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Measuring Amplifiers - Page 24

post #691 of 1913
4/27/08 at 12:21pm
Audio comedy,who is noy hyping his products ? Everyone is. Its called being a good salesman. Sugar coating it all to look better to the buyer.

Now where is my PMPO rated PRC made clone of a clonned clown?
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post #692 of 1913
4/27/08 at 12:48pm
Quote:


This is the part I don't get. If they already have their test, took the time to come here and post and call into question the OP test methods, which is fine, why not clarify and post their test methods.....as you stated they already have their tests. I don't think it took any guts personally.....posting their test methods would have. Look, I highy doubt Dayton makes this amp in house, more likely they just have some third party design it, build it and stamp their name on it.

Bingo, you can't run in and yell foul without offering an alternative.

Where are his graphs? :P

The bottom line really is that it doesn't matter though. People will still buy it and use it for projects.
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post #693 of 1913
4/28/08 at 6:21am
Having not heard from PE on Friday I called PE this morning. Had a nice chat with Eric in the customer service department. The note worthy parts of our conversation are as follows.

The 512watt amp is the same at the 1024watt amp internally. (so buy the 512 and get out your screwdrivers)(the 512 is 300$ the 1024 is 400$)
The bias on the input stage is the only difference.
He has tested this amp before and has seen 800watts out of the one he tested.

He did not call the testing methodologies into question(good customer service) and did offer a TESTED replacement. We also have setup to have the amp sent directly to Eric for testing when it arrives.

The saga continues.
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post #694 of 1913
4/28/08 at 12:56pm
I must say impressed with parts express so far
Disapointed in Dayton. Maybe you got a missmarked 512? Eager to see the results and hope it works out well for you.
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post #695 of 1913
5/11/08 at 8:45am
Thread Starter 
I just received one of these.........


and I will be measuring it later this week. Here is a picture of the back of this unit.


Chuck
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post #696 of 1913
5/11/08 at 8:51am
Thread Starter 
For those of you so inclined.

All the IC's are 4558D op amps. The wall wart transformer is a 3 pin 16.5 VAC X 2, 250 ma unit. This allows them to get their +-15 VDC for the op amps.

After seeing how the filters operate, measuring S/N ratio, distortion, etc. I will try and modify the unit to be able to output a balanced +4 signal. It should only take a single IC, 2 capacitors, and a female panel mount XLR connector.

Chuck
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post #697 of 1913
5/11/08 at 9:40am
Is that the H@LF box project?
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post #698 of 1913
5/11/08 at 10:56am
Quote:
Originally Posted by augerpro View Post

Is that the H@LF box project?

Looks like its the Elemental Designs EQ device.

I look forward to your measurements and the addition of the balanced XLR +4 output.
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post #699 of 1913
5/11/08 at 11:28am
Bah, I thought that last pic was thrown in as a teaser. Nevermind me.
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post #700 of 1913
5/14/08 at 4:52pm
Thread Starter 
fireanimal has ever so kindly sent me a Crown XTi1000 power amplifier to put on the bench and see what it will do. When I received the unit and took it out of the box, the amp rattled. I did not want to turn it on with a rattle inside so I took the top cover off (3 torx screws) and found that the AC fuse had been knocked out of its fuseholder by UPS. While I had it open I took pictures of the insides.

Front Inside

Top Inside

Rear Inside

Power Supply

AC Inlet
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post #701 of 1913
5/14/08 at 5:03pm
Thread Starter 
Here are the results for 8 ohms, 4 ohms, and 2 ohms testing. There is a difference between the 8 ohm and 4/2 ohm test. Because of the 'clipping' behavior of this amplifier, I was able to run the 8 ohm test at full power and then see where the distortion was. For the 2 & 4 ohm tests, I had to run the amp up to its factory rated distortion and then measure power level. The amp is rated for 0.5% THD at 8 ohms and 4 ohms, and then rated at 1% THD for 2 ohms. When this amplifier clips at 4 or 2 ohms it does not really 'clip' in the classic sense, i.e. square off the waveforms, it goes into oscillation. At 2 ohms the amp would run at 0.1% THD and then jump to 10% THD and produce no more voltage. I did not want to damage the amp so I just ran it up to before oscillation and measured from there at 2 ohms. As a side note, while testing at 2 ohms, it took less than 90 seconds for the amplifiers thermal lights come on but the amp did not shut down nor was the case very warm to the touch. I am going to let the amp cool down and rest before doing 8 & 4 ohm mono tests.



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post #702 of 1913
5/14/08 at 5:21pm
Whats up with the output power at 20 hz? Did you ever get a second Dayton plate amp to test or is that a dead issue?
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post #703 of 1913
5/14/08 at 5:30pm
Let me be the first to say . . . . . "That sucks"!
Unless there is something significantly wrong with this particular amp, the S/N ratio is only average. The best it can do for power is at 1000HZ and even THAT doesn't come near advertised. Then look at the discrepancy at 20HZ for the left channel . . . . . 26 watts!!??
And you might as well not even think about using this amp on a 2 OHM load . . . . .
No wonder this amp has the reputation amongst the pros as NOT to be used as a sub amp.
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post #704 of 1913
5/14/08 at 6:04pm
Surely there is something wrong with an amp that produces 26 W on one channel at 20 Hz at 8 ohms and 225 on the other channel. Is the amp defective?

