Berti Jacobs wrote on Mon, 28 December 2009 17:37 |
Hello everybody, I'm in the process of building 8 LAB's (4 per side) I'm wondering whats the better way to power them: 1 Itech 8000 per 4 LAB's or 2 Itech4000 per 4 LAB's ?? thanks for any advice Berti |
Elliot Thompson wrote on Tue, 29 December 2009 19:44 | ||
Two amplifiers are always better than one from a longevity standpoint. Many amplifiers claim they can deliver 2-ohms per channel however, how long is not guaranteed. If you are looking for worry free results, buy two amplifiers, use them at 4-ohm per channel than, trying to extract every ounce of reserve energy from one amplifier loaded in a 2-ohm per channel load. Best Regards, |
jeffhtg (Jeff Kenney) wrote on Wed, 10 February 2010 05:01 | ||||
unless your talking about powersoft.. |
Nathan Short wrote on Mon, 15 February 2010 17:34 |
Powersoft K10dsp is the only amp I have torture tested that will put out a continuous 50hz sine wave minute after minute @ 76v per output, off a 20 amp circuit. Damn hard to find another amp that can do that. Not magic, just damn fine engineering. |
Nathan Short wrote on Mon, 15 February 2010 22:58 |
Oops, I just went back over my notes The powersoft had to go back to an old business partner before I did round 2 of my last 2 weeks of torture testing. The Powersoft K10dsp would max out at 67v drawing an average of 26amps @ 50Hz near input limit PL380 60v drawing 29 amps consistantly. |
Nathan Short wrote on Mon, 15 February 2010 14:58 |
The most interesting thing was finding a flaw in the PLX3602 that at 30Hz and 15K channel 2 would behave normally and channel 1 would try and put out 81v!!! Danger Danger! and the amp would go into overdrive and try and pull 33amps from the wall. |
Nathan Short wrote on Sat, 20 February 2010 14:16 |
My purpose in widening the scope of my testing with tone into near limit on the amps is the growing use by us in electronic music. Dubstep is changing the way we need to measure amplifiers as many of the bass lines are long droning synth lines. This will reveal a weak sub amp very quickly, and many amp manufacturers are stepping up the robustness of the amplifiers. I would hate to be doing a show where the DJ or Electronic musician played a high note, or used a "sweep" effect while performing, and 1- I nuke my drivers on Ch 1, 2 - I blow half my PD. Who knows? This is why I try to abuse the amps any way I can think of before I let the professional Idiots beat them up in my installs. |
Nathan Short wrote on Mon, 22 February 2010 14:38 |
Never mind Bob, I don't have time to argue semantics over my quickly worded posts. Everyone knows that the potentiometers on the RMX series blow, are cheap, degrade quickly, and otherwise ruin a perfectly good budget amp line. I will never sell them for an install, but make plenty of money upgrading and fixing them then reselling to my friends. It is wonderful To see that the PL340 and 380 series have wonderful current management and do what they are supposed to do. It is very odd that I can easily, get one channel of a 3602 to put out 81 volts while the other measures perfectly, and that the amp even tries to pull 33amps from the wall. This is my only question. How and why is the 3602 able to do this. Seems pretty dangerous, and a complete failure of the "clip limiter" circuit in the amp. Whatever that might be. |
Nathan Short wrote on Mon, 22 February 2010 14:31 |
I don't see how it is a cheap shot, just the truth. The quick and easy method to reproduce my findings. Take an oscillator, Run it into a midas venice, set the level to 0. |
Quote: |
Buss the channel. Run Masters to 0. Masters are plugged directly into the amplifier. |
Quote: |
Amplifier was tested on 2 dummy loads. I will explain the first. A 4 element 4x 7.8-8.2 ohm 2000w water heater elements suspended in a bucket of water. This provides an easy impedance that doesn't seem to drift more than .2ohm when hot. |
Quote: |
Test leads from a BnK multimeter were attached to the individual leads one one of the resistors , and at the amp different times. |
Quote: |
The amp was plugged into a military grade distro, with a current meter. The distro was plugged into two seperate 100amp breakers, 1 per circuit of the 2 circuit unit. The unit has 40amp breakers. both circuits went back to the same panel ground, and seperate neutral bus. |
