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Old 4th April 2006, 02:51 AM   #1
snkby is offline snkby  United States
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Default do ucd modules behave like

chip-amps wrt soar ?
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Old 5th April 2006, 04:06 PM   #2
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can you elaborate on that question?
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Old 5th April 2006, 09:30 PM   #3
BWRX is offline BWRX  United States
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and maybe put in english this time around?
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Old 6th April 2006, 03:59 AM   #4
snkby is offline snkby  United States
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Default no problem. do ucd modules behave

like chip-amps with regards to Safe-Operating-ARea ?

like with the lm series chips there is an optimal power supply voltage that provides the most output and cleanest signal but doesnt go into the s-o-ar far enough to put it *on alert*.

by getting closer to the edge of the soar to get more output the amp starts getting more sensitive to current.

so you end-up with a more powerful amp that is looking for a good excuse to self-protect because it has gotten more sensitive to reacting.

thats the way it was explained to me by a guy that worked for nasa building satellites.

the reason i ask is because my pair of ucd180 modules being driven with +-42v wants to shutdown during those big transients and or sustained relatively high spl.

i know the self-protect mode is 52v but i dont know how the amp senses self-protect.

might i still get enough power and not cause self-protect by running them a little lower like +-35v ?

i havent seen a published supply voltage for optimal sound AND power.

ive seen only for maximum power.

thanks.
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Old 6th April 2006, 08:43 AM   #5
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Hi,

I knew what you meant just didn't see why you'd ask.

There's really no defined relation between SOA and optimal parameters, though they can often coincide in some way, but optimal is always found within the soa.

I think your NASA friend gave you a round-about explanation of things like parasitics... early effect for instance, where a higher voltage can cause faster reactions, still different from SOA.

What you really ought to consider at this point is use a more scientific approach rather than grasp at straws, and keep the topic going in the same thread until the problem gets solved. You'll be able to expect a higher degree of help that way.

Next try giving a detailed description of the problem. For instance, what's the load you're attempting to drive? What do you consider to be "those big transients"? Does the amp actually shut off (hint, look at the LED) or does it simply clip?

I'd also recommend you do yourself two big favors. #1 Read the data sheet closely and understand it.

"i havent seen a published supply voltage for optimal sound AND power."

The data sheet gives "Recommended Operating Conditions". That's for sonics, and reliable performance.

It also gives "Absolute Max Ratings", which more less relates to what you might consider to be the upper limits of the SOA.

Obviously what you want to do is respect the max ratings by staying below them, and select something within the recommended ratings at worst case. There's a healthy range to play with, so you can work out the power you end up having based on your component selection/requirements.

Don't be so set in your ideals that you're not willing to experiment. For instance try using a reasonable length of wire for you rails (less than six inches), especially at that gauge. See how that sounds. I guarantee you better than 5' of 14AWG wire!

Have you tried the bigger transformer? (higher VA)

I wouldnt' be too shocked to find that the smaller VA may suffer from a harsher clipping, conduction angle likely being far more severe, and far worse load regulation with the smaller transformers.

Have you tried anything recommended to you in the other two threads that you started on this topic? If so what were the results, if not, why?

I can almost promise you it's not the modules at fault but the implementation.
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Old 6th April 2006, 04:18 PM   #6
snkby is offline snkby  United States
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Default thanks classd4sure ! i wasnt able

to try the larger va xformer because 1 of the caps i wanted to use was bad.

going to the salvage yard today and hope to find some caps and xformer i can use.

cant really make the power umbilical any shorter until i find a chassis to put everything into.

at that point i can get the umbilical down to maybe 12 inches.

the speaker load is nominal 6ohm but the sensitivity is pretty low like 84db.

if i can find just a couple of nice big caps today i will use the 670va xformer and post back.

ive never thought the modules were at fault somehow.
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Old 10th April 2006, 10:07 PM   #7
snkby is offline snkby  United States
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Default gaaahhh!! can someone explain this ?

i finally found some some nice elna 15kuf63v caps on a discarded subwoofer plate-amp that i could use for my ucd180 psu.

i use my 670va xformer 0v-69v to a metal-case 25a monolithic rectifier and series the 2 caps for +/-48v.

these are measured values without the amp hooked-up.

i build the psu and let it idle for about 1/2hr and measure again and get -47.8v and +48.8v which is the same 1v difference the amp is playing with now with my first psu.

i unplug the psu and use a big 100ohm resistor to bleed the caps to 0v on each side.

i then install the psu to power the amp.

the amp powers up and then goes off after a few seconds.

i measure the rails again and get 63v on 1 of the rails and i pull the psu out and install the original and everything works fine again.

the psu is sitting idling right now and measures -47.8v and +48.8v.

i have bypass caps and 1kohm resistors across both caps.

why is the psu going weird when hooked-up to the amp ?

thanks.
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Old 11th April 2006, 03:19 AM   #8
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Default Re: gaaahhh!! can someone explain this ?

Quote:
Originally posted by snkby
i finally found some some nice elna 15kuf63v caps on a discarded subwoofer plate-amp that i could use for my ucd180 psu.

i use my 670va xformer 0v-69v to a metal-case 25a monolithic rectifier and series the 2 caps for +/-48v.

these are measured values without the amp hooked-up.

i build the psu and let it idle for about 1/2hr and measure again and get -47.8v and +48.8v which is the same 1v difference the amp is playing with now with my first psu.

i unplug the psu and use a big 100ohm resistor to bleed the caps to 0v on each side.

i then install the psu to power the amp.

the amp powers up and then goes off after a few seconds.

i measure the rails again and get 63v on 1 of the rails and i pull the psu out and install the original and everything works fine again.

the psu is sitting idling right now and measures -47.8v and +48.8v.

i have bypass caps and 1kohm resistors across both caps.

why is the psu going weird when hooked-up to the amp ?

thanks.

Damn you have some bad luck huh?

Any chance you can post a diagram of how you wired it all?

Include color code of the transformer wires.

Are you sure all these parts are good?
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Old 11th April 2006, 04:08 AM   #9
snkby is offline snkby  United States
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Default hey classd4sure ! the past few weeks

have been filled with stuuf that has made me want to dig a hole and bury my head for a while.

dont know if you are familiar with the movie the princess bride but there is this guy who always says --inconceivable!-- in this lispy way that i just have to say when when this stuff happens. lolololoo

the transformer i have used for other projects without any problems.

no wire color code as its all labelled bolt/nut terminals.

the rectifier is now suspect because the last caps i tried with the same xformer and rectifier led to the same result with 1 rail going really high and the other of course going down for the balance of voltage.

next try is a different rectifier.

could a bad rectifier cause this ?

at idle the rails are within .5v of each other but under load the rails get unbalanced.

going to try posting a schematic now. ucd180 psu schmatic
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Old 11th April 2006, 04:35 AM   #10
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It looks like you left your center tap disconnected.... find where it is on the transformer and connect it to your cap common point, should fix it I think.

I trust your screen is earthed? Needs to be.
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