dual lm3886 41hz supply?

[nightanole]

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.

 

[Mooly]

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.

 

[nightanole]

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.

 

[nightanole]

wait a minute, couldnt i just make a full wave ct rectifier for the 41hz? that would half the voltage and double the current.

 

[Mooly]

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

 

[Mooly]

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.

 

[nightanole]

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

 

[Mooly]

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.

 

[Mooly]

Do you really need that current capability though ? much simpler if not.

 

[nightanole]

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.

 

[Gopher]

nightanole -

I assume you haven't physically wired it as you show where +ve and -ve supplies are shorted to GND or you're going to get a loud bang as your caps explode.

Assuming that's not the case, why have you linked +PGND to the -ve supply and -PGND to the +ve supply and not the other way around?

Am I missing something here?

 

[nightanole]

Try this thought. The top powersupply is a carbon copy of the bottom power supply. so the top of each power supply is positive, and the bottom of each power supply is negative. Series them together and you get 60 volts with a center tap. Connect the tops to the tops, and the bottoms to the bottoms, and you get parallel arrangement.

There really isnt a negative rail like with a regulated setup, its really just 2 30volt powersupplies thanks to the fact the center rail isnt connected on the pcb.

If you go back further you will see im really just connecting the positive posts of the caps together, and the negative posts together.