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Old 14th January 2005, 11:12 AM   #581
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Netlist
I looked at the wuffwaff spreadsheet and would like to verify one of its calculations. When you put in a value for bias say 8A, is the spreadsheet calculating it as only only one half of the amp? IOW, only two of the four mosfets on the hifizen board will carry the burden of these 8A?
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Old 14th January 2005, 11:45 AM   #582
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Next to the bias cel the explanation sounds:
"total bias for one channel being one monoblock"

So this would be the four mosfets in your case.

/Hugo
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Old 14th January 2005, 12:52 PM   #583
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Agreed. So in the case above where 8 amps are input for bias with 4 mosfets to carry the load, the bias in each FET is only 2A correct?
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Old 14th January 2005, 02:48 PM   #584
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Yes but watch cel B22 and his comment.
Depending on the supply voltage you can easily overbias a mosfet.
Better put a couple more to stay in the SOA.

/Hugo
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Old 14th January 2005, 11:20 PM   #585
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Quote:
Originally posted by Netlist
We hided them a bit too much to be useful but its all there.
No kidding!

BTW, past sense of hide is hid.
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Old 22nd January 2005, 10:56 PM   #586
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I plan on using a regulated supply, so wouldn't say 700 VA be enough?

I'm not sure how much would be gained with a regulated supply. At least regulation with semiconductors. The project would get rather complex. Wouldn't Mr. Pass be using regulation if it was worthwhile? Also, I thought the circuit design took care of the problems associated with small variations in the power supply.
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Old 23rd January 2005, 01:03 AM   #587
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Regulation is fine with me, as long as it is followed by a
big steaming pile of capacitor to ground afterword - about
the same amount that an unregulated supply would have.

/pass/: You can never be too rich or have too much capacitance.
Too thin is out, as it is apparently possible.
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Old 23rd January 2005, 05:14 AM   #588
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I have long advocated a regulated supply followed by capacitance, preferably lots of it. Film caps if you can afford it. Certain commercial manufacturers use regulation with no capacitance and sound damned good. But then someone does something rude--like, say, hit a drum--and the sound drifts away on a thin whisp of a breeze. This leads people to say that regulated supplies have no dynamics. This should be recognized as a partial truth. The amended version should say that regulated supplies with no capacitors have no dynamics.
I will freely grant that regulating the main power buss in an amplifier can be an intimidating task, but there's no excuse for not regulating the rails in preamps and such. I attribute the glorious sound I get from my main tube amps to the power supply, not the circuitry (which is really fairly normal). I regulate the first and second stages, and the bias supply. All separately. That's another nifty trick if your circuit and budget allow for it. Keeps one stage from modulating the others via the rail. Marvelous, simply marvelous.
Do not, repeat, do not regulate the front end of an Aleph or Aleph-X separately from the output stage. Regulate the whole thing or not at all. You have to consider each circuit individually as to whether it can be broken up into separate rails.

Grey
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Old 24th January 2005, 10:59 AM   #589
sippo is offline sippo  Germany
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Hy,

i have an Aleph 4 and would like to use the case for an Aleph-X. It runs normally at about 57 degrees, heatsinks are 21" wide, 14" high and 1,5" thick per side. What max. output power can i drive save in this case. I look more for voltage swing but current, so what values would you recommend.

Thanks in advance

Frank
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Old 24th January 2005, 06:00 PM   #590
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I moved the 'calculation' here: Calculating the AlephX

/Hugo
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