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Measuring Amplifiers - Page 55

post #1621 of 1917
You lied.
I saute'd beets and onions with a chocolate sauce . . . . now it's me . . . . Sickneedhelp.

Re: the amp, if Chuck attempts to destroy the amp with loads, the breaker/fuse will save it every time, right?
post #1622 of 1917
Quote:
Originally Posted by Sickneedhelp View Post

Chuck, based on your substantial experience fixing amplifiers, it's a given that you also know how to kill one. When you receive the 1600, please make a serious attempt to kill it either before or after you run the tests, your choice. Sustained mains above 140VAC might make for messy blown supply caps. Sustained sine wave at clip above 20kHz unloaded should eventually fry the zoble network as the output filter resonates. I'd consider those limits of the bounds.

It's interesting that you give him permission to try and destroy the amp. But I would prefer that if he decides to do that, that he do so AFTER he runs tests, and not before.
post #1623 of 1917
This is just bragging, and hoping Chuck won't publish the real test data. Heck if i would want to destroy an amp (be it even of my own design), i have plenty of ways to. For the time being i just think i'll get another beer.

It's not that i don't believe in class D and their awesome efficiency. It's just that every class D amp i've played with skimped on the output capacitors "heck we can get the same output ripple with 1000uF that class AB gets with 10000uF", totally forgetting about the actual power holding capacity (in Joules) of the caps. This is why a properly designed class AB amp will sound more "ballsy" than a similar class D amp. I have 25-30W class AB amps that are able to deliver more than 150W on transients. But are they worth being rated 150 watts? No. They sure kick louder than class D though.
post #1624 of 1917
Quote:
Originally Posted by MBentz View Post

So with that in mind, I would propose measuring how long the amplifier can deliver various voltages limited by 1% THD into various resistive loads. The absolute instantaneous maximum would be determined by the unloaded rail voltage (so just measure the rail voltage). Then I would set the output to 1dB lower than the rail voltage and measure how long it can deliver output before reaching 1% THD. Then drop the output 1dB and continue dropping by 1dB increments everytime 1% THD is hit. You can probably stop the test once it takes longer than 1 min to reach 1% THD. And then you'll want to repeat at 10Hz, 100Hz, 1kHz, and 10kHz into resistive loads of 2, 4, 8, and 16 (so sixteen total plots). What you're measuring is the output level limited by 1% THD over time, so what you should see is an exponentially decaying curve starting at the rail voltage until it reaches the steady state capabilities of the amplifier.

With this information, you can look at the amplitude envelope of your source material to determine if your amp can accurately reproduce the source material. If you want to be really crazy, you can even throw in the frequency content of the music against the impedance response of your speakers to determine where the breaking point is.

Sadly, such a test would be difficult to do accurately without automated gear. The new APx525 series should be capable of it though. The other problem is that you have the thermal history from delivering the higher output levels before stepping down the output...so it will look worse than a real case scenario. You might even want to measure the output when limited by 0.1% THD and 10% THD too.

The real problem with trying to find a single meaningful amplifier marketing spec that is that it requires many variables to fully describe all the behavior of an amplifier, and it is incredibly dependent on the source material and speakers being used.

Anyways, just a thought about how I might go about measuring an amplifier and capture some information about the time domain nature of its performance.

Great post Mike. The test you describe makes a lot of sense since anything involving speakers or musical content will be far too variable. It also sounds like it would be a bit tedious. Automating the process would be desirable if possible. What is the APx525 you mention? Perhaps the addition of a multitone test spanning a very wide freq range would be worthwhile too.
post #1625 of 1917
Thread Starter 
Quote:
Originally Posted by Sickneedhelp View Post

Chuck, based on your substantial experience fixing amplifiers, it's a given that you also know how to kill one. When you receive the 1600, please make a serious attempt to kill it either before or after you run the tests, your choice. Sustained mains above 140VAC might make for messy blown supply caps. Sustained sine wave at clip above 20kHz unloaded should eventually fry the zoble network as the output filter resonates. I'd consider those limits of the bounds.

Actually it is getting harder and harder to kill them. Protection these days is very good.

NO, I don't look to hurt the amp at all. I prefer to give it back to you the way I received it. I have large displays for AC voltage and current draw and I will not be testing extensively above 20 KHz. (I will probably check and see if it can do 40K but just for a short time at low power!).
post #1626 of 1917
Quote:
Originally Posted by LINEARX View Post

You lied.
I saute'd beets and onions with a chocolate sauce . . . . now it's me . . . . Sickneedhelp.

