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Old 29th July 2003, 01:03 AM   #1
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Default bias current: Zen vs. Aleph

Zen V4 has only single stage, about 2A biased.
Aleph5 (60W/ch) has three stages biased with 0.5A per stage.
Aleph4 (100W/ch) has six stages biased with 0.4A per stage.
Aleph3 (30W/ch) has two stages biased with 1A per stage.
Aleph2 (100W/ch) has six stages biased with 0.5A per stage.
Aleph1.2 (200W/ch) has 12 stages biased with 0.33A per stage.

For Alephs, the bias current for each stage is lower.
We know the benefits of higher bias current.
What do you think?
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Old 29th July 2003, 01:38 AM   #2
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As far as I understand, the interest is in the total bias current at the output node (speaker terminal), not in each current through each transistor.

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Old 29th July 2003, 01:43 AM   #3
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That would be correct. Also, the Alephs benefited not only
from the Aleph current source, which can easily be used to
reduce the bias current needed.

The other thing to consider is that the Zens, having less loop
gain, generally required some more bias to remain as linear
at the output as an Aleph.
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Old 29th July 2003, 08:38 AM   #4
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Default Operating Point

As I known, the operating point of the mosfet would be varied with the bias current and Vds. The total bias current for parallel stages depends on the power rating.

How to determine the bias current for each stage? What are the decision variables? It seems not be mentioned in the articles of Zens and Alephs.

Thanks.
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Old 29th July 2003, 07:45 PM   #5
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Peter:

For Nelson's commercial offerings (the alephs), he tends to try to limit dissipation to about 25W per device. If you look at the rail voltages and those bias currents, I think that you would find the dissipation to be similar among the Aleph designs.

On the zen, he was willing to make it higher, since the same safety factor isn't required for home-built equipment as commercial stuff.
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Old 30th July 2003, 05:35 PM   #6
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Default Re: Operating Point

Quote:
Originally posted by Peter Huang
As I known, the operating point of the mosfet would be varied with the bias current and Vds. The total bias current for parallel stages depends on the power rating.

How to determine the bias current for each stage? What are the decision variables? It seems not be mentioned in the articles of Zens and Alephs.
We run the bias current as high as we dare. Usually the
determining factor is that we don't want consumers injuring
themselves on the heat sinks.
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Old 4th August 2003, 05:39 AM   #7
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Thanks to Nelson Pass and all the others.

Because of simple circuit and high bias current, I believe the sound of Zens must be extraordinary.
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