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Review and Measurements of Crown XLS 1502 Amp

mitchco

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#21
This is a review and detailed measurements of the Crown XLS 1502 "PA" Power Amplifier. It is on a kind loan from a member who bought it new and drop shipped it to me. It retails for USD $349 including free Prime shipping from Amazon. At that price, it seems like an incredible value.​
@amirm Thank you for measuring this amp. Do you have the means to measure output impedance to calculate damping factor over a frequency range? Thanks again.
Mitch
 

Blumlein 88

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#22
This amplifier has analog inputs only.

Dave.
Yes, but if we feed it a 12 khz high level tone, that has to be digitized by the AD, then converted back by the DA, and if there are jitter effects they should show up as sidebands all the same. It is the sidebands in the analog output of a DAC we check with such testing. The clocks aren't locked between the AD/DA in the amp and the AP test unit AD.
 

dreite

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#23
Yes, but if we feed it a 12 khz high level tone, that has to be digitized by the AD, then converted back by the DA, and if there are jitter effects they should show up as sidebands all the same. It is the sidebands in the analog output of a DAC we check with such testing. The clocks aren't locked between the AD/DA in the amp and the AP test unit AD.
Yes, I understand, but that's not a j-test.
But, actually it's my fault for misinterpreting your query. You said "jtest" and not "J-Test." A big difference there depending upon..... :)
Cheers,
Dave.
 

jasonq997

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#24
Not what I was hoping to see, but at the same time this piece of equipment does exactly what it is advertised to do. This is a really good PA amp, but not a great piece of hifi gear. Thank you for taking the time to do this @amirm.
 

RayDunzl

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#25
This is a really good PA amp, but not a great piece of hifi gear.
I wonder what in the circuitry is creating this noise level... -100dB...

1546831157115.png
 

AnalogSteph

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#26
Bad graph scaling is bad. Fundamental ought to be at ~+18 dBu, so the harmonics you see are -100-ish dB down. The noise is, well, possibly ADC noise, or noise from the amp itself (Class D can be on the noisy side).

@amirm, just a hunch, but could you test whether SNR gets any better with higher input level (maybe +10 or +16 dBu) and input gain turned down? I presume your level was rather low, like the 1.4 Vrms sensitivity spec? The specs say
Signal to Noise >103dB (at .775Vrms, 6dB lower)
I do have to wonder why you got no more than 100 dB out of the unit, usually reputable pro audio manufacturers tend to get their specs right.
(Of course, even 103 dB remains pathetic for a high-power amp, and the sub amp recommendation seems about right.)
 

amirm

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#27
@amirm, just a hunch, but could you test whether SNR gets any better with higher input level (maybe +10 or +16 dBu) and input gain turned down?
Doesn't seem to at multiple levels I tested. Here is an example with left channel two notches down in gain and right channel at max for the same power:

Crown XLS 1502 Amplifier Dashboard Measurements.png


I have set the reference correctly on the FFT now. As we see, there is a complete spray of even and odd harmonics resulting in much reduced SINAD. The bandwidth for this measurement is 22.4 kHz so I also upped the FFT to show the full spectrum being measured for SINAD.
 

amirm

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#28
I do have to wonder why you got no more than 100 dB out of the unit, usually reputable pro audio manufacturers tend to get their specs right.
I think their spec is a-weighted? Also, my setup for speaker measurement doesn't allow very low noise measurements due to long cables and such. I need to tidy that up so small differences are probably fine.
 

amirm

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#29
Either or both 1W and 180W would be good, thx!
I ran the test from memory and I thought you asked for 130 watt so that is what you are going to get. :)

Crown XLS 1502 Amplifier THD+N vs frequency Measurements.png


Note that I had to dial down the bandwidth to 22.4 kHz which means there is no sense in looking at 20 kHz. Anything higher and SINAD would massively drop due to all the noise and harmonics in ultrasonics.

Here is the 90 kHz bandwidth I normally like to use for this test:

1546834710362.png
 

RayDunzl

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#30
I don't recall rising harmonics like that...

Let's see the Multitone...
 

amirm

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#31
Since there is an AD/DA step how about a jtest? Maybe at low, moderate and high power.
Here it is at 5 watts:

1546834963996.png


Everything is buried in noise looks like. Jacking up the power to 180 watts makes them show up though:

1546835076286.png


Don't know if this is ADC/DAC clock jitter or modulation frequency jitter of amplifier. It is a good test to run on future class-D amps to see what we have.

Here is the wideband version of above by the way:

1546835168891.png
 

amirm

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#32

RayDunzl

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#33
That looks better than I might have expected given the previous results...
 

AnalogSteph

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#34
Honestly, I always have a hard time interpreting the multitone results. No idea how they relate to traditional CCIF / SMPTE measurements. 12 kHz harmonics seem rather high, but that doesn't mean this has to translate to IMD... noise-shaped PWM isn't necessarily behaving like a traditional amp. High-power 3rd sure is skyrocketing at HF, nothing altogether unexpected in a Class D amp.
 
Last edited:

Blumlein 88

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#35
Here it is at 5 watts:

View attachment 20011

Everything is buried in noise looks like. Jacking up the power to 180 watts makes them show up though:

View attachment 20012

Don't know if this is ADC/DAC clock jitter or modulation frequency jitter of amplifier. It is a good test to run on future class-D amps to see what we have.

Here is the wideband version of above by the way:

View attachment 20013
Thanks for doing this.

I wonder looking at these results if the modulation frequency jitter of the amp isn't the reason for the elevated noise level in general.
 

RayDunzl

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#37
Are you starting to use the metric system in the US?
Not very much.

Some technical things. Automotive hardare. Tires - mixed - width is metric, rim is inches - mine are 215/60r15.

Have Soft Drinks in 2 liter bottles.

Medicine - milligram, cc, etc

That's about all.
 
Last edited:

andreasmaaan

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#39
I ran the test from memory and I thought you asked for 130 watt so that is what you are going to get. :)

View attachment 20008

Note that I had to dial down the bandwidth to 22.4 kHz which means there is no sense in looking at 20 kHz. Anything higher and SINAD would massively drop due to all the noise and harmonics in ultrasonics.

Here is the 90 kHz bandwidth I normally like to use for this test:

View attachment 20010
Many thanks Amir :)

The numbers don’t look great but looking at the actual graphs it all looks rather benign to me.
 

Sal1950

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#40
And thanks for this review. One many people have wanted for some time.
Yes there has been a lot of talk on the Crown PA amps suitability for Hi Fi use and this pretty much answers that.
Thanks to Amir and the loaning member!
 
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