Hooking up Charlize to the PC power supply, with some weird results

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Hello guys,

One of the quirks of having an Antec Sonata computer case is that it comes with a custom designed PSU that has an external 12V & 5V rail. This means that I can try to connect my Charlize to a SMPS anytime I want. All I lacked was the proper connector.

Well today I finally munstered enough determination to go to RS and get one of those cheap molex female adaptors. Once I got home I unhooked my Charlize from its usually battery power source, and connected it straight to the 12v rail form my computer PSU. And... it sounds great! But......

Once in a while the whole amp would drop out during a particularily loud phrase, and proceed to produce silence (or a very small amount of audio) for several seconds. Afterwards power would suddenly "kick back" and everything would be fine for an indefinte period of time, until this thing happens again.

I guess this would be a PSU issue? Would it help if I put in some big *** caps btw the SMPS and the Charlize? I'm thinking of putting in snubers as well.

Also, what ended my testing was that while testing I accidentall bumped my speakers. All of a sudden the amp went bezerk and proceeded to continuously output a flat voltage that pushed my cone's travel to its extremes and held it there. This persisted until I finally unplugged the amp out of panic. And now I'm afraid to turn my amp back on :(

Anyways, I just wanted to post this quickly before I go to bed. I'll see if everything's allright in the mornig.
 
eVITAERC said:
Hello guys,

One of the quirks of having an Antec Sonata computer case is that it comes with a custom designed PSU that has an external 12V & 5V rail. This means that I can try to connect my Charlize to a SMPS anytime I want. All I lacked was the proper connector.

Well today I finally munstered enough determination to go to RS and get one of those cheap molex female adaptors. Once I got home I unhooked my Charlize from its usually battery power source, and connected it straight to the 12v rail form my computer PSU. And... it sounds great! But......

Once in a while the whole amp would drop out during a particularily loud phrase, and proceed to produce silence (or a very small amount of audio) for several seconds. Afterwards power would suddenly "kick back" and everything would be fine for an indefinte period of time, until this thing happens again.

I guess this would be a PSU issue? Would it help if I put in some big *** caps btw the SMPS and the Charlize? I'm thinking of putting in snubers as well.

Also, what ended my testing was that while testing I accidentall bumped my speakers. All of a sudden the amp went bezerk and proceeded to continuously output a flat voltage that pushed my cone's travel to its extremes and held it there. This persisted until I finally unplugged the amp out of panic. And now I'm afraid to turn my amp back on :(

Anyways, I just wanted to post this quickly before I go to bed. I'll see if everything's allright in the mornig.


I don't think you should have attempted that. Just to guess I'd say your power supply doesn't output more than 1 amp on that 12 volt rail and you likely need more than twice that, so it's little wonder you ran into difficulty. Overloading your PSU like that won't help it much either. I don't think caps will help you with this, it just doesn't have the current capability.

You might get away with powering two 8 ohm speakers in series for a 16 ohm load, or 32ohm earphones.
 
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All PC PSUs have the Molex connector +12V Grd Grd +5v

The Molex +12V rail usually is over 6Amp and up to 20Amp.

It's the -12V rail that is usually .5 to 1 amp and is NOT the 4 pin molex connector, it is in the main Block Motherbord connector.

My guess is that the voltage strayed from 12V, as voltage on PC PSU vacillate wildly. I bet the PSU was jumping from 10V to 12.5 volts and your amp crashes on the low dips...

Check out with voltmeter with load and see...
 
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Hard drives, Floppies, etc are designed to operate on the these fluctuating volltage PC PSU's (hey, maybe that's whaty computers crash so damn much!!), so they can work with the voltage swings better than, say, these amps, which are a bit more sensitive to voltage swings.

The issue of PC PSUs not having enough amps is what I disagree with. It is the copious amount of Amps that make these SMPS so perfect for this technology, as long as they can control voltage swings.

As far as requirement for the +5V to be loaded for the +12V rail to operate consistently, I have hooked up quite a few amp boards to just the +12V/Grd rails to do a simple power and sound check, without connection to the +5V rail, and has always worked.

Again, these are crappy, older ATX PC PSUs I have, not anything special like what NUUK may have.

Put a voltmeter acros the pins and see if the voltage drops when the Charlize crashes...and stay away from that homicidal speaker...
 
john65b said:
The issue of PC PSUs not having enough amps is what I disagree with. It is the copious amount of Amps that make these SMPS so perfect for this technology, as long as they can control voltage swings.

The PSU regulation is rated at "Voltage returns to within 3% in less than 1ms for a 20% load change". Is that enough? Both 12V rails in my PSU is rated for 16A.
 
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If your amp board min voltage is 11 volts, you may be out of luck with this particular PSU with these voltage swings.

For example, the TA2024 board min voltage is 9v (I'm recalling this from memory) , so this psu would be fine. But a TA2020 min voltage is a bit higher (11V??), and may have issues...

Your +12V rails (not -12V rail) specs out at 16A, correct?
 
Thanks for the correction on the current output capability I see I was way off.

I'm out of ideas but 3% regulation wouldn't drop it much below 12V, even then, you'd have to load it down alot.

Test with a dummy load if you can, preferably resistive, see if it handles that OK. Perhaps some extra decoupling of the supply like through a common mode choke, if it doesnt' have it built in already, would be of some help.

That's it for me I'm out of ideas. Good luck.
 
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You had mentioned that the PC was on during your test...maybe there was a major draw on the PSU from the PC at the time and the amp tripped...

Get the PSU completely out of the computer. On the main motherboard block (I am talking an ATX Power supply here, not AT), jump the green wire connector (there should only be one) to any black (there is one next to the green wire). This will allow you to turn on the PSU from the back switch without a connection to the PC.

The green wire jumper is needed or else the PSU will not turn on.

Now connect that PSU molex connector (the yellow wire is +12v, and the adjacent black is ground) to the amp board without the computer and see how it fares...first at low volume...

I should work...my only other thought is with 16 - 20+ amps, maybe too many amps on the TA2020?? Were you playing HIGH VOLUME when it tripped?

A quick check on the TA2020 spec will say min/max voltage and min/max amps...I kinda remember remember an 8 - 10 Amp max per chip...which could be it...
 
I had always heard that the external connector on antec psu's were only good for some measly .5a or 1a output. The reason i somewhat recall is because i remembered never to hook up too many external fans for fear of overloading it.

This is based upon foggy memory and i very well could be wrong, but i do remember reading something to that effect, which in turn kept me from running too many external fans at the same time.
 
Okay guys, managed to solve my problem.

Turns out it's not the PSU at all. Turned out that my new speakers were a bit experimental (see the FR125-Spiral project thread at Fullrange) so the impedence kinda fluctuated wildly. I have since tuned the cab so that the impedence is more controlled. The charlize is now behaving VERY nicely, out of the same external plug ;)

Btw, for future refrence, I phoned the Antec guys and they said that the external rails share the same 24A source (24A total, not 2 rails at 16A each, my bad) as the rest of the system. This made the load of the charlize fairly insignificant, and it certaily seems so for the last few hours that I have had it on. I recommend this approach to anyone who has a Sonata case and want to find a quick and dirty source to power it!

OKay, new problem: Has anyone measured the DC at the speaker terminals for the Charlize? Mine is 30mV and 120mV for the two channels :bigeyes:
Is this normal?
 
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