Minimum Bias Current for Zen?

Matt MacBeth · 21st May 2002, 03:06 PM

Mendelson's has a 38V 1.6A supply for $4. Is 1.6A and 38V enough for a Zen (monoblock)?

Does a current source still give the same advantages with a regulated switching supply, or is a current source not needed (beneficial)?

Thanks!
Matt

PassFan · 21st May 2002, 04:00 PM

The original Zen article calls for an Avel 4040 which is 25v x 25v at 230 va. That secondary is good for around 4.6 amps. If you multiply your sec. volts x sec amps your looking at around 60 va. This is only 1/4 of what is called for and seems to be pushing it a lot. It's your call but be prepared to lose your transformer as it will attempt to supply the circuit with whatever it demands current wise. Nelson over rates power supplies though I think he only doubles or triples them. Your only looking at around 60.00 bucks for the Avel and I think the're still in business. Good Luck

PassFan · 21st May 2002, 04:16 PM

After further checking the supply for Nelsons modified Zen is 30volts at 5 amps this is a little closer at 150va. Nelson states that he actually preffered the PI filter over the regulated supply though can't explain why. As for your current source question we'll have to wait for someone else to answer that and they'll probably be checking in soon. Good Luck.

paulb · 21st May 2002, 07:48 PM

Careful with confusing AC VA with DC watts. Typically you'll need a VA rating of twice the DC power required. So for 30VDC at 5 amps, figure on a transformer of 300VA.

Matt MacBeth · 23rd May 2002, 07:41 PM

So, this supply may be a little too weak? (It's a switching power supply, not just a transformer).

Is the min. bias current 2A? (I haven't seen anything lower) It seems that a lower bias (1.6A) will still work, but with a little more distortion.

Nelson Pass · 23rd May 2002, 08:04 PM

Yeah, it's a little weak, although you can make 1.6
amps work, particularly if it's constant, but you'll
be running the supply at its rating, which is not usually
a good idea.

One of the things about regulated switching supplies supplies
is that when they say 1.6 amp, you don't want to imagine
1.7 amps for even a fraction of a second, whereas good
old analog (and unregulated) supplies will deliver more
poop for short durations without a fuss.

21st May 2002, 03:06 PM	#1
Matt MacBeth diyAudio Member Join Date: May 2002 Location: Lexington, KY	Minimum Bias Current for Zen? Mendelson's has a 38V 1.6A supply for $4. Is 1.6A and 38V enough for a Zen (monoblock)? Does a current source still give the same advantages with a regulated switching supply, or is a current source not needed (beneficial)? Thanks! Matt

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21st May 2002, 04:00 PM	#2
PassFan diyAudio Member Join Date: Aug 2001 Location: Central FL	The original Zen article calls for an Avel 4040 which is 25v x 25v at 230 va. That secondary is good for around 4.6 amps. If you multiply your sec. volts x sec amps your looking at around 60 va. This is only 1/4 of what is called for and seems to be pushing it a lot. It's your call but be prepared to lose your transformer as it will attempt to supply the circuit with whatever it demands current wise. Nelson over rates power supplies though I think he only doubles or triples them. Your only looking at around 60.00 bucks for the Avel and I think the're still in business. Good Luck

21st May 2002, 04:16 PM	#3
PassFan diyAudio Member Join Date: Aug 2001 Location: Central FL	After further checking the supply for Nelsons modified Zen is 30volts at 5 amps this is a little closer at 150va. Nelson states that he actually preffered the PI filter over the regulated supply though can't explain why. As for your current source question we'll have to wait for someone else to answer that and they'll probably be checking in soon. Good Luck.

21st May 2002, 07:48 PM	#4
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	Careful with confusing AC VA with DC watts. Typically you'll need a VA rating of twice the DC power required. So for 30VDC at 5 amps, figure on a transformer of 300VA.

23rd May 2002, 07:41 PM	#5
Matt MacBeth diyAudio Member Join Date: May 2002 Location: Lexington, KY	So, this supply may be a little too weak? (It's a switching power supply, not just a transformer). Is the min. bias current 2A? (I haven't seen anything lower) It seems that a lower bias (1.6A) will still work, but with a little more distortion.

23rd May 2002, 08:04 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	Yeah, it's a little weak, although you can make 1.6 amps work, particularly if it's constant, but you'll be running the supply at its rating, which is not usually a good idea. One of the things about regulated switching supplies supplies is that when they say 1.6 amp, you don't want to imagine 1.7 amps for even a fraction of a second, whereas good old analog (and unregulated) supplies will deliver more poop for short durations without a fuss.