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Luke's basic amplifier tests


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Assuming those are pure 304 stainless steel of 369 g, you can anticipate them to heat up at a rate of about 6.5 deg C per second with 1200W applied for a total of 32.5 deg C, maximum, over a 5 second period.  This is a maximum figure because as the element gets hotter, it starts to transfer heat to its surroundings.  If run for a long time (in water, of course) the temperature eventually stabilizes, but your tests will probably be way too short for that, even though they are submerged in water.

 

So what does 32.5 deg C do for resistance?  This data sheet for a 304 stainless steel product gives resistivity values of 28.4 @ 20 deg C and 45.8 @ 659 deg C.  This probably isn't the best data to use for this, but with some linear interpolation, I estimate you'll see about a 3% increase in resistance between the start and end of a single test.  This is probably a pretty reasonable error.  However, be aware that errors could increase and accumulate if the coil does not have time to cool between tests.  If you can measure the resistance with enough precision to see this effect or just get temperature readings on the coil you can avoid this issue.

 

FWIW, I've read that resistance doesn't change as much with respect to temperature in stainless steel as is does in many other metals, so this appears to be a very good material choice for this purpose.

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Hey I resemble that remark!  

The output power of a K20 vs an X4 K20:  145 V RMS for less than a second at 2.05 ohms both channels driven Then it limits to 58 V then it goes down to 52.  This means 10.5 kw per channel for

EDIT: The testing methodology was updated to use a non-reactive load (water heater elements). I purchased 10 of these (Camco 6000w 240v low watt density): https://www.amazon.com/Camco-Screw--Foldb

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Finally got around to finishing the wiring on the bucket.  One channel is 2.009ohm, and the other is 1.990ohm. 

 

I think I'll test Vpp with CEA bursts at 80, 40, 20, 10, and 5hz, and then do a 12 second test at 20hz to see how long the amps can maintain their power.  I'll of course upload a screenshot of the 12 second test. 

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Any input on this type of format?  For the CEA burst tests, I pushed the amp as far as it could while maintaining a clean wave.  

 

 

CC4000 - Bridged

 

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12 second 20hz sine wave:

 

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The CC4000 maintained 324Vpp / 3,280w RMS for 3.5 seconds and then its magnetic circuit breaker (power switch) tripped.  

 

As you can see, it maintained 324Vpp until it powered itself off:

 

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Edited by lukeamdman
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XLS 2500 - Bridged

 

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Summary of the 12 second 20hz sine wave test:  The XLS 2500 maintained 242Vpp / 1,830w RMS for around 2.7 seconds and then dropped to 218Vpp / 1,485w RMS over the next second and was able to maintain that for about 5 seconds.  The output then gradually decreased to 194Vpp / 1,176w RMS for the last second or so.  At the very end of the 12 seconds the thermal light for channel 1 was lit but self-recovered after a few seconds.  

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SpeakerPower SP2-12000 - Both channels driven*

 

*Both channels were driven equally but the measurements below are only from a single channel.  The SP2-12000 can output these numbers below per channel (x2).

 

 

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Summary of the 12 second 20hz sine wave test:  This was run with both channels driven like the CEA-2010 burst testing.  The SP2-12000 maintained 308Vpp / 5,927w RMS for 2.5 seconds and then over the next second decreased to 228Vpp / 3,248w RMS and maintained that for another 2 seconds.  It then gradually decreased again to 206Vpp / 2,651w RMS and held that for 4.5 seconds until the end of the 12 second test.  

 

At the end of the 12 seconds the amp was still cold to the touch and the fans were idle.

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For the SP2-12000 testing, a fluorescent light near my work bench was flickering, so I wonder if I had some voltage drop.  I was expecting the 12k to hold full power for closer to 4 seconds, but maybe my 240v 30A circuit is holding it back?

 

Also, just in case I wasn't very clear, that's with both channels running equally but I'm only measuring the voltage off a single channel.  So all in all that amp was outputting a total of 12,000w RMS for 2.5 seconds, which is really close to factory specs.  

 

That also means for 2.5 seconds the power supplies were outputting over 110A combined!  For the last 4.5 seconds they were outputting over 70A, and I'm sure well before that point the capacitors were completely drained.  

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Lab Gruppen IPD 2400

 

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Summary of the 12 second 20hz sine wave test:  

 

2ohm both channels driven:

 

62.8Vpp / 246w RMS for 0.5s
60Vpp / 225w RMS for 0.8s
56.8Vpp / 202w RMS for 1.2s
53.2Vpp / 177w RMS for 2.4s
50.8Vpp / 161w RMS for 12s
 
2ohm single channel driven:
 
77.6Vpp /  376w RMS for 2.3s
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Keep up with these test! Your test, Ricci's and some others from the DIY community helped me to convince a client to get the best possible.

I know it is not directly related with Luke's measurements, but I wanted to share a review with you about the Powersoft X4 (and for X8 at the same time, being 2 of htem in a single package)

 http://www.powersoft-audio.com/en/docman/1012-x-seriestestrevieweng/file

That is a resonably way of review-ing amps IMHO

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