250 at 8ohm I get: SQRT(1400)=37.42v SQRT(1500)=44.73v Voltage Gain = 20*LOG(Vout/Vin) Voltage Gain = 20*LOG(37.42/1.6)=27.38 Voltage Gain = 20*LOG(44.73/1.6)=28.94 However if I look at the listed voltage gain from above it says 40. In addition when I put it in a calculating program of voltage gain to DB it gives the original converted numbers I posted. Am I missing something? 

11th September 2014, 04:26 AM  #4  
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11th September 2014, 05:01 AM  #5  
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I think you're pushing the current limits of the A1000SMPS ( see attachment ) Can you do an impedance measurement of your speakers ? just download REW and follow instructions. take the minimum impedance and calculate the current at max RMS output and see if this fits in the current limit of the A1000SMPS . I use this wonderful PSU for years now to supply 5 x L15D's at +/ 50Volts and it's (almost) impossible to trip the current limiter , but my speakers are all above 8 ohms . with the above impedance you could calculate a gain factor which prevents the current limiter to trip . Good luck ! Cheers , Rens
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11th September 2014, 05:14 AM  #6  
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11th September 2014, 07:54 AM  #7  
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Cheers , Rens
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