2 Wall Wart PS Question

[Sherman]

I have come into possession of a few power supplies. They provide 24VDC and a little over 3 amps each. They are sort of heavy duty wall-warts.

So, the question is... could I take two of these to make a GC power supply? I'm thinking I could use one to provide V+ (connecting the + side to V+ and the other side to PG) and the other to provide -24VDC by using the "-" output to V- and the other side to PG.

Since they were freebies I could just try it but they appear to be pretty nice with regulated output so I'd rather not let the magic smoke out, I'll find something else for them to power.

[gmphadte]

If they have regulated output, it is not correct to use them in this manner, since they both will have regulator on one polarity i.e.+ or -

Gajanan Phadte

[mcs]

Yes, you can do that. But are they linear supplies? Powersupplies of that size are normally switchmode supplies which may be very noisy. If they are heavy they should be OK...

Best regards,

Mikkel C. Simonsen

[psychosteve]

when i was younger, i tried similar a thing, trying to get a power supply for a project, never got it to work, always let the majic smoke out the case.

the reason, so ive found out is that you efectivly create a short between the + on one, to the - on the furthest supply.

so unless you find some one who has done this before and can tell you exactly how to do it, i wouldnt try.

having said that, you may be able to conect each supply to a seperate power capacitor, then to the board, simmilar to the way you would do it with a battery supply!! but i wouldnt take my word for it. see you soon, steve.. ..

[falcott]

I once used a single wall pack to power a Pig Nose guitar amp. I was not impressed by the sound at all, compared to battery power. Horrible. It would have to be regulated at least.

[amisdad]

couldn't you use a rail splitter like TLE2426CLP?

[paulb]

Using two wall warts should work if the outputs are isolated from one another. It may be that the + or - terminals are connected to AC power line ground (if they have a 3-pin plug), in which case you can't unless you clip off the ground pin - not recommended.
You can use a multimeter to measurement resistance from the outputs to the ground pins (not while they're plugged in, of course). Or plug them both into a power bar, which is NOT plugged into the wall, then measure resistance between the two sets of output leads. If there is no connection, you're good to go. Connect - on one to + on the other and voila.

The TLE rail splitter is only for low current applications, like a preamp or headphone amp. Not for power amps.

[carlmart]

Originally posted by amisdad
couldn't you use a rail splitter like TLE2426CLP?

Rail splitters work fine for low current applications. For power amps you are better off by using a single supply with the total voltage and then adding a large cap at the output, as specified on the LM38XX datasheet.

Using the walmarts should be good choice, as long as the voltages are the same and that you add extra capacitance.

Don't demand high currents from them though, that is don't parallel chips or use current hungry speakers.

The outputs should be isolated, so you only have to join the V+ terminal from one box to the V- of the other to create a PS ground, and use the remaining V- and V+ for your supply.

No danger of shortcircuit if you do it properly.

Before you plug this series connection to the wall, use a meter to check the remaining ends are not shorted, but that should be hard to do if you do things well.


Carlos

[Sherman]

Thanks for all the input! The upshot of everything below is that I will give this a try. I now have a couple things to check before hooking it up that should help keep me from letting the magic smoke out.

If I live through this I'll report back!

Originally posted by gmphadte
If they have regulated output, it is not correct to use them in this manner, since they both will have regulator on one polarity i.e.+ or -

Gajanan Phadte

They do say "Regulated" on the label.

Originally posted by mcs
Yes, you can do that. But are they linear supplies? Powersupplies of that size are normally switchmode supplies which may be very noisy. If they are heavy they should be OK...

Best regards,

Mikkel C. Simonsen

They are big and heavy. They aren't strictly wall warts as they have a three prong AC plug that runs to the box. That said, I would guess they are switchmode, but I don't see anything to indicate that on the label. Time to disassemble one I guess.

Originally posted by psychosteve
...

the reason, so ive found out is that you efectivly create a short between the + on one, to the - on the furthest supply.


so unless you find some one who has done this before and can tell you exactly how to do it, i wouldnt try.

... see you soon, steve.. ..

I would run them into caps before connecting to the chip so I would think it should work like the BrianGT PS board. We'll see.

Originally posted by falcott
I once used a single wall pack to power a Pig Nose guitar amp. I was not impressed by the sound at all, compared to battery power. Horrible. It would have to be regulated at least.

Well the supply is regulated, or at least the word "Regulated" is on the label. I don't know what current a Pig Nose draws but most wall wart type supplies I've seen supply less than 1A and I wouldn't be surprised to find the sound worse than batteries. These though are over 3A which should be enough for a GC. (I'm currently running one using a 120VA transformer powering both channels so using two of these would at least match that.)

Originally posted by amisdad
couldn't you use a rail splitter like TLE2426CLP?

I don't know to be honest. I will try to do some research on that.

Originally posted by paulb
Using two wall warts should work if the outputs are isolated from one another. It may be that the + or - terminals are connected to AC power line ground (if they have a 3-pin plug), in which case you can't unless you clip off the ground pin - not recommended.
You can use a multimeter to measurement resistance from the outputs to the ground pins (not while they're plugged in, of course). Or plug them both into a power bar, which is NOT plugged into the wall, then measure resistance between the two sets of output leads. If there is no connection, you're good to go. Connect - on one to + on the other and voila.

The TLE rail splitter is only for low current applications, like a preamp or headphone amp. Not for power amps.

I hadn't thought about one of the lines being connected to AC ground. It doesn't seem likely but I'll have to check that. If that isn't an issue I'll proceed from there.

I am thinking that I will run each supply's output into a 1000uF to 1500uF cap and connect the PG+ and PG- between the caps. (I'll start with some cheap Xicon caps just in case!)

Originally posted by carlmart


Rail splitters work fine for low current applications...

Using the walmarts should be good choice, as long as the voltages are the same and that you add extra capacitance.

... No danger of shortcircuit if you do it properly.

Carlos

I have one GC running with a 120VA transformer supplying two channels and it sounds very good. Though that one is running on about 32VDC and this one would be 24VDC. Lower voltage to the chip, less output power but that is OK as I have almost completed some 95dB efficient speakers.

These are labeled to be the same voltage and a check with my multimeter shows them to be exactly the same. So far so good.

I'm going to give this a try but probably not until next week at the earliest. Have to finish a couple other things before I start a new project!

[Stocker]

What a bunch of pessimists! Nevermind the haters.

Take them apart! If the transformers are close to the same you can use them in parallel or series. regulated, whatever. That they are heavy indicates non-switchers.

YES you can use them but it may be less simple than just plugging them up to the same load.