NEW Aleph-X calculation sheet: AXE-1 - Page 2 - diyAudio
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Old 30th January 2004, 04:04 PM   #11
jam is offline jam  United States
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Old 30th January 2004, 07:04 PM   #12
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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. Im thankfull for any constructive critisism or ideas how to improve AXE-1. I will look at these and when theres enough new stuff there will be an AXE-2.........
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Old 30th January 2004, 07:46 PM   #13
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1 or 2 decimal places in B16 and B75
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Old 31st January 2004, 02:39 AM   #14
MikeW is offline MikeW  United States
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Default 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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Old 31st January 2004, 04:25 AM   #15
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Hello,

Congratulation for your spreadsheet.

I constructed, there are some months, 2 monophonic Aleph-X,

http://www.passdiy.com/gallery/alephx-p4.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 XA-200 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 Aleph-X clones operate. I would need more of power on low impedance

If someone has a solution!!!

Best regards

jl.m@tele2.fr
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Old 31st January 2004, 06:46 AM   #16
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Mike,

Im 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 AX-200, 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 ac-current-gain.

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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Old 31st January 2004, 10:19 AM   #17
MikeW is offline MikeW  United States
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Would that be 2.5 amps or 5 amps per MOSFET?
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Old 31st January 2004, 11:19 AM   #18
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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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Old 31st January 2004, 03:53 PM   #19
MikeW is offline MikeW  United States
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4 MOSFETs with 5 amps each is 10amp total bias?
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Old 31st January 2004, 05:16 PM   #20
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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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