Skynyrd77's Thank Godamighty , Finally My Own WOPL Build Thread!!

I was just watching a vid of a dude blowing up a amp using 0.5ohms :evil4:
 
Well, a PL has a protection circuit on it that limits current to the drivers, don't know if that's happening or not, but I believe it is.......
 
Skynyrd77 said:
Wow! That's crazy. Some car amps run 2 ohm don't they?
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Yep, this was a car amp also. You could see a circle heating up red hot on the top case and some smoke out the back. He was using a D'Amore Amplifier Dyno AD-1 to do it. I was waiting for flames so it really was not all that impressive LOL

Here's the vid, that Amp Dyno is a cool piece of equipment Lee!

http://youtu.be/865jrg8hMUo
 
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laatsch55 said:
Well, a PL has a protection circuit on it that limits current to the drivers, don't know if that's happening or not, but I believe it is.......
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Ok in real life listening. Would what you just did have smoked the dc protect? Or is there another protection that your thinking is what's saving it?
 
Got to 200 into 2 before the screaming of the output stage got unbearable.......
 
Skynyrd77 said:
Ok in real life listening. Would what you just did have smoked the dc protect? Or is there another protection that your thinking is what's saving it?
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There is a current limit protection circuit on the driver board, it protects the amp output stage, usually.....whioch I think is what's happening....
 
The DC protect would have tripped on the first bad clip...
 
At 4 oms loads, it clips at 55volts....that equals 14 amps of current.....
At 8 ohms load it clips at 63 volts....that equals 8 amps current.......

Things are not linear...so there is a voltage component to the protection circuit??
 
BPI Model 250...2,000 watt load bank..same one used at the PL factory, engineering dept...adjustable from 4-16 ohms, and if you patallel the resistors adjutable from 2-8 ohms....
 

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laatsch55 said:
BPI Model 250...2,000 watt load bank..same one used at the PL factory, engineering dept...adjustable from 4-16 ohms, and if you patallel the resistors adjutable from 2-8 ohms....
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Very cool! And it's even the same that they used! They called it a 700. They wernt to far off I guess eh?
 
Well, in a no-holds-barred amp with a power supply designed for it, going from 8 onms load to a 4 ohm load your wattage should double. This amp consistently clips at 505 into 8, but can only get 378 into 4. Something isn't right here. Joee touched on it about the front end voltage dropping with the rail voltage, as the stock board has a zener regulated low voltage supply. so it drops as the rails drop. Not so on his board. From what little I know about te protection circuit, it was designed to limit damage to the output stage should excessive current be drawn. This limit was also tailored after the output of the day which was the XPL-909....not very robust by today;s 21196's...

So it's entirely possible there is something wrong with the protection circuit.... Joe could tell us, but I'm trying to reason through it, hence the ampere figures.
 
Ok I understand now. Had it backwards for a sec. Yeah that's not right to get 500 at 8ohm but only 375 at 4ohm.
 
Exactly, I've had another stocker at 700 watts into 4 before I started popping 8 amp fuses. There are evidently some current hogs in the output stage...meaning some excessively leaking transistors....I think...
 
laatsch55 said:
Exactly, I've had another stocker at 700 watts into 4 before I started popping 8 amp fuses. There are evidently some current hogs in the output stage...meaning some excessively leaking transistors....I think...
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See this is something peewee should start really paying attention to. He super smart. I think if he put his mind to it he would soak this up like a sponge!!
 
Maybe he should take up electronics at the local college in night courses....


So, my reluctance toi twist the amplitude knob to the far right is directly proportional to the meters being smoked. That can happen. If an output goes at these kind of amperages....I don't know if it would fare well so I'm gonna shut this down until we understand it better. It's obviously sick. How did it sound Jase?/ I'll run a THD & N sweep before I shut it down also...
 
laatsch55 said:
Maybe he should take up electronics at the local college in night courses....


So, my reluctance toi twist the amplitude knob to the far right is directly proportional to the meters being smoked. That can happen. If an output goes at these kind of amperages....I don't know if it would fare well so I'm gonna shut this down until we understand it better. It's obviously sick. How did it sound Jase?/ I'll run a THD & N sweep before I shut it down also...
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i didnt listen to it much. but it wasnt horrible but it wasnt the 939 or bertha by no means. and i nvr pushed her hard either i was afaid for my speaks
 
It's damn noisy, residual is 465 microvolts on one and 2.6 MILLIVOLTS on the other. THD & N is good, Signal to noise ratio is 30db on one channel and 80 on the other... 2.6 millivolts is a TON of residual noise, should have ben able to hear that buzz for a mile...
 
laatsch55 said:
At 4 oms loads, it clips at 55volts....that equals 14 amps of current.....
At 8 ohms load it clips at 63 volts....that equals 8 amps current.......

Things are not linear...so there is a voltage component to the protection circuit??
Click to expand...

The protection circuit limits current X voltage = power dissipation in the power transistors.

It's similar to a power supply protection circuit that I discovered by accident a long time ago that measures the voltage X current in the transistor, but the difference is that this amplifier protection circuit measures the voltage X current in the load instead. This means that the operation of the amplifier protection circuit is not affected by relatively minor fluctuations in power supply voltage.
The amplifier protection circuit automatically reduces the current limit if there is too little voltage across the load, caused by the load resistance or impedance being too low.
It's operation much more similar to a power supply foldback current limiting circuit.
 
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