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.
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.
"There is no greater mistake than the hasty conclusion that opinions are worthless because they are badly argued." -- Thomas H. Huxley
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.
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.
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.
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.
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.
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
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!
Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.