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30th January 2004, 04:04 PM  #11 
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Location: Auburn, CA, USA


30th January 2004, 07:04 PM  #12 
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Join Date: Aug 2001
Location: Ingolstadt Germany

David,
just up the bias and the amp will double into lower impedances (untill again the current limit is reached). You can even test 60A of bias without anything getting hot and thanks for all the compliments!!!!! william P.S. I´m thankfull for any constructive critisism or ideas how to improve AXE1. I will look at these and when there´s enough new stuff there will be an AXE2.........
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30th January 2004, 07:46 PM  #13 
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Location: Michigan

1 or 2 decimal places in B16 and B75
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Rodd Yamashita 
31st January 2004, 02:39 AM  #14 
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Location: North of Boston

Total bias question for one channel
If total bias is 4 amps for one channel. There are 4 outputs. One amp per output. The current out of the power supply shoul be 2 amps from the positive rail and 2 amps from the negative rail. So total power from the transformer should be 4 times the rail voltage. Is this correct?
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MikeW 
31st January 2004, 04:25 AM  #15 
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Join Date: May 2003
Location: France

Hello,
Congratulation for your spreadsheet. I constructed, there are some months, 2 monophonic AlephX, http://www.passdiy.com/gallery/alephxp4.htm The schematic is the one of Blitz slightly modified with 24 IRFP240 MosFets. Voltage: ±31V Bias: 8A Power 200 Watts / 8 ohms With AC current gain: 50% 125 watts / 4 ohms 62 watts / 2 ohms 31 watts / 1 ohm With AC current gain: 60% 200 watts / 4 ohms 100 watts / 2ohms 50 watts / 1 ohm On the forum, Mr. Nelson Pass says that AC current gain = 69%, it is too high It is the particularity of these circuits, the power decrease if the impedance of the speakers decrease. I wonder if it is true with the XA200 of PassLabs. There is perhaps a trick. On the XA200 Owners Manual, it is written: Max Output Current: ± approx. 15 A How to have 15A with a bias of 8 or 8,5A without overshooting 69% of ac current bias? With my Renaissance 90 INFINITY speakers (87dB and very low impedance 1 to 2 ohms mini) in a large room, the DC protection circuit of my AlephX clones operate. I would need more of power on low impedance If someone has a solution!!! Best regards jl.m@tele2.fr 
31st January 2004, 06:46 AM  #16 
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Join Date: Aug 2001
Location: Ingolstadt Germany

Mike,
I´m not shure I understand your question but power from the transformer is total bias multiplied by total voltage (V+ and V). For +10V 10V and 10A this gives 20V x 10A = 200W This is the power that is constantly drawn. Jlm, there is no trick. The specs from the AX200, 160 and the Alephs are a bit confusing. The only way to get a given peak output current is to have enough bias or to up the accurrentgain. The infinity is probably one of the worst loads for the Aleph (X or not) So here I would lower the voltage to 20V and up the bias the same amount so the total dissipation stays the same for example 20V, 12A 60% gives 81 watts 8ohm 162 @4Ohm 225 @2Ohm William
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31st January 2004, 10:19 AM  #17 
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Would that be 2.5 amps or 5 amps per MOSFET?
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MikeW 
31st January 2004, 11:19 AM  #18 
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Join Date: Aug 2001
Location: Ingolstadt Germany

That would be 10A in total,
how much per fet depends on the amount of fets you use, with 4 fets it would be 5A per fet, with 8 2.5A etc. etc. william
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31st January 2004, 03:53 PM  #19 
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4 MOSFETs with 5 amps each is 10amp total bias?
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MikeW 
31st January 2004, 05:16 PM  #20 
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Join Date: Aug 2001
Location: Ingolstadt Germany

Mike,
if you take 100 1 Ohm resistors and put them all after each other (in series), then you take a power supply and put 100 Volts across the first and the last of the 100 resistors, there will flow a current of 1A through each resistor, how much is the total current now 100A? or 1A? William
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