Re: the amp, if Chuck attempts to destroy the amp with loads, the breaker/fuse will save it every time, right?

Soorrrrry Linearx Have you tried sticking your fingers down your throat and heaving? Not sure what the brown and green will look like when mixed on your shoes however.

At the speed the amplifier is switching, the breaker will be too slow to save anything. Nasty load angles, spikes, etc., will have to be protected via onboard circuitry. If Chuck manages to kill it, then I overlooked something and learn from the experience.
post #1627 of 1917
Quote:
Originally Posted by Th3_uN1Qu3 View Post

This is just bragging, and hoping Chuck won't publish the real test data. .......

What makes you think Chuck won't publish the data? I thought the whole purpose of getting Chuck involved was to have the amp tested by somebody everyone trusts.
post #1628 of 1917
Quote:
Originally Posted by Sickneedhelp View Post

Soorrrrry Linearx Have you tried sticking your fingers down your throat and heaving?

LOL, sounds like my marital vows to my first wife . . . . and I haven't worn shoes ever since.
post #1629 of 1917
Quote:
Originally Posted by Ricci View Post

Great post Mike. The test you describe makes a lot of sense since anything involving speakers or musical content will be far too variable. It also sounds like it would be a bit tedious. Automating the process would be desirable if possible. What is the APx525 you mention? Perhaps the addition of a multitone test spanning a very wide freq range would be worthwhile too.

http://ap.com/products/apx525

It's a new box from audio precision that has the awesome analog front end they're known for, but all of the data capture is done with your computer over USB. With the right modules, it's set up for doing Class D amplifier measurements along with a series of other tests. The amplifier load would of course need to be external to the unit though.

I think you're looking at about a $16k entry price though...real lab gear tends to be that way though. The only reason I mentioned this particular unit is because it has really cool automation features that would make this measurement a piece of cake.

Btw, I was thinking about what I proposed earlier and it'd probably be more meaningful to do smaller steps. Most amplifiers will do 6dB peaks, which would only be 6 iterations at 1dB steps. Regardless, the main intent is to look at how long each power level can be sustained, and then extrapolate that to the dynamic range requirements for specific source material.
post #1630 of 1917
looks like kyle just stepped up (post #6).

http://www.avsforum.com/avs-vb/showthread.php?t=1236585

chuck, are you up for testing an smps from behringer? obviously, he is not looking to kill one, just get some third-party trusted measurements.
post #1631 of 1917
Thread Starter 
Let me do the Peavey from JD first, then I can do the Behringer. The Peavey was shipped last week so I should get it soon and maybe measured during next weekend. But, yeah, I will put the Behringer on the bench.

Chuck
post #1632 of 1917
chuck, thanks man. without your honest and consistent measurements, many of us would be lost and confused in ampland, as there is just so much b.s. out there, you know. your work is very much appreciated. thanks again.
post #1633 of 1917
Hey Chuck, I'm 15 mins away from you. Interested in testing a Crest CC4000 and Crown CE1000 & CE2000?
post #1634 of 1917
Chuck,

Any testing on that Peavey as of yet?

James
post #1635 of 1917
Has anyone ever tested a Marathon MA-5050? I noticed what seems to be a decent deal on one and I'm wondering if it's a good amp for sub duty. Thanks guys.
post #1636 of 1917
Quote:
Originally Posted by cmryan821 View Post

Has anyone ever tested a Marathon MA-5050? I noticed what seems to be a decent deal on one and I'm wondering if it's a good amp for sub duty. Thanks guys.

This guy had 2 going sour in 5 minutes, i would not put too much faith in them till proven they can do the job without going up in smoke.
http://www.avsforum.com/avs-vb/showt...5#post18075635
post #1637 of 1917
Has anyone tried the Dayton SA1000 Subwoofer Amp? I like the built-in PEQ and am thinking of getting one for a DTS-10.

Thanks.
post #1638 of 1917
Quote:
Originally Posted by dondino View Post

Has anyone tried the Dayton SA1000 Subwoofer Amp? I like the built-in PEQ and am thinking of getting one for a DTS-10.

Thanks.

As I posted in the DTS-10 thread, its going to be almost the same as the plate amp and that amp has been measured in this thread.