Quote: |
Channel 1 was found, when starting to engage the clip led by driving the output of the midas past +4, to start putting out a lot more voltage than Channel 2. Channel 2 behaved normally like almost every other amp at the test. Channel 1 could be made to put out 81v when the clip light was moderately active. The current meter on the Distro showed 33amp draw. |
Quote: |
What else can I tell you. A few of my EE friends, as I am not an EE, gave the testing a thumbs up, and a great way to check for thermal limits also. The 3602 was found to exibit this behavior at 30Hz and 15kHz, I did not push the test further for fear of ruining the amp. |
Nathan Short wrote on Mon, 22 February 2010 16:21 |
since the amp has no "0" level the near "0" measurement was set to at "no clip" "solid -6" The second measurement was taken as an average of moderate clip light flashing, but not solid or heavy. |
Nathan Short wrote on Mon, 22 February 2010 14:21 |
The bucket was set up to run 2 elements per load in parallel. 4ohm. I will go ahead and type up my full measured list for the 3602. since the amp has no "0" level the near "0" measurement was set to at "no clip" "solid -6" The second measurement was taken as an average of moderate clip light flashing, but not solid or heavy. It will go as follows Noise Vat"0"/V at "clip", amps/amps Pink 6db crest 33v/45v 15a/21a 30Hz na /60v na /33a 50Hz 40v/60v 24a/33a 85Hz 50v/60v 27a/32a 1kHz 45v/60v 24a/31a 15kHz na/na 33a Dance Music Light ,hard, limit 20v/41v/50v 10a/21a/26/ |
Nathan Short wrote on Mon, 22 February 2010 20:19 |
Hey guys, I am ordering this http://www.syscompdesign.com/OrderStep1.html I have heard great things about it. |
Quote: |
Once I have my scope set up, I should be able to very much further refine my process. Thanks for all the replies, but this is beating a dead horse now. The people who obviously have the rest of the proper testing equipment I do not have, want answers I cannot give them at this time. I am slowly building my equipment up. Maybe we could approach this more constructively with a full set of amps from various brands, and set some sort of "real world" standard. I approached this out of frustration from what I believe to be inflated specs from manufacturers. And wanted to gather my own tables of real output voltage at common levels of use and abuse. |
Quote: |
IE see the performance of low and high level gear in my own situation. Plain and simple 3602 has an issue. So I will be happy and glad to continue putting PL340's and 380's on my rigs. They are rock solid, and a joy to work with. |
Nathan Short wrote on Mon, 22 February 2010 20:19 |
Plain and simple 3602 has an issue. So I will be happy and glad to continue putting PL340's and 380's on my rigs. They are rock solid, and a joy to work with. |
Nathan Short wrote on Tue, 23 February 2010 13:07 |
Sorry Bob, As I am not an EE, this is just a losing conversation for me. I wish you would be more helpful, but at the same time, I guess that other people have actually helped me more understand what I am trying to explain, so all in all, I have my answers. To put it better. The PL380 and 340 both do excellent jobs of only drawing a certain ammount of amperage under a heavy load. They do their jobs well, and with repeatable results that satisfy my needs. And to be very hones, I have had zero failures of PLX and PLX2 in the last 7 years. Good power, good ventilation, and proper wiring on the installs, and bam the amps do their job. The 3602 testing I did just confirmed my personal experience that every now and then, with the right DJ doing the right thing. Ch1 will blow a VC right out of the basket, while Ch2 will not. Clip limiter on Ch1 not effective. But who knows. Evidently not me. |
Nathan Short wrote on Tue, 23 February 2010 18:45 |
Holy crap. Wow. Take oscillator, run into console, plug into amp, run amp on 4ohm high wattage resistors each channel. Measure voltage at 15kHz and 30Hz at different times. For however you feel is long enough. NOT THAT HARD. Channel 1 on 3602 will put out near 81v when clip light starts to flash, Channel 2 on 3602 will behave more normally at 60v and lower. There has to be a reason I can do this easily. For the love of god, this is not that crazy of a scenario. Any help, or is this too sketchy of a signal flow for my results. |
