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Old 5th December 2002, 09:12 PM   #1
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Default Switching power supply

Hi guys,

Can I use a switching power supply with a Zen amp? Is there any problem as long as it delivers the requested volts?

Thomas B
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Old 5th December 2002, 09:13 PM   #2
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Why not?
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Old 6th December 2002, 01:15 AM   #3
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Just check the output noise under load with a 'scope. All SMPS's will have *some* residual noise (as do linears) so a little extra output filtering caps wouldn't go astray perhaps, depending on just how good the unit is. Use low esr types that specify the esr at high frequencies. When you get the thing going, please publish the great results and benefits so that the anti-SMPS crowd can put you straight.
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Old 6th December 2002, 07:16 PM   #4
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As long as you don't mind the dismal sound...Make sure you do listen to a linear supply in comparison. Then you may decide to just keep the heatsink from that photo.


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Old 6th December 2002, 08:42 PM   #5
joensd is offline joensd  Germany
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A common practice is to follow the switcher with a low drop linear regulator (for example LT108x) which would cause minimal extra dissipation.
This should get you the best performance.
But IŽd try it without first.
Let us know how it works out.

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Old 6th December 2002, 08:49 PM   #6
haldor is offline haldor  United States
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That didn't take long.

I for one would like to hear a really refined amp built with a high quality switcher, just to see how well it works. Rectifier noise in a linear supply can be nasty, yet we seem to be able to handle it without any problem. No reason I can think of that we shouldn't also be able to handle residual switching noise as well. I would pay attention to the physical location of the power supply relative to the amps input wiring and circuitry to avoid inducing noise in low level signals.

Also, I would not just blindly add a lot of external capacitance to any supply, check the manufacturer's literature for recommendations on how to reduce ripple and noise from the output. I'll bet they have an application note on using their products in specialised apps.

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Old 6th December 2002, 08:52 PM   #7
JBL is offline JBL  Canada
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The switching frequency of most smps is very high. I would pay more attention to the transient respons. Altought that in class A amp the power is fluctuating alot less than in a class B so it may be better their than linear ps.
Jonathan Blanchard (J.Bl.)
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Old 6th December 2002, 09:22 PM   #8
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JBL, the switching frequency in most SMPS is not very high (well it is all relative) compared to the audio band. The feedback loop typically ends up in the low KHz range which is unlikely to be optimal given that the potential mess it can cause in that important section of the audio band.

High frequency switchers are more expensive and difficult to produce.

I would be very interested in trying out the switcher shown, perhaps with some added LC filtering on the output (both lines).

Another "problem" you might have with the supply is that you will likely not have -0+ rails, only 0+ rails. This means you have to consider alternatives to referencing the audio signal to ground.

Another issue with SMPS is that they typically have relatively poor performance at low power output. Looks like the unit in question is a 40A unit. You will be unlikely to draw anywhere near that with your amp. If I knew something about the topology of the SMPS, I might be able to suggest ways of setting it up to be good at lower current (unless it is a resonant mode device -- in which case I won't even bother trying). Potential remedies is added inductance in primary or secondary, increase switching frequency etc.

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Old 6th December 2002, 09:33 PM   #9
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Default it's interesting to look at your diodes

for creating some of the mess also -- just take a look on your scope.
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Old 6th December 2002, 09:36 PM   #10
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You can check with www.euroteksrl.it and look around. I was considering using two single phase 20A/24V units to power two 25W Balanced Zen monoblocks.

Thomas B
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