The biggest issue is the SSF that exists at 18Hz...you will not get any power down to 10Hz. Not sure that matters though, its your choice.

The EP2500 is a better purchase period (lower cost and more power).
post #1639 of 1917
No testing on the Peavey yet??
post #1640 of 1917
Thread Starter 
Quote:
Originally Posted by exojam View Post

Chuck,

Any testing on that Peavey as of yet?

James

I should have the results ready to upload by Wednesday this week.

Chuck
post #1641 of 1917
Chuck,

Thanks for the reply. I hope all is well down in the sunshine state.

I picked up a Marathon MA-5050 recently and am running my subs off it now. I have not had a chance to try and pound them as of yet even though I do beleive the Marathon can put out more than the subs can handle. I took the EP2500 that was running them and moved it to L-R and took my Crown XTi100out of the mix. Overall I am starting to get a little happy with the setup.

James
post #1642 of 1917
Quote:
Originally Posted by chasw98 View Post

I should have the results ready to upload by Wednesday this week.

Chuck



Excellent. Here's hoping it tests well!
post #1643 of 1917
Sweet!!! It's Wednesday!!! Can't wait to see the results so we can do some comparisons. I miss the amplifier testing and sub testing threads.....so glad to see this back with a new test to add to the collection.
post #1644 of 1917
http://crownaudio.com/amp_htm/xls_drivecore.htm

Thought I'd throw this out there. PWM and it's relatively cheap. I recall PWM being pimped out like crazy here a while back. I believe the CE4000 utilizes this technology. Only $600 for the the XLS2500.

I'm partial to Crown, they always have delivered fantastic results for me and have had no problems during gigs whatsoever. I'm running two XTI4000s.
post #1645 of 1917
Quote:
Originally Posted by Spezzy View Post

http://crownaudio.com/amp_htm/xls_drivecore.htm

Thought I'd throw this out there. PWM and it's relatively cheap. I recall PWM being pimped out like crazy here a while back. I believe the CE4000 utilizes this technology. Only $600 for the the XLS2500.

I'm partial to Crown, they always have delivered fantastic results for me and have had no problems during gigs whatsoever. I'm running two XTI4000s.

The CE4000 is a switching amp, but not sure it's the same technology.
post #1646 of 1917
Thread Starter 
Quote:
Originally Posted by Woodfiend View Post

Sweet!!! It's Wednesday!!! Can't wait to see the results so we can do some comparisons. I miss the amplifier testing and sub testing threads.....so glad to see this back with a new test to add to the collection.

The best laid plans of mice and men......

Unfortunately my wife and I were in an auto accident (no one hurt, not our fault) and it has changed my schedule for the week to some degree as you can imagine. So the results will be delayed until Saturday. Apologies to all but that's life. I didn't count on buying a new car this week.
post #1647 of 1917
Wow, sorry to hear that. Glad you are OK, cars can be replaced.

Take care of you and yours, we'll still be here when you have the time.
post #1648 of 1917
Chuck,

The most important thing is that you two are OK.

Testing stuff can wait.

James
post #1649 of 1917
No need to apologize. We are just glad to hear everyone is okay! Family always comes first even over great hobbies such as this. Good luck with the car hunt!
post #1650 of 1917
Thread Starter 
After all this time, here are the test results of a Peavey IPR-1600 provided by Peavey themselves and JD (sickneedshelp). I think they are to be applauded for letting a garage amateur have one of their new amplifiers when there are so few reviews out yet.

BUT, I must qualify the results that you see. I am not sure how to put this but the best analogy I can come up with is this. For any of you old enough to remember Ford's and Chevy's from the 60's & 70's, they were fairly easy to keep running. No computers, no automatic functions, no traction control, etc. You could set the points with a matchbook and they would run. Now imagine working on a car made past the year 2000 with that technology. You would be lucky if it would get started again.

That is what it has been like for me trying to apply solid state sine wave/THD testing to a modern Class D amplifier. I got the measurements, but they do not match what the factory can squeak out of it with computer based test equipment, active filters, etc.

When these amps are put on the bench at the manufacturer, they are hooked up to Audio Precision units with AP filters that will essentialy take the testing out of the operators hands. The test gear will get set with a 20 ms on/ 10 ms off burst tone that will automatically go from 20-20KHz and spit out a nice file with all the data you want to publish. I can't do that at home.

So what follows is what I measured on my test equipment.

Chuck
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