I'm going to repost Jerrold's post in the other thread that just got closed again just so we have it here:
"I DID get a short look at the 7 PRO schematic a while back....... NO B&O module...... In fact, the unit I know about that is closest to the 7PRO power amp topology is the old Ampeg PB 250, the first Ampeg Class-D unit. Really pretty close, although we used a different limiter system in the PB250.
"IIRC the 7PRO has, in the "C" version, a supply-voltage-responsive clip limiter. I think they had an opto in earlier versions. If my recollection is correct, the "cut-out" issues might be related to that....it can be tricky to get those limiters to work just right. And if you don't, you can get "issues" with long pulse lengths and other stuff that would cause a cut-out in a class-D amp, as has been reported in "some" units..... "some" maybe being the ones with the wrong ratio of resistor values due to tolerances.
"And most overcurrent limiters have some form of time-delay on them.... if you get a long pulse from the modulator, the output current in the pulse can get too high and trip the overcurrent detector. Then you wait for whatever time is inherent in the overcurrent shutdown circuit before output resumes.
"I'm not going to get into the really gory details of the design, I don't want to, and would have to go back and get another look at the schematic. And, I don't "give away Loud's store", it's theirs, not mine.
"I was told, however, that the 7PRO is a Loud China design, under the direction of the guy (Jonathan Chen) who ran that operation and apparently has since left. I am not so sure that the US Loud engineering folks themselves are so delighted with all the details of it..... maybe yes, maybe no, I have heard various noises about THAT, and it doesn't matter anyway.
"I didn't see any reason why the unit wouldn't put out the full 1000 watts, unless something about the SMPS was limiting the power, which, depending on line voltage, is quite possible. I do not think the main voltages were regulated in any way by the SMPS, which means it can drop under load or with line voltage.
"I would assume BGM knows how to deal with mains voltage, etc.
"Burst mode power, or whatever you call it, is not new, QSC happily uses it.....And before them, even Crown quoted it in their specs (in addition to "real" specs). IIRC, the PLX amps are rated to 2 ohms, but you don't dare run them at 2 full power in test for long. There was, I believe, a note that tests should be no longer than 3 or 5 seconds, since a blocking capacitor in the SMPS would die a horrible death if the test were carried longer. QSC has a good rep, though.
"And, the automated test gear is nice, and good, and gives a lot of info. There can be a place for the old school plain oscillator and THD analyzer, though..... it lets you do a 'survey" so much faster, adjusting on the fly to whatever the odd thing under test ends up doing.
"I am sure the BGM folks know how to run their extra-cool stuff... I'm just sayin........."
"I DID get a short look at the 7 PRO schematic a while back....... NO B&O module...... In fact, the unit I know about that is closest to the 7PRO power amp topology is the old Ampeg PB 250, the first Ampeg Class-D unit. Really pretty close, although we used a different limiter system in the PB250.
"IIRC the 7PRO has, in the "C" version, a supply-voltage-responsive clip limiter. I think they had an opto in earlier versions. If my recollection is correct, the "cut-out" issues might be related to that....it can be tricky to get those limiters to work just right. And if you don't, you can get "issues" with long pulse lengths and other stuff that would cause a cut-out in a class-D amp, as has been reported in "some" units..... "some" maybe being the ones with the wrong ratio of resistor values due to tolerances.
"And most overcurrent limiters have some form of time-delay on them.... if you get a long pulse from the modulator, the output current in the pulse can get too high and trip the overcurrent detector. Then you wait for whatever time is inherent in the overcurrent shutdown circuit before output resumes.
"I'm not going to get into the really gory details of the design, I don't want to, and would have to go back and get another look at the schematic. And, I don't "give away Loud's store", it's theirs, not mine.
"I was told, however, that the 7PRO is a Loud China design, under the direction of the guy (Jonathan Chen) who ran that operation and apparently has since left. I am not so sure that the US Loud engineering folks themselves are so delighted with all the details of it..... maybe yes, maybe no, I have heard various noises about THAT, and it doesn't matter anyway.
"I didn't see any reason why the unit wouldn't put out the full 1000 watts, unless something about the SMPS was limiting the power, which, depending on line voltage, is quite possible. I do not think the main voltages were regulated in any way by the SMPS, which means it can drop under load or with line voltage.
"I would assume BGM knows how to deal with mains voltage, etc.
"Burst mode power, or whatever you call it, is not new, QSC happily uses it.....And before them, even Crown quoted it in their specs (in addition to "real" specs). IIRC, the PLX amps are rated to 2 ohms, but you don't dare run them at 2 full power in test for long. There was, I believe, a note that tests should be no longer than 3 or 5 seconds, since a blocking capacitor in the SMPS would die a horrible death if the test were carried longer. QSC has a good rep, though.
"And, the automated test gear is nice, and good, and gives a lot of info. There can be a place for the old school plain oscillator and THD analyzer, though..... it lets you do a 'survey" so much faster, adjusting on the fly to whatever the odd thing under test ends up doing.
"I am sure the BGM folks know how to run their extra-cool stuff... I'm just sayin........."