Edit: I see that it's obviously a typo.
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post #705 of 1913
5/14/08 at 6:14pm
Can you bridge it for a 4 and 8 ohm load and see what it shows? The manual says 1400 and 1000 watts. I am interested since I have this model pushing my sub bridged at 4 ohms.
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post #706 of 1913
5/14/08 at 6:20pm
Thread Starter 
Quote:
Originally Posted by geoffstgermaine View Post

Surely there is something wrong with an amp that produces 26 W on one channel at 20 Hz at 8 ohms and 225 on the other channel. Is the amp defective?

Edit: I see that it's obviously a typo.


Oops. Sorry. I made a mistake proofreading myself.

Chuck
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post #707 of 1913
5/14/08 at 6:37pm
*strikes xti off of his list*
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post #708 of 1913
5/14/08 at 7:21pm
OK, Chas I'll wait until you can complete all your testing and update/correct the charts. But still, this highly touted Pro amp looks suspect.
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post #709 of 1913
5/14/08 at 7:38pm
Chuck,

I went back and read the beginning of this thread and did not see what I was looking for so I will ask. Did the Crown have the 1.4 volts rms in for the signal to put the amp at full rated power?

Sensitivity (volts RMS) for full rated power at 4 ohms 1.4V
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post #710 of 1913
5/14/08 at 7:48pm
What is this mumbo jumbo ! Under 90W into a 4Ohm load.... Crown better not clown around ,this is pathetic. 90W ...something is wrong.

Into an 8Ohm load is delivers around 225 and under 90 into 4...

This is not correct,I am calling Clown...I mean Crown to look into this mess.

Doing worse than a miserable plate amp...absolute disgrace.No excuses here. I am going to stomp a mud hole in my XTi's if this is true.
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post #711 of 1913
5/14/08 at 9:09pm
Quote:
Originally Posted by TheEAR View Post

This is not correct,I am calling Clown...I mean Crown to look into this mess.

LOL, give em a piece of your mind EAR!
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post #712 of 1913
5/15/08 at 12:08am
This is the best thread I have read in a while, lots of good info; keep up the hard work.

The circuitry inside that Crown XTi1000 does not look very impressive... how many farads is that? In fact, it actually looks like it is missing pieces

I am curious to see how the ED LT/1300, Velodyne, JL and SVS plate amps compare to the other plates already measured
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post #713 of 1913
5/15/08 at 12:27am
I'm impressed by the generous, thick heat sinks, but that's about it.
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post #714 of 1913
5/15/08 at 4:57am
The amp was replaced with a PLX1202 which is rated at 1200 watts, while the crown was 1400. I now have way more headroom with the QSC than I did with the Crown before clipping.

I was suspect that the amp was junk.

Thanks for testing it.
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post #715 of 1913
5/15/08 at 5:22am
Well, it does not seem to have tested well but I think mine sounds very with my sub. I have started a thread on Crowns forum to see if they feel like commenting on this test.
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post #716 of 1913
5/15/08 at 7:10am
I spoke with a "tech" at Crown,he found this ...SURPRISING. LOL

It cannot be,I mean come on under ...an easy 4 Ohm load the amp falls like a stone(20Hz),this makes teh Dayton amp look like a Goliath in comparison.

Under 8Ohms it delivers what it should,why whis sudden collapse? It is not like it was asked to drive a 1 Ohm load.

Le me get a puke bucket...the Sonic T amp delivers more...


chasw98,

Can you try the 4 Ohm test @ 30Hz just to see? DSP in cause...?
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post #717 of 1913
5/15/08 at 7:13am
Thread Starter 
I will be doing more testing tonight, especially at the lower end of the spectrum to see what frequency the power falls off or IF I made a mistake in setup or measurement. (exojam, I will check the sensitivity, but I thought I set the amp to defaults, i.e. no DSP at all). And I will finish the mono testing.

Chuck
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post #718 of 1913
5/15/08 at 7:25am
Thread Starter 
Here is the datasheet from the Crown website for the XTi series of amplifiers. 2 points to notice are that the frequency response is only given at a 1 watt power level and the power output is only rated at 1Khz. The same holds true for the owners manual. Here is a link to the Crown document. http://www.crownaudio.com/pdf/amps/139472.pdf

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post #719 of 1913
5/15/08 at 8:58am
Quote:
Originally Posted by BassThatHz View Post

This is the best thread I have read in a while, lots of good info; keep up the hard work.

The circuitry inside that Crown XTi1000 does not look very impressive... how many farads is that? In fact, it actually looks like it is missing pieces

I am curious to see how the ED LT/1300, Velodyne, JL and SVS plate amps compare to the other plates already measured

They use the same curcuit board for the XTi1000-4000. Not looking impressive,it is all about the numbers and here I agree it is not impressive...even troubling. The output collapsed at 4 Ohms,there is a crater in the ground ...it is so bad!
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post #720 of 1913
5/15/08 at 11:07am
That's why I created this thread. My gut feeling that something
is odd.


http://www.avsforum.com/avs-vb/showthread.php?t=1022451
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