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Old 4th September 2010, 05:08 PM   #1
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Default dual lm3886 41hz supply?

Ok I have a 300va dual 21vac transformer. I also have a chipamp 3886 kit, and a 41hz amp something or another (takes 20-35volt).

Is is possible to make an external power supply and run both of these from it (not at the same time)?

From the looks, they need to be in series with ct for the gainclone, and parallel for the tripath. I wish there was some magical regulator that would invert 1 channel of the gain clone powersupply.
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Old 4th September 2010, 05:14 PM   #2
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Whats a 41hz amp

The 21vac tranny will give around -/+30 volts DC after rectification etc. That's fine for the 3886 I would have thought.

You can still use the +30 volt DC rail to feed something else if that's what you mean.
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Old 4th September 2010, 05:35 PM   #3
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Its an amp4 so its rated for 20-30volt. I could use just 1 half of the 3886 kits power supply. But wouldnt that mean using half the va of the transformer so half the regulation? The amp4 is recommended at 100va so it might work.
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Old 4th September 2010, 05:58 PM   #4
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wait a minute, couldnt i just make a full wave ct rectifier for the 41hz? that would half the voltage and double the current.
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Old 4th September 2010, 06:00 PM   #5
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A 300va tranny with 2 of 21vac windings is rated at 7 amps per winding. The regulat ion should be the same percentage figure quoted for the tranny I would have thought.

And yes 21 vac at 7 amps is approx 150 va... half the total
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Old 4th September 2010, 06:04 PM   #6
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Quote:
Originally Posted by nightanole View Post
wait a minute, couldnt i just make a full wave ct rectifier for the 41hz? that would half the voltage and double the current.
Draw it so we know what you mean. To get the full VA rating of the tranny at 21 vac would need both windings to be used... so that means with them in parallel... and for the CT gainclone they are in series.
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Old 4th September 2010, 06:18 PM   #7
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http://a.imageshack.us/img691/5422/psrev3schtest.gif

Eh that this idea would not work if the pgnd's are connected. They are not on the power supply pcb, but they are on the lm3886 modules (makes the ground). So i could install a switch i guess. If i dont then i would have just grounded out both supplies

Last edited by nightanole; 4th September 2010 at 06:25 PM.
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Old 4th September 2010, 06:30 PM   #8
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Understand you now... yes that looks OK.

If you use the same PSU for a CT gainclone you would have to be careful how you implement the connections... different plug/sockets maybe to connect each amp, only one at a time of course, to avoid shorting the rails out.
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Old 4th September 2010, 06:31 PM   #9
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Do you really need that current capability though ? much simpler if not.
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Old 4th September 2010, 07:12 PM   #10
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This is a last ditch scenario if it cant fit the 300va transformer in. If i cant the next size down is 100va, which i might have to stack to of those to get to fit too.
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