Nathan Short wrote on Tue, 23 February 2010 19:38 |
Well then as this is the case with both of the new 3602's I just got in over a week ago , now I know. The amps sound great though. But this problem makes me want to go back over a lot of my installs and make damn sure ch1 never even gets near clip. I will sacrifice the sound a bit for safety. |
Nathan Short wrote on Wed, 24 February 2010 13:44 |
I am a firm believer that the pots on my amps should always be at full. This makes sure that the only fiddling that can go on is in a reduction direction. |
Quote: |
The amp when driven by a 15kHz or 30Hz sine wave at full gain on the amp, driven into slightly flashing limit, regardless of switching the inputs back and forth, Channel 1 81v unwaivering Channel 2 60v + or minus 3v very stable |
Quote: |
Going further in input level will cause a solid clip indication on the amp leading me to believe I am doing nothing positive. Going on what I measured many many amps on in similar conditions The 3602 should be putting out about 60v per channel for the test I was doing. 60v would be in the expected range of the rest of my results. 81v is the anomalous reading. |
Nathan Short wrote on Fri, 26 February 2010 22:13 |
I really wish some other people would try this, or QSC itself, and Just say what they find. But I don't really expect them to say if they find a flaw... Gotta wait for my new scope. |
Nathan Short wrote on Mon, 01 March 2010 16:41 |
I am not paranoid. But If I was a manufacturer had known there was an issue, a nice PM would have shut me up right quick. |
Quote: |
The second issue, is this, why cant QSC go out to the warehouse, open up a couple and give this a try? Two things might happen, "hey wow, we made this happen too!" or "damn, we could not do this , no matter how hard we tried, and we blew up the power supply trying" |
Quote: |
Not one word from other users, or the manufacturer. So unless, my scope could come more quickly... I could go around with my oscillator and bucket to any number of 10 bars in the city, and see if it was just something I never noticed, or it is just these two new ones. |
Quote: |
And a public forum is probably not the best place for this problem to be hashed out, but again, no one contacted me as this happened/unfolded. And I can return these amps any time. |
Nathan Short wrote on Mon, 01 March 2010 19:00 |
I have pretty much figured that the problem is at the onset of clip light indication. Unfortunately I do not have the luxury of doing more tests this past week as bids and shop work have taken all my time and a lot of 15hr days. At different gain pot settings, driven by different levels of input, swapping both sides of the amps input to make sure the problem is not upstream in the signal flow. My basic conclusion is that at 30Hz and lower, and at 15kHz and higher, the ability of channel one to grossly outperform the output of channel 2 is unmistakable and possibly dangerous to my loudspeakers. I would suspect the clip limiter is in some way at fault. Channel 1 is consistantly able to put out 81v as measured by a voltmeter at the load of 4ohm. Channel 2 is able to consistantly put out in the 60v range. This is the symptom, and I need a doctor to help diagnose the disease. Or design flaw, I would normally not drive an amp quite this hard in an install, but the test is to show me these weaknesses and I need to be prepared for all sorts of DJ abuse scenarios. I will most certainly keep at it, when I have more time, and my new tools, I will gather many more notes, post a video, and grab some big old beater subs To also use as a load. I just wish someone else would try it. Until then I am going to enjoy the PL340's and 380's that are proving to do an excellent job. |
Nathan Short wrote on Mon, 01 March 2010 22:06 |
You know JR that brings up a great point, there might be some odd impedance problem at both ends of the audio spectrum. I am gonna hook up my woofer tester and run an impedance sweep on both of the bucket loads. I am pretty sure I tried both channels on of most of the amps on both dummy loads, but as I was taking mostly averages, when the amplifiers put out within 6v +or- I was pretty happy. That is why the 81v>60v was the one that really got me worried. |