bias current: Zen vs. Aleph
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 29th July 2003, 01:03 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, 01:38 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, 01:43 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.
 29th July 2003, 08:38 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, 07:45 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
Nelson Pass
The one and only

Join Date: Mar 2001
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.

 4th August 2003, 05:39 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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