bias current: Zen vs. Aleph

Peter Huang · 29th July 2003, 02:03 AM

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?

jh6you · 29th July 2003, 02:38 AM

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.

Nelson Pass · 29th July 2003, 02:43 AM

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.

Peter Huang · 29th July 2003, 09:38 AM

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.

vpharris · 29th July 2003, 08:45 PM

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.

Nelson Pass · 30th July 2003, 06:35 PM

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.

Peter Huang · 4th August 2003, 06:39 AM

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.

29th July 2003, 02:03 AM	#1
Peter Huang diyAudio Member Join Date: Jul 2002 Location: Taiwan	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?

29th July 2003, 09:38 AM	#4
Peter Huang diyAudio Member Join Date: Jul 2002 Location: Taiwan	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.

29th July 2003, 08:45 PM	#5
vpharris diyAudio Member Join Date: Dec 2001 Location: Philadelphia	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. __________________ Vince Harris

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29th July 2003, 02:38 AM	#2
jh6you Account Disabled Join Date: Aug 2002 Location: Near to the Pacific Ocean	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.

29th July 2003, 02:43 AM	#3
Nelson Pass The one and only Join Date: Mar 2001	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.

4th August 2003, 06:39 AM	#7
Peter Huang diyAudio Member Join Date: Jul 2002 Location: Taiwan